What is a servo press?

A servo press uses servo motors for precise force and position control during forming operations.

How do I calculate servo press tonnage?

Use our free tonnage calculator at servopress.club/tonnage-calculator.html

Encoder battery - when to replace? What if it dies mid-run?

ryan_ops

The encoder battery warning light came on our Yaskawa drive. Press is still running fine but I'm nervous. How urgent is this?

Can I change the battery with the press powered on or do I need to shut down? If I shut down, will I lose the home position? The manual is unclear on this — it says "replace battery with power on" but our safety guy says we can't open the drive cabinet while energized.

Also, how often should I be replacing these proactively? This one lasted about 3 years. Is that normal?

anna_plc

Replace it. Now. A dead encoder battery means the absolute position is lost on the next power cycle. The press won't know where the slide is and you'll need to re-home —which on some presses requires a service technician. The battery costs $15. The service call costs $2,000+. Replace every 2 years regardless of voltage reading.

raj_pm

We learned this the hard way. Battery died on a Friday night, press lost home position. Couldn't run until Monday when the Yaskawa tech came out. Lost an entire weekend of production —about $45,000 in our case. Now we replace every battery in January, no exceptions. It's on the annual PM schedule in red.

carlos_mx

One thing people miss ??check the battery voltage under load, not just open circuit. We had batteries showing 3.4V on a multimeter but dropping to 2.1V when the encoder actually drew current. The encoder's low-voltage alarm never triggered because it only checks periodically.

Also, if you're running multiple presses, standardize on one battery type and keep spares in the maintenance crib. We use the Mitsubishi ER6V for everything ??Yaskawa, Fanuc, Mitsubishi encoders all take the same 3.6V lithium. Buy a box of 10, label them with install date using a paint pen right on the battery.

For the "what happens if it dies" question ??on Fanuc drives you get ALM 300 (absolute position lost) and the press won't move until you do a return-to-reference. On our older press that takes 45 minutes because you have to jog to a known mechanical position first. Newer Yaskawa drives with the multi-turn encoder can sometimes recover automatically if the battery was only dead briefly.

mchen_servo

One thing I'll add ? the "replace with power on" instruction is correct and it's the whole point of absolute encoders. The encoder retains position data in volatile memory while powered. You swap the battery, the encoder never loses power from the drive's 5V supply, and you're done. Takes 30 seconds.

The safety concern is real though. What we do: lock out the main motor circuit but leave the drive control power on. That way the cabinet is safe to open (no high voltage on the bus) but the encoder still has its 5V keep-alive. Check your drive manual for the specific procedure ? on Yaskawa Sigma series there's a dedicated battery connector accessible without exposing the power terminals.

On replacement interval: 2 years is aggressive but safe. I've seen Yaskawa ER6V batteries last 4-5 years in climate-controlled plants, but in shops with wide temperature swings (hot summers, cold winters) they degrade faster. The 3.4V-under-load issue carlos_mx mentioned is real ? we had the same thing on a Fanuc setup. Now we check voltage under load during every quarterly PM. If it's below 3.0V loaded, it gets replaced regardless of age.

Pro tip: label every battery with the install date using a paint pen. Sounds basic but when you have 12 presses and batteries scattered across different PM cycles, that label saves you from guessing.