Necessary equipment list for biodegradable plastic twin screw compound production line

A biodegradable plastic twin screw compound production line is not a conventional compounding line with a different recipe loaded into it. The equipment list changes because the materials change: PLA, PBAT, PBS, PHA and starch blends are hydrolysis-sensitive, thermally narrow, and in several cases physically awkward to convey and meter. Every machine group on the line, from the dryer at the inlet to the bagging scale at the outlet, has to be specified against those three constraints. This guide walks the line stage by stage in the direction the material flows and lists what each stage actually needs, what the key parameters are, how to select between options, and where projects most often go wrong.

Kerke, a Wanplas factory, has built co-rotating parallel twin-screw compounding equipment for more than twelve years from a 19,997-plus square meter plant, with over 2,000 machines running in 70-plus countries and a team of more than 100 people. Biodegradable plastic compounding is one of the factory’s core application industries alongside masterbatch production, engineering plastic compounds, cable compounding and wood-plastic composites, so the equipment list below reflects line layouts that have been shipped, commissioned and run in production rather than a generic catalog checklist.

1. Why a biodegradable compound line needs its own equipment list

Three material behaviors drive nearly every deviation from a standard polyolefin compounding line, and understanding them makes the rest of the equipment list read as a set of logical consequences rather than an arbitrary shopping list.

Hydrolytic sensitivity dictates the upstream section

PLA, PBAT, PBS and PHA are polyesters. In the melt, residual water attacks the ester linkage and cuts molecular weight irreversibly. The visible symptoms are familiar to anyone who has run a wet polyester: smoking at the die, strands that snap in the water bath, foamy or hollow pellets, a melt flow rate that drifts upward through the shift, and finished parts that fail tensile and impact specifications. This is why the upstream section of a biodegradable line carries a full central drying and conveying system with a minus 40 degrees Celsius dew point rather than a simple hot-air hopper dryer. It is also why closed conveying, sealed day hoppers and short residence time between dryer and feed throat are equipment decisions, not operating habits.

A narrow thermal window dictates the extruder and melt train

PLA processes at roughly 170 to 200 degrees Celsius melt temperature, and begins measurable thermal degradation not far above that. PBAT is more forgiving but still degrades with long residence at high shear. Starch-based compounds carry moisture and can scorch. The consequence is an extruder specified for high torque at moderate screw speed rather than high speed at low torque, a screw configuration with mild kneading intensity and short reverse elements, tight barrel temperature control, and a melt train designed for the shortest possible residence path. Long, dead-volume-heavy melt piping and oversized filtration chambers are as harmful here as an overly aggressive screw.

Difficult bulk handling dictates the feeding section

Biodegradable formulations rarely consist of easy free-flowing pellets alone. Recipes routinely combine a base polyester pellet, a second polyester pellet, a fine mineral filler such as calcium carbonate or talc, a starch or plant-fiber powder, a chain extender masterbatch dosed at fractions of a percent, and often a liquid plasticizer. Powders bridge, ratholes form in hoppers, fibers do not flow at all, and low-percentage additives need a metering resolution that a volumetric screw cannot deliver. That is why the feeding section on a serious biodegradable line is a bank of loss-in-weight feeders with different discharge geometries, not one hopper and a screw.

The six stages of the line

1. Stage 1 — Upstream raw material handling: drying, conveying, storage, metal separation, powder fluidization and gravimetric feeding.
2. Stage 2 — Extrusion: the co-rotating twin-screw extruder, its barrel and screw configuration, heating and cooling, and gearbox.
3. Stage 3 — Melt conveying and filtration: gear melt pump, screen changer, instrumentation, safety devices and vacuum devolatilization.
4. Stage 4 — Pelletizing: strand, water-ring or underwater route, plus dewatering, classification and drying of the pellets.
5. Stage 5 — Downstream handling: pneumatic conveying, homogenizing silos, sampling, weighing, packing, metal detection and palletizing.
6. Stage 6 — Utilities and services: cooling water, compressed air, dust extraction, electrical distribution, safety systems and laboratory quality control.

2. Master equipment list for the complete production line

The table below is the single-page answer to the question this article asks: what equipment must be on a biodegradable plastic twin screw compound production line, and what can wait. Mandatory items are those without which the line cannot produce saleable, specification-compliant pellets. Optional items improve consistency, yield, labor cost or product range, and are frequently added in phase two once the line is running.

Table 1. Master equipment list for a biodegradable compounding line, all six stages

Equipment	Function on the line	Key parameters to specify	Mandatory or optional
Central dehumidifying dryer	Removes bound moisture from polyester resins before the feed throat	Dew point minus 40 degrees Celsius; hopper volume for 3 to 4 hours residence at rated output; 60 to 80 degrees Celsius for PLA, 60 degrees Celsius for PBAT, 70 degrees Celsius for starch blends	Mandatory
Drying hoppers with insulated cones	Holds resin at drying temperature with plug flow	Cone angle 60 degrees or steeper; internal spreader cone; temperature uniformity within plus or minus 3 degrees Celsius top to bottom	Mandatory
Vacuum and pneumatic loaders	Moves dried resin, filler and regrind to feeders without ambient pickup	Closed loop with dry-air return for polyesters; conveying rate at least 1.5 times line consumption; stainless contact surfaces	Mandatory
Raw material silos and day bins	Bulk storage and shift buffer between deliveries and the line	Volume for 8 to 24 hours of production; level sensors; sealed vent filters; nitrogen or dry-air blanket where specified	Optional above bag-fed lines
Magnetic separator and metal detector	Protects screws, barrel and screen changer from tramp metal	Rare-earth magnetic rods 10,000 to 12,000 Gauss; drawer type at each infeed; metal detector at packing for product safety	Mandatory
Powder bridge breaker and fluidizing unit	Prevents arching and ratholing of filler and starch powder	Vibrating or air-pad type; suited to bulk density 0.3 to 1.2 g/cm3; sized to feeder hopper geometry	Mandatory for filled recipes
Loss-in-weight feeder, main resin	Meters the base polyester into the main feed throat	Metering accuracy plus or minus 0.5 percent; single or twin screw discharge; range turndown at least 20:1	Mandatory
Loss-in-weight feeders, auxiliary	Meters second resin, filler, additive masterbatch and fiber	2 to 4 units; twin-screw discharge head for powder; vibratory tray for fiber; hopper agitation matched to material	Mandatory, count varies
Liquid metering pump	Injects plasticizer, oil or liquid additive into the barrel	Piston or gear type, 0.1 to 5 kg/h typical; heated line; pressure rating above local melt pressure; check valve at injection nozzle	Optional, recipe dependent
Co-rotating twin-screw extruder	Melts, disperses, devolatilizes and pumps the compound	Do/Di 1.55 to 1.75; L/D 40 to 48:1; specific torque 8 to 11 N.m/cm3; 300 to 600 rpm; 8 to 12 barrel zones	Mandatory
Side feeder, twin-screw type	Introduces filler, fiber or heat-sensitive additive downstream of the melting zone	1 to 2 units; matched to main screw diameter; forced venting on the side feeder barrel for entrained air	Mandatory for filled recipes
Vacuum devolatilization system	Removes moisture, monomer and volatiles from the melt	Water-ring vacuum pump; minus 0.08 to minus 0.095 MPa; two-stage venting on PLA and starch lines; condensate separator	Mandatory
Gear melt pump	Stabilizes die pressure and decouples throughput from extruder pressure build	Die pressure fluctuation within plus or minus 2 percent; throughput gain 8 to 15 percent; heated body with independent temperature zones	Optional below 500 kg/h, mandatory for underwater route
Screen changer	Filters gels, char and contamination out of the melt	Single plate, dual plate, hydraulic quick-change or continuous belt; 40 to 120 mesh pack; minimal dead volume for PLA	Mandatory
Melt pressure and temperature sensors	Process monitoring, interlocks and quality traceability	Sensors before and after filtration and at the die; melt thermocouple with immersion probe; data logged to the control system	Mandatory
Rupture disc safety device	Protects operators and equipment from overpressure	Set below the design pressure of the weakest melt-path component; alarm and shutdown interlock	Mandatory
Pelletizing system	Converts melt into pellets by strand, water-ring or underwater route	Strand below 500 kg/h; water-ring 300 to 1500 kg/h; underwater above 800 kg/h; die-face heating and blade pressure compensation on underwater units	Mandatory, route selected by capacity
Centrifugal dewatering unit	Separates pellets from process water	Residual surface moisture below 0.3 percent; rotor speed and screen aperture matched to pellet size	Mandatory for wet routes
Vibrating classifier screen	Removes long pieces, doubles, fines and dust from the pellet stream	Two-deck design; upper deck for oversize, lower deck for fines; aperture matched to 2 to 5 mm pellet	Mandatory
Pellet after-dryer	Drives residual surface and near-surface moisture out of hygroscopic pellets	Fluidized-bed or hot-air type; 40 to 55 degrees Celsius for PLA to avoid tackiness; residence 3 to 10 minutes	Mandatory for PLA-rich compounds
Pneumatic pellet conveying	Moves pellets from the pelletizer to silos and packing	Dilute phase with elbow protection; velocity controlled to limit angel hair; dry-air conveying for hygroscopic grades	Mandatory
Homogenizing and blending silo	Averages out batch-to-batch variation before packing	Volume equal to 4 to 8 hours output; gravity blending internals or mechanical stirrer; discharge mass flow design	Optional but strongly advised
Automatic sampler	Takes representative samples for melt flow rate and moisture checks	In-line diverter type; sample interval programmable; sample bottle labeling by batch code	Optional
Automatic weighing and bagging	Fills and seals 25 kg bags or 500 to 1000 kg bulk bags	Weighing accuracy plus or minus 0.1 percent; bag sealing or stitching; dust extraction hood at the fill spout	Mandatory at commercial scale
Palletizer and stretch wrapper	Stacks and secures finished bags for shipment	Robotic or gantry type; throughput matched to bagging rate; pallet pattern programmable	Optional
Dual-circuit cooling water system	Cools barrel zones, gearbox oil, pellet water and vacuum system	Tower loop for pellet water; chilled loop at 8 to 15 degrees Celsius for barrels and oil cooler; flow measured in cubic meters per hour against installed power	Mandatory
Compressed air system	Drives valves, pneumatic conveying, blade actuators and packing	0.7 MPa working pressure; dried and filtered to instrument quality; receiver sized for peak demand	Mandatory
Dust extraction and workshop ventilation	Captures filler and starch dust at transfer and packing points	Capture velocity at hoods; cartridge filtration; ATEX-rated design in dust zones	Mandatory for filled recipes
Laboratory QC package	Verifies that every batch meets specification before release	Melt flow rate tester, Karl Fischer moisture titrator, DSC, tensile and impact testers, color spectrophotometer	Mandatory for certified product

