01
Bore and face come out out of square
A bearing bore that drifts 0.03 mm off-axis after a second setup makes the arm oscillate at every repeat point. Repositioning the part means re-zeroing, and the stack-up shows up as backlash in the field.
Robotics & Automation
5-Axis CNC Machining of High Quality Robotic Arm Joints
We machine joint housings, bearing bores and couplings for high quality robotic arm builds. One setup, one datum, tight bore-to-face geometry. First-article and final inspection reports ship with the parts.
±0.005 mm toleranceØ400 mm rotary table16 simultaneous 5-axis centersFrom one prototype to 10,000+ partsRa 0.8–1.6 μm as standard
16Simultaneous 5-axis centers
±0.005 mmAchievable tolerance
4,000 mmMaximum part size
15 yearsIn metal machining
Where joints go wrong
Joint problems that start at the machine, not the assembly line
02
Wall thickness varies around the housing
Thin walls deflect under clamp pressure. If the housing is machined in three ops, the wall on one side scallops. The joint still fits, but stiffness drops and the arm loses repeatability under load.
03
Assembly eats the tolerance budget
Bore, face, bolt pattern and dowel holes all carry their own tolerance. Machine them in separate setups and the errors add up. The arm passes bench test, then fails cycle testing after a few thousand moves.
04
Surface finish drives seal life
A bore left at Ra 3.2 μm wears the seal lip faster than one at Ra 0.8 μm. The leak shows up months later, and by then the whole joint has to come off the arm.
How we hold the geometry
One setup per joint, one datum through every feature
The bore, the face and the bolt pattern come off the same setup so the stack-up stays inside ±0.005 mm.
Setup strategy
Simultaneous 5-axis keeps the bore and face in one operation
A robotic arm joint is a stack of features that only work together: bearing bore, mounting face, bolt circle, dowel holes, seal groove. Cut them in three operations and each re-clamp adds error. On our 16 simultaneous 5-axis machining centers, the part stays on one fixture from roughing to finishing. The rotary table indexes to the next face instead of the operator moving the part.
That matters most on parts with an angled axis. A joint housing at 45° to the mounting face is awkward on a 3-axis mill and needs a custom angle plate. On a 5-axis center the table tilts to the feature and the tool reaches it in one pass. We hold ±0.005 mm on bore position and perpendicularity across the joint body.
- 1Rotary tableØ400 mm trunnion, indexed for each face
- 2One datumBore and face measured from the same origin
- 3Angled featuresMachined without a custom angle fixture
Thin walls and bores
Clamping and tool path control wall deflection
Joint housings are usually thin-walled aluminum or titanium. Clamp too hard and the wall springs back after unclamping, so the bore measures round on the CMM and out-of-round once it is free. We rough with light radial engagement, leave 0.3 mm for finishing, and let the part cool before the final pass.
Bore finishing is a separate step with its own parameters. A reamer or a boring head with a fine feed, depending on the diameter and the surface finish called out on the drawing. Standard output is Ra 0.8–1.6 μm; where a seal runs, we finish to Ra 0.2–0.8 μm.
- 1RoughingLight radial engagement, controlled heat input
- 2Finishing0.3 mm stock, part cooled before final pass
- 3Bore finishRa 0.2–0.8 μm where seals run
Selection guide
Which machining route fits your joint
Pick by feature count, wall thickness and bore tolerance.
| Joint type | Best route | Why |
|---|---|---|
| Compact wrist joint, Ø80–150 mm | 5-axis, one setup | Bore and angled face in one datum |
| Thin-wall aluminum housing | 5-axis + stress-relief | Keeps wall round after unclamping |
| Bearing bore under Ø50 mm | Mill-turn + fine boring | Roundness held to half the tolerance |
| Large base joint, over 1,000 mm | 5-axis on 4,000 mm travel | One part, no splice or weld |
| Prototype bracket, 1–20 pcs | 3-axis + 5-axis finish | Lower setup cost at low volume |
| Titanium joint, high load | 5-axis, slow speeds | Heat kept out of the thin sections |
What we machine
Parts we run for robot arm builders
01
Joint housings
Bearing bores, mounting faces and bolt circles cut in one setup on 5-axis centers.
02
Couplings and flanges
Spline and keyway fits, pilot diameters, dowel holes held to drawing.
03
Bearing housings
Bore roundness and perpendicularity to the mounting face.
04
Gearbox and actuator bodies
Pocketed bodies with thin walls, finished without distortion.
05
End effectors and brackets
Low-volume runs from one prototype upward, no tooling charge.
