CNC Machining China Factory Services

When turned and milled features must be concentric or timed, mill-turn cuts them in one setup, removing re-fixturing error. It is the DFM answer to relationship tolerances.

The trigger word on the drawing is usually a relationship callout: a bore that must be concentric to a turned diameter, a cross-hole that must sit at a specific angle to a keyway, a flat that must be timed to a thread. Machining those across two separate setups means the relationship survives only as well as the re-clamping does. Mill-turn machines them in one setup, so the relationship is machined rather than assembled, and the tolerance the drawing asks for is the tolerance the process actually delivers. The review flags which relationships are load-bearing and routes only those to mill-turn.

When does a part need grinding?

Grinding is the finishing step for surfaces that must be flatter, rounder, or smoother than a cutting tool can deliver, or for ±0.002 mm dimensions. The DFM review decides up front whether a part needs it.

The decision is rarely about the whole part; it is about one or two surfaces. A bearing seat, a sealing face, or a bore that must run true often carries the only ground features on an otherwise milled or turned part. The review isolates those surfaces, states the grinding stock they need, and leaves the rest of the part on the cheaper process. Asking the mill to hold a grinder's tolerance on every surface is the expensive way to get one surface right.

How does the review cut the services you need?

The review often reduces the number of services a part requires: a corner radius removes EDM, a wall tweak removes a 5-axis setup, a tolerance relaxation removes grinding. The cheapest service is the one you do not need.

Which secondary operations are bundled?

• Surface finishing: standard and hard anodizing, zinc / nickel / silver / gold / chrome plating, powder coating, painting, brushing, mirror polishing.
• Heat treatment: vacuum, bright, carburizing, nitriding, and stress-relief aging. In-house ovens reach 500 °C (fine for aluminum and low-temperature steel stress relief); titanium stress relief above that is outsourced to a qualified partner.
• Deburring, tapping, laser marking, assembly: included as your print requires.

Bundling secondary operations is not a convenience; it is a way of keeping the part under one control plan. When finishing and heat treatment sit in the same building as machining, the dimension after coating and the distortion after hardening are the same shop's problem to solve, not a hand-off between two suppliers who can each blame the other. You get one lot record and one accountable party, which is worth more than any single secondary operation listed on its own.

Feature-level rules that decide whether a service is cheap or expensive

Manufacturability lives at feature level. These are the checks run on a model before a route is chosen, and each one has a cheaper version that keeps the function.

Feature	What makes it expensive	What to change
Pockets	Depth that forces a long, slim cutter, so feed drops and an extra pass recovers size	Open access, reduce depth, or split the feature across two faces
Internal corners	A radius smaller than a standard cutter, which needs a special tool and a slow contour	Match the radius to a common cutter, ideally above a third of the pocket depth
Deep holes	Depth beyond about five times diameter, where pecking and chip evacuation dominate the cycle	Reduce depth, step the bore, or allow a larger diameter
Threads	Full-depth threads in blind holes, and fine pitches in hard material	Thread only the engagement length actually needed
Thin walls and tall ribs	Cutting force pushes the wall, so passes get lighter and the wall springs back	Add local thickness or a small draft, or widen tolerance on that wall
Large flat faces	Stress released during roughing moves the face and forces a second finishing operation	Allow a stress-relief step, or call flatness only where it mates
Tolerance everywhere	Every feature at ±0.003 mm (milling) / ±0.002 mm (turning) adds CMM time on features that do nothing	Tighten interfaces, leave the rest at general tolerance

Which machine group each service runs on, and what that means for your part

Service names hide the decision that matters, which is where the part is loaded. Prismatic work with features on one or two faces goes to the 3-axis group, 50+ machines strong, so capacity is rarely the constraint. Multi-face parts go to the 4-axis and 5-axis groups, 20+ machines each, where the value is removing re-fixturing rather than the extra axes themselves. Turned parts go to 25+ lathes, and small-diameter, slender parts go to sliding-head machines built for that job. Parts whose turned and milled features must be timed to each other go to mill-turn, where one setup replaces two and the relationship is machined instead of assembled. Ground work goes to 7+ grinders for surface, centerless and cylindrical finishing to ±0.002 mm.

Ask which group your part lands in before you compare quotes. The answer explains the price better than any hourly rate, and it also tells you how much parallel capacity stands behind your delivery date.

How finishing and heat treatment are sequenced

Sequence decides whether a finish survives. Parts that need hardening are rough machined first, heat treated, then ground to final size, because grinding after hardening is the only order that absorbs distortion. In-house ovens cover vacuum, bright, carburizing, nitriding and stress-relief aging up to 500 °C, which handles aluminum and low-temperature steel stress relief; titanium stress relief above that range is placed with a qualified partner and declared as an external step. Coating comes last: standard and hard anodizing, zinc, nickel, silver, gold and chrome plating, powder coating, painting, brushing and mirror polishing, with thickness measured on a Fischer gauge and corrosion performance checked by salt spray where the print calls for it.

The detail worth settling early is whether coating thickness sits inside or outside a toleranced dimension. Deciding that on the drawing costs nothing; discovering it at final inspection costs a batch. Send a STEP or IGES file with a toleranced drawing to [email protected] and the route, including finishing sequence, comes back with the quote.

How do you choose between 3-axis, 4-axis and 5-axis for a given part?

