How to Get CNC Machine Work Done: 6 Proven Steps

• 1
  Key takeaways
• 2
  What you need before you ask for CNC machine work
• 3
  How to read a CNC quotation without guessing
• 4
  Matching the part to the right machine and setup
• 5
  Tolerance, finish and inspection: what to specify and what to skip
• 6
  How to get CNC machine work done: 6 steps
• 7
  Which process and setup fit your part

Most delays on a machining job start before the spindle turns. A supplier cannot quote what is not on the drawing, so the first real step is to make the package complete. That means a 3D model plus a 2D drawing that states which dimensions are critical. If the drawing says "general tolerance" only, expect a quote that assumes the loosest reading, or a list of questions back.

State the material grade, not just the family. Aluminum 6061-T6 and 7075 behave differently in thin walls; 304 stainless work-hardens faster than 303. A grade-specific callout lets the shop pick speeds, feeds and tooling that hold your tolerance without extra operations. If the part sees heat, wear or salt water, say so. The shop can then suggest a heat treatment or a coating inside the same quote.

Quantity shapes the process. One prototype is usually cut from plate on a three-axis or five-axis mill with soft jaws. A 10,000-piece run may move to a dedicated fixture, a mill-turn center, or die casting plus secondary machining. Tell the supplier both numbers if you know them, even if the second one is only a forecast. It changes the quote you get back.

Finish and marking belong in the same package. Anodizing, electroless nickel, bead blasting and laser marking all add steps and handling. Laser-marked text needs a minimum character height of 1.5 mm to stay readable after coating. A part that arrives without the marking you expected is a rework, not a finish problem.

A useful quote lists four things: unit price, tooling or setup cost, lead time, and what is included in inspection. If any of those is missing, ask. Unit price alone hides the setup charge, and setup is often the larger number on a one-off part. On a 500-piece order the same setup spreads thin and the unit price drops, which is why quantity matters at quoting time.

Check the tolerance line first. A quote written at ±0.05 mm is not the same job as one at ±0.005 mm, even when the drawing looks identical. The tighter number needs better machines, temperature control, and more inspection. If the quote is much lower than the others, read the tolerance and finish lines again before you celebrate.

Lead time should be broken into stages. At GreatLight, quotation and free DFM analysis come back within 12 hours, production can start within 24 hours, and parts ship in 3–5 days. Those numbers apply to normal machining work, not to exotic material with a long mill lead time. Ask what starts the clock: PO receipt, material arrival, or drawing approval.

Finally, ask what happens if a dimension is out. A supplier that offers free rework for quality problems and a clear remedy for parts that cannot be reworked is easier to work with than one that only quotes low. Get that answer in writing before the PO, not after the inspection report.

Machine choice follows geometry, not habit. A flat bracket with through-holes is fine on a three-axis mill. A part with faces at several angles, deep pockets, or a requirement that hole positions stay true to a curved surface is a five-axis job, because fewer setups mean fewer accumulated position errors. GreatLight runs 16 simultaneous 5-axis centers, 12 four-axis mills, 27 three-axis machines and 16 mill-turn centers, so the setup can be picked to fit the part instead of the other way round.

Size decides the envelope. The largest travel here is 4,000 × 400 × 150 mm for long parts, with medium envelopes of 750 × 1,150 × 550 mm and 600 × 600 × 600 mm, and compact machines at 500 × 500 × 450 mm and 500 × 310 × 200 mm. A Ø400 mm rotary table covers round work that needs indexing. If your part sits near an envelope limit, say so early. Fixture and tool clearance, not just part size, decide whether it fits.

Thin walls and long bores are the usual trouble spots. Aluminum walls below 1 mm deflect under cutting force and need light passes and support. Deep bores need a boring bar with enough stiffness, or the diameter drifts along the depth. Mention these features; a shop that knows them will add a roughing stage and a stress-relief pause rather than cut to final size in one pass.

Material availability matters more than most buyers expect. Common grades in aluminum, stainless, steel, copper and brass, titanium and engineering plastics are normally stocked, but a special grade can add days before the first chip. Send the grade in the RFQ and the shop can confirm stock instead of discovering the gap after the PO.

Do not tolerance everything tight. Each tight callout adds measurement time and sometimes a process step. Mark the fits, the mating surfaces and the datums; leave the rest at a general tolerance. A drawing with twenty ±0.005 mm dimensions costs more than the same part with three critical ones, and it does not run any better.

Surface finish follows function. Ra 1.6–3.2 μm is normal as-machined territory for brackets and housings. Sealing faces and bearing seats usually want Ra 0.8–1.6 μm. Optical and sliding contact surfaces can call for Ra 0.2–0.8 μm, which means slower passes, finer tools, and often a finishing operation after the main cut. Name the surface and the value; "smooth" is not a specification.

Inspection should be planned, not promised. At GreatLight every part is inspected before shipment, with raw material checks, in-process monitoring and a final inspection, and reports are available on request. A 99.99% qualification rate is the result of that routine, not a substitute for it. Ask which dimensions are measured on a CMM and which with hand tools, and ask for the report format before the run starts.

Certifications matter when your part goes into a regulated product. ISO 9001:2015 covers general quality management; IATF 16949:2016 applies to automotive work; ISO 13485:2016 to medical devices; ISO 27001:2022 to information security for customer data. If your industry needs one of these, say so at RFQ stage so the paperwork is planned alongside the machining.