Dust free workshop space demand for electronic plastic twin screw compound line

Electronic-grade modified plastics are no longer a niche. Connectors, sensor housings, LED frames, battery separators, IC encapsulation compounds and optical films all depend on engineering plastics and functional masterbatches whose performance collapses the moment a stray black spot, gel or metal-wear fragment lands inside the pellet. The twin-screw compounding line is where that purity is either protected or destroyed, and the workshop around it is the first line of defense. Planning the dust-free workshop space for an electronic plastic twin-screw compound line is therefore an engineering problem, not a finishing touch. Kerke, a Wanplas factory with more than 12 years of focused experience in co-rotating parallel twin-screw compounding extruders, helps material producers size the clean zone, grade the room by contamination risk, and select KTE-series machinery whose footprint and output match the target ISO 14644 class. This guide explains why electronic compounding needs controlled space, what cleanliness level is realistic, exactly how much floor area each part of the line consumes, and how to balance capital cost against the particle budget your downstream customers demand.

Why Electronic-Grade Compounding Demands a Dust-Free Workshop

The phrase electronic plastic covers a wide family of materials: glass-fiber-reinforced polyamide for connectors, flame-retardant polybutylene terephthalate for relays, liquid-crystal polymer for high-frequency parts, antistatic acrylonitrile-butadiene-styrene for device housings, and mineral- or talc-filled polypropylene for thin-wall components. What they share is an unforgiving tolerance for inclusions. A single carbonized particle or a speck of rust can create a short circuit path in a miniature connector, a weak point in a sealed relay, or a visual defect on a cosmetic cover that fails outgoing inspection. In conventional commodity compounding, such defects are diluted across tonnage and rarely noticed. In electronic-grade material, they are sampled, imaged and rejected.

The contamination that ruins these compounds does not only arrive with the resin. It is generated and carried inside the workshop itself. Ambient air in a typical industrial bay carries millions of particles per cubic meter, ranging from textile fibers and skin flakes to abrasive dust from nearby grinding or packaging operations. Operators shed skin and clothing lint. Forklifts stir floor dust. Open bag dumping releases fine powder that floats and resettles on every surface, including the open mouth of a loss-in-weight feeder. Even the machine contributes: screw and barrel wear, screen-changer seal erosion and gearbox mist can introduce metal and oil mist into the melt path if the surrounding air is dirty.

This is why a dust-free, graded workshop is not luxury for electronic compounding but a process prerequisite. The objective is not to enclose the entire extruder in a bubble, which would be expensive and impractical, but to control the zones where contamination transfers into the product: raw-material introduction, melt filtration, pellet cutting and cooling, pellet conveying, and the clean silo where finished material waits for packing. By surrounding those zones with filtered, positive-pressure air and separating dirty activities from clean activities, a producer can hold ISO 14644 Class 8 or Class 7 conditions at a fraction of the cost of a fully classified cleanroom.

Kerke approaches the problem from the equipment side as well as the room side. The KTE-series co-rotating twin-screw extruder is built around a self-cleaning kneading screw configuration with computer-aided screw assembly, which minimizes dead spots where degraded material accumulates and later breaks off as black spots. Tight barrel sealing, a closed gravimetric feeding path and an integrated screen changer reduce the pathways by which airborne dust enters the melt. Combined with a correctly sized clean zone, this lets a material producer hit demanding inclusion limits without resorting to exotic, oversized facilities.

The second reason a controlled workshop matters is consistency. Electronic compounders often run the same tightly specified recipe for years, switching colors or additive packages in batches. A dusty, uncontrolled room makes every changeover a contamination risk, because residual powder from a previous run redistributes through the air and settles into the next batch. A graded, filtered workshop with dedicated gowning and material airlocks keeps each campaign clean and reproducible, which is exactly what automotive and consumer-electronics supply chains require when they audit a compounder.

