What this guide covers
If you are setting up or expanding a plastic zipper line, the injection molding machine is the single most important machine you will buy. It is what turns plastic granules and a roll of tape into a finished zipper chain. This guide explains what the machine produces, how the process works, where it fits in the line, and what to check before you order — written by a factory that builds these machines.
What a zipper injection molding machine makes
A zipper injection molding machine produces two things:
- Resin (plastic) zipper teeth — the interlocking elements of a plastic zipper, moulded directly onto both edges of the woven tape.
- Plastic stops — the top and bottom stops, and the pin-and-box parts on open-end plastic zippers, are also injection-moulded.
The result is the chunky, often colourful teeth you see on jackets, sportswear, backpacks and luggage. Because the teeth are moulded in place, plastic zippers are strong, light and easy to produce in bold colours.
How the moulding process works
The process is continuous. POM (polyoxymethylene) plastic granules — colour-matched in advance — are melted in the machine and injected under pressure into a precision long-chain mould. The mould forms a row of teeth onto both tape edges at the same time, then the chain advances and the next section is moulded. Two details matter for quality and cost:
- The mould is the precision part. Tooth shape, pitch and how cleanly the teeth grip the tape all come from the mould, so mould quality decides zipper quality.
- Scrap is recycled. Trimmed runner waste from each shot is reclaimed by a crusher and blended back with fresh POM, which keeps material cost and waste low.
The machines in a plastic zipper line
The injection molding machine does not work alone. A complete resin zipper line runs a sequence:
- Tape weaving — the polyester tape the teeth are moulded onto.
- Colour mixing — the POM is blended with colour masterbatch before moulding.
- Teeth injection moulding — the core machine, with its long-chain mould.
- Scrap recycling — a crusher reclaims runner waste back into the feed.
- Dyeing and winding — the chain is finished and wound into yardage.
- Downstream finishing — gapping, slider mounting, plastic stop injection (open-end and closed-end), and cutting.
For how this fits the whole picture across all zipper types, see how zippers are made, step by step.
Injection vs coiling vs stamping
The most common mistake when sourcing is assuming one machine makes every zipper. It does not — the teeth are formed differently for each type:
| Zipper type | How teeth are formed | Machine |
|---|---|---|
| Plastic / resin | POM injection-moulded onto tape | Injection molding machine |
| Nylon | Monofilament coiled and sewn on | Coiling + sewing machine |
| Metal | Stamped from flat wire | Stamping / downstream machines |
So an injection molding machine is the right choice if you are making plastic zippers. For a side-by-side of the equipment each type needs, read nylon vs metal vs plastic zipper machines.
How to choose an injection molding machine
- Mould quality and fit. The long-chain mould determines tooth quality — confirm the supplier makes its own moulds and can match them to your tape and tooth size.
- Automation level. Fully automatic machines need fewer operators and hold tighter consistency than semi-automatic ones.
- Colour and material handling. Check colour-changeover time and whether POM scrap recycling is built in.
- Output and tooth size range. Confirm the machine covers the zipper sizes (e.g. #3, #5, #8) you plan to sell.
- Certification and support. For export, the machine should be CE certified, with installation, operator training and spare-parts supply confirmed in writing.
For a full vendor checklist, see how to choose a zipper machine supplier.
Jeso's resin zipper machines
Jeso, the machinery brand of Wenzhou Primo Zipper Group, has built zipper machinery as a direct factory since 1984. For plastic zippers we supply the full resin line — the injection molding machine and its long-chain mould for the teeth, colour-mixing and scrap-recycling units, and the downstream machines that inject the plastic stops for both open-end and closed-end zippers — all CE certified and backed by installation, operator training and lifetime technical support across 160+ countries. Because we run our own mould-making workshop, the moulds are matched to the machines, so the tooling and equipment fit together.
Ready to compare the whole line? Start with our zipper making machine buyer's guide.
FAQ
- What is a zipper injection molding machine?
- A machine that injects molten POM plastic into a long-chain mould to form the teeth of plastic (resin) zippers onto the tape, and to mould the plastic stops. It is the core machine of a resin zipper line.
- Can it make nylon zippers?
- No. Nylon teeth are coiled from monofilament and sewn on, not injection-moulded. Injection is for plastic zippers; metal teeth are stamped from wire.
- What plastic is used?
- POM (acetal) — colour-matched before moulding, with trimmed scrap recycled back into the feed.
- What else is in a plastic zipper line?
- Tape weaving, colour mixing, the injection moulding machine and mould, scrap recycling, dyeing and winding, then gapping, slider mounting, plastic stop injection and cutting, plus testing.