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When you request a quote for Delrin parts, the quality of your CAD package decides how fast and how accurate that quote will be. A clean, complete file lets a machining supplier price the job within hours. A vague one triggers rounds of clarification emails, and every round adds days to your project. This guide walks through exactly what a delrin cnc machining supplier needs from your files before they can give you a firm price.
For any part with three-dimensional geometry, send a STEP file (.step or .stp). STEP is a neutral format that carries the complete solid geometry without being tied to any specific CAD software, so the supplier's CAM system can read it directly and program toolpaths from the model. For flat, profile-cut parts, a DXF file at exactly 1:1 scale is acceptable.
Two formats cause problems at the quoting stage. STL files are mesh data built for 3D printing; they do not contain accurate machinable surfaces, so most machine shops will reject them. Native files such as .sldprt or .f3d only work if the supplier happens to run the same software and version, which you cannot count on. Always export to STEP, and name the file clearly with the part number and revision, for example "housing_1042_revB.step" rather than "untitled.step".
A STEP file carries geometry only. It says nothing about tolerances, threads, surface finish, or material. Those requirements belong on a 2D drawing, usually sent as a PDF, and for any functional part the drawing is the document that governs if the two ever disagree. A quote based on a model alone is really only a rough estimate.
A quote-ready drawing includes a title block with part name, part number, revision, material, and finish; front, top, and side orthographic views plus section views for internal pockets or bores; dimensions on every feature that matters; a general tolerance block (a common default is linear ±0.1 mm, angular ±0.5°); and full thread callouts such as M6×1.0-6H with depth stated for blind holes. If GD&T is used, every datum must be fully defined so the supplier can actually inspect the callout.
Delrin (POM acetal) is one of the most dimensionally stable engineering plastics. Unlike nylon, it absorbs very little moisture, so it holds tight tolerances after machining instead of drifting overnight. That stability is the main reason engineers choose it for gears, bushings, and precision fixtures, and it means tolerances around ±0.02 mm on critical features are realistic at a capable shop.
Two things still deserve attention. First, Delrin expands with heat more than metal does, so if the part operates at elevated temperature, note the operating range on the drawing so the supplier can advise. Second, resist over-tolerancing. Applying ±0.02 mm to every dimension of a simple spacer forces extra inspection time into the quote without improving the part. Tighten only the features that functionally need it: mating bores, press-fit pins, sealing faces. Shops with strong process control, such as an ISO 9001:2015 certified delrin cnc machining supplier holding tolerances down to ±0.002 mm on precision features, will still quote faster when your tolerance scheme is disciplined.
Surface finish is specified with Ra values, and each step smoother costs machining time. Ra 3.2 µm is a standard milled finish suitable for most faces. Ra 1.6 µm fits mating and sliding surfaces. Ra 0.8 µm is for bearing bores and precision sealing faces. Delrin machines cleanly and often reaches a smooth finish straight off the tool, so secondary polishing is rarely needed. Call out finish only on the faces where it matters and let the rest run as-machined.
A quote is built from more than geometry. Your RFQ package should also state:
The errors that slow quoting down are remarkably consistent: sending an STL instead of a STEP; a DXF exported at the wrong scale; a revised drawing submitted without incrementing the revision field; dimensions on the drawing that conflict with the 3D model; writing "Delrin or similar" without stating whether substitution is allowed; and tolerances far tighter than the application needs. Each one forces the supplier to stop and ask, and each question adds a day.
The formula is simple: a clean STEP file, a complete PDF drawing, disciplined tolerances matched to Delrin's behavior, and a clear RFQ package covering grade, color, quantity, and lead time. Put those together and the quoting process shrinks from weeks of emails to a single exchange. ANOK Precision Manufacturing machines Delrin and the full range of engineering plastics through its plastic cnc machining services, with DFM feedback built into the quoting process. Send your files today and get a firm, accurate quote back fast.