Metal and plastic selection decides tolerance, finish, tool life and cost before a single cut is made. This part of the CNC machining complete engineering guide shows how to pick a workpiece grade from geometry, load and surface target.
Most of these are visible in the drawing, not on the machine.
Soft or gummy stock moves under the tool. Walls spring back after the vise opens, bores go oval, and the report reads out of tolerance on parts that looked correct during the cut. Re-cutting usually means a new blank.
A hardened or abrasive workpiece can double cycle time. Small end mills wear mid-run, the corner radius drifts, and the last parts of the batch no longer match the first ones. Nobody notices until inspection.
Anodizing on high-copper aluminium comes out blotchy and dark. Black oxide on 300-series stainless barely changes colour. The finish is ordered, paid for, and rejected at incoming inspection.
POM and PA move with humidity. A part gauged on a dry afternoon can measure differently the next morning. Tight bores and press fits fail slowly, in the customer's hands, months after delivery.
Three inputs decide the grade before toolpaths are written.
Aluminium covers most enclosures, brackets and heat-sink bodies. 6061-T6 machines fast and welds cleanly. 7075 gives roughly twice the yield strength of 6061 and still cuts well, which suits aerospace ribs and loaded brackets. 2024 is stronger in fatigue but its copper content makes anodizing uneven, so we usually steer cosmetic parts to 6061 or 6082.
Stainless is chosen for corrosion and hygiene rather than strength. 303 is the free-machining grade and produces the best chip control and finish. 304 and 316L are tougher and work-harden at the cut, so feeds have to stay aggressive. 17-4PH gives high strength after a simple aging treatment. For wear parts, 440C holds an edge and a polish that 316 cannot.
Engineering plastics win when the part needs electrical insulation, low weight or chemical resistance. POM is dimensionally stable and machines like brass, so it suits gears and bushings. PEEK holds stiffness at high temperature and survives steam and solvents, at a much higher blank cost. HDPE and PP are chemically inert and cheap, but they are soft and will not hold a press fit for long.
Titanium and nickel alloys are chosen for strength-to-weight and heat resistance. Ti-6Al-4V (TC4) is the common grade. It conducts heat poorly, so the cutting edge runs hot while the part stays cool. Sharp tools, low surface speed and generous coolant are not optional here. Magnesium machines fast but the chips are a fire risk, and Inconel is slow by nature.
Use this as a first filter, then confirm with the load case.
| Material | Typical use | Watch out for |
|---|---|---|
| 6061-T6 aluminium | Enclosures, brackets, heat sinks | Lower yield than 7075 |
| 7075 aluminium | Aerospace ribs, loaded brackets | Poor weldability, costlier blank |
| 303 stainless | Shafts, fittings, high-volume turning | Lower corrosion resistance than 316 |
| 316L stainless | Medical, marine, food equipment | Work-hardens, slower cutting |
| 17-4PH stainless | Valve bodies, high-strength shafts | Needs aging after machining |
| POM (acetal) | Gears, bushings, insulators | Not for high temperature |
| PEEK | Chemical and steam service | High material cost |
| Ti-6Al-4V | Lightweight structural parts | Slow cutting, tool wear |
| HDPE | Chemical tanks, covers | Soft, low stiffness |
One shop for prototypes and production runs, from a single part to 10,000+ pieces.
Simultaneous 5-axis work for contoured surfaces, deep pockets and parts that would need several setups on a 3-axis machine. Sixteen 5-axis centers are available.
Three-axis milling, four-axis milling and mill-turn centers. Maximum processing size 4,000 mm for long structural parts and shafts.
Machined prototypes and bridge parts so a design review does not wait on a hard tool. Production can start within 24 hours of drawing release.
Brackets, chassis and covers where a machined solid part would waste material. We can combine sheet and machined parts in one assembly.
Polymer prototypes for fit checks and jigs, useful when the final part will be machined in a different grade.
