Precision couplings

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In one of my research meetings with my advisor, Prof. David Trumper, we were discussing about motors and motor couplings. He mentioned about how the metal bellows for precision couplings are manufactured using electroforming process.

I did some more search on the topic, and found that they are very useful torque transmission elements which are very rigid torsionally and accommodate misalignments in other 5 degrees of freedom – parallel misalignment (2), axial (1), angular misalignment (2). How the bellows are manufactured is an interesting engineering problem. There is a very nice presentation about flexible vs rigid couplings by Design World here.

Comparison of Servo couplings

Comparison of Servo Couplings – Source

There are many ways of manufacturing bellows:

  • Forming
  • Welding
  • Hydroforming
  • Electroforming

Electroforming is a very interesting process where the inverse profile is turned on an aluminum mandrel and then steel is deposited on the mandrel with a defined layer thickness using electrodeposition process. The aluminum mandrel is then dissolved by keeping it in a caustic solution which dissolves the aluminum mandrel leaving the deposited steel bellows. Very fine tolerances and sharp features can hence be obtained.

A very good description of the process is given on the Servometer website.


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