1.Typical Structures and Material Selection
Common structures of robotic arm joint components include: flanges, bearing mounting holes, threaded interfaces, oil passage channels, etc. The primary materials used are aluminum alloys (6061-T6, 7075-T6) and alloy steels (40Cr, 42CrMo), with titanium alloys selected for some high-end applications.
Aluminum alloy: lightweight, easy to machine, suitable for high-speed processing, but prone to deformation in thin-walled sections.
Alloy steel: High strength and wear resistance, suitable for heavy-duty joints, but tool wear is significant. TiAlN-coated tools should be selected with high-pressure internal cooling.
2, Difficulties and Countermeasures in Processing
1. Thin wall deformation control
The wall thickness of the joint shell is often less than 3mm, which can cause vibration and tool misalignment during processing. Countermeasure:
Separate rough and fine processing: reserve 0.5-1mm margin for rough processing, and perform fine processing after 24 hours of natural aging.
Auxiliary support: Fill the cavity with low melting point alloy or gypsum to enhance rigidity.
Symmetric machining: alternate milling on both sides to balance cutting stress.
2. High coaxiality guarantee
The coaxiality requirement for bearing holes is usually ≤ 0.01mm. Recommended process:
One time clamping: Complete the machining of all holes in one clamping on a five axis machine tool to avoid secondary positioning errors.
Boring instead of milling: For deep holes, using precision boring cutters is easier to ensure cylindricity than milling cutters.
In machine measurement: Immediately use a measuring head to detect after precision machining, and compensate for machining if there is a deviation.
3. Threads and sealing grooves
There are often grease channels and sealing ring grooves inside the joints. Note:
Thread: For small threads below M3, it is recommended to use a tap for tapping, while for large threads, a thread milling cutter can be used to reduce the risk of chipping.
Sealing groove: The roughness of the groove bottom should reach Ra1.6 μ m or above, otherwise the sealing ring is prone to wear. Special groove milling cutters can be used for one-time molding.
3, Surface treatment and precision maintenance
Aluminum alloy joint parts are usually subjected to hard anodizing with a film thickness of 30-50 μ m and a hardness of ≥ HV400. Before oxidation, it is necessary to reserve dimensional allowance, and after oxidation, use a diamond reamer to correct the threads and bearing holes to ensure the final fitting accuracy.
Steel parts can be plated with electroless nickel or hard chromium, with a uniform coating that does not affect thread fit. For high-speed rotating shaft components, dynamic balance testing is required to control the unbalance within G2.5 level.
4, Key points of inspection and assembly
Three coordinate measurement: focus on detecting the positional accuracy and cylindricity of the bearing hole, as well as the perpendicularity of the flange end to the reference axis.
Assembly trial cutting: Assemble the processed joint parts with harmonic reducers and motors to check for interference and smooth rotation.
Cleanliness: Residual chips or burrs are strictly prohibited inside the joint, and high-pressure air guns and ultrasonic cleaning are required.
The processing of robotic arm joint parts is a systematic engineering that requires comprehensive control from design, materials, processes to inspection. Our company has five axis machining centers, three coordinate measuring instruments, and surface treatment production lines, providing one-stop services from prototype to mass production. Welcome to send drawings for consultation.
