0050a// Parallelism Re-alignment at Assembly Level

In this post, we will discuss about how parts attributes affect assembly alignment and the possibility of re-alignment the parts to meet the functional requirement.

Picture above shown a harmonic driver with two adapters for actuation. In order to make sure the movement trajectory of mating surface within a plane with acceptable tolerance, two adapters mating surfaces should parallel to each others.

Therefore, the ideal case of mating surfaces should look like the picture shown below:

However, assembly process may introduce variables into this orientation control when the part's surface is not perfect.

When design change is infeasible, dismantle the part and re-assemble become easiest solution. For complex design with tight orientation requirement, CMM (Coordinate Measurement Machine) measurement become important tool to verify workmanship for assembly process.

For demonstration purpose, we using harmonic drive above for 2D realignment procedure.

First, using CMM measurement machine to get the coordinate/orientation information from the assembly (mathematical detail will discuss in future).

If the measurement result shown, the parts oriented as scenario 1, the parallelism can recover by loosen the bolt at right side and tighten the bolt at left side.

If the measurement result shown, the parts oriented as scenario 2, the parallelism can recover by loosen the bolt at left side and tighten the bolt at right side.

Then, put the assembly for measurement again to verify its parallelism. If the parallelism still not meet your expectation, repeat the alignment process which shown above until its meet your expectation.

All in all, dismantle and reassemble assembly change lot of its geometrical attributes (don't even need to change any of the parts' geometry). Therefore, understand and verify for the variables in the assembly process is very important,

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