Robotics CNC Machining in China: Precision Parts That Move

Robotics · CNC Machining Robotics CNC Machining in China: Precision Parts That Move Joints, actuators, housings and fixtures machined to ±0.005 mm, because every tolerance stacks into how the robot moves. One supplier for the metal and the board. Request a quoteSee services 80+CNC machines in-house: 50+ 3-axis, 20+ 4-axis, 20+ 5-axis, 25+ lathes, 7+ grinders ±0.005 mmHeld on critical joint, bore and bearing-seat features Cpk ≥ 1.67Target on key characteristics; ≥1.33 on general features No MOQQuoted from a single piece through to volume Robots are unforgiving customers for a machine shop. A housing that fits fine on the bench still costs you repeatability once it is bolted to the end of a 1.2 m arm. So we quote robotics work off the drawing and the stack-up, not off a part count. Machined in Dongguan, Guangdong since 2006 (Zhuohang), under ISO 9001, IATF 16949 and ISO 14001. What robotics CNC parts look like Joints and bearing seats, actuator housings, motor mounts, end-effector brackets, shafts and fixtures. Robotics is precision-machining-intensive: a joint 0.01 mm out of round becomes a wobble at the end effector, amplified by arm length. See the matching EMS page. Robotics part families we machine most Joints and bearing seatsThin-wall rings where the bore is the whole part.Concentricity and runout under 0.005 mmGround or hard-turned bearing fitsTurned and milled in one setup on mill-turn centers Actuator and gearbox housingsDeep pockets, cross-drilled cable paths, sealing faces.Flatness on seals, position on bolt patterns5-axis to avoid re-fixturingAssembled with the driver board if you want Reducer and gear componentsFlexsplines, output flanges, pinions for harmonic and cycloidal drives.Checked on a dedicated gear measuring centerNitrided or carburized through vetted partnersProfile verified before and after heat treat End effectors and toolingGrippers, quick-change plates, vacuum manifolds, camera brackets.Light, stiff 7075 or 6061 structuresHard-anodized sliding jawsFast-iteration work, often one or two pieces Shafts and linear partsBall-screw ends, spline shafts, slender turned parts.Ground to 0.002 mm on diameterSwiss lathes for long, small-diameter workStraightness controlled after grinding, not assumed Robot links, frames and structural housings Links are the structural segments that carry one joint at each end and everything downstream in between. A machined link is rarely a simple box: it has a bearing bore at each end, a stiffening web pattern through the middle, and just enough wall to hold threads without adding grams the arm has to accelerate. We cut links from 6061-T6 and 7075-T651 billet and finish both bores in one setup, so the center distance and parallelism between them land in spec rather than depending on a re-fixture. Frames do the same job at the system level — a robot base, a gantry beam, a mobile platform chassis, or a weldment replaced by a one-piece machined plate. The requirement is flatness and squareness across large surfaces plus accurate dowel and bolt patterns, so the assembly repeats every time it is taken apart and rebuilt. On a 1300 mm base we hold flatness and position across the full envelope, which is why a machined frame beats a fabricated weldment whenever a robot must repeat to a few hundredths of a millimeter. Robotics vs. general CNC: where the tolerance bar moves General machining is usually judged on size — is the dimension in spec? Robotics work is judged on geometry — is the bore concentric to the face, is the face square to the bore, do the two ends of a link line up? A part can pass every dimensional check and still walk a robot's tool center point off target, because the errors that matter are relational, not absolute. That shifts the whole workflow. Robotics parts spend more time on the CMM measuring concentricity, runout, true position and perpendicularity than on simple length checks. Datum schemes matter as much as the tolerance values, and the shop must hold the part the way the robot will — fixtured off the same datums, not whatever face is convenient. Batch sizes are smaller and mix is higher, so the same operators, fixtures and CMM programs carry from a one-piece prototype to a production run. Materials for robotics machining Aluminum 7075 for stiff, light structures; stainless for wear surfaces; titanium where weight and strength both matter. Every bar is XRF-verified against its mill certificate. Material selection guide. Most robotics BOMs land on 6061-T6 for brackets, 7075-T651 where deflection is the constraint, 304 or 316 for washdown cells, and 17-4 PH for shafts and pins. Titanium Gr5 shows up on cobot arms and mobile platforms. We also run brass, copper, magnesium and engineering plastics, so a mixed assembly needs no second vendor. Aluminum 6061-T6 and 7075-T651 6061-T6 is the default robotics aluminum: it machines cleanly, anodizes evenly, welds when needed, and costs less. Use it for brackets, covers, frames and any part where stiffness comes from geometry rather than alloy. 