How to read the mandatory versus optional column

The mandatory classification assumes a commercial line producing compound for sale under a compostability claim. A pilot or captive line that feeds its own downstream converting operation can defer the homogenizing silo, the palletizer, the automatic sampler and, in some cases, the bagging line, because the product moves straight into an internal hopper. What cannot be deferred is anything that touches moisture control, metering accuracy, melt filtration or safety. Those four categories determine whether the pellets meet specification at all, and retrofitting them into a running line always costs more in downtime and rework than buying them with the line.

3. Stage 1A: central drying and material conditioning

Drying is the single highest-leverage equipment decision on a biodegradable compounding line, because every downstream parameter is measured against a melt whose molecular weight has already been fixed by the moisture that entered the feed throat. A line with a perfect extruder and an inadequate dryer will make out-of-specification pellets every day it runs. A line with a modest extruder and a properly sized central drying and conveying system can hold specification for years.

Central drying and conveying system

Duty. Deliver resin to the feeders at a controlled temperature and a verified residual moisture level, without re-absorption between the dryer outlet and the feed throat.

Key parameters. The process air dew point must be minus 40 degrees Celsius at the hopper inlet, measured at the inlet and not at the desiccant bed outlet. Air flow is typically 1.8 to 2.5 cubic meters per hour per kilogram of hourly throughput, depending on resin and hopper geometry. Return air filtration protects the desiccant. Each hopper needs its own temperature control loop, because the drying temperatures for the resins on a biodegradable line are not the same.

Table 2. Drying parameters by biodegradable resin family

Resin	Drying temperature	Drying time	Target moisture	Critical equipment note
PLA (neat pellet)	60 to 80 degrees Celsius	4 hours	Below 250 ppm	Do not approach the glass transition region with unagitated static beds; softened pellets bridge and fuse into blocks in the hopper cone
PLA (crystallized grade)	80 degrees Celsius	4 hours	Below 250 ppm	Crystallized grades tolerate the higher end of the range; amorphous grades must stay lower
PBAT	60 degrees Celsius	3 hours	Below 500 ppm	Low melting point and soft pellets; use gentle conveying velocity to limit fines and angel hair
PBS and PBSA	60 to 70 degrees Celsius	3 to 4 hours	Below 400 ppm	Similar handling to PBAT; check supplier data for grade-specific limits
Starch-based blends and native starch	70 degrees Celsius	2 to 4 hours	Below 1 percent, recipe dependent	Some formulations deliberately retain moisture as a processing aid; the dryer must be able to hold a target, not simply dry to the floor
PHA and PHBV	60 to 70 degrees Celsius	2 to 3 hours	Below 300 ppm	Very narrow thermal window; minimize hot residence time between dryer and extruder
Calcium carbonate and talc filler	100 to 110 degrees Celsius	1 to 2 hours	Below 0.1 percent	Filler moisture is often overlooked and is a frequent cause of vent-port steaming

Selection notes. Size the hopper on residence time at rated line output, not on nominal volume. A 4-hour PLA hopper on a 500 kg/h line means roughly 2 tonnes of live capacity, and a hopper that is nominally large but has a shallow cone will channel and give some pellets 30 minutes of residence while others get 8 hours. Specify a spreader cone, a 60-degree or steeper cone angle, and insulated walls. Where two or more resins run simultaneously, specify separate hoppers rather than one big one with a changeover procedure.

Common mistake. Buying a compressed-air dryer or a hot-air dryer to save on the upstream budget. Hot-air units at ambient dew point cannot take PLA below roughly 500 to 800 ppm on a humid day, which is not enough. The second common mistake is running a dry hopper and then conveying the dried resin through an open loop with ambient air, which restores several hundred ppm in the pipe. Closed-loop conveying with dry return air solves this and should be quoted as part of the drying package rather than as a separate afterthought.

Regrind and rework conditioning

Compounding lines generate start-up purge, strand break scrap and off-specification pellets. On a biodegradable line this rework is doubly moisture-sensitive because it has already seen one heat history. Equipment needed: a low-speed granulator with a sound enclosure for purge and strand scrap, a dedicated small drying hopper for rework, and a separate loss-in-weight feeder if rework will be dosed back at a controlled percentage. Dosing rework by shovel into the main hopper is the fastest way to lose control of the melt flow rate specification.

4. Stage 1B: conveying, silos, metal separation and powder handling

Between the warehouse and the feeder hoppers sits a set of unglamorous equipment items that decide whether the line runs unattended or requires an operator with a rubber mallet. On filled and starch-based biodegradable recipes, this is where most unplanned stops originate.

Vacuum and pneumatic loaders

Duty. Transfer resin, filler and rework from bags, silos or drying hoppers to the feeder hoppers on demand, controlled by level sensors.

Key parameters. Conveying capacity at least 1.5 times line consumption so refill cycles are short and the feeder hopper level band stays narrow. Suction lance or bag-dump station at the pickup point. Stainless steel contact parts and a filter with automatic reverse-jet cleaning for powders. For hygroscopic polyesters, use a dry-air loop rather than ambient air.

Selection note. Match the loader refill cycle to the loss-in-weight feeder refill logic. A feeder in volumetric fallback during refill is a feeder that is not controlling weight, so short and frequent refills are better than long and rare ones. As a rule, keep refill events under 20 seconds and no more frequent than every 3 minutes.

Common mistake. Under-sizing the filter area on powder loaders. A blinded filter drops conveying rate, the feeder hopper runs low, the refill cycle lengthens, and metering accuracy quietly deteriorates without any alarm being raised.

Silos, day bins and bag-dump stations

Duty. Buffer between raw material delivery and continuous line consumption.

Key parameters. Live volume for 8 to 24 hours of production per material, continuous level measurement, sealed vent filters, and a discharge geometry designed for mass flow rather than funnel flow. On lines using 25 kg bags rather than bulk delivery, a bag-dump station with integrated dust extraction and a bag compactor is the equivalent item.

Common mistake. Specifying funnel-flow cones on fine mineral fillers. The material in the center channel moves and the material at the wall does not, which produces both ratholing and first-in-last-out segregation. Mass flow geometry, or at minimum a properly sized fluidizing arrangement, avoids this.

Magnetic separation and metal detection

Duty. Two different jobs with two different machines. Magnetic separators at the infeed protect the screws, barrel bores and screen changer from tramp ferrous metal. A metal detector at the packing station protects the customer and is often a condition of food-contact supply agreements.

Key parameters. Drawer-type rare-earth magnetic rods at 10,000 to 12,000 Gauss at every infeed point, including the rework line. A cleaning schedule and a logged cleaning record. At packing, a through-flow metal detector with automatic reject and a test-piece verification routine at shift start.

Common mistake. Installing magnets and never cleaning them. A saturated magnet rod passes metal. Build the cleaning interval into the shift checklist and specify easy-clean drawer housings so the operator can actually do it in 30 seconds.

Powder bridge breakers and fluidizing devices

Duty. Keep fine, cohesive powders flowing into the feeder screw at a constant bulk density.

Key parameters. Vibrating hopper walls, air-pad fluidizers, internal agitators or flexible-wall massagers, selected by material. Bulk density range 0.3 to 1.2 g/cm3 covers most fillers and starches. The device must not aerate the powder so aggressively that the feeder screw delivers a fluctuating bulk density, which is a different failure mode with the same root cause.

Common mistake. Using a single fluidizing solution for all powders. Precipitated calcium carbonate, ground calcium carbonate, talc, native starch and wood flour have completely different flow behaviors. Specify the agitation per material, and if the recipe portfolio is broad, specify interchangeable feeder hoppers.

5. Stage 1C: gravimetric feeding architecture

On a compounding line, the feeders define the recipe and the extruder only executes it. A twin-screw extruder is a starve-fed machine: whatever mass the feeders deliver per unit time is what the line produces, in the ratio the feeders set. If the feeders drift by 2 percent, the compound drifts by 2 percent, and no amount of screw configuration will correct it.

How many feeders does a biodegradable line need

The practical answer is one main feeder plus two to four auxiliary feeders. A typical PLA-PBAT-starch film compound uses five metering points: PLA pellet, PBAT pellet, starch or filler powder, chain extender or compatibilizer masterbatch, and a liquid plasticizer. A simpler filled PLA compound for rigid articles might use three. Specify at least one spare feeding position on the extruder frame and one spare barrel port, because recipe portfolios always grow.

