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

Yaskawa Sigma-7 A.810/A.820 alarm - anyone seen this?

tom_diedesign

Our Yaskawa Sigma-7 is throwing A.810 and A.820 alarms intermittently. Sometimes A.810, sometimes A.820, no pattern I can see. Press runs fine for hours then suddenly faults out.

Encoder cable was replaced 6 months ago. Connections look tight. Drive firmware is current. The alarm log shows they happen at random points in the stroke — not always at the same position.

Anyone dealt with these? The Yaskawa manual just says "encoder communication error" which isn't very helpful. Is this a cable issue, encoder issue, or drive issue?

anna_plc

A.810 is almost always the battery. Replace it and the alarm clears after a power cycle. But A.820 is more serious —it means the encoder's internal checksum failed, which usually means the encoder itself is failing. Don't just clear it and keep running. Replace the encoder before it fails completely mid-stroke.

raj_pm

We keep spare encoder batteries in every press cabinet and changed our replacement schedule from 3 years to 2 years after getting burned twice. The batteries cost $15 each. The downtime from a dead battery on our line runs about $5,000 per incident including the service call and lost production. We label each battery with the install date using a permanent marker so anyone can see at a glance how old it is.

mchen_servo

anna_plc is right about A.820 — don't ignore that one. We had an encoder fail mid-cycle on a 200-ton press because someone kept clearing A.820 for a week straight. The ram drifted about 3mm past BDC before the overtravel limit caught it. Bent the lower die shoe. $12k lesson.

On the battery side, we switched to lithium batteries (ER6V, not the standard alkaline) and get 4+ years out of them now. The Yaskawa spec says 2 years for the standard battery but in my experience they start getting flaky around 18 months, especially if the press sits powered off over long weekends.

One thing nobody mentioned: if you get A.810 after a power outage, check your UPS. The encoder needs continuous power to maintain absolute position. We added a small UPS just for the servo drives on each press — about $200 per press. Haven't had an A.810 since.

greg_engineer

Had the exact same A.810/A.820 combo on a Sigma-7 running a 200-ton Komatsu last year. The A.810 was the battery like everyone says, but the A.820 turned out to be heat-related -- the encoder was mounted right next to a hydraulic line and the internal temp was cooking it. Moved the hydraulic line 6 inches and added a small heat shield, no more A.820.

One thing I would add -- if you are getting A.820 intermittently, check the encoder connector pins with a loupe. I have seen corroded pins cause the same symptom -- checksum fails when the connection resistance drifts. Clean the pins with DeoxIT and see if it clears up before you order a new encoder.