7075-T651 is the step up — roughly 80% higher yield strength, so a link or gripper jaw can be thinner and lighter for the same stiffness. The trade is cost and corrosion resistance; 7075 is zinc-heavy and does not anodize as cosmetically even as 6061, which matters on exposed parts. Titanium Gr5 (Ti-6Al-4V) for weight-critical structures Titanium Gr5 earns its place on the end of an arm and on mobile platforms, where every gram is paid for in motor torque and battery. Its strength-to-weight ratio is roughly double that of aluminum at about 60% higher density, so a titanium link is lighter than an equivalent aluminum one at equal strength. It machines slower, needs rigid setups and low thermal drift, and it galls in sliding contact — but on weight-critical structures the math usually wins. Alloy data in the ASM Handbook. Steel for shafts, gears and housings Steel is the right answer when a part wears, transmits torque or needs a hard surface: 17-4 PH for shafts and pins that harden without heavy distortion, 4140 and 4340 for loaded members, and case-hardening grades for gears and splines where the core stays tough while the surface goes hard. Steel also delivers the stiffness-to-cost ratio aluminum cannot, on joints and reducer housings where deflection is the constraint and weight is not. Weight reduction and thin walls Weight is a robotics spec, not a preference. Mass on the moving end of an arm multiplies into torque at the base and inertia at every joint, so a gram saved at the wrist is worth more than a gram saved at the base. Two levers do most of the work: material choice and wall thickness. Thin walls are where weight leaves the part and where machinists earn their pay. In aluminum we routinely machine 1 mm walls in pocketed link bodies and 0.8 mm in lightly loaded regions, but a thin wall is a spring: it deflects under the cutter, chatters, and can distort after the part comes out of the fixture. The counters are high-speed paths with light engagement, stress-relieved stock, and sequenced roughing so the part stays stiff until the last pass. In titanium we keep walls a little thicker because the material moves more per unit of cutting force. The cheapest weight reduction is geometry: pocket the web, thin the flanges, rib instead of thickening, and stop adding material you do not need. A machined pocket replaces a solid block at the cost of cycle time, not tooling, and the stiffness you keep is the stiffness that matters. Tolerances and GD&T that matter 0.005 mm on milling and turning, 0.002 mm on grinding and wire EDM. Concentricity and runout for rotating parts; position and flatness for mating faces. Critical features are CMM-verified. GD&T explained. Tolerance stacks and true position A robot arm is a serial chain, which makes it an error amplifier. An angular error at one joint becomes a linear error at the tool center point, scaled by the length of everything downstream of it. That is why a single bearing seat matters: a 0.01 mm eccentricity at the elbow shows up multiplied at the wrist. We treat each part as one line in that stack-up, which is how we decide where a tight tolerance earns its cost and where it is just noise. True position is the workhorse control for robotics interfaces. A bolt circle located with a true position callout ties every hole back to a datum reference frame, so the housing and its mating part are controlled as a pair rather than hole by hole. We machine the datums first, locate the pattern from them, and verify the same way on the CMM with the drawing's modifiers — usually MMC on clearance holes and RFS where a press fit or dowel does the locating. Two rules keep stacks cheap. Control one thing from one datum; do not chain dimensions, because every link in the chain adds its own tolerance. And let the drawing say which features locate and which just float — a dowel pair locates, and the bolts only clamp. Precision, rigidity and where the error goes Tolerance on a robotics part is never an isolated number — it is one line in an error budget that ends at the tool center point. Three things dominate: the bearing fit, the squareness of the mounting face to the bore, and deflection under load. We machine the first two and fixture to protect them; the third is a DFM