What the E0021 alarm means

The actual axis position lagged the commanded position beyond the allowed window; the servo stops the axis. This is one of the faults our repair team handles on Nachi AW / FD series systems — the cause is usually identifiable within the first on-site inspection.

Most common causes

  • Mechanical interference or collision
  • Brake not fully releasing
  • Worn reducer or gearing
  • Payload heavier than configured
  • Drive tuning degraded
Field note: the first item on this list is what we find most often on real machines. Check it before you go deeper.

Step-by-step field fix

  1. Remove any interference
  2. Check the axis brake release
  3. Inspect the reducer and drive train
  4. Verify payload and inertia settings
  5. Reduce speed on the failing move; if it persists, check drive tuning and encoder
Safety first: never bypass safety circuits or force contactors closed. If the alarm involves E-stop chains, brakes or drive power, and you are not a trained robot technician, contact a professional — wrong moves here can cost you a robot or an injury.

Still stuck? Get an engineer on the phone — right now

Tell us the alarm code, the robot model and what was happening when the alarm came up. Our engineers run these diagnostics every day, and remote diagnosis by phone or video call is free.

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Hotline: +86-20-39029800 · WhatsApp: +86-188-1886-2860

Related Motion & Path alarms

E0012 — Robot Cannot Reach Recorded Point E0022 — Deviation Error E0025 — Position Jump (Jump Position)
Other brands: we also keep field-fix libraries for Omron · ESTUN · INOVANCE and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the Nachi E0021 alarm mean?

The actual axis position lagged the commanded position beyond the allowed window; the servo stops the axis. In field practice it belongs to the motion & path family of faults.

QCan I clear a Nachi E0021 alarm myself?

Sometimes. Work through the step-by-step checks on this page — the first listed cause is what we find most often in the field. If the alarm returns after two attempts, or the fault involves power, brakes or safety circuits, stop and call a qualified robot service engineer.

QHow fast can a Henghuan engineer help?

On-site response in the Pearl River Delta within 30 minutes to 3 hours, across mainland China in 1-3 business days, and worldwide within 2-5 business days. Remote diagnosis by phone/WhatsApp/video is available immediately.

Written by the Henghuan Robotics repair team from field service experience. Alarm descriptions are our own summary for troubleshooting reference and may vary by controller and software version — when in doubt, check your Nachi documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by Nachi.