CONTROL ARM

Challenge

Assembly of the isolator bushings into the upper and lower control arms used in the automobile and truck industry.

How do you make an assembly to a tolerance more than six times tighter than the stack up of the tolerances of the parts to be assembled? The specification calls for a total tolerance of ±0.6mm on the bushing position. This tolerance must be held despite the fact that the bushings themselves have a ±2.0mm tolerance (“and they fall pretty randomly within that range”), and the stamped control arms they are installed in exhibit considerable variation.

Solution

With closed loop feedback from external position transducers built into the fixturing/tooling, the Promess Electro-Mechanical Assembly Press (EMAP) measures the assembly as it is being made, compensating for variations in the individual parts, making as assembly within tolerance every time. Typically, the bushing position is being held to better than ±0.1mm.

Additional benefits the customer received by using the Promess EMAP were as follows:

• The Promess system functions as both a press and a gage, simultaneously. It measures while it makes the assembly and stores the information for later analysis.
• The Promess system also has the added feature of full force versus position signature monitoring to ensure the press fit of each bushing is up to specification. This information is also stored for later analysis.

Position transducers, built into the machine fixture, measure critical dimension information and give feedback to the Promess Electro-Mechanical Assembly Press (EMAP) during the assembly operation.