conversation. FeatureTypical spec we holdHow it is verified Bearing bore diameter0.005 mm, H6/H7 fitsCMM plus plug gauge at the machine Bore-to-face perpendicularity0.005 mm over 50 mmHexagon GLOBAL S CMM Ground shaft diameter0.002 mmCylindrical grinder, bench micrometer Bolt-pattern position±0.02 mm MMCCMM, first article and in-process Surface finish, sliding facesRa 0.4 µm or betterRoughness and contour tester Envelope: 1300 × 700 × 600 mm milled, Ø720 × 1280 mm turned — an arm casting or base plate need not be split into weldments. Finishing for robots Anodizing for wear and appearance, hard coat where surfaces slide, plating for corrosion. Matched to duty. Surface finishing guide. Anodizing Type II sulfuric anodizing is the default finish on aluminum robotics parts: a 5–25 µm oxide layer that takes color and seals the surface against corrosion. The layer grows roughly half inward and half outward, so it adds a few microns of thickness — enough to matter on a press fit or a tight thread. That is why we mask bearing bores and re-check fits after coating. Hard coat (Type III) Hard anodizing builds a 25–100 µm layer with a surface hardness around 60–70 HRC, on sliding surfaces such as gripper jaws, tool-changer plates and wear rails. It is thicker than decorative anodize, so we account for the buildup on mating features and diamond-lap or ream critical bores back to size after coating. Plating and passivation For steel parts we specify the finish to the duty: electroless nickel for corrosion and a uniform deposit in bores, zinc for cost, passivation on stainless. Coatings run through the same audited partners as heat treat, so a part comes back with the same lot traceability it left with. DFM for robotics machined parts Apply tolerances only where the stack-up demands; design for stiffness and machinability; standardize radii. A DFM note up front beats a scrap run. The complete DFM guide. Thin walls Give walls a thickness floor and tell us the real load, so we can thin where it is safe and stiffen where it is not. Avoid abrupt changes in wall thickness, and radius the root of a rib so the cutter does not dig a stress riser. Threads In aluminum, thread milling beats tapping for thin walls and hard-to-reach holes: it leaves a cleaner thread, cannot break a tap inside a finished part, and lets us control fit. Where a thread will be assembled repeatedly — gripper jaws, tool plates, end-effector mounts — specify a steel or stainless insert up front instead of wearing out the aluminum. Heat and distortion Heat treat changes a part, and the part comes back different. Gear and shaft steels move during carburizing or nitriding, so we leave grind stock and finish critical surfaces after. Aluminum releases stress when we cut deep pockets into bar, so we sequence roughing to let the part move, then finish. Say which surfaces are functional and which are just there, and the DFM note we send back stays short. Prototypes, pilot builds and volume Robotics programs iterate hard, then ramp fast. Our MOQ is one piece, so the shop that cuts your third design spin also builds the production run — same fixtures, same operators, same CMM program. StageTypical lead timeWhat you get Simple prototype, 1–10 pcsAbout 3 daysPart plus dimensional report on critical features Standard part, multi-opAbout 7 daysFirst-article inspection, written DFM feedback Complex or finished partAbout 30 days10–20 process steps, heat treat and plating included Lead time tracks process steps, not part size — anything with an outside operation sits at the long end, so tell us the finish early. RFQs get a reply in about 30 minutes during China business hours. How we quote a robotics part Send the STEP or IGES model and the 2D drawing with GD&T, the material and finish, and your volume and tolerances. We return a DFM note flagging the features that drive cost or risk failure, the achievable tolerance, and a lead time — and where we can, the specific change that cuts the part's cost. Tell us the iteration cadence so we can plan prototype spins. Request a quote. The supply chain behind the part We machine in Hengli, Dongguan — inside the Pearl River Delta cluster that supplies much of the world's robotics hardware. Geography is the real advantage: bar stock, anodizing, gear cutting, heat treat and PCB assembly all sit within a short drive, so a design change on Monday can be back on the CMM by Friday. In-house80+ CNC machines, 20+ inspection instruments, 6,800 m²Turning, milling, mill-turn, grinding, marking, deburring, cleaning100+ staff, 80%+ skilled technicians, 1,000,000+ parts a year Managed for youHeat treat, anodizing and plating through audited partnersDriver