The wear parts that decide whether your machine produces a consistent part or an inconsistent one. Nitrided 38CrMoAlA, SKD61 and bimetallic, hard-chrome plated, precision machined to your drawing or sample — for Chinese and imported machines alike.
Replacing a screw on its own, while the barrel is already worn, buys you a few weeks and then the problem returns. It is worth looking at the whole plasticizing path at once.
The material choice is driven by the resin, the glass or mineral content, and how long you need the set to last. Over-specifying is wasted money; under-specifying means a second replacement in two months. Here is how we normally decide.
The standard choice and the one most orders need. Good wear resistance, holds melt temperature stability, and costs the least of the three options.
A tougher alloy deposited on the flight edges over a tough core. The answer when abrasive material is the problem, not time.
Chrome plating is about corrosion resistance and surface quality, not wear resistance. It also needs a barrier layer underneath to stop the chrome blistering.
Where heat resistance or a specific corrosion environment demands a different base grade.
This is the question we are asked most often, usually from a buyer who suspects they are paying for a machine problem that is actually a wear part problem. In order of reliability:
Shot weight no longer holds steady. Cushion varies shot to shot. And the clearest signal of all: the injection pressure needed to fill the same part keeps climbing while the mould and resin have not changed. That upward drift is wear, and it will not fix itself.
Visible wear on the screw flights, a shiny or flattened section where the flight was originally curved, or a measurable diameter loss against the drawing. On the barrel, a groove you can feel with a fingernail at the feed zone. Viscosity or resin drag on a rebuilt screw should fall back close to original figures.
Black specks, colour streaks, or a burnt smell that returns shortly after a purge. Constant purging, rising cycle time, and unstable dimensions on the part. These appear late, because wear is already well advanced by the time they show.
If you can, send the old screw or a few photographs of it with the wear clearly visible, plus the machine brand, model and screw diameter. We will measure the actual wear against the original diameter and confirm the specification and dimensions from that, rather than from an estimate. If the wear is moderate, a rebuild of your existing screw may be viable and cheaper than a new one — we will tell you when that is the case.
These are the brands we handle most often. But the determining factor is always the screw diameter, barrel length and internal bore — if you give us those, most machines are straightforward regardless of who built them.
| To specify correctly, send us | Why it matters |
|---|---|
| Machine brand and model | Confirms the machine family and which variant of the screw design applies |
| Screw diameter and length | The two primary dimensions — everything else is derived from these |
| Barrel internal diameter | Must match the new screw's major diameter. A worn barrel with a new screw leaks and does not plastise correctly |
| Resin, and filled or unfilled | Determines nitrided versus bimetallic, and whether a mixing head is needed |
| Daily running hours | Sets the duty cycle, which sets the wear allowance |
| Old part or photos of it | Allows actual wear measurement instead of estimation |
Drawing, old part, or just machine model plus screw diameter. Photos are acceptable if you cannot measure — send them and we will work from those.
Material grade, treatment, dimensions and L/D ratio agreed in writing before we quote. Nothing is assumed on your behalf.
Unit price, lead time and shipping method settled up front. Typically 10–25 days depending on size and specification.
Machined, treated and dimensionally checked before packing. Large pieces by freight, small items by courier, tracking sent with the documents.
One-off pieces and repeat batches are both welcome, and a new customer usually starts by ordering one or two pieces to test before committing to a full set. Dimensional accuracy is checked before shipping, not sampled from. If a part arrives and does not fit, or the dimensions are wrong, contact us straight away — we will put it right, at our cost. And if your existing screw is only moderately worn, we will say a rebuild is viable rather than sell you a new one.
We will confirm the specification, the dimensions and the price — usually within 4 hours on business days. No drawing? Send a photo of the old part and the nameplate.