Finally, the workshop design protects the machinery itself. Fine abrasive dust drawn into the control cabinet, servo drives or the gearbox lubrication system accelerates failure. A clean environment around the electrical and hydraulic enclosures, plus positive pressure that keeps dust out of the cabinet cooling air, extends mean time between failures and supports the continuous operation that electronic material contracts expect. The space plan is thus a reliability investment, not only a quality measure.

ISO 14644 Cleanliness Classes and Particle Budgets

ISO 14644-1 defines cleanroom classes by the maximum permitted number of airborne particles equal to or larger than a specified size, measured per cubic meter of air. For electronic plastic compounding, the two relevant grades are Class 8, often called the 100,000-class in legacy terminology, and Class 7, the 10,000-class. Class 8 permits up to 3,520,000 particles of 0.5 micrometer or larger per cubic meter, while Class 7 tightens that ceiling to 352,000 per cubic meter. Moving one class tighter multiplies the air-handling burden roughly by a factor of two to four, so the choice between Class 8 and Class 7 should be driven by the actual inclusion limit of the end product rather than by a blanket aspiration for cleanliness.

Most engineering-plastic and functional-modified materials for electronics are comfortably produced under Class 8 conditions, provided the feeding and pelletizing sub-zones are well managed. Class 7 becomes necessary when the compound is destined for connectors, IC encapsulation, optical components or any application where a single visible or electrically active inclusion causes field failure. Some ultra-demanding optical or medical-adjacent electronic grades even push toward Class 6, but that is rare for twin-screw pelletizing and usually reserved for downstream clean handling rather than the extrusion room itself.

The particle budget is only half the story. Equally important is the air-change rate, expressed as air changes per hour, which describes how many times the room volume is replaced with filtered air in an hour. A higher air-change rate clears transient contamination faster, for example after a bag is opened or a screen pack is changed. It also sustains the positive pressure differential that stops dirty air leaking inward through doors and penetrations. The table below maps the common electronic-compounding grades to their particle ceilings and practical air-change ranges.

Cleanliness Class, Particle Limit and Air-Change Reference

ISO 14644 Class	Max 0.5 µm particles per m³	Max 5 µm particles per m³	Typical air changes per hour	Typical electronic application
Class 8 (100k)	3,520,000	29,300	15 to 25	General engineering plastic, flame-retardant compounds, antistatic housings
Class 7 (10k)	352,000	2,930	30 to 60	Connectors, relays, IC encapsulation, optical-grade masterbatch
Class 6 (1k)	35,200	293	70 to 150	Specialty optical film, medical-adjacent electronic grades
General industrial bay	Not classified	Not classified	2 to 6 (dilution only)	Machine service area, gearbox and hydraulic enclosures

The numbers above are ceilings, not targets. A well-run Class 8 compounding zone usually operates well below the 3.52 million limit because the dominant contamination sources have been removed by zoning, gowning and local extraction at the feeder. The air-change rate is the real design lever: undersize it and the room lingers dirty after every intervention; oversize it and the energy and filter cost climb without improving the pellet. Kerke engineers typically model the transient after a bag-dump event to set the air-change rate, then size the fan filter unit coverage to deliver that rate with margin.

Another practical point is monitoring. ISO 14644 requires particle counting at defined locations and a documented certification method. For an electronic compounding workshop, continuous particle monitoring at the feeder and pelletizing zone gives early warning when a filter saturates or a door is left open. This is far more valuable than a one-time certificate, because the room is a working environment that is opened, cleaned and reclassified repeatedly during production.

Full Line Equipment Layout and Per-Unit Footprint

A complete electronic-grade twin-screw compounding line consists of more than the extruder. The product path runs from raw-material handling through melting, mixing, filtration, pelletizing and finally clean storage. Each unit occupies floor space, and each has a different tolerance for ambient contamination. The art of the layout is to place the contamination-sensitive units inside the controlled zone and the service-heavy units on its boundary, then connect them through sealed interfaces so dust cannot cross.