Table 3. Feeder configuration by material type on a biodegradable compounding line

Metering point	Material	Feeder type	Discharge geometry	Typical dosing accuracy	Feed location
Main	Base polyester pellet, PLA or PBAT	Loss-in-weight	Single concave screw	Plus or minus 0.5 percent	Main feed throat, barrel zone 1
Auxiliary 1	Second polyester pellet	Loss-in-weight	Single concave screw	Plus or minus 0.5 percent	Main feed throat, combined inlet
Auxiliary 2	Mineral filler or starch powder	Loss-in-weight with agitation	Twin concave screws	Plus or minus 0.5 to 1.0 percent	Side feeder, downstream of melting zone
Auxiliary 3	Additive or chain extender masterbatch	Loss-in-weight, micro range	Twin screws, fine pitch	Plus or minus 0.5 percent at low rate	Main throat or second side feed
Auxiliary 4	Natural fiber, wood flour, cellulose	Loss-in-weight, vibratory tray	Vibrating tray or flexible wall	Plus or minus 1.0 percent	Side feeder with forced venting
Liquid	Plasticizer, oil, liquid additive	Piston or gear metering pump	Heated injection nozzle with check valve	0.1 to 5 kg/h range, plus or minus 1 percent	Injection port after the first melting zone

Loss-in-weight feeder: what to specify

Duty. Continuously weigh the feeder hopper and control the discharge screw speed so that mass loss per unit time equals the setpoint, then refill volumetrically and return to gravimetric control.

Key parameters. Metering accuracy of plus or minus 0.5 percent on a 2-sigma basis is the working standard for compounding. Turndown range of at least 20:1 so one feeder can cover a family of recipes. Load cell resolution appropriate to the smallest dose on the line: a feeder dosing 2 kg/h needs far finer resolution than one dosing 400 kg/h, which is why one large feeder cannot cover both. Vibration isolation between feeder and extruder frame, because load cells read machine vibration as mass change.

Selection notes. For powders always specify a twin-screw discharge head. Single screws in cohesive powder produce pulsating discharge that the control loop chases rather than corrects. For fibers use a vibratory tray, because any screw will compact and bridge natural fiber. For low-dose additives, consider a dedicated micro feeder rather than running a large feeder at the bottom of its range, where relative error is worst. Kerke supplies volumetric metering systems, twin-screw side feeders, crammer feeders, loss-in-weight feeders and liquid feeders as part of its feeding system range, so the feeding bank can be matched to the recipe rather than to a catalog default.

Common mistake. Mounting feeders on the extruder platform without isolation, then blaming the feeder supplier for poor accuracy. The second common mistake is placing feeders in the path of a workshop ventilation draft; a cross-draft over an open feeder hopper produces a slow apparent mass change that the control loop dutifully corrects for, injecting error into the recipe.

Side feeder

Duty. Introduce filler, fiber or heat-sensitive additive into the melt after the base resin has melted, so the additive experiences less shear and less thermal history.

Key parameters. Twin-screw, co-rotating, driven independently with variable speed. Screw diameter matched to the main extruder so that conveying capacity exceeds the required feed rate by a comfortable margin. The side feeder barrel needs a vent, either atmospheric or connected to the vacuum system, because powder carries a large volume of entrained air into the melt channel. Without that vent, air backs up and the feed rate becomes erratic.

Common mistake. Undersizing the side feeder for high filler loadings. A 50 percent calcium carbonate loading at 800 kg/h means 400 kg/h of low bulk density powder must physically fit down the side feeder throat. If the side feeder is at its limit, the line output is capped there and not at the extruder.

Liquid injection

Duty. Add plasticizer or liquid additive directly into the melt at a controlled rate.

Key parameters. Piston metering pump for the 0.1 to 5 kg/h range, heated and insulated supply line for viscous liquids, injection nozzle with a spring-loaded check valve rated above the local melt pressure, and a mass flow meter for verification. Place the injection port after melting is complete and before a mixing section that can distribute the liquid.

Common mistake. Injecting liquid into a partially filled screw section. Liquid injected where the channel is not fully filled runs backward along the barrel wall to the feed throat and floods the solids conveying zone. The injection port must sit at a fully filled, pressure-generating location, which is a screw configuration decision as much as an equipment decision.

6. Stage 2: the co-rotating twin-screw extruder

The extruder is the only machine on the line that simultaneously melts, mixes, disperses, devolatilizes and pumps, which is why it carries the largest single share of the line investment index and the largest share of the technical risk. For biodegradable compounds the specification priorities are torque, thermal control and residence-time control, in that order.

Screw geometry and machine class

Do/Di ratio. The ratio of outer to inner screw diameter sets the free volume in the channel. A ratio of 1.55 to 1.75 covers biodegradable work. The higher end gives more free volume, which favors low bulk density fillers, starch and fiber, and improves devolatilization area. The lower end gives a deeper root and higher torque capacity per unit diameter, which favors highly filled and high-viscosity compounds. For a mixed portfolio of PLA, PBAT and filled blends, a ratio around 1.65 to 1.75 is the usual compromise.

L/D ratio. Specify 40:1 to 48:1. Below 40:1 there is not enough length to melt, add filler through a side feeder, mix, devolatilize in two stages and build pressure without compressing one of those functions to the point of failure. Above 48:1 the residence time and thermal exposure start to work against PLA and PHA. Lines dedicated to simple two-resin blends can run 40:1; lines that will handle starch, fiber and reactive extrusion should be at 44:1 to 48:1.

Specific torque. Specify 8 to 11 N.m per cubic centimeter. Specific torque, not motor power, is the honest measure of what a compounding extruder can do, because it determines how much work can be put into the material at a screw speed low enough to keep the melt cool. Neat polyester blends sit comfortably at 8 to 9. Highly filled starch and mineral compounds, and any reactive chain-extension work, benefit from 10 to 11.

Screw speed. A working range of 300 to 600 rpm. Note that biodegradable compounds are usually run at the lower half of that band. High speed generates shear heat that a narrow-window polyester cannot absorb, so the design intent is high torque at moderate speed, not maximum rpm.

Barrel zones. Eight to twelve independently controlled zones. More zones means finer control of the melting profile, which matters when the difference between a good PLA compound and a degraded one is 10 degrees Celsius in two zones.

Barrel construction

Duty. Contain pressure, transfer heat in and out, and provide the ports for side feeding, venting and liquid injection.

Key parameters. Specify a modular, segmented barrel design in 4D blocks so the configuration can be rearranged when the recipe portfolio changes. Bimetallic liners with a surface hardness of HRC 58 to 62 are the standard for filled formulations, and they are not optional when calcium carbonate, talc or glass is in the recipe. Specify closed barrel blocks, side-feed blocks, atmospheric vent blocks and vacuum vent blocks as separate items so the layout is explicit in the order.

Selection note. Ask for the barrel block layout drawing before the order is confirmed and check three things: that a side-feed port exists at the right L/D position for the filler loading planned, that a vent port sits immediately after the side feeder to release entrained air, and that the second vacuum port sits far enough downstream for the melt to have homogenized before final devolatilization.

Common mistake. Accepting a nitrided barrel to reduce initial cost on a mineral-filled biodegradable compound. Wear rates on filled compounds can be several times higher, and once the bore has worn, output falls, melt temperature rises and dispersion quality drops. Replacing worn barrel sections on a running line costs far more in downtime than the bimetallic upgrade would have cost at order stage.

Screw elements and configuration

Duty. Convert motor torque into the specific sequence of conveying, melting, dispersive mixing, distributive mixing, devolatilization and pressure build that the recipe requires.

Key element types.

• Conveying elements: forward-flighted, various pitches. Long pitch at the feed throat for intake capacity, shorter pitch where pressure must be built.
• Kneading blocks: offset angles of 30, 45, 60 and 90 degrees. Narrow 30-degree forward blocks give gentle distributive mixing; 90-degree blocks give strong dispersive action with high energy input; reverse-offset blocks build a melt seal.
• Reverse elements: create a pressure-consuming seal that fully fills the channel, needed before a vacuum port and after liquid injection. Keep them short on PLA, because they concentrate residence time and shear at one point.
• Toothed mixing elements: gear-type or slotted mixing elements that give distributive mixing at low energy input. These are the workhorse for PLA-PBAT blends where the goal is uniform distribution without shear heat.

Configuration principle for biodegradable compounds. Use a low-shear architecture: gentle melting with 30-degree and 45-degree kneading blocks rather than a wall of 90-degree blocks, toothed mixing elements for distribution, short reverse elements only where a seal is genuinely required, and a metering section long enough to stabilize the flow into the die without excessive pressure. The design target is a melt temperature at the die within about 15 degrees Celsius of the barrel setpoint. If the melt runs much hotter than the barrels, the screw configuration is putting in more mechanical energy than the recipe needs.

Selection note. Kerke uses computer-aided screw assembly design with kneading co-type geometry that gives strong self-cleaning behavior and good element interchangeability, so a screw set can be reconfigured between recipes rather than replaced. The functional set the screw must deliver is standard across the industry: material transport, plasticization, shearing, dispersion, homogenization, exhaust and pressure building. What varies is the intensity balance between them, and that is where biodegradable configurations diverge from masterbatch or engineering plastic configurations.

Common mistake. Buying a general-purpose screw configuration and expecting it to run PLA. A masterbatch configuration built around high dispersive intensity will overheat PLA within the first hour. Insist that the screw configuration be quoted against the actual recipe list.

Heating and cooling

Duty. Hold each barrel zone at setpoint against the heat generated by the screws and the heat lost to the environment.