06
Rapid prototypes
Machined prototypes in 3–5 days to check fit before tooling.
Capability range
Machines, sizes and materials
| Item | Range | Notes |
|---|---|---|
| 5-axis centers | 16 simultaneous | Ø400 mm rotary table |
| Maximum part size | 4,000 mm | 4,000 × 400 × 150 mm travel |
| Tolerance | ±0.005 mm | ±0.0002 in |
| Surface finish | Ra 0.2–3.2 μm | Ra 0.8–1.6 μm as standard |
| Aluminum | 6061, 7075, 2024, 6082 | Anodizing available |
| Stainless | 303, 304, 316L, 17-4PH | Passivation on request |
| Titanium | TA2, TC4 (Ti-6Al-4V) | Slow speeds, controlled heat |
| Order quantity | 1 to 10,000+ | No minimum order quantity |
Why GreatLight
What you get on the shop floor
±0.005
Tolerance held on the part
Bore position and perpendicularity checked against the drawing, not against a sample.
100%
Inspection before shipment
Raw material check, in-process monitoring and final inspection on every batch.
12 h
Quote with DFM notes
We return a quotation and a free DFM analysis within 12 hours of receiving files.
24 h
Production start
Once the drawing is signed off, machining can start within 24 hours.
3–5 d
Parts ship
Standard parts ship in 3–5 days after production start.
ISO
Certified processes
ISO 9001:2015, IATF 16949:2016, ISO 13485:2016, ISO 27001:2022.
7,600 m²Manufacturing space
127High-precision CNC machines
150Technicians on staff
3Wholly-owned plants
Industry requirements
What these industries ask for, and what we deliver
Robotics and automation
Joint housings and couplings for arms with repeatability requirements in the tens of microns.
- ±0.005 mm
- Ra 0.8–1.6 μm
- 100% inspection
Aerospace and defense
Actuator bodies and brackets where traceability and material certificates are part of the order.
- IATF 16949
- Material certs
- First-article report
Industrial machinery
Heavy base joints up to 4,000 mm machined in one piece, no splice or weld.
- 4,000 mm travel
- One setup
- 3–5 day shipping
FAQs
Questions engineers ask before sending drawings
How do I know my joint needs 5-axis and not 3-axis?
Count the faces the part has to be clamped on. If the bearing bore, the mounting face and the bolt pattern sit on three different planes, a 3-axis mill needs three setups and each re-clamp adds error.
If the joint has an angled axis or a compound angle, 5-axis is usually cheaper than building a custom fixture, even at low volume.
What tolerance can you actually hold on a thin-wall housing?
±0.005 mm is our standard capability, and we hold it on bore position and perpendicularity. On a thin-wall part, the limiting factor is often the wall itself, not the machine.
When the wall is under 3 mm, we rough, let the part cool, then finish with light cuts. If the drawing tolerance is tighter than the wall can hold, we tell you before machining rather than after.
Which materials do you recommend for a joint housing?
6061-T6 and 7075 cover most aluminum joint housings. 7075 gives higher strength where the wall is thin. 6082 is common in Europe and machines well.
For higher load or corrosion resistance, 17-4PH stainless and TC4 titanium are both in stock. Titanium needs slower speeds and more attention to heat in thin sections.
Can you machine a joint from one piece instead of a weldment?
Yes, up to 4,000 mm. The large 5-axis centers have 4,000 × 400 × 150 mm travel, so a base joint that would otherwise be welded can be cut from solid.
One piece removes the weld inspection step and the distortion that comes with it. It also means the bore and the mounting face share a datum.
What do you need to quote a robotic arm joint?
A 3D model and a 2D drawing with tolerances, material and finish. If the drawing is not finished, send the model and tell us the function of each critical feature.
We return a quotation and free DFM analysis within 12 hours.
How do you handle surface finish on a seal bore?
Standard output is Ra 0.8–1.6 μm. Where a seal or O-ring runs, we finish to Ra 0.2–0.8 μm and check the bore with a profilometer.
If the drawing does not specify finish, tell us where the seal sits and we will set the parameter accordingly.
Can you keep the drawings confidential?
Uploads are secure and confidential. An NDA is available on request before you send files.
We are certified to ISO 27001:2022 for information security management.
Do you have a minimum order quantity?
No minimum order quantity. We run from one prototype to 10,000+ part runs on the same process.
Prototypes ship in 3–5 days so you can check fit before committing to a production run.
Send your robotic arm joint drawing
We return a quotation and free DFM analysis within 12 hours, inspect every part before shipment, and run from one piece upward.
12-hour quote100% inspectionNo minimum order quantityNDA on request
