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Most servo press maintenance programs cover the obvious items. Here are the ones that get skipped.
Mechanical (Often Missed):
- Eccentric shaft bearing preload: Check annually with a dial indicator. Preload loss causes slide position drift that looks like a control problem.
- Connecting rod bearing clearance: Measure with Plastigage. Clearance above 0.08mm on a 200-ton press indicates bearing replacement needed.
- Counterbalance cylinder rod seal: Pressure test at 110% of operating pressure.
- Brake/clutch wear indicator: Check it. Do not wait for stopping time to increase.
Electrical (Often Missed):
- Drive cooling fan: Check airflow with a piece of tissue paper. Fans degrade gradually.
- DC bus capacitor ESR: Measure with an LCR meter. High ESR causes DC bus ripple that triggers false alarms.
- Encoder cable insulation resistance: Test with a 500V megger. Values below 1 megaohm indicate insulation breakdown.
- Safety relay contact resistance: Contacts above 0.5 ohm should be replaced.