Key parameters. Cast aluminum heater bands with embedded elements, zone-by-zone cooling by fan or by water channel, and control precision of plus or minus 1 degree Celsius. On biodegradable lines, cooling capacity matters more than heating capacity. The heaters are only needed at start-up and at low throughput; in steady production the challenge is removing shear heat fast enough. Specify water cooling on the melting and mixing zones for lines above roughly 300 kg/h, and air cooling only on the low-load zones.

Common mistake. Accepting a control loop that overshoots. A zone that cycles plus or minus 5 degrees Celsius around setpoint will spend part of every cycle above the degradation threshold of PLA. Ask for the actual control accuracy under load, not the display resolution.

Gearbox and drive

Duty. Split motor torque into two parallel shafts at very close center distance while carrying the full axial thrust from the screws.

Key parameters. A distributive high-torque gearbox with a rated input power matched to the motor, hardened and ground gears, forced lubrication with an oil cooler and oil filtration, and a documented service life rating referenced to AGMA or ISO 6336 methods. Thrust bearing arrangement is the critical detail, because axial load in a co-rotating twin-screw machine is high and concentrated in a very small space.

Selection note. Ask for the gearbox torque rating and the service factor, and confirm that the oil cooler is fed from the chilled water circuit rather than from the pellet water loop, which runs warm and carries fines.

Common mistake. Ignoring the oil temperature alarm setpoint during commissioning. Gearbox oil running consistently hot is the earliest available warning that the thrust bearings are being overloaded, usually because the die or screen pack is generating more backpressure than the configuration was designed for.

7. Kerke KTE series: real machine configurations

Once the geometry requirements above are settled, the practical question becomes which machine size matches the intended output. Kerke builds the KTE series of parallel co-rotating twin-screw extruders from KTE-16B laboratory units through to KTE-135D production machines, with output from 30 kg/h upward, and each machine can be optimized on aspect ratio, barrel structure, screw arrangement, exhaust arrangement, feeding configuration and electrical control. That last point matters for biodegradable work: the same frame size can be delivered as a masterbatch machine or as a biodegradable compounding machine, and the difference is in exactly the parameters discussed in the previous section.

Table 4. Kerke KTE series twin-screw extruder configuration guide for biodegradable compounds

Model	Screw diameter	Typical L/D	Screw speed	Indicative output on PLA and PBAT blends	Typical role
KTE-16B	16 mm class	40 to 48:1	Up to 600 rpm	Laboratory scale, gram to low kilogram per hour	Formula trials, chain extender screening, DSC sample preparation
KTE-35D	35 mm class	40 to 48:1	300 to 600 rpm	Pilot to small production, tens of kg/h	Pilot line, sample production for customer qualification, specialty grades
KTE-50D	50 mm class	40 to 48:1	300 to 600 rpm	Entry production band	Small commercial line, strand pelletizing route
KTE-65D	65 mm class	44 to 48:1	300 to 600 rpm	Mid production band	Mainstream compounding, strand or water-ring route
KTE-75D	75 mm class	44 to 48:1	300 to 600 rpm	Upper mid production band	Filled starch blends with side feeding, water-ring route
KTE-95D	95 mm class	44 to 48:1	300 to 600 rpm	High production band	Continuous single-grade production, underwater pelletizing route
KTE-110D	110 mm class	44 to 48:1	300 to 600 rpm	Very high production band	Large-volume film-grade compound supply
KTE-135D	135 mm class	44 to 48:1	300 to 600 rpm	Maximum production band	Dedicated single-recipe plants, underwater pelletizing with melt pump

Output figures for any twin-screw extruder depend on the recipe, the filler loading, the melt viscosity, the screw configuration and the pelletizing route, so the bands above are indicative for planning rather than a guarantee. Kerke confirms achievable output against a specific recipe during the pre-order technical review and demonstrates it during the pre-shipment test run, which is the correct way to handle a capacity commitment.

Configuration options that change the machine, not just the label

Table 5. Kerke KTE configuration options relevant to biodegradable compounding

Option	What it changes	When to specify it for biodegradable compounds
Aspect ratio optimization	Adjusts L/D between 40:1 and 48:1 by adding or removing barrel blocks	Specify 44:1 or more when the recipe needs side feeding plus two-stage devolatilization
Barrel structure	Selection and sequence of closed, side-feed, atmospheric vent and vacuum vent blocks; bimetallic lining	Always specify bimetallic liners at HRC 58 to 62 for mineral-filled and starch-filled recipes
Screw arrangement	Element sequence, kneading block angles, reverse element placement, mixing element type	Low-shear configuration with toothed mixing elements for PLA-rich and PHA recipes
Exhaust arrangement	Number and position of vent ports, atmospheric versus vacuum, condensate handling	Two-stage vacuum for PLA, starch blends and any recipe with volatile plasticizer
Feeding configuration	Main feeder, side feeders, crammer feeder, loss-in-weight bank, liquid feeder	Twin-screw side feeder for filler above roughly 20 percent loading; vibratory feeder for natural fiber
Electrical control	PLC and HMI architecture, recipe storage, data logging, remote access	Recipe management and batch data logging are effectively required for certified compostable product traceability
Double-stage system	KTE-SE mother-baby arrangement, twin-screw first stage feeding a single-screw second stage	Consider for heat-sensitive or highly volatile formulations where the second stage decouples devolatilization from pressure build
Triple-screw configuration	Three-screw geometry for special materials and enhanced distributive mixing	Consider for difficult dispersion tasks where conventional twin-screw shear would overheat the polymer

8. Stage 3: melt conveying, filtration and devolatilization

Between the last screw element and the die face there is a short section of equipment that determines pellet consistency, gel content and how much of the day is spent changing screens. On biodegradable lines it also determines how much thermal history the polymer accumulates after mixing is complete, which is dead time with no process benefit.

Gear melt pump

Duty. Take melt at low and fluctuating pressure from the extruder and deliver it to the die at high and constant pressure, so that the extruder screws work on mixing rather than on pressure generation.

Key parameters. Displacement matched to the throughput band, heated body with independent temperature control, inlet and outlet pressure transducers with closed-loop speed control, and a suction pressure controller that holds the extruder discharge at a low constant value. The performance targets are die pressure fluctuation within about plus or minus 2 percent and a throughput increase of 8 to 15 percent compared with the same extruder running without a pump.

Selection notes. A melt pump is optional on a strand line below about 500 kg/h, where a stable water bath and a good die will produce acceptable strands without it. It becomes effectively mandatory for underwater pelletizing, where die-face pressure stability directly controls pellet size distribution, and for any line where the compound will later feed a sheet or film die. For PLA, specify a pump with minimal internal dead volume and streamlined flow channels, because material trapped in a stagnant pocket will degrade and eventually release as black specks.

Common mistake. Installing a melt pump without a suction pressure control loop. Running the pump in fixed-speed mode against a varying extruder output either starves the pump or over-pressurizes the extruder discharge, and both are worse than having no pump at all.

Screen changer

Duty. Remove gels, char, unmelted filler agglomerates and foreign contamination from the melt before it reaches the die.

Table 6. Screen changer types for biodegradable compounding

Type	Operating principle	Investment level	Best fit on a biodegradable line	Limitation
Single-plate manual	Slide plate with one screen position, line stops to change	Low	Laboratory and pilot lines; clean pellet-only recipes	Production stop at every screen change; not viable for filled recipes
Dual-plate hydraulic	Two screen positions, one active while the other is serviced	Medium	Mainstream choice for most commercial biodegradable lines	Brief pressure disturbance during changeover; some melt loss
Hydraulic quick-change piston	Piston shifts a fresh screen into flow in a fraction of a second	Medium to High	Lines running recycled or contaminated feedstock alongside virgin polyester	Higher maintenance content; seal wear on filled compounds
Continuous belt filter	Screen band advances automatically as pressure rises	High	High-contamination feedstock and continuous non-stop operation	Highest investment; more consumables; longer melt residence path

Key parameters. Screen pack combinations of 40 to 120 mesh are typical, usually as a coarse-medium-fine sandwich supported by a breaker plate. Filtration area must be sized so that pressure rise between changes is gradual; an undersized filter on a filled compound will need changing several times per shift. For PLA specify the shortest melt path and the smallest dead volume available in the chosen type, because residence time at the filter is residence time at temperature with no mixing benefit.

Common mistake. Specifying an overly fine screen pack on a mineral-filled biodegradable compound. Fine mesh will capture filler agglomerates that are a normal part of the compound, blind rapidly, and drive both pressure and melt temperature up. Filter to remove contamination, not to compensate for poor dispersion.

Instrumentation and safety devices

Duty. Make the melt state visible, protect the equipment and protect the operator.

Key parameters. Melt pressure transducers before the filter, after the filter and at the die, so filter differential pressure is a directly measured value rather than an inference. A melt thermocouple with an immersion probe at the die adapter, because a surface-mounted sensor reads the metal, not the polymer. A rupture disc set below the design pressure of the weakest component in the melt path, with an interlock that stops the drive. Torque, motor current, screw speed, melt pressure and all zone temperatures logged continuously and tied to the batch record.

Common mistake. Treating the rupture disc as a formality and setting it near the maximum pressure of the strongest component. The disc exists to protect the weakest link, and on a compounding line that is usually the screen changer seal or the die adapter bolts.

Vacuum devolatilization system

Duty. Pull moisture, residual monomer, degradation volatiles and entrained air out of the melt so the pellets are void-free and the compound is odor-free.

Key parameters. A water-ring vacuum pump is the standard choice for compounding because it tolerates the polymer vapor and fines that would foul a dry pump. Working vacuum of minus 0.08 to minus 0.095 MPa. A cyclone and condensate separator between the vent port and the pump. A vent stuffer or vent screw on the port itself if the compound has a tendency to rise into the vent, which starch-filled and fiber-filled compounds commonly do.

