L-Shaped CNC Right Arm Rod, Internal Spline to Bolted Flange, Hollow Body

About This Part

This arm rod is the link between two rotating joints in automated equipment. One end carries an internal spline ring that mates with a motor or gearbox shaft; the opposite end is a bolted flange that secures the wrist or end effector. Between them runs a hollow cylindrical body bent into an L, and that hollow section is the design decision: it removes mass from a moving axis without giving up torsional stiffness, which shows up directly in acceleration and energy use.

The load path is mixed. The spline transmits torque while allowing radial alignment at assembly, the flange carries bending and the bolted connection, and the body sees both. That is why the two end interfaces are machined in a single setup on a five axis center: the spline bore and the flange bolt pattern come off the machine with their mutual position set by the machine axes rather than by a second clamping, so concentricity between the ends does not accumulate setup error. The finished rod rotates true, which is what a moving axis needs and what vibration complaints are usually about.

The internal spline is cut with dedicated tooling and verified with go and no-go gauges rather than judged by eye, and the flange hole positions are checked on the CMM together with spline dimensions and overall length. Body surfaces are polished; critical mating surfaces are held to Ra 0.8 or better because a polished interface on spline and bearing seats wears more slowly and runs quieter than a machined finish left as cut.

Material follows load and environment. Aluminum 7075-T6 carries the strength to weight ratio most automation arms want; stainless steel is available where corrosion or washdown calls for it. Bar stock arrives against mill certificates, and a second qualified source is held for common bar diameters so a material shortage does not stop a running batch. Every shipment leaves with a packing list, material certificate and CMM inspection report.