What the C57A1 alarm means

A joint brake did not release when commanded; the joint does not move and the controller stops the motion. We are very familiar with this alarm on Universal Robots CB3 / e-Series (UR5/UR10/UR16/UR20) systems — usually the first on-site inspection is enough to confirm the cause.

Most common causes

  • Brake solenoid or brake coil failed
  • 24 V brake supply wiring broken
  • Mechanically stuck brake from corrosion or contamination
  • Wrong brake release signal routing after maintenance
Field note: Our ticket data shows the first cause is by far the most common — start there to avoid dead ends.

Step-by-step field fix

  1. Listen/feel for the brake click when enabling servos on the affected joint
  2. Measure the 24 V at the brake connector during release command
  3. Check brake wiring continuity
  4. Try the manual brake-release procedure (support the arm first)
  5. Replace the brake assembly or motor if the brake is mechanically dead
Safety first: For Universal Robots c57a1, a failed brake means a vertical axis can drop - a person underneath is a severe-accident case, so we require mechanical support first and no repeated power-on trials. On site you may not carry out the first step yourself: Listen/feel for the brake click when enabling servos on the affected joint. Beyond that it is a dropping vertical axis work - leave it to a professional. On Universal Robots c57a1: the only safe self-action is stopping the axis, holding power off and supporting the arm mechanically; gap measurement, torque testing and brake replacement are engineer work.

How we diagnose brake faults on site

Universal Robots c57a1 belongs to the brake family. On Universal Robots c57a1 the failing stage is joint-integrated drives (motor, drive and harmonic reducer in one joint) on the UR control box (CB3 / e-Series) - the electromagnetic brake: brake supply, coil, friction lining and mechanical gap - directly tied to whether an axis can drop. We start reading Universal Robots c57a1 at the PolyScope event and alarm pages; codes carry a C prefix (C15x, C5x, C7x).

The chain involved in Universal Robots c57a1 runs: brake control signal -> brake supply circuit -> electromagnetic coil -> friction lining and disc -> axis holding.

Universal Robots c57a1 differs from every other family in one way: Brake alarms differ from every other family in one way: they carry real injury risk. A failed brake means a vertical axis can drop, and a person underneath is a severe-accident case. So our first action is not diagnosis - it is having the customer stop that axis, hold power off and support the arm mechanically if needed; absolutely no repeated power-on trials. Only once that is safe do we measure brake supply voltage and coil resistance and inspect lining wear. These alarms always jump the dispatch queue.

Field notes on this page cover Universal Robots c57a1 (Brake Release Failure); written by the Henghuan