The core train, in process order, is as follows. First, a loss-in-weight feeder or a group of gravimetric feeders meters each powder, pellet and liquid additive with high accuracy. Second, the co-rotating twin-screw extruder, here a Kerke KTE-series machine, melts, disperses and homogenizes the formulation inside the barrel. Third, a melt pump stabilizes die pressure. Fourth, a continuous screen changer removes gels and hard inclusions. Fifth, the melt is cut into pellets either by strand pelletizing with a water bath and pelletizer, or by underwater pelletizing for dust-free, spherical output. Finally, pellets are conveyed to a clean silo and packed under filtered air.

Footprint depends on machine size, but the relationship is predictable. A gravimetric feeder station is compact, yet the surrounding clearance for bag handling and maintenance is what drives the reserved area. The extruder itself is long because of its L/D ratio, and the barrel length grows with screw diameter. The melt pump and screen changer add length at the die end. Pelletizing needs a water system, a cutting chamber and a dryer, while the clean silo needs headroom plus a packing booth. The table below gives representative single-unit footprints and the cleanliness grade each unit prefers.

Equipment List, Single-Unit Footprint and Cleanliness Requirement

Line unit	Representative single-unit footprint (m²)	Minimum clearance around unit (m)	Preferred cleanliness	Contamination risk if exposed
Loss-in-weight feeder station (multi-feeder)	6 to 10	0.8 to 1.2	Class 8, Class 7 for optical grades	High: open feed throat draws airborne dust
KTE twin-screw extruder (36 to 75 mm)	12 to 22	1.0 to 1.5	Class 8 on barrel, sealed to clean zone at feed	Medium: sealed barrel, but vent port can ingest air
Melt pump (gear type)	2 to 4	0.6 to 0.8	Class 8	Low: fully enclosed, sealed bearings
Continuous screen changer	2 to 3	0.6 to 0.8	Class 8	Low to medium: seal area needs clean air
Underwater pelletizing system	8 to 14	1.0 to 1.2	Class 7 preferred for electronic grades	High: cut pellets and water are contamination receivers
Strand pelletizing (bath, puller, cutter)	10 to 16	1.0 to 1.5	Class 8	Medium: strands exposed during transfer
Clean silo and packing booth	6 to 12	0.8 to 1.0	Class 7 to Class 8	High: finished pellets exposed during bagging

The footprint figures are the equipment envelope only. Real planning must add the aisle network. Personnel aisles of 1.2 to 1.5 meters let operators reach feeders and the control panel without brushing against open material paths. Material aisles of 1.5 to 2.0 meters accommodate vacuum-conveying lines, water piping, the pellet-conveying hose and maintenance routes for removing the screen-changer slide or the pelletizer die. A maintenance strip of at least 1.0 meter behind the gearbox permits screw extraction, which for a 75 mm machine with 56 L/D is a long, heavy operation needing clear floor space.

Screw extraction deserves special attention in the space plan. When the line is stopped for a配方 change or a wear inspection, the screw stack is pulled axially out of the barrel. For a KTE-75 with 56 L/D, that screw assembly can be more than 4.5 meters long. The layout must reserve a straight pull path equal to the machine length plus the screw length, or provide a screw-pulling trolley and a side bay. Cramming the extruder against a wall is the most common layout error we see, and it turns a routine cleaning into a multi-hour struggle that tempts operators to shortcut the procedure and risk cross-contamination.

Zoning ties the footprint to the cleanliness grade. The feeder, pelletizer and silo sit in the controlled zone with filtered supply air. The extruder barrel and gearbox straddle the boundary: the feed throat is inside the clean zone, while the drive end, hydraulic power unit and electrical cabinet sit in the general service area separated by a low wall and a sealed floor penetration. This hybrid zoning captures the contamination-sensitive points without paying cleanroom rates for the entire machine hall, which is the key to a realistic dust-free workshop budget.