Selection note. Specify two-stage venting for PLA and starch-based lines: an atmospheric vent early, immediately after the side feeder, to release the large volume of air that comes in with the powder, and a vacuum vent late, after homogenization, for the fine devolatilization. A single vacuum port doing both jobs will be overwhelmed by the air load and will pull unmelted powder into the vacuum line.

Common mistake. Undersizing the condensate handling. Starch and plasticized recipes release a surprising water and organic load, the separator fills, and the pump loses vacuum. Specify a separator with a level control and automatic drain rather than a manual vessel someone remembers to empty.

9. Stage 4: pelletizing routes compared item by item

Pelletizing is the second largest equipment decision on a biodegradable line and the one most often made on price rather than on material behavior. Three routes are in common use, and for biodegradable compounds the choice is driven by output band, melt viscosity, filler loading and how much the customer cares about pellet shape.

Route 1: strand pelletizing

Equipment set. Strand die, water cooling bath with adjustable length, strand guide rollers, air knife or blower dewatering section, and a strand pelletizer with a rotating knife rotor against a fixed bed knife.

Key parameters. Strand count matched to die and output; bath length 1.5 to 4 meters depending on throughput and melt temperature; water temperature typically 25 to 45 degrees Celsius; blower dewatering with two or three air knives for hygroscopic compounds; pelletizer cutting length adjustable between roughly 2 and 5 mm.

Where it fits. Investment level Low. Best below about 500 kg/h. Excellent for laboratory, pilot and small commercial lines and for frequent recipe changes, because cleaning a strand bath is fast and cheap.

Biodegradable-specific note. PLA and PBAT strands absorb water in the bath and PLA strands are brittle when cold and tacky when warm. Specify reinforced air-knife dewatering with at least two stages, and keep the bath as short as the cooling duty allows. Where the compound is very tacky, an air-cooled strand route with a long conveyor and blower cooling avoids water contact altogether at the cost of floor space.

Common mistake. Running the bath cold to shorten it. Chilled bath water makes PLA strands brittle, they shatter at the pelletizer intake, and fines content rises. Warmer water and a longer bath give better results than colder water and a short one.

Route 2: water-ring die-face pelletizing

Equipment set. Die plate with an annular hole pattern, rotating blade holder cutting directly at the die face, water-ring housing that catches the pellets in a swirling water film, transport pipe, centrifugal dryer and classifier.

Key parameters. Output band roughly 300 to 1500 kg/h; blade set with spring or pneumatic pressure adjustment; die-face temperature control; water flow rate matched to output so pellets are quenched but not chilled into an unpumpable slurry.

Where it fits. Investment level Medium. The mainstream choice for mid-capacity biodegradable lines. Pellets are rounder and more uniform than strand pellets, which improves downstream feeding behavior in the customer’s converting machines and reduces dust.

Biodegradable-specific note. The short water contact time is a genuine advantage for hygroscopic polyesters compared with a strand bath. The compromise is that the die plate must stay hot while the water stays cool a few millimeters away, so die-face heating and thermal isolation quality is what separates a water-ring system that runs and one that freezes off every hour.

Common mistake. Under-specifying die-face heating on a low melting point compound such as PBAT-rich blends. Freeze-off at the outer holes narrows the effective die area, pressure rises, and pellet size becomes irregular across the pattern.

Route 3: underwater pelletizing

Equipment set. Heated die plate submerged in a water chamber, rotating blade assembly with automatic blade pressure compensation, process water circuit with pump, temperature control and filtration, centrifugal dryer, classifier, and a start-up diverter valve.

Key parameters. Output above about 800 kg/h; process water temperature controlled by material, typically well below the melting point but warm enough to avoid thermal shock; blade pressure compensation to maintain constant contact as the blades wear; die-plate heating by electric cartridge or heat transfer fluid; pellet water loop with fines filtration.

Where it fits. Investment level High. The route of choice above 800 kg/h, for low-viscosity melts that will not form stable strands, and for highly filled compounds where strand breakage would otherwise dominate the day. It gives the best pellet geometry of the three routes, which matters when the compound is sold into film extrusion or injection molding where feeding consistency is critical.

Biodegradable-specific note. Water temperature control is more critical than on polyolefins. Too cold and PLA pellets craze and produce fines; too warm and PBAT-rich compounds agglomerate in the transport line. Specify a process water temperature control loop with real control authority, not just a heat exchanger and a hope.

Common mistake. Pairing an underwater system with an extruder that has no melt pump. Underwater pelletizing wants constant die pressure, and an extruder alone cannot deliver that at the required stability. The pump is part of the underwater package in practice even when it appears as a separate line item in the quotation.

Table 7. Three pelletizing routes compared for biodegradable compounds

Criterion	Strand pelletizing	Water-ring die-face	Underwater pelletizing
Investment level	Low	Medium	High
Practical output band	Below 500 kg/h	300 to 1500 kg/h	Above 800 kg/h
Pellet shape	Cylindrical, cut-end variation	Rounded, good uniformity	Spherical to lens, best uniformity
Fines generation	Higher, especially on brittle PLA	Moderate	Lowest
Water contact time	Longest	Short	Short but fully immersed at cut
Suitability for low melt viscosity	Poor, strands break	Good	Excellent
Suitability for high filler loading	Poor to fair	Good	Excellent
Recipe changeover speed	Fastest	Medium	Slowest
Operator skill required	Low	Medium	High
Utility demand	Low	Medium	High, water loop plus die heating
Floor space	Long and narrow	Compact	Compact but tall with the water skid
Melt pump required	Optional	Recommended	Effectively mandatory

Kerke cutting and pelletizing systems

Kerke builds the pelletizing section as part of its own scope rather than treating it as a bought-in accessory, which keeps the die, the melt pump interface and the cutter under one engineering responsibility. The available routes cover the full range described above.

Table 8. Kerke cutting system range and matching application on biodegradable lines

Kerke cutting system	Principle	Typical biodegradable application	Investment level
Water-cooled strand pelletizing	Strands quenched in a water bath, dewatered, then cut	PLA and PBAT compounds below 500 kg/h; pilot and specialty grades	Low
Air-cooled strand pelletizing	Strands cooled on a conveyor by forced air, then cut	Tacky or highly hygroscopic compounds where water contact must be avoided	Low
Air-cooled die-face hot cutting	Cut at the die face, pellets cooled and conveyed by air	Low-output specialty compounds and additive concentrates	Low to Medium
Water-ring die-face hot cutting	Cut at the die face into a water ring, then dewatered	Mainstream mid-capacity PLA, PBAT and starch blend production	Medium
Eccentric water-mist hot cutting	Cut at the die face with controlled mist cooling	Compounds needing gentler quenching than a full water ring	Medium
Underwater granulation system	Cut under water at a heated submerged die plate	High-capacity lines, low-viscosity melts, highly filled starch compounds	High

Pellet handling equipment after the cutter

Three machines belong to the pelletizing stage even though they sit after the cut, and all three are frequently left out of first-draft equipment lists.

• Centrifugal dewatering unit. Separates pellets from process water by rotor action against a screen. Target residual surface moisture below 0.3 percent. Screen aperture and rotor speed must be matched to pellet size, otherwise fines pass into the water loop and eventually block the die.
• Vibrating classifier screen. A two-deck screen removes oversize doubles and long tails on the upper deck and fines and dust on the lower deck. On biodegradable compounds this is not cosmetic: oversize pellets bridge in the customer’s dryer and fines burn in the customer’s extruder feed zone.
• Pellet after-dryer. A fluidized bed or hot-air unit that drives off residual surface and near-surface moisture. Keep the temperature in the 40 to 55 degrees Celsius range for PLA-rich compounds, because higher temperatures make the pellets tacky and produce agglomerates in the bag.

10. Stage 5: downstream handling, homogenizing and packing

Everything after the classifier exists to protect the quality that the extruder just created and to get it into a bag with a batch number on it. This section of the line is where quality is lost quietly, through moisture pickup, segregation and cross-contamination, rather than dramatically.

Pneumatic pellet conveying

Duty. Move pellets from the pelletizing area to silos and to the packing station.

Key parameters. Dilute-phase conveying with velocity controlled to limit angel hair generation; long-radius or wear-back elbows; grounded conveying pipe to control static; dry-air conveying for hygroscopic grades where the pellets will sit in a silo for hours before packing.

Common mistake. Running conveying velocity too high because it is easier than tuning it. PLA and PBAT pellets smear against elbows at high velocity and generate angel hair, which then contaminates the batch and blocks screens in the customer’s plant.

Homogenizing and blending silo

Duty. Average out short-term variation so that a 20-tonne shipment has one melt flow rate value rather than a distribution.

Key parameters. Live volume equal to 4 to 8 hours of production; gravity blending internals with multiple draw tubes or a mechanical stirrer; mass-flow discharge geometry; level measurement and a discharge control valve.

Selection note. This is technically an optional item, and it is the optional item that most improves customer-perceived quality. A compound that varies by 15 percent in melt flow rate between the start and the end of a production run will be rejected by a demanding film converter even if every individual sample is inside the specification band.

Automatic sampling

Duty. Take a representative sample at a programmed interval for melt flow rate, moisture and color checks, without an operator putting a scoop into the pellet stream.

Key parameters. In-line diverter sampler with programmable interval and sample volume; automatic labeling by batch code; sample retention rack for the retention period required by the customer or certification body.

Weighing, bagging and metal detection

Duty. Fill, weigh, seal and identify the finished product.

