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Conjugate Cam minimize Backlash - Case Erector

saurabhjain
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Case Erector Mechanism opens case as it loads conveyor

This mechanism is used to erect pre-glued cases from a magazine and place on an indexing conveyor.  The mechanism forces the case to open as it is pulled from the magazine.

Conjugate Cams eliminate backlash and reduce overall cam stress

If a disk cam drives the mechanism, then unless gravity is sufficient to hold the roller on the cam, a spring or air cylinder is needed to keep the roller in contact.

This will effectively double the contact stress on the cam and increase the required drive torque and induce drive speed fluctuations.

Alternatively a groove cam could be used.  This will prevent a possibility of the cam roller bouncing, however, there will inevitably be backlash which will be traversed during acceleration reversals.  When backlash is traversed, the roller looses contact with one flank and smashes into the other flank. This can cause vibrations and lead to premature failure and reduced precision in the tool motion.

Conjugate cams, although more expensive, overcome most of these problems.  Two separate cams with separate followers that are preloaded onto the cam flank to eliminate backlash.  Springs are not required reducing the contact stress on bearing forces.

The cams should ideally be machined in the same setup so that both profiles are truly conjugate.

 

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Example model simulations for Packaging Machine Design.

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