Kerke KTE Series Twin-Screw Extruders for Clean Compounding

The KTE series from Kerke is a parallel co-rotating twin-screw compounding extruder family spanning laboratory units such as the KTE-36 up to large production machines. For electronic-grade material, three sizes cover the full spectrum from formula development to mass production: the KTE-36, the KTE-50 and the KTE-75. All share the same modular building-block screw and barrel concept, so a screw configuration qualified on the 36 mm lab machine transfers predictably to the 75 mm production machine, which is essential for scaling a validated electronic recipe without re-optimizing the entire shear and residence profile.

The long residence time and high mixing intensity of twin-screw compounding are exactly what electronic formulations need. Flame retardants, conductive carbon black, glass fiber and mineral fillers must be dispersed to a tight distribution with no agglomerates, while heat-sensitive additives such as some antistatics and antioxidants must survive the melt without degradation. The KTE barrel is divided into configurable zones with independent temperature control, side feeding for delayed filler addition, and an optional vent or vacuum exhaust that removes volatiles before they become voids or gels in the pellet.

From a cleanliness standpoint, the KTE design helps in three concrete ways. First, the kneading blocks are computer-aided and self-cleaning, leaving little stagnant material to overheat and carbonize into black spots. Second, the barrel sections are sealed with metal gaskets and the feed throat can be enclosed and connected directly to the gravimetric feeder, eliminating the open hopper that would otherwise inhale workshop dust. Third, the die end is prepared for a melt pump and screen changer, so fine filtration is built into the standard process rather than bolted on as an afterthought.

Below is a representative specification set for the three electronic-compounding sizes. Exact values vary with screw configuration, motor choice and whether side feeding or liquid injection is fitted, so these should be read as a planning baseline rather than a fixed datasheet. Kerke tunes screw element arrangement, L/D ratio, exhaust position and electrical control for each customer formulation during project engineering.

Kerke KTE-36 / KTE-50 / KTE-75 Specification for Electronic Compounding

Parameter	KTE-36	KTE-50	KTE-75
Screw diameter (mm)	36	50	75
L/D ratio range	40 to 48	40 to 56	40 to 56
Max screw speed (rpm)	600	500 to 600	400 to 500
Drive power (kW, typical)	11 to 22	45 to 90	160 to 315
Output range (kg/h)	30 to 120	120 to 350	400 to 1200
Recommended role	Lab formula trial, R&D	Pilot, small production	Mass production
Side feeder option	Optional	Yes	Yes, twin-screw
Control system	PLC + HMI, recipe management	PLC + HMI, recipe management	PLC + HMI, recipe management, remote monitoring

The L/D ratio deserves a note for electronic materials. A longer barrel, toward 52 or 56, gives more residence time for difficult dispersions such as conductive carbon black or high-load mineral filler, and more room for a vacuum vent that cleans the melt. A shorter 40 L/D is sufficient for easy-filled compounds and saves both floor length and drive power. Because the KTE barrel is modular, the same machine frame can accept different L/D configurations by adding or removing barrel sections, which is useful when a producer shifts between formulations that demand different mixing intensity.

Recipe management is another clean-compounding feature. Each validated electronic formulation is stored as a screw-speed, temperature-profile, feeder-ratio and vacuum set of parameters on the PLC. Recalling the recipe eliminates the operator judgement that causes batch-to-batch drift, and the data log becomes part of the quality record that electronics customers increasingly demand during audits. Kerke machines support remote monitoring through the control network, so the Wanplas engineering team can review process data and support troubleshooting without an on-site visit.

Melt Pump, Screen Changer and Pelletizing for Low-Contamination Output

The extruder alone does not make a clean pellet. The final purity is set at the die, where the melt is filtered and cut. Two units earn their place on every electronic-grade line: a gear-type melt pump and a continuous screen changer. The melt pump sits between the extruder and the screen changer or die, and its job is to take the pulsating, fluctuating pressure from the screw and deliver a steady, controllable pressure to the die. Steady pressure matters because it lets the screen changer run a finer mesh without surging, and it keeps pellet size uniform at the cutter.