Key parameters. Net weighing accuracy of plus or minus 0.1 percent; 25 kg valve or open-mouth bags for the standard commercial pack; 500 to 1000 kg bulk bags for large-volume supply; heat sealing or stitching matched to bag type; dust extraction hood at the fill spout; inline metal detector with automatic reject and a documented test-piece verification at shift start; date, batch and grade printing on every bag.

Common mistake. Sizing the bagging station on average output. Bagging is a batch operation with a cycle time, and if the station cannot keep pace with peak line output the pellets back up into the silo, or worse, an operator opens a bypass and packs by hand without batch traceability.

Palletizing and wrapping

Duty. Stack and stabilize finished bags for storage and shipment.

Key parameters. Robotic or gantry palletizer with programmable pallet patterns; throughput matched to the bagging rate; stretch wrapper with adjustable film tension. This is a labor-cost decision more than a quality decision, and it is a reasonable phase-two purchase on a first line.

11. Stage 6: utilities, plant services and safety

Utilities are the equipment category most frequently discovered late, usually during installation when the electrical supply turns out to be insufficient or the cooling tower cannot hold water temperature in summer. Every item below should be quantified during the layout phase, not after the machines arrive.

Table 9. Utility requirements for a biodegradable compounding line

Utility	Served equipment	Specification	Sizing guidance
Tower cooling water loop	Pellet water, water-ring or underwater circuit, vacuum pump seal water	Open loop, 28 to 34 degrees Celsius typical supply, with side-stream filtration	Heat load dominated by the melt enthalpy removed at the cutter; size on line output and melt temperature drop
Chilled water loop	Barrel zone cooling, gearbox oil cooler, feed throat jacket	Closed loop, 8 to 15 degrees Celsius, treated water with corrosion inhibitor	Flow in cubic meters per hour estimated against installed main motor power and the fraction of shear energy that must be removed
Feed throat cooling	Extruder feed section	Separate branch of the chilled loop with its own valve	Small flow but non-negotiable; a warm feed throat causes bridging on low melting point resins
Compressed air	Valves, blade actuators, pneumatic conveying, air knives, bagging	0.7 MPa working pressure, dried and filtered to instrument quality	Receiver sized for peak simultaneous demand including air-knife dewatering, which is the largest single consumer
Dust extraction	Bag-dump station, feeder hoppers, classifier, bagging spout	Cartridge filtration with reverse-jet cleaning; capture velocity set at each hood	Design against the dustiest material in the recipe portfolio, usually talc or native starch
Workshop ventilation	Extrusion hall	General ventilation plus local extraction over the die and vent area	Sized for heat rejection from motors and heaters as well as for air quality
Electrical distribution	Whole line	Main distribution panel with per-machine protection; voltage and frequency confirmed for the destination country	Installed load is typically two to three times the extruder main motor rating once dryers, chiller, vacuum, downstream and packing are included
Dust explosion protection	Powder handling zones	ATEX-rated components, grounding and bonding, explosion venting or suppression as assessed	Required wherever combustible starch, cellulose or fine organic powder is handled in quantity
Fire detection and suppression	Extrusion hall and storage	Detection tied to the plant system; extinguishing media appropriate to polymer and dust	Coordinate with local authority requirements at the layout stage
Effluent and water treatment	Pellet water loop blowdown	Fines separation before discharge; closed loop preferred	Starch-containing process water carries organic load and must not go straight to drain

Layout and floor space

A complete biodegradable compounding line is longer than most first-time buyers expect, because the drying section, the extruder, the pelletizing section and the packing section are effectively four machines in series with maintenance access around each. Two dimensions matter beyond the footprint itself: the screw pull-out length in front of the extruder, which must equal at least the full screw length plus handling clearance, and the vertical height above the drying hoppers and silos for loader access. Wanplas provides factory layout planning, utility design and workshop planning support as part of turnkey scope, which is worth using before the building is finalized rather than after.

Noise, ergonomics and operator safety

Granulators, blowers, vacuum pumps and air knives are the noise sources. Enclosures on the granulator and silencers on the blower discharge handle most of it. Guarding on the pelletizer knife rotor, interlocks on the screw pull-out cart, thermal shielding on the die area and a clearly marked purge collection position with a heat-resistant container are the safety items most often missing on lines assembled from mixed sources. On a line supplied as a package these are engineered in and covered by the CE declaration.

12. Laboratory and quality control equipment list

A biodegradable compound is sold on certified properties, which means the laboratory is production equipment and not overhead. Without in-house measurement, a plant cannot release batches, cannot investigate a customer complaint and cannot hold a compostability certification with any confidence.

Table 10. Quality control equipment for a biodegradable compounding plant

Instrument	What it measures	Why it matters on a biodegradable line	Priority
Melt flow rate tester	Melt mass-flow rate and melt volume-flow rate	The single fastest indicator of hydrolytic or thermal degradation; a rising melt flow rate through a run means moisture or heat is cutting the chains	Essential, first purchase
Karl Fischer moisture titrator	Water content in parts per million	Verifies the dryer is actually delivering below 250 ppm on PLA rather than merely running	Essential, first purchase
Differential scanning calorimeter	Glass transition, crystallization and melting behavior	Confirms blend composition, crystallinity development and whether a nucleating package is working	Essential for formulation work
Tensile testing machine	Tensile strength, modulus, elongation at break	Core mechanical specification for film, bag and rigid article grades	Essential
Impact testing machine	Izod or Charpy notched impact strength	Verifies the toughening effect of PBAT content and impact modifier in rigid grades	Essential
Color spectrophotometer	Color coordinates and color difference	Batch-to-batch color consistency, which customers check before they check anything else	Essential for colored grades
Laboratory oven and desiccators	Sample conditioning before testing	Test results on unconditioned hygroscopic samples are not comparable between batches	Essential
Analytical balance	Sample mass to four decimal places	Underpins moisture, ash and density determinations	Essential
Ash content furnace	Inorganic filler content	Verifies that the filler feeder is delivering the recipe percentage, independently of the feeder display	High for filled grades
Laboratory twin-screw extruder	Small-batch compounding for formula development	Allows recipe development without occupying the production line; a KTE-16B class unit fills this role	High for own-formula producers
Laboratory press and film blowing unit	Sample plaque and film preparation	Converts pellets into testable specimens that represent the customer’s process	Medium
Capillary rheometer	Viscosity versus shear rate	Predicts behavior in the customer’s converting process better than melt flow rate alone	Optional, advanced laboratory
Gel permeation chromatograph	Molecular weight distribution	The definitive measurement of hydrolytic degradation; usually outsourced at first and brought in-house later	Optional

A practical staging plan is to buy the melt flow rate tester, Karl Fischer titrator, balance, oven and tensile tester with the line, add DSC and the spectrophotometer within the first year, and outsource molecular weight analysis until volumes justify the instrument. What should not be staged is moisture measurement, because on a polyester line it is the measurement that explains most other results.

13. Investment allocation by equipment group, without prices

Budgeting a compounding line is easier when it is expressed as a share of the whole rather than as absolute figures, because the ratios stay reasonably stable across capacities while absolute values do not. The table below uses a line investment index in which a baseline 300 kg/h biodegradable compounding line with strand pelletizing equals 100 points. The index is a planning tool for allocating budget between equipment groups; it is not a quotation and carries no currency.

Table 11. Investment allocation index, baseline 300 kg/h configuration equals 100 points

Equipment group	Share of line investment index	Relative level	Notes on where the range moves
Main twin-screw extruder with drive and control	35 to 45 percent	High	Higher share when specific torque, bimetallic barrels and 48:1 L/D are specified
Feeding system, loss-in-weight bank and side feeders	10 to 16 percent	Medium	Rises steeply with the number of metering points and with micro-dosing accuracy requirements
Central drying and conveying system	8 to 14 percent	Medium	Rises with hopper residence time, number of separate resins and closed-loop dry conveying
Pelletizing system with dewatering and classifying	10 to 22 percent	Low to High	Low for strand, medium for water-ring, high for underwater with process water skid
Melt pump, screen changer and instrumentation	5 to 10 percent	Medium	Upper end when a continuous belt filter and a full melt pump package are included
Downstream conveying, silos, packing and palletizing	8 to 15 percent	Medium	Upper end when homogenizing silos and robotic palletizing are in scope
Utilities: chiller, tower, compressed air, dust extraction	6 to 12 percent	Medium	Rises with underwater pelletizing and with ATEX requirements in dust zones
Laboratory and quality control package	3 to 7 percent	Low to Medium	Upper end when DSC and rheology are included from day one
Installation, commissioning, training and spares	4 to 8 percent	Low to Medium	Depends on destination, local labor availability and training scope

Where cost-cutting is safe and where it is not

Reasonable savings. Defer the palletizer and stretch wrapper. Defer the automatic sampler. Start with a dual-plate hydraulic screen changer instead of a continuous belt filter. Buy the homogenizing silo in phase two if the initial customer base is tolerant. Outsource molecular weight testing. Use 25 kg bagging manually assisted at first if volume is low.

False savings. A hot-air dryer instead of a dehumidifying dryer. Volumetric feeders instead of loss-in-weight feeders. Nitrided barrels on a mineral-filled recipe. An extruder with lower specific torque than the recipe portfolio requires. Skipping the second vacuum vent. Undersizing the chiller so barrel zones cannot hold setpoint in summer. Each of these reduces the initial index by a few points and then costs a multiple of that in scrap, downtime and lost customers.