boards, sensors and cable assemblies on our EMS sideHousing plus populated board delivered as one assembly One purchase order, one quality system, one person to call. See how the EMS side works. Why China for robotics CNC machining The robotics supply chain concentrates in the Pearl River Delta for a reason that has little to do with the hourly rate: every process a robot part needs sits inside one cluster. Bar stock, extrusion, anodizing, gear cutting, heat treat, plating, wire EDM and PCB assembly are all a short drive apart, so a part moves between operations in hours rather than days, and a design change does not sit in a shipping queue between vendors. That density matters most during iteration, when you spin three versions of a joint housing in a month and every cycle between drawing and CMM report is dead time on your schedule. A local shop with in-house machining and a managed finishing network turns that cycle in days. The second reason is vertical integration. Nex-G machines the housing and assembles the driver board under one quality system, so the mechanical and electrical halves of an actuator arrive as one tested assembly with one lot number. The third is cost: skilled machining at Chinese rates, behind an IATF 16949 quality system, moves the build-versus-buy line on a lot of robotics hardware. You are not paying less for the same tolerance; you are paying less for the same tolerance plus the board, the finish and the inspection report. Nex-G capability at a glance Machining 80+ CNC machines in-house — Mazak, Brother, TSUGAMI and Sodick ±0.005 mm standard on milled and turned features, tighter on critical joint and bore features ±0.002 mm on ground and wire-EDM features Cpk ≥1.67 on key characteristics, ≥1.33 on general features Machined in Dongguan, Hengli since 2006 (Zhuohang) — 6,800 m², 100+ staff Quality and delivery ISO 9001, IATF 16949 and ISO 14001; IATF scope excludes design (clause 8.3) URS audit due 2027 — current and auditable MOQ of one piece; leads of about 3, 7 and 30 days by process steps Machined parts and assembled boards under one quality system This is the same shop that ran to the 1.67 bar we commit on key characteristics. Robotics parts get the same control plan and the same evidence pack. Traceability on machined parts PFMEA on the machining process, control plans on critical features, first-article and CMM inspection, and lot-level traceability — under an IATF-capable quality system. See the quality system. Traceability runs through MES and ERP, so a lot number resolves back to the mill cert, the machine and program, the process parameters, the operator and the inspection data. Robotics customers get the same evidence pack. How to choose a robotics CNC supplier in China Four questions worth asking before you place the order Who inspects the critical features, and on what? Ask for the CMM make and the report format, not just "we have a CMM." What is the Cpk commitment on key characteristics? A number without a control plan behind it is a marketing number. Is the prototype shop the production shop? Handing your program to a different plant at ramp is where tolerances quietly move. Is material verified or just certified? We XRF every incoming bar, because paperwork and metal occasionally disagree. Certificates are the floor, not the answer: ISO 9001:2015, IATF 16949:2016 and ISO 14001:2015, all current and auditable. What matters more is whether the shop can show you the control plan for your part. Supplier vetting checklist. Building a robot?Send the joint or housing drawings — we will confirm the tolerances and quote the metal and the board together.Request a quote Frequently asked questions What tolerance can you hold?±0.005 mm on milling and turning, ±0.002 mm on grinding and wire EDM. Can you machine and assemble with the driver board?Yes — one supplier for the actuator housing and the board. Which materials do you machine?Aluminum, stainless and titanium — all XRF-verified against mill certs. What drives robotics machining lead time?Prototype spins and material availability; our prototype line turns parts in days. Do you have a minimum order quantity?No. We quote and build from one piece, and the same shop scales it to volume. Can you machine harmonic drive and reducer components?Yes. Gear geometry is verified on a dedicated gear measuring center; carburizing and nitriding run through audited partners. What inspection documentation comes with the parts?First-article report and CMM data on critical features; on request the process flow chart, control plan, PFMEA and SPC study. Related articlesRobotics EMS: Drivers, Sensors and ControlGD&T Explained5-Axis CNC Machining