Knowledge Hub · Plastics machinery series
Seven plastics machines,
opened up part by part
What each part does, which spec to check when you buy, what it looks like when it wears, and what to inspect on schedule. Written for plant owners, maintenance technicians, process engineers and buyers comparing machine quotations.
Marketing Department, Advanced Chem Solutions · 22 Oct 2026
How this series differs from the processing series
The plastics processing series explains the principle of each process: how pellets become a part. This series opens the machine itself, unit by unit and part by part, and answers the questions that come up on the shop floor: how to tell a worn screw, how many tonnes of clamp force a mould needs, what adjusts thickness across a sheet die, and which auxiliary makes colour or properties drift.
ACS does not make or sell machines. We design additive and masterbatch formulations. Knowing the machine helps us choose the right formulation, because shear, residence time and the way masterbatch is dosed differ from machine to machine, and many problems that look like formulation problems actually come from worn parts.
The heart every machine shares: screw and barrel
Injection machines, blow moulders and every extrusion line start with the same melting unit. Pellets drop from the hopper into the feed throat, the turning screw carries them forward, heat from the heater bands and shear from the screw melt them, and the melt is pushed through a screen pack to the die or nozzle. Understanding this part applies to every machine in the series.
These parts wear over time on every machine, and the symptoms are similar.
- Worn screw and barrel: the gap between flight tips and barrel wall widens, more melt slips backward, output drops, melt temperature fluctuates, and colour or masterbatch disperses less well than before. Wear is much faster with glass- or mineral-filled resins.
- Failed heater band or thermocouple: one zone runs too cold or too hot. The display can still look normal if a thermocouple has come out of its well; check heater current and compare with the barrel surface temperature.
- Overheated feed throat: pellets soften and stick together before they reach the screw (bridging) and feeding becomes erratic. Keep the throat cooling water flowing.
- Blocked screen pack: pressure before the screen keeps rising. The more recycled resin you run, the more often screens need changing.
- Gearbox and thrust bearing: change the gear oil on schedule; unusual noise or heat is the first warning.
The seven machines at a glance
| Machine | Main units | Parts that wear or need frequent care | Numbers to check on the spec | Related process |
|---|---|---|---|---|
| Injection molding machine | Injection unit, clamping unit, drive, control | Screw, check ring, nozzle, toggle links, tie bars | Clamp force, shot volume, tie-bar spacing, mould height range | Injection molding |
| Blow molding machine | EBM: extruder, parison head, moulds · ISBM: preform oven, stretch rod, high-pressure air | Die and mandrel, pinch-off edges, IR lamps, air system | Maximum container size, cavities, parison control points | Blow molding |
| Sheet extrusion line | Extruder, flat die, roll stack, edge trim, winder or cutter | Die lips, roll surfaces, screen pack, trim knives | Output kg/h, die width, sheet thickness range | Extrusion · Thermoforming |
| Blown film line | Extruders, annular die, air ring, bubble tower, nip, winder | Die lips, air ring, nip rollers, corona electrodes | Die diameter, number of layers, layflat width | Extrusion |
| Pipe & profile line | Extruder, die, vacuum sizing tank, cooling tanks, haul-off, cutter | Die, vacuum pump, spray nozzles, haul-off pads, saw blade | Pipe diameter range, output, cooling length | Extrusion |
| Twin-screw compounder | Gravimetric feeders, gearbox, segmented twin screws, vents, pelletiser | Screw elements and barrel, pelletiser knives, die holes, vacuum line | Screw diameter, L/D, torque, output | Making masterbatch and compounds |
| Auxiliary equipment | Conveying, drying, masterbatch dosing, mould temperature control, chillers, granulators | Filters, desiccant, load cells, granulator knives | Drying throughput, dew point, dosing accuracy, cooling capacity | Every process |
What to check before accepting a new machine or buying a used one
- Ask for the spec in numbers and compare it with the parts you will actually make, not just the machine size. For an injection machine, check clamp force, shot volume and tie-bar spacing together.
- Run a trial with your own resin and mould or die if you can, and record what the machine actually achieves.
- Used machines: have screw and barrel wear measured, look at the repair history, check for hydraulic oil leaks, and test the safety gates and emergency stops.
- Enough auxiliary capacity: an undersized dryer, chiller or masterbatch doser keeps the main machine from running at full capacity.
- Spare parts and manuals: ask where fast-wearing parts come from, how long they take, and whether there is a maintenance manual your technicians can read.
Read machine by machine
Injection molding machine
Injection unit, screw and check ring, toggle and hydraulic clamps, drives, and choosing clamp force
Read →
Blow molding machine (EBM / ISBM)
Parison head, wall-thickness control, moulds and pinch-off, preform oven and stretch rod
Read →
Sheet extrusion line
Coat-hanger die, adjustable lips, 3-roll stack and thickness gauging
Read →
Blown film line
Spiral die, air ring, IBC, BUR and frost line, through to the winder
Read →
Pipe & profile extrusion line
Pipe die, vacuum sizing tank, cooling tanks, haul-off and cutter
Read →
Twin-screw compounding line
The machine that makes masterbatch: feeders, screw elements, kneading blocks, vents and pelletising
Read →
Auxiliary equipment
Dryers, masterbatch dosers, mould temperature controllers, chillers and granulators
Read →General knowledge for understanding only. Numbers are typical reference ranges. Selection, installation, operation and maintenance must follow the machine maker's manual and instructions and your plant's safety rules.
Not sure whether a part problem comes from the machine or the formulation?
Send us the machine, resin and symptom. We will help you decide whether to start checking the machine or the formulation. No charge.