The machine class is a consequence of the feature layout, not a preference. Count the faces that carry machined features, check whether any angle is unreachable from a single orientation, and the answer falls out.

Part signature	Machine class	Why
Features on one or two faces, no angled surfaces	3-axis	One or two setups cover it; adding axes adds cost, not capability
Features on three or four faces that share a rotation axis	4-axis	The rotary axis indexes faces without a manual re-fixture
Features on several faces with compound angles	5-axis	Reaches angled features in one setup that would otherwise need multiple tilt fixtures
Turned body carrying milled detail that must be timed	Mill-turn	Machines the turned and milled relationship in a single setup

The cost question follows the same logic in reverse: a part routed to too many axes wastes machine time, and a part routed to too few wastes setups. The review matches the part to the class that reaches every feature with the fewest re-clamps, and the price difference between classes is mostly the difference in that setup count.

What DFM rules apply to threads and deep holes?

Threads and holes are where small drawing habits quietly add operations, so they get their own pass in the review.

Feature	The expensive version	The DFM fix
Blind-hole threads	Full-depth thread running to the bottom of a blind hole	Thread only the engagement length the fastener actually uses, and leave a clearance at the bottom
Fine-pitch threads in hard material	A fine pitch that breaks taps and slows the cycle	Use the coarsest pitch the load allows
Deep holes	Depth beyond about five times diameter, forcing pecking and long tooling	Reduce depth, step the bore, or open the diameter where function allows
Cross-drilled passages	Burrs where drilled holes intersect inside a bore	Design the intersection so a burr cannot hide where no external check reaches

The thread rule and the hole rule share the same root: the drawing often asks for more than the fastener needs. A bolt only engages over a few diameters of thread, and a hole only needs to be deep enough for the chip to clear. Matching the callout to the actual engagement is free, and it removes the tap breakage and the pecking cycles that would otherwise sit inside every unit cost.

What this shop actually runs

If you ask for capability evidence, you deserve a specific answer. This facility operates 100+ CNC machines across 6,800 m2 in Dongguan, China, staffed by 100+ people. The machines, listed by category:

• 5-axis machining centres (10+) - Mazak VARIAXIS I-600 (510/910/510 mm travel, 12,000 rpm, 22 kW, 71.6 N·m, 30-tool BT40) and Mazak INTEGREX I-250H S (B-axis 0.0001°, 24 kW, 124 N·m, 38-tool HSK-A63). Run on compound-angle parts, single-setup multi-face prismatic work, and aerospace fittings where datum transfer loss is unacceptable.
• 3-axis / 4-axis machining centres (50+) - Brother SPEEDIO S500Z2N / S700Z2N (10,000 rpm, 14/21-tool ATC, 0.7 s tool-to-tool, Z-axis 2.2 G) and Mazak VCE-430A L / VCE-570C L (10,000 rpm, 118 N·m, 24-tool ATC). Run on prismatic parts, plates, brackets, housings.
• Swiss-type turning centres (10+) - Citizen Cincom A20-3F7 (Φ20 mm, 10,000 rpm), TSUGAMI B0206-III / B0205-III (Φ20 mm, 0.1 µm), STAR SR-32JII / SR-32J Type N (Φ32 mm, 8,000 rpm). Run on long, slender rotational parts at ±0.002 mm.
• CNC turning centres (20+) - HEADMAN T70M/1250 (720 mm swing, 117 mm bore, 3,000 rpm, BMT75 12-station turret). Run on shafts, bushings, flanges up to ±0.002 mm.
• Wire EDM (5+) - Sodick AQ535L (550/350/300 mm travel, ±20° taper, 800 kg workpiece). Run on hardened tool steel, internal splines, sharp internal corners that milling cannot reach.
• Inspection: Hexagon CMM + 20+ gauges - Hexagon CMM for coordinate measurement, plus vision system, profilometer, hardness tester, coating thickness gauge, XRF for material verification. The 10:1 rule (gauge 10x more accurate than the band) is applied to every feature.
• Machine highlights - VARIAXIS I-600: one-setup multi-face 5-axis + MAZA-CHECK auto-calibration; INTEGREX I-250H S: DONE-IN-ONE mill-turn, B-axis 0.0001° + Ai thermal shield; SPEEDIO S500Z2N / S700Z2N: Z-axis 2.2 G + 0.7 s ATC; Swiss-type: guide-bush switchable + 0.1 µm resolution.

Tolerance bands: ±0.003 mm milled, ±0.002 mm turned, ±0.002 mm ground or wire-cut. Capability indices: Ppk >= 1.67 at the initial study; Cpk >= 1.33 ongoing in production.

Certifications: ISO 9001:2015 (116024/A/0001/UK/En) · IATF 16949:2016 (131941/A/0001/SM/En, design clause 8.3 excluded) · ISO 14001:2015 (116024/B/0001/UK/En), held by Dongguan Zhuohang Ltd (USCC 91441900MA4UWT6X39, since 2005).

Service area: we supply Austria, Belgium, the Czech Republic, Denmark, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Spain, Sweden and the United Kingdom in Europe; Brazil, Canada, Mexico and the United States in the Americas; China, Israel, Japan, Singapore and Sri Lanka in Asia; Australia and New Zealand in Oceania; and South Africa in Africa, with worldwide delivery from China.

Contact: Felipe Iglesias, [email protected], +86 13126536955.

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