Hollowing a joint does not fail at the bore — it fails at the thin wall between two stiff features. If the wall is uniform, the section that carries the bending moment is the same as the section that carries nothing, and the joint feels light but deflects under load.

We start from the load case: reducer torque, wrist payload, cable window position. The wall map is then built with 2.2 mm where the shell only closes the geometry, 4.0-6.0 mm around the bearing seats and the mounting bosses, and ribs that run from the bore boss straight to the bolt pattern instead of stopping at the cavity edge. The result is a hollow joint whose stiffness comes from the rib direction rather than from extra material.

• Wall map, not one number — every zone has a specified thickness, and the drawing shows it.
• Ribs on the load path — X-lattice between bore boss and bolt circle, R3 root fillets.
• Ultrasonic verification — wall thickness scanned on 100% of parts, not sampled.
• Film thickness compensation — bores pre-sized for the 15-20 µm anodizing layer.

1. Load-path and wall review — torque, payload and cable routing confirmed; thin-wall zones and rib directions agreed on the drawing before material is cut.
2. Billet and material verification — 6061-T6 plate or billet received by heat number, ultrasonic check for internal defects, 3.1 material certificate.
3. Rough machining — all six faces and the cavity opened with 0.8 mm allowance, material removed symmetrically to balance stress.
4. First stress relief — low-temperature stress relief so the 2.2 mm walls do not move after finishing.
5. Semi-finish and rib forming — ribs, bosses and cavity semi-finished with a constant-engagement toolpath; wall thickness measured in process.
6. Second stress relief — a second cycle after the cavity is opened, which is where thin-wall joints normally warp.
7. 5-axis finishing — mounting face, bore bosses and bolt pattern finished in one clamping from a single datum.
8. Bore finishing — both H7 bores finish bored and reamed to 0.01 mm coaxiality, with roundness checked on the machine.
9. Surface and verification — masked anodizing 15-20 µm, bores re-checked, ultrasonic wall scan plus CMM report shipped with the part.

• Wall map — 1.8 mm to 8.0 mm, zone by zone, agreed before machining.
• Ribs — X-lattice, straight, or dropped for a fully open cavity.
• Interface — bore sizes, bolt pattern (M3-M10), dowel pin positions, cable window shape.
• Material grade — 6061-T6 for cost, 7075-T6 for stiffness, 6082 for weldability.
• Sampling — 1 piece to validate stiffness, then the same program runs to volume without a line change.

Hollow joints are usually the part that defines the arm's kinematics, so the drawing is the product. We treat it that way.

• NDA before drawings — mutual NDA and non-circumvention signed before the first file is transferred.
• Isolated machining area — access-controlled cell, dedicated machines and staff, no phones or photography inside.
• Codified routing — traveler cards and labels carry internal codes instead of your part number and project name.
• Data control — programs and models on an access-controlled server, isolated per project, destroyed at project end with a written record.
• No display — drawings, part photos and customer logos never enter sample cabinets, catalogs, the website or social media.

Dongguan Changxinda Precision Technology Co., Ltd. — founded in 2008, 90-102 staff, ISO 9001:2015 certified, annual sales USD 10-20 million, export share 50-60%, serving Europe, North America, Japan and Southeast Asia.

Machining, stress relief, surface treatment and CMM inspection all run on one site, so the tolerance chain closes inside the factory instead of being reopened on the customer's line. Capacity is about 12,000 aluminum parts per month, with 5-axis and 4-axis machining centers, turn-mill centers, CNC lathes, surface grinders and wire EDM, supported by CMM, 2.5D vision measuring machines, roughness testers and ultrasonic thickness gauges.

1. 01 Consumer Electronics — Phone, tablet and laptop housings · heat sinks · camera brackets · VR/AR headset structural parts · smart wearable housings
2. 02 Automation & Industrial Equipment — Automation jigs · fixtures · module frames · transmission sliders · motor mounts · sensor housings · conveyor line components
3. 03 Semiconductor & Vacuum Equipment — Vacuum chambers · vacuum fittings · semiconductor equipment precision bases · thermal insulation parts · inspection fixtures
4. 04 Medical Devices — Surgical instrument bases · medical device housings · endoscope components · aesthetic equipment structural parts (medical grade aluminum / stainless steel)
5. 05 Automotive — EV motor housings · battery end plates · sensor brackets · lamp structural parts · aftermarket parts · hydraulic valve blocks
6. 06 Aerospace & UAV — Aircraft structural parts · UAV frames · landing gear components · avionics instrument housings (lightweight precision parts)
7. 07 Optics & Photonics — Optical lens barrels · lens mounts · light source heat sinks · camera module brackets · inspection optical stages
8. 08 Telecommunications — 5G heat sink cavities · filter housings · signal adapter brackets · telecom equipment enclosures
9. 09 Robotics — Robotic arm joint parts · robot bases · reducer housings · AGV chassis structural parts
10. 10 Instruments & Meters — Inspection equipment housings · precision gauge bases · flow meter parts · laboratory equipment components

Two shifts, 07:30-22:00, six days a week, with weekend shifts added in peak season. Machine capacity is locked weekly for volume programs, so a rush order never displaces a batch schedule.

• Sampling — 7-10 days, validated on your bench before the batch is released.
• Batch — 15-20 days from deposit and drawing approval.
• Buffer stock — semi-finished stock kept for repeat models, cutting repeat lead time by about 30%.
• Shipping — DHL/FedEx/UPS samples in 3-5 days; air or sea for volume; EXW Dongguan, FOB Shenzhen or CIF.
• Documents — FAI report, 3.1 material certificate, dimensional report and packing list with every shipment.

Send STEP / IGES / DWG / PDF and receive DFM feedback plus a formal quotation within 24 hours.

Dongguan Changxinda Precision Technology Co., Ltd. · ISO 9001:2015 · Dongguan, Guangdong, China