14. Capacity to line configuration recommendation

The table below converts a target output into a concrete configuration, including the recommended Kerke extruder frame size, the pelletizing route and the supporting equipment set. Use it as a starting point for a technical discussion, not as a final specification, because filler loading and recipe viscosity shift the boundaries.

Table 12. Requirement to configuration recommendation for biodegradable compounding lines

Target output	Typical product	Recommended Kerke extruder	Pelletizing route	Feeders	Melt pump	Key auxiliary notes
Laboratory, formula development	Trial batches for PLA, PBAT, PHA and starch screening	KTE-16B	Water-cooled strand, bench scale	1 main plus 1 auxiliary	Not required	Small dehumidifying dryer; laboratory QC package is the real investment here
50 to 150 kg/h	Specialty compounds, small-lot compostable grades	KTE-35D	Water-cooled strand	1 main plus 2 auxiliary	Optional	Single dryer hopper set; manual bagging acceptable
150 to 350 kg/h	Compostable bag compound, entry commercial supply	KTE-50D	Water-cooled strand or air-cooled strand	1 main plus 2 to 3 auxiliary	Optional	Central drying with two hoppers; classifier and after-dryer mandatory for PLA-rich grades
350 to 700 kg/h	Film-grade PLA-PBAT blends, filled rigid grades	KTE-65D	Water-ring die-face hot cutting	1 main plus 3 auxiliary, twin-screw side feeder	Recommended	Two-stage venting; chilled water on melting zones; homogenizing silo advised
700 to 1100 kg/h	Starch-filled compounds, high-volume film compound	KTE-75D	Water-ring or underwater	1 main plus 3 to 4 auxiliary, twin-screw side feeder	Recommended to mandatory	Dust extraction with ATEX assessment; bulk bag packing station
1100 to 1800 kg/h	Continuous single-grade commercial supply	KTE-95D	Underwater granulation	1 main plus 4 auxiliary plus liquid pump	Mandatory	Process water skid with temperature control; bulk silo storage; automatic bagging
1800 to 2800 kg/h	Large-volume compostable resin production	KTE-110D	Underwater granulation	1 main plus 4 to 6 auxiliary	Mandatory	Bulk delivery and silo infrastructure; continuous screen changer worth evaluating
Above 2800 kg/h	Dedicated single-recipe plant	KTE-135D	Underwater granulation	Recipe-specific bank	Mandatory	Full plant utility design; redundancy planning on chiller and vacuum
Heat-sensitive or highly volatile recipe at any output	PHA-rich or high-plasticizer compounds	KTE-SE double-stage system	Route by output band	Recipe-specific bank	Depends on second-stage design	Second stage decouples devolatilization from pressure build and lowers thermal load

Application industries this line serves

Biodegradable compounding is one of Kerke’s core application industries within the plastic compound category, alongside engineering plastics, cable compounding, PVC compounding, thermoplastic elastomers and wood-plastic composites, and alongside the masterbatch category covering color, filler, additive, black and textile masterbatch. On the biodegradable side, the compounds produced on these lines end up as compostable shopping and waste bags, agricultural mulch film, food service items such as cutlery and straws, coffee capsules, disposable tableware, thermoformed food trays, fruit and vegetable packaging nets, and injection molded caps and closures for compostable packaging. The same equipment platform also handles recycled PET flake compounding, pet food and textured protein processing, which matters for plants that want a second revenue stream from the same asset.

15. Certifications, standards and documentation

An equipment list is incomplete without the paperwork that lets the equipment be installed and the product be sold. Two separate certification tracks apply, and they are frequently confused: one covers the machinery and one covers the compound.

Machinery track

• CE marking under the Machinery Directive. Required for installation in the European Economic Area. Covers guarding, interlocks, emergency stop architecture, electrical safety and the technical file. Confirm which entity issues the declaration of conformity for a multi-machine line, because a line assembled from separately certified machines still needs a conformity assessment as an assembly.
• ISO 9001. A manufacturing quality management framework at the equipment supplier. It does not guarantee performance but it does mean that inspection records, material certificates and traceability for critical parts such as screws, barrels and gearboxes exist and can be produced.
• ATEX and dust explosion assessment. Applies where combustible dust is handled, which includes native starch, cellulose fiber and wood flour. The assessment defines zones, and equipment inside those zones needs appropriate ratings, grounding and bonding.
• Electrical standards for the destination. Voltage, frequency, panel construction standard and language of labeling must be specified at order stage, not discovered at installation.

Product track

• EN 13432. The European standard for packaging recoverable through composting and biodegradation. It sets requirements on disintegration, biodegradation, heavy metals and ecotoxicity, and it is the basis for most compostability marks in Europe.
• ASTM D6400. The corresponding North American specification for plastics designed to be composted in municipal and industrial facilities.
• EU 10/2011. Applies to plastic materials and articles intended to come into contact with food, and governs which substances may be present and at what migration limits.
• GB 4806 series. The Chinese national standards for food contact materials and articles, relevant for compounds sold into or manufactured in that market.
• ISO 17088. An international specification for compostable plastics, often referenced alongside the regional standards above.

The equipment consequence of the product track is traceability. A compostability certification requires that a finished lot can be traced back to specific raw material lots, specific process conditions and specific quality results. That means the control system must log recipe, feeder setpoints and actual rates, barrel temperatures, melt temperature and pressure, and it must tie those records to a batch number that follows the product to the bag label. Specify data logging and recipe management in the electrical control scope rather than assuming it comes as standard.

16. Twelve equipment items buyers forget

The following items appear in almost every commissioning punch list and almost no first-draft equipment list. Each is inexpensive relative to the line and expensive to add later.

1. Screw pull-out cart and lifting device. Screws must come out for cleaning and reconfiguration. Without a cart and a rail, a screw change becomes an all-day job with a forklift and a risk of damaged elements.
2. Spare screw element set. Kneading blocks and reverse elements wear first. A spare set of the high-wear elements keeps a changeover to hours instead of weeks.
3. Spare barrel liner sections. On filled recipes the melting and mixing sections wear ahead of the rest. Having the two highest-wear sections on the shelf turns a production crisis into a planned maintenance stop.
4. Purge collection container and purge material stock. Start-up and shutdown on PLA needs a purge sequence and somewhere hot polymer can go safely.
5. Die plate cleaning oven or fluidized bath. Underwater and water-ring die plates need periodic deep cleaning. Manual cleaning with drills damages the holes.
6. Rework granulator with sound enclosure. Start-up lumps and strand scrap have to become feedable material, and a production granulator in the extrusion hall without an enclosure is a noise problem.
7. Portable moisture analyzer at the feed throat. A quick check at the point of use catches a failing dryer before a shift of product is compromised.
8. Second set of feeder hoppers and screws. Changing between a powder recipe and a pellet recipe is far faster with a second hopper and screw set than with cleaning.
9. Vacuum line cleaning provisions. Vent ports and vacuum lines block with condensed volatiles and carried-over powder. Removable spool pieces and a cleaning routine prevent an unplanned stop.
10. Pellet water fines filtration. Without it, fines circulate and eventually block die holes on water-ring and underwater systems.
11. Calibration weights for the loss-in-weight feeders. Feeder accuracy is a claim until it is verified, and verification needs certified weights and a documented interval.
12. Compressed air dryer of adequate capacity. Wet compressed air ruins air-knife dewatering and corrodes pneumatic actuators, and the air dryer is routinely sized for the old plant load rather than the new line.

Five configuration errors that limit output

• Side feeder capacity below filler demand. The line output ceiling ends up set by the side feeder, not by the extruder that was carefully selected.
• Single vent doing two jobs. Air from powder and volatiles from the melt both routed to one vacuum port produces carry-over into the vacuum line and lost vacuum.
• Chiller sized for winter. Barrel zones that hold setpoint in February drift in July, and the melt temperature drifts with them.
• Water bath too short for the melt temperature. Strands enter the pelletizer soft, deform at the cut, and produce oversize and doubles that the classifier then rejects as scrap.
• Downstream conveying velocity untuned. Angel hair in the finished product is generated after all the process control effort is complete.

17. Testing, installation, training and spare parts

An equipment list becomes a working line only through the services wrapped around it, and those services should be written into the order with the same precision as the machine specifications. Kerke, a Wanplas factory with more than twelve years of experience in research, design, manufacturing and service, delivers biodegradable compounding lines as integrated turnkey scope rather than as a crate of separately specified machines.

Combined run testing before shipment

The single most valuable service item is a combined run test at the factory before the line ships. The extruder, feeders, melt pump, screen changer, pelletizer, dewatering unit and classifier are assembled and run together on the customer’s actual recipe or the closest available equivalent. What this test proves cannot be proven any other way: that the feeders hold their accuracy while the extruder vibrates next to them, that the screw configuration produces the target melt temperature at the target output, that the die and cutter combination gives the intended pellet geometry, and that the control system’s interlocks behave correctly under load. Customers are welcome to attend and witness the run, and Wanplas maintains an open factory policy for exactly this purpose.

Installation and commissioning

Kerke engineers travel to site for mechanical and electrical installation supervision, utility connection verification, dry-run checks, first melt, recipe loading and production ramp-up. The commissioning sequence for a biodegradable line has an order that matters: verify the dryer performance with an independent moisture measurement first, calibrate every feeder against certified weights second, establish the barrel temperature profile third, then start the pelletizer, and only then start optimizing output. Plants that reverse this order spend the commissioning week chasing symptoms.

Operator and maintenance training

Training covers three audiences. Operators learn start-up and shutdown sequences, purge procedures for polyester changeovers, recipe loading, routine checks and alarm response. Maintenance technicians learn screw pull-out and reassembly, element sequence documentation, screen changes, blade replacement and pressure compensation, gearbox lubrication schedules and vacuum system cleaning. Process and quality staff learn the relationship between feeder rates, screw configuration, temperature profile and the resulting melt flow rate, moisture and mechanical properties. Training can run at the Kerke factory during the pre-shipment test and again on site during commissioning.