The continuous screen changer holds one or two pleated filter screens and slides a fresh screen into the melt path while the spent screen exits, all without stopping the line. For electronic compounds, a fine mesh traps gels, charred particles, unmelted agglomerates and the occasional metal-wear fragment before they reach the die. Because the slide is sealed and the exchange is automatic, operators are not exposed to open melt and the clean zone is not disturbed by manual screen changes, which on older lines are a major contamination event.

Pelletizing method is a direct cleanliness decision. Strand pelletizing pulls extruded strands through a water bath, across a puller and through a rotary cutter, then dries them. It is robust and inexpensive, but the strands are briefly exposed to the room during transfer, and the drying step can generate fines if poorly tuned. Underwater pelletizing cuts the melt directly at the die face under a flow of process water, producing spherical, dust-free pellets with minimal fines and almost no exposure of the product to room air. For electronic grades where fines and cross-contamination are the enemy, underwater pelletizing inside the controlled zone is the stronger choice despite its higher equipment and water-treatment cost.

Kerke supplies a full cutting and pelletizing system adapted to electronic requirements, including water-cooled strand pelletizing, air-cooled strand pelletizing, air-cooled die-face hot cutting, water-ring die-face hot cutting, eccentric water-mist hot cutting and the underwater granulation system. The selection depends on the material thermal sensitivity, the required pellet shape and the cleanliness target. For most electronic engineering plastics, the water-ring or underwater option paired with a closed-loop water system gives the best combination of shape control and contamination exclusion.

Kerke Pelletizing System Options for Electronic Grades

Pelletizing method	Pellet shape	Fines / dust level	Room exposure	Best fit
Water-cooled strand	Cylindrical	Medium	Medium (strand transfer)	General engineering plastic, easy formulas
Air-cooled strand	Cylindrical	Medium	Medium	Heat-sensitive, water-averse compounds
Air-cooled die-face hot cutting	Near-spherical	Low to medium	Low	Masterbatch, filled compounds
Water-ring die-face hot cutting	Spherical	Low	Low	Color masterbatch, engineering plastic
Underwater granulation	Spherical, uniform	Very low	Very low (sealed die)	Electronic, optical and high-purity grades

Water treatment is the hidden cost of wet pelletizing, and it is worth planning from day one. The process water carries fine polymer dust and filler that must be filtered and, for closed-loop systems, cooled and clarified before reuse. A poorly maintained water loop becomes a contamination source in its own right, depositing scale or biological growth that ends up on the pellet. Kerke configures the water system with the pelletizer so the loop stays clean, and the whole pelletizing enclosure is placed inside the controlled zone so the only air the pellets ever meet is filtered.

Taken together, the melt pump, screen changer and chosen pelletizer act as the final quality gate. The extruder sets the dispersion; these downstream units set the cleanliness. Skipping or under-specifying them to save budget is the fastest way to produce a technically well-compounded material that still fails the inclusion limit of an electronics customer.

Capacity Versus Workshop Area Budget

With the unit footprints established, the next question is the total room. The relationship between throughput and area is not linear, because support functions such as gowning, airlocks, water treatment, electrical room and maintenance storage scale more slowly than production volume, while the controlled envelope scales with the longest machine and the pelletizing island. The table below gives a planning budget that has worked for several electronic-compounding installations: net equipment envelope plus aisles, FFU plenum and changeover storage.

Capacity and Suggested Workshop Area Budget

Target output (kg/h)	Typical KTE model	Net equipment envelope (m²)	Total workshop area (m²)	Recommended class
30 to 120	KTE-36	45 to 65	90 to 130	Class 8
120 to 350	KTE-50	80 to 110	150 to 220	Class 8, Class 7 if optical
400 to 700	KTE-75	140 to 190	260 to 360	Class 8 to Class 7
800 to 1200	KTE-75, extended	200 to 260	380 to 480	Class 7 preferred
1500 to 2000	Dual KTE-75 or larger frame	300 to 400	560 to 720	Class 7, zoned Class 6 islands

These areas assume a single line. A plant running two or three parallel lines does not triple its floor requirement, because the gowning, airlock, water-treatment and electrical rooms are shared, and the aisles can be rationalized. A two-line hall typically needs only about 1.6 to 1.7 times the single-line area. This sharing is the main reason electronic compounders plan capacity expansion as additional parallel lines under one clean envelope rather than as separate rooms.

