See How CNC Processing Is Produced, From Drawing to Finished Part

• 1
  What matters before you send a drawing
• 2
  See How CNC Processing Is Produced: The Full Sequence
• 3
  Quotation, DFM Review and Material Prep
• 4
  Programming and Machine Setup
• 5
  Cutting, Surface Finishing and Inspection
• 6
  Seven Steps to a Finished Part
• 7
  Which Process Fits Your Part

CNC processing is not one operation. It is a chain of decisions that starts with a STEP file and ends with a boxed part and an inspection report. Each link in that chain changes what the next one can do. A wall thickness you leave at 0.8 mm may force a slower feed rate, which pushes the cycle time up, which moves the delivery date. Engineers who understand the chain write better drawings. Buyers who understand it ask better questions.

We run 127 high-precision CNC machines across three wholly-owned plants in Dongguan and Singapore, covering 7,600 m². That includes 16 simultaneous 5-axis machining centers, 12 four-axis mills, 27 three-axis machines and 16 mill-turn centers. Maximum processing size is 4,000 mm, with travels from 4,000 × 400 × 150 mm down to 500 × 310 × 200 mm. A Ø400 mm rotary table handles round work that would otherwise need a second setup.

The sequence below is the same whether you order one prototype or a 10,000-part run. What changes is the tooling, the fixture investment and how much of the inspection is sampled versus 100%. For prototypes, we usually machine from billet. For runs above a few hundred, we look at whether casting or extrusion would cut material cost without hurting the tolerances you actually need.

• 1
  Single setup winsEvery additional setup adds a datum shift. If a 5-axis cycle can reach all critical faces, take it.
• 2
  Call out datumsGD&T without a clear A-B-C datum scheme makes inspection ambiguous.
• 3
  Match finish to functionRa 1.6–3.2 μm is fine for most brackets. Sealing faces need Ra 0.8–1.6 μm or better.

Send a STEP or IGES file with a 2D drawing that carries tolerances, datums and finish callouts. Without the 2D drawing, we have to assume general tolerances, and that assumption usually costs you money later. We return a quotation and a free DFM analysis within 12 hours. The DFM report flags features that will be slow, fragile or impossible: internal corners tighter than the tool radius, pockets deeper than four times the cutter diameter, and threads that run out into a fillet.

Material choice sets the baseline. Aluminum 6061-T6 is the default for enclosures and fixtures because it machines fast and holds a good finish. 7075 is stiffer and stronger but galls more easily, so we slow the spindle and use more coolant. Stainless 303 machines freely; 316L does not, and it work-hardens if the feed is too light. Titanium Ti-6Al-4V needs low surface speed and constant feed to keep heat out of the cut. Plastics like PEEK and POM move with temperature, so we rough, let the part rest, then finish.

Material prep is dull work that decides everything after it. Bar stock gets sawn to length plus 3–5 mm for facing. Plate gets checked for flatness before it goes on the table; a plate that is 0.3 mm out of flat will not hold ±0.005 mm on a thin wall. For castings, we check for porosity and hard spots, because both will break a small end mill.

• 1
  2D drawing requiredTolerances and datums belong on the drawing, not in an email.
• 2
  Free DFM in 12 hoursWe flag cost drivers before you commit to a design.
• 3
  Check flatness firstOut-of-flat stock limits achievable tolerance no matter how good the machine is.

CAM programming converts the model into toolpaths. The programmer picks tool sizes based on the smallest internal radius and the deepest pocket. A rule we use: keep pocket depth under four times the cutter diameter, or step down with a smaller tool and accept the extra cycle time. Roughing removes 60–70% of the stock with a high-feed or adaptive path. Semi-finishing leaves 0.2–0.3 mm on the walls. Finishing takes that last pass at a lighter chip load to hit the surface finish.

Setup is where accuracy is won or lost. We zero the part against the datum called out on the drawing, not against the nearest convenient face. For 5-axis work, we probe the stock and let the control compensate for position before the first cut. Fixtures are designed so the part is supported under the cutting load. A thin wall that is unsupported during roughing will deflect, spring back, and come out oversize.

Common mistakes at this stage: using a vise on a part that needs full support, programming a finish pass before stress has been relieved, and assuming the machine will hold a tolerance that the setup cannot repeat. If a feature needs ±0.005 mm, we plan the inspection method at the same time we plan the toolpath. If we cannot measure it, we cannot promise it.

Cutting runs to the programmed parameters. For aluminum 6061, we typically run carbide at 2,000–3,000 SFM with a 0.05–0.15 mm/tooth feed. Stainless 316L drops to 200–350 SFM. Titanium is slower still, at 100–200 SFM, with high-pressure coolant aimed at the cutting edge. If the chip comes off blue, the speed is too high or the feed is too low. If it comes off as dust, the feed is too low and the tool is rubbing.

Surface finishing is a separate operation with its own lead time. Anodizing builds a layer, so we mask threads and bores that must stay in tolerance. Electroless nickel adds 0.01–0.025 mm per side. Powder coating is thicker and softer, so it goes on non-critical cosmetic faces. Bead blasting hides tool marks but slightly rounds edges. Laser marking needs a minimum character height of 1.5 mm to stay legible after finishing.

Inspection closes the loop. We check raw material on arrival, monitor in-process at each setup, and run a final inspection before shipment. Every part in the shipment is inspected, not sampled, and reports are available on request. For a ±0.005 mm feature, that means a CMM or a high-accuracy gauge, not calipers. If a dimension is out, we catch it before the box is sealed, not after it reaches your dock.