Spare parts and after-sales support

Wanplas applies a group-wide service policy across all its factories, and it applies to biodegradable compounding lines supplied by Kerke: USD 500 in free parts every year, free replacement of parts damaged within the warranty period, a transportation guarantee, a production capacity guarantee, and a quality standards guarantee. For a compounding line the recommended initial spare parts holding is a set of high-wear screw elements, one spare barrel liner section for the melting zone, a full set of screens and breaker plate gaskets, pelletizer blades and bed knife, feeder screw and hopper seals, melt pressure transducers, heater bands for the most-used zone size, and vacuum pump seals.

Remote support and long-term optimization

Control systems can be specified with remote access so that engineers can review trend data, compare a current run against the commissioning baseline and guide an on-site technician through diagnosis without waiting for travel. Over a line’s life, the most common support requests on biodegradable compounding are recipe extensions into new resin grades, output increases through screw reconfiguration, and pelletizing route upgrades as volume grows. All three are easier when the original supplier holds the design records for the barrel layout and screw configuration, which is another argument for keeping the line under one engineering responsibility.

Factory capability behind the equipment

The service commitments above rest on manufacturing capability: a 19,997-plus square meter plant, more than 2,000 machines operating in over 70 countries, a team of more than 100 people, and recognition as a top-five twin-screw extruder supplier in China. Kerke’s declared focus, summarized in the phrase we know compounding extruder, is narrow by design. The factory builds laboratory twin-screw extruders, the KTE series of parallel twin-screw extruders, triple-screw extruders, double-stage extrusion systems, SE series single-screw extruders for recycling duty, complete cutting and pelletizing systems, sheet extrusion lines that compound and sheet in one step, and the auxiliary equipment range covering high-speed mixers, granulators, pulverizers, chillers and extruder core parts. For anything outside the compounding category, Wanplas supplies matched equipment from within the group so a plant can be sourced as one project.

18. Frequently asked questions

What is the minimum equipment set for a biodegradable compounding line?

The irreducible minimum is a dehumidifying dryer capable of a minus 40 degrees Celsius dew point, at least three loss-in-weight feeders, a co-rotating twin-screw extruder with 40:1 to 48:1 L/D and side feeding capability, a vacuum devolatilization system, a screen changer, a pelletizer with dewatering and classification, and a cooling water circuit. Everything else on the master list improves consistency, yield, labor cost or product range. Without those seven items a line cannot make pellets that meet a published specification.

Why does PLA need a dew point of minus 40 degrees Celsius when other resins do not?

PLA is a polyester and hydrolyzes in the melt. Water attacks the ester bond and permanently reduces molecular weight, which shows up as strand breakage, low tensile strength, rising melt flow rate and inconsistent pellets. Ambient-air dryers cannot reliably take PLA below roughly 500 to 800 ppm on a humid day, whereas a minus 40 degrees Celsius dew point reaches below 250 ppm within a four-hour cycle at 60 to 80 degrees Celsius. The dew point requirement is a consequence of the chemistry, not a specification preference.

How many loss-in-weight feeders should I budget for?

Budget one main feeder plus two to four auxiliary feeders, and leave one spare feeding position on the frame. A typical PLA and PBAT film compound uses five metering points: two resins, a filler or starch powder, an additive or chain extender masterbatch, and often a liquid plasticizer. Recipe portfolios reliably grow after start-up, and adding a feeder position to an existing extruder frame is far harder than specifying it at order stage.

Can one extruder handle PLA, PBAT and starch-filled compounds?

Yes, provided it is specified for the hardest case. That means bimetallic barrel liners at HRC 58 to 62 for the filled recipes, specific torque at the upper part of the 8 to 11 N.m per cubic centimeter band, a twin-screw side feeder sized for the highest filler loading, two-stage venting, and a screw configuration that can be rearranged between recipes. A machine specified only for neat polyester blends will run filled compounds poorly and will wear quickly.

Which pelletizing route should I choose for a 600 kg/h line?

At 600 kg/h both water-ring die-face cutting and strand pelletizing are technically feasible, and water-ring is usually the better choice. It gives rounder pellets with less water contact time, which suits hygroscopic polyesters, and it handles a lower melt viscosity than strands will tolerate. Strand pelletizing remains attractive at that output if the plant runs many short recipe changes, because cleaning a strand bath is much faster than cleaning a die-face system.

Do I need a melt gear pump?

It is optional on strand lines below about 500 kg/h and effectively mandatory for underwater pelletizing. A gear melt pump holds die pressure fluctuation within roughly plus or minus 2 percent and typically raises throughput by 8 to 15 percent, because the extruder screws no longer have to build discharge pressure and can work on mixing instead. On PLA it has a second benefit: lower extruder discharge pressure means lower shear heating in the final screw section.

What installed electrical power should I plan for?

Plan for an installed load that is typically two to three times the extruder main motor rating once the central dryer, chiller, vacuum pump, side feeders, pelletizer, dewatering unit, conveying blowers and packing are all counted. The dryer and the chiller are the two largest non-extruder consumers on a biodegradable line. Confirm the destination voltage and frequency at order stage so the panels are built correctly rather than modified at site.

How much cooling water does the line need?

Two circuits are needed. The tower loop serves the pellet water and the vacuum pump and carries the bulk of the heat removed from the melt at the cutter. The chilled loop at 8 to 15 degrees Celsius serves barrel zone cooling, the gearbox oil cooler and the feed throat jacket. Flow in cubic meters per hour is estimated from installed motor power and the share of shear energy that must be removed, and it should be sized against summer ambient conditions rather than annual averages.

Which certifications apply to the machinery and which to the pellets?

For the machinery, CE marking under the Machinery Directive covers safety for the European market, ISO 9001 covers the supplier’s manufacturing quality system, and an ATEX assessment applies where combustible starch or cellulose dust is handled. For the pellets, EN 13432 and ASTM D6400 govern compostability claims, ISO 17088 is often referenced alongside them, and EU 10/2011 and the GB 4806 series apply to food contact end uses. The two tracks are independent and both need planning at project start.

How much floor space and building height should I allow?

Allow for four machine groups in series with maintenance access around each, plus a screw pull-out zone in front of the extruder equal to at least the full screw length plus handling clearance, plus vertical height above the drying hoppers and silos for loader access. The pull-out zone is the dimension most often forgotten, and a line installed too close to a wall permanently converts a two-hour screw change into a full-day exercise.

Can I start with strand pelletizing and upgrade to underwater later?

Yes, and it is a sensible phasing strategy, provided the extruder and the melt train are specified for the future route from day one. That means ordering the extruder with the discharge flange and adapter arrangement that will accept a melt pump, leaving physical space and utility stubs for the process water skid, and sizing the electrical distribution for the additional load. Retrofits fail when the original line was sized exactly to the initial configuration with no allowance for growth.

What quality control equipment should be in place before the first commercial batch?

At minimum a melt flow rate tester, a Karl Fischer moisture titrator, an analytical balance, a conditioning oven and a tensile testing machine. These five instruments let the plant verify the dryer, detect degradation, confirm the mechanical specification and release a batch with documentation. DSC, a color spectrophotometer and an ash furnace should follow within the first year, particularly for filled and colored grades.

19. Conclusion and next step

A biodegradable plastic twin screw compound production line is best specified as six connected stages rather than as a list of machines, because the requirements propagate along the material flow. Hydrolytic sensitivity forces a minus 40 degrees Celsius central drying and conveying system and closed material handling upstream. Difficult bulk solids force a bank of loss-in-weight feeders with material-specific discharge geometry. The narrow thermal window forces a high-torque, moderate-speed co-rotating twin-screw extruder at 40:1 to 48:1 L/D with bimetallic barrels, a low-shear screw configuration and two-stage devolatilization. Melt sensitivity forces a short, low-dead-volume melt train with a gear pump and a properly sized screen changer. Pellet quality and output band decide between strand, water-ring and underwater pelletizing. Everything downstream exists to preserve what has already been achieved, and the utilities and laboratory decide whether the line can hold specification and prove it.

Kerke, a Wanplas factory with more than twelve years in twin-screw compounding, a plant of over 19,997 square meters, more than 2,000 machines running in over 70 countries and a team of more than 100 people, configures these lines against the recipe rather than against a catalog. The KTE series covers everything from KTE-16B laboratory units for formula development to KTE-135D production machines, with cutting systems spanning water-cooled and air-cooled strand, air-cooled and water-ring die-face hot cutting, eccentric water-mist cutting and full underwater granulation. Feeding systems, side feeders, crammer feeders, liquid feeders and the auxiliary range are supplied from the same factory, and Wanplas supplies matched equipment from elsewhere in the group where a project extends beyond the compounding category. Every line is combined-run tested before shipment, installed and commissioned by factory engineers, backed by operator and maintenance training, and covered by the group service policy including USD 500 in free parts every year.

If you are planning a biodegradable compounding line, the most useful next step is to send the specifics rather than a general enquiry: the resin systems you intend to run, the filler and additive loadings, the target output in kilograms per hour, the pellet form your customers expect, the certifications you need to hold, and the utilities available at your site. With that information the Kerke engineering team will return a stage-by-stage equipment list, a barrel and screw configuration proposal, a utility schedule and a layout drawing matched to your building. You are also welcome to visit the factory, watch a comparable line run, and bring your own raw materials for a trial run before any commitment is made.