Ceiling height is a second budget item that is easy to forget. The FFU plenum above a Class 7 zone needs 0.6 to 1.0 meters of void, the clean silo and bag-filter may need 5 to 7 meters of headroom, and the crane or hoist for screw handling adds another meter. A workshop planned at a standard 4 meter clear height may be too short for the silo and plenum combination, forcing expensive later modifications. Kerke’s layout team models the vertical stack as carefully as the floor plan, because a dust-free workshop fails just as surely from a cramped ceiling as from a dirty floor.

Utility routing also eats area if planned late. Vacuum conveying lines from outside buffer silos, process-water supply and return, cooling-water loops, compressed air, electrical trunking and the data network all want defined trays and chases. Leaving these for the installer to route on the floor guarantees crossed paths, blocked aisles and contamination traps. The budget figures above already reserve space for overhead and perimeter utilities, which is why they sit above a bare equipment count.

HVAC, FFU Air Volume and Personnel or Material Flow Separation

The heating, ventilation and air-conditioning design turns the space plan into an actual clean zone. For most electronic compounding workshops, the workhorse is the fan filter unit, a self-contained module combining a fan and a HEPA or ULPA filter that supplies filtered air downward through the ceiling. Coverage, meaning the fraction of ceiling fitted with FFU modules, sets both the air-change rate and the uniformity of the downward flow that sweeps particles away from the product.

For Class 8, ceiling FFU coverage of 10 to 25 percent with 15 to 25 air changes per hour is usually adequate, because the dominant strategy is dilution and positive pressure rather than laminar sweep. For Class 7, coverage rises to 30 to 60 percent and air changes to 30 to 60 per hour, approaching the unidirectional-flow regime where particles are carried straight down and out through low return grilles. The plenum above the ceiling must be at least 0.6 meters deep for Class 7 to let the air develop a reasonable flow pattern before reaching the product.

Air volume is straightforward to estimate. A 300 square meter Class 7 zone at 40 air changes per hour needs 300 times 3 times 40, or 36,000 cubic meters per hour of filtered supply, plus margin for filter loading and leakage. That volume drives fan power, HEPA filter count and the cooling load, because all that air must be conditioned. The energy cost of a clean zone is real and scales with class, which is why over-specifying to Class 6 when Class 8 would do is a recurring budget mistake we help customers avoid.

Personnel and material flow separation is where many otherwise good workshops fail. Operators must enter through a gowning airlock: shoe cleaning, hair cover, coverall, gloves, then a pass-through into the clean zone. Raw materials should never enter through the same door. Instead, bulk bags or supersacks are opened in a separate material airlock or, better, vacuum-conveyed directly from outside buffer silos so the powder never becomes airborne in the clean room. Finished bagged pellets leave through a third route, often a pass-through that keeps the clean side from being opened to the warehouse.

The airflow logic is simple but strict: clean air flows from the pelletizing and silo end toward the general service end, and from overhead down to low returns. Any penetration, such as a door left open to the warehouse or a return grille placed high on a wall, short-circuits the flow and pulls dirty air across the product path. Pressure cascades help: the cleanest zone is most positive, the gowning airlock is intermediate, and the outside is lowest, so leaks always move outward. Kerke coordinates the layout with the HVAC engineer so equipment penetrations, such as the extruder drive shaft seal and the pelletizer water lines, do not breach the pressure boundary.

