Precision plastics · machined first, moulded only when it earns it

Fifty parts machined, or five hundred moulded. The drawing decides, not the salesman.

Engineering plastics are where a prototype quietly becomes a product. The same drawing that costs $40 a part at fifty pieces can cost $6 at five hundred — but only if it was designed for a mould, and only after somebody pays for the tool. This page is about choosing the process honestly instead of defaulting to one.

Send a drawing PEEK in detail

Machined POM gears, PEEK bushing and PTFE seal ring

Four materials cover most of the work.

Listed with what each one is bad at, because the failure is usually the reason a part needs remaking.

Material	Good at	Bad at	Typical part
PEEK (unfilled, GF30, CF30)	Temperature, creep, chemical resistance, wear	Cost; moves after machining unless annealed	Bushings, insulators, pump parts, wafer handling
PTFE	Lowest friction, widest chemical resistance	Cold flow under load, very high thermal expansion	Seal rings, gaskets, lab hardware
POM (acetal)	Dimensional stability, machinability, low moisture uptake	Acid resistance, UV, paint adhesion	Gears, cams, manifolds, jigs
PPS / PI	Temperature and dimensional stability, low outgassing	Brittleness, price, limited stock shapes	Semiconductor fixtures, high-temp housings

These are material properties, not a claim that every shape in every material is available here. Stock shape and thickness decide what can be cut from what; if a 60 mm PEEK rod is not on the shelf, the quote says so rather than substituting a grade that behaves differently.

Machining or moulding: the arithmetic, not the sales pitch.

The crossover is usually somewhere between 100 and 300 pieces, and it depends on part size and on how much of the geometry a mould can actually form.

CNC machining — from 1 piece

No tooling. You pay for material, programming and spindle time.
Design can still change between parts; nothing is frozen.
Tight features stay achievable: undercuts, side holes, thin walls.
Unit price stays flat — 50 or 500, the part costs about the same each.
Right answer below roughly 100 pieces, and any time the design is still moving.

Injection moulding — from 100 pieces, aluminium tool

Tooling is a separate, visible line on the quote. It is yours, and it is not reused for anyone else.
Unit price drops sharply with quantity, which is the entire point.
The geometry is frozen at tool sign-off — that is the trade.
An aluminium tool is good for thousands of shots; a steel tool is a different conversation and a different shop.
Right answer when the design has stopped moving and the quantity will not fall.

What this shop does not do: high-volume steel tooling, hot-runner production moulds, or family tools for a million shots. When your quantity passes what an aluminium tool makes economic sense for, the honest answer is to move the part to a production moulder — and we will say so.

Tolerance in plastic is not tolerance in metal.

A ±0.02 mm callout on POM is a different request from the same callout on aluminium. Here is what actually moves the number.

Factor	What it does	What to put on the drawing
Thermal expansion	PTFE moves about ten times as much as steel per degree	The temperature the part is measured at, and the temperature it runs at
Moisture uptake	PA and POM grow in humid air; PEEK and PTFE barely move	Whether the part is measured dry or conditioned
Machining stress	Cutting releases locked-in stress; a pocket can bow hours later	Whether annealing is allowed, and whether the part must be stable over days
Creep under load	PTFE flows at room temperature under steady load	The load and whether it is continuous
Wall thickness	Thin walls deflect while being cut	A minimum wall, or permission to add support material

Site standard for machined plastics is quoted per feature — commonly ±0.05 mm, tighter on a named feature where the material allows it. The number on the quote is the one that applies; a table cannot know whether your part is a 10 mm bushing or a 200 mm plate.

What to send.

The drawing, with the material grade named — "PEEK" and "PEEK GF30" are different parts.
Quantity now, and quantity in a year — this decides machining versus moulding.
Service temperature and medium — decides grade more than strength does.
Whether the design is frozen — if not, machining is the cheaper route even at higher unit price.
Any food, medical or cleanroom requirement — it changes material sourcing, not just paperwork.

Accepted files: STEP, IGES, DXF, STL, or a PDF drawing.

What comes back: two quotes when both processes are viable — machined and moulded, with the tool on its own line — so the crossover is a number you can see instead of an argument.

Send the drawing before the design freezes.

The cheapest moment to find out that a 0.8 mm wall will not fill, or that a bore needs a draft angle, is before the tool exists. That review is free and it comes back with the quote.

Send a drawing for review

Or email 4220015@gmail.com — two working days for a reply.