Chicago CNC Precision Processing: A Shop-Floor Guide

Precision processing starts with a simple question: does the geometry need the tool to reach more than one side in a single setup? A 5-axis machine tilts the tool or the part while cutting, so a compound angle, a deep pocket with a curved floor, or a port face that sits off the main axis can be finished without re-fixturing. That matters most when a second setup would add stack-up error, not just time.

Thin-wall parts are a different case. A wall under 1 mm will deflect under cutting force, so the answer is often a lighter radial cut with more axial passes, or a support fixture. If the wall also has to hold ±0.005 mm over 200 mm, we will usually rough it, stress-relieve, then finish. Ask for that sequence early. It changes the price.

Parts with deep bores, cross-holes, and blended radii often need both milling and turning. We run 16 mill-turn centers for exactly that reason. One chucking plus one milling pass beats three separate setups on a manual fixture, and the concentricity callout stays real instead of becoming a negotiation at inspection.

When the part is a simple prismatic block with no angled features, a 3-axis machine is cheaper and just as accurate. We keep 27 of them. Putting that job on a 5-axis center wastes spindle time and adds cost without adding tolerance. Match the machine to the drawing, not to the brochure.

Our working tolerance is ±0.005 mm (±0.0002 in) on features that need it. That number is not a default. It applies to specific dimensions on a controlled drawing, and it costs more than a general ±0.1 mm block. Tell us which dimensions are functional. If a mounting hole only needs clearance, say so and we will not chase it.

Surface finish moves the price in the same way. As-machined parts sit around Ra 1.6–3.2 μm. A sealing face or a bearing bore may need Ra 0.8–1.6 μm, and optical or medical contact surfaces can go to Ra 0.2–0.8 μm. The finer the finish, the slower the pass and the more tool changes. Each step is measurable, so we quote it separately.

Material choice affects both tool life and stability. Aluminium 6061 and 7075 cut fast and hold fine detail. Stainless 304 and 17-4PH work-harden, so feeds and speeds must be right or the surface tears. Titanium TC4 and Inconel need low cutting speeds and rigid setups. PEEK and carbon fibre machine well but wear tooling quickly.

We inspect 100% of parts before shipment, with raw material checks, in-process monitoring, and a final inspection. Reports come on request. That routine is what keeps the qualification rate at 99.99% across production runs.

We run 127 high-precision CNC machines across three wholly-owned plants covering 7,600 m², with 150 technicians. The fleet includes 16 simultaneous 5-axis machining centers, 12 four-axis mills, 27 three-axis machines, and 16 mill-turn centers. That mix lets us route a job to the machine that fits rather than forcing every part through one process.

Size range runs from compact work at 500 × 310 × 200 mm up to 4,000 mm maximum processing size, with a large-travel envelope of 4,000 × 400 × 150 mm. Medium work sits at 750 × 1,150 × 550 mm and 600 × 600 × 600 mm. Rotary work uses a Ø400 mm table when the part needs indexed faces around a bore.

Materials we machine daily include aluminium 6061-T6, 7075, and ADC12; stainless 303, 316L, 17-4PH, and 440C; steel 1018, 4140, and 4340; copper C110 and C36000 brass; titanium TC4 and Inconel; and plastics such as POM, PEEK, PC, and carbon fibre.

Finishing is handled in the same supply chain: anodizing in clear, colour, hardcoat, or conductive; electroless nickel, zinc, silver, and gold plating; powder coating and black oxide; bead blasting, tumbling, brushing, and polishing; plus laser marking down to 1.5 mm character height.

Send a 3D model and a 2D drawing with the critical dimensions marked. We return a quotation and a free DFM analysis within 12 hours. The DFM notes usually cover wall thickness, tool reach, thread depth, and any feature that will need a second setup. Fixing those before cutting is cheaper than fixing them after.

Production can start within 24 hours of a released order, and parts ship in 3–5 days. There is no minimum order quantity. We run one prototype, a 50-piece pilot, or a 10,000+ part run on the same equipment and the same inspection routine. Historical late-delivery probability is below 2%.

Uploads are secure and confidential, and an NDA is available on request. If your program needs controlled documentation, ISO 9001:2015, IATF 16949:2016, ISO 13485:2016, and ISO 27001:2022 certificates cover our quality and information handling. Ask for the scope statement if you need it for supplier approval.

Aerospace, automotive and EV, medical devices, robotics, electronics, industrial machinery, and new energy teams all send us work. The common thread is a drawing with real tolerances and a date that matters. Tell us both.