Anodizing, plating, powder coating, black oxide, bead blasting, brushing and polishing, plus laser marking down to 1.5 mm character height.
| Item | Range | Notes |
|---|---|---|
| Tolerance | ±0.005 mm (±0.0002 in) | Confirmed per feature on the drawing |
| Fine finish | Ra 0.2–0.8 μm | Polishing or fine boring |
| Standard finish | Ra 0.8–1.6 μm | Typical milled or turned surface |
| As machined | Ra 1.6–3.2 μm | No secondary operation |
| Maximum size | 4,000 mm | Large travel 4,000 × 400 × 150 mm |
| Rotary table | Ø400 mm | For radial features and slots |
| Inspection | 100% before shipment | Reports on request |
| Materials | Aluminium, steel, stainless, copper, titanium, plastics | Grades listed in our material library |
Numbers we can stand behind on a purchase order.
Fifteen years of cutting metal and plastic, with 3 wholly-owned plants and 7,600 m² of floor space across Dongguan and Singapore.
Sixteen simultaneous 5-axis centers, twelve four-axis mills, twenty-seven three-axis machines and sixteen mill-turn centers.
About ±0.0002 in on features that allow rigid fixturing and a stable material. We confirm per feature before quoting.
A quotation with free DFM feedback within 12 hours. Production can start within 24 hours once drawings and material are confirmed.
Raw material check, in-process monitoring and final inspection on every order. Reports are available on request.
ISO 9001:2015, IATF 16949:2016, ISO 13485:2016 and ISO 27001:2022. Uploads are confidential and an NDA is available.
High-strength aluminium and titanium ribs where weight and traceability both matter.
Brackets, housings and busbar parts that must repeat dimensionally across a run.
Joint housings and end-effector plates with tight bore alignment and light weight.
316L and PEEK components that need clean surfaces and documented inspection.
6061-T6 or 6082 anodize evenly and cut cleanly, so they give the most predictable cosmetic result.
Avoid 2024 and other high-copper grades if the part will be anodized in a visible colour. The copper content makes the oxide uneven and dark.
It is worth it when the part carries real load or you are removing material to save weight. 7075 gives roughly twice the yield strength of 6061.
For brackets, covers and fixtures that only locate other parts, 6061 costs less and machines faster.
Yes, with limits. Tool steel and 17-4PH can be machined before heat treatment or after aging, depending on the final hardness.
Tell us the target hardness and the features that must hold tolerance. Above a certain hardness the practical answer is to machine soft, then grind or EDM the critical surfaces.
300-series stainless work-hardens at the cut. If the tool rubs instead of cutting, the surface tears and the next pass cuts harder material.
Feeds and speeds need to stay aggressive, and 303 is the better choice when the part does not need 316 corrosion resistance.
POM is the default for gears, bushings and insulators because it is stable and machines cleanly.
PA absorbs moisture and moves with humidity, so avoid it for tight fits. PEEK is for high temperature and chemical exposure, and it costs far more per blank.
Yes. Anodizing needs aluminium, black oxide suits steel and stainless, and plating can be applied to steel, copper and brass.
Powder coating covers most metals and adds thickness, so it cannot go on a tight tolerance surface.
A 2D drawing or 3D model, the material grade if it is already decided, and the surfaces that matter.
If the grade is open, we will suggest one from the load case, the finish and the quantity. Quote and DFM feedback come back within 12 hours.
Yes. There is no minimum order quantity, so a single machined part and a 10,000+ piece run use the same process and inspection route.
The fixturing and inspection plan scale with the quantity, not with the size of the first order.
We review the grade, the tolerance and the finish together, then quote within 12 hours.
12-hour quote100% inspectionNo MOQNDA on request
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Upload your 3D model or 2D drawing and get a quotation with a free DFM analysis. Maximum processing size 4,000 mm.
CNC Metals 13 grades
CNC Plastics 10 grades
Machines & processes 12 options
Surface & post-processing 10 options
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