One more practical measure is local extraction at the loss-in-weight feeder. Even in a clean room, opening a bag of powder releases a puff that the room air eventually clears but that can settle on nearby surfaces first. A small localized capture hood at the feed throat, exhausting to a filtered return, removes that puff at the source and keeps the general air-change load lower. This is cheaper than upgrading the whole room class to compensate for a single dusty point.

Application Industries and End Products

The dust-free twin-screw compounding line exists to serve industries where a contaminated pellet is a failed part. Kerke machines and the Wanplas group’s compounding expertise cover a broad set of electronic and adjacent applications, and each carries its own purity expectation that the workshop grade must meet.

Connector and terminal compounds are the largest electronic use. Glass-fiber-reinforced polyamide 66 and polyamide 6, often with flame retardant and a lubricity package, are molded into connectors for automobiles, computers and consumer devices. These parts have thin walls and tight tolerances, so a black spot or gel can block a mold gate or create a weak seal. Class 8 is typical, with Class 7 for high-reliability automotive connectors.

Relay and switch housings use flame-retardant polybutylene terephthalate and polycarbonate blends. Here the concern is both inclusion and consistency of the flame-retardant dispersion, because a streaky batch burns unevenly in testing. The twin-screw line disperses the halogen-free or brominated system uniformly, and the clean workshop prevents conductive carbon or metal dust from bridging contacts.

Antistatic and conductive compounds serve device housings, trays and packaging that must dissipate static without shedding particles. Carbon-black or carbon-fiber loading must be dispersed to a precise, repeatable level, and the pellet must stay dust-free so it does not contaminate clean assembly lines downstream. Underwater pelletizing plus a Class 7 zone is the common configuration.

LED and lighting components use polycarbonate, polymethyl methacrylate and light-diffusing filled compounds where any inclusion scatters light and shows as a bright defect in the lit product. Optical-grade masterbatch for these parts pushes toward Class 7, sometimes with a Class 6 island at the pelletizing die.

Battery and energy materials are a fast-growing electronic adjacency. Separator coatings, conductive binder compounds and insulated housings for cells all demand low metallic inclusion, because stray metal in a cell is a safety risk. The clean workshop plus fine screen filtration directly serves this requirement.

Finally, cable compounding for electronic and data cables needs uniform dispersion of flame retardant and filler with controlled gel content, since a gel becomes a weak spot in thin insulation. The same KTE line that serves connectors serves cable compounds, which is why a flexible dust-free workshop pays back across several product families rather than a single grade.

How to Select the Right Line and Workshop Grade

Selection starts from the product, not the machine. Define the target output, the most demanding inclusion limit among your customers, the filler load and the number of formulations you will run. Then map those to a KTE model and a workshop class. The table below is a practical decision aid used in Kerke project engineering.

Requirement to Model and Workshop-Grade Recommendation

Customer requirement	Recommended KTE model	Pelletizing method	Workshop class	Relative capital cost
New formula development, 30 to 120 kg/h	KTE-36	Strand or water-ring	Class 8	Low
Pilot and small series, 120 to 350 kg/h	KTE-50	Water-ring or underwater	Class 8	Medium
Mass production, 400 to 1200 kg/h	KTE-75	Underwater	Class 7	High
High filler load, glass fiber or mineral above 40 percent	KTE-50 or KTE-75 with side feeder	Water-ring or underwater	Class 8 to Class 7	Medium to High
Optical or LED-grade, zero visible inclusion	KTE-50 or KTE-75	Underwater, fine screen	Class 7, Class 6 island at die	Very High
Battery or conductive compound, low metal inclusion	KTE-75	Underwater	Class 7	High

The relative capital cost column intentionally uses grades rather than numbers, because the final figure depends on local construction, utility prices and the exact machine configuration. What holds universally is that the workshop class is the largest swing factor after the machine itself. Moving from Class 8 to Class 7 roughly doubles the air-handling and filter cost and adds plenum construction, while moving to Class 6 can multiply the HVAC budget several times. The disciplined approach is to set the class at the lowest level that satisfies the hardest customer spec, then invest the saved budget in better filtration and pelletizing rather than in a blanket cleaner room.

A second selection principle is to size the machine for the steady-state requirement with modest headroom, not for peak bursts. An oversized extruder running at low fill and low screw speed is harder to stabilize and more prone to residence-time variation, which hurts dispersion. Kerke typically recommends the model whose mid-output band matches the contract volume, so the line runs in its proven window. Capacity growth is then met by adding a parallel line under the same clean envelope, which also improves supply reliability through redundancy.

For producers who also run recycling or regrind streams, the Wanplas group supplies matched upstream and downstream equipment so a single facility can handle both virgin electronic compounds and qualified recycled content under separate, graded zones. The key is never to mix the dirty recycle handling with the clean electronic line; the two are physically separated by airlocks and dedicated ventilation, with the recycled material only rejoining the clean stream after it has passed melt filtration inside its own enclosed train.

Service and Support from Kerke and the Wanplas Group

Buying the line is the start; running it cleanly for years is the real test. Kerke, as a Wanplas factory, delivers the group’s shared service commitments alongside its own compounding expertise. Every line is run through factory acceptance testing before shipment, including continuous operation checks that verify thermal stability, screw alignment and control response under load. This pre-shipment validation means the machine arrives calibrated and the customer’s clean workshop is not the first place a problem is discovered.

On-site installation and commissioning are carried out by Kerke engineers who also train the customer’s operators and maintenance staff on the specific screw configuration, recipe management and clean-room operating discipline. Because the workshop cleanliness depends as much on operator behavior as on the HVAC, the training covers gowning, bag-handling, screen-change procedure and the cleaning cycle that protects the next formulation from the previous one.

The Wanplas group backs every factory with a free-parts policy of USD 500 of spare parts every year, together with warranty replacement of damaged components and an open-factory policy that welcomes customers to audit the production and quality system in person. Remote monitoring through the control network lets the Kerke and Wanplas engineering teams review process data, diagnose drift and recommend adjustments without waiting for a service trip, which keeps the line in its validated window and the pellet inside specification.

Spare-parts availability is planned around the wear items that matter for cleanliness: screw elements, barrel liners, screen packs, cutter blades and seals. Keeping these on a scheduled replacement program prevents the gradual wear that silently raises inclusion levels long before a hard failure occurs. Kerke supplies wear-part kits matched to the running formulation and throughput, so the maintenance plan is tied to the actual duty rather than a generic calendar.

For customers planning a new facility, Kerke and the Wanplas group can support the layout from machine envelope through utility interface, advising on ceiling height, plenum depth, airlock position and utility routing so the clean workshop is right the first time. This upstream involvement is cheaper than retrofitting a cramped or under-ventilated room after commissioning, and it aligns the equipment footprint with the ISO class the product demands.

Conclusion

A dust-free workshop for an electronic plastic twin-screw compound line is a coordinated system of machine, room and procedure. The contamination-sensitive points are the feeder, the melt path and the pelletizing and silo zones, and those are the places that earn filtered, graded air. Most electronic engineering plastics run comfortably at ISO 14644 Class 8, while connectors, IC encapsulation and optical grades call for Class 7, with Class 6 reserved for special islands at the die. The floor area scales from about 90 square meters for a 30 to 120 kg/h KTE-36 lab or pilot line to 380 to 480 square meters for an 800 to 1200 kg/h KTE-75 production line, with ceiling height and utility routing planned alongside the footprint. Kerke’s KTE-36, KTE-50 and KTE-75 co-rotating twin-screw extruders, paired with a melt pump, continuous screen changer and underwater or water-ring pelletizing inside the controlled zone, give electronic compounders a validated, reproducible route to low-inclusion pellets. If you are planning a clean compounding workshop or need to match a machine and room grade to a specific electronic formulation, send your target output, filler load and inclusion limit to the Kerke engineering team for a tailored line and layout proposal, and visit the Wanplas group factory to see the KTE series running under controlled conditions before you commit.

Frequently Asked Questions