Maintenance

Calibrate each machine in compliance with an ISO standard, and keep those data as reference. Then periodically recalibrate the machines noting changes in these data until each one fails. An analysis of the data after each failure usually show a marker that portends the failure which you can then use in the future as a diagnostic indicator. This should work because I was once in this sort of business.

I hope that this is helpful

A good way is to follow up the recommendations from operation manual for each equipment.