Guides / Cost
Delrin CNC Machining Cost: How a Quote for an Acetal Part Is Built
September 21, 2026
An acetal quote is not mostly machine time, which is why comparing shops on hourly rate tells you very little. Here is what the number is actually made of and which parts of it you control.
Stock is a larger share than you expect
In aluminium work, material is often a modest line. In acetal it is frequently the largest single cost on a mid sized part.
Three things drive it:
Form. Rod, plate and tube are priced differently and suit different parts. A round part from rod wastes little. The same part milled from plate wastes most of the block. If your part is round, saying so lets the shop buy rod.
Grade. Natural homopolymer and copolymer sit at the baseline. PTFE filled, glass filled, ESD, food contact and detectable grades all cost more per kilo, sometimes considerably.
Availability. A grade and size that is on the shelf is cheap and fast. One that has to be ordered in adds cost and often a week. This is the single most common reason a quoted lead time is longer than you hoped.
Setup and programming are paid once
CAM programming, fixture design, tool setup and the first article check happen once per order regardless of quantity.
This is why quantity moves the per part price so sharply at the low end and so little at the high end. Going from 5 to 50 pieces often cuts the per part price by more than half. Going from 200 to 400 changes it very little.
If a repeat order is likely, say so. A shop that knows the fixture will be used again prices the first order differently.
Workholding is its own line
Acetal is soft. It marks under standard jaws and it springs under clamping pressure, which means a part machined in a hard vice can be correct in the machine and wrong on the bench.
Shops solve this with soft jaws cut to the part, vacuum plates, sacrificial fixtures and lower clamping pressure spread across more clamps. All of that is setup time.
On a thin or awkward acetal part, workholding can be the largest single line in a small quantity quote. That is worth knowing before assuming a shop is padding.
Annealing is the lead time surprise
A stress relief cycle between roughing and finishing is what tight tolerances on thick acetal parts usually need. It adds oven time, which is modest, and calendar time, which is not. A day is the practical minimum and more is common when parts wait for an oven load.
This is the most common reason two quotes for the same drawing differ widely. One shop read the tolerance and put an anneal in. The other did not. Neither is wrong, they made different assumptions about an underspecified drawing.
Deburring and inspection
Acetal holds a fine flexible burr that folds over rather than breaking off. On a part with many intersecting features, deburring is real hand time that scales linearly with quantity, unlike setup.
Inspection scales with how many dimensions the drawing marks as critical. A drawing with a blanket tight general tolerance forces the shop to inspect everything.
Where a typical quote lands
For a mid sized machined acetal part in modest quantity, a rough shape of the cost looks like this:
| Element | Share of a small run quote | Scales with quantity? |
|---|---|---|
| Stock | Large | Yes, linearly |
| Setup and programming | Large at low quantity | No, fixed per order |
| Workholding and fixturing | Moderate to large | No, fixed per order |
| Machine time | Moderate | Yes, linearly |
| Annealing, if required | Moderate | Partly, oven loads batch |
| Deburring | Moderate | Yes, linearly |
| Inspection and paperwork | Small to moderate | Partly |
The two fixed lines are why a quote for a handful of parts looks so high per piece.
Six drawing changes that lower the number
- Open the general tolerance and mark only the critical features. The single biggest lever on most acetal drawings.
- Increase internal corner radii to a standard cutter size. A 0.4 mm corner in a deep pocket forces a small tool and many passes.
- Increase a thin wall by half a millimetre. It may remove the need for a custom fixture.
- Convert blind holes to through holes where function allows. Chips clear, bores stay on size.
- Allow grade substitution with an approval note. Lets the shop use stock it already has.
- Say which faces are functional. The shop spends finishing and inspection effort where it matters and not elsewhere.
None of these change what the part does.
How to compare quotes that differ a lot
Ask each shop three questions:
- Did you include a stress relief cycle? If so, why?
- What stock form and grade did you price?
- What did you assume about the general tolerance?
Three short answers will explain almost any gap. If one shop assumed an anneal and the others did not, the drawing needs a line about it, and then everybody is quoting the same part.
Want quotes you can actually compare? Send your RFQ with the drawing and the quantity, and we match you with up to three shops that machine acetal. Reply within 24 business hours.
Frequently asked questions
Why is my quote for 10 pieces so much more per part than for 200?
Programming, fixturing and first part checks are paid once per order. On 10 pieces that fixed cost is split ten ways. On 200 it almost disappears into the part price. The machine time per part barely changes.
Why do two shops quote the same Delrin drawing very differently?
Most often because one assumed a stress relief cycle and the other did not, or one read the general tolerance as applying to every dimension. Both are drawing gaps rather than pricing differences. Ask each shop what it assumed.
Is Delrin cheaper to machine than aluminium?
Machine time is usually lower because acetal cuts fast and tool life is long. Stock cost per kilo is often higher than common aluminium grades, and acetal parts need more careful workholding. On a small part the two often land close.
Need a quote for this part?
Send the drawing. We match you with up to 3 shops that machine acetal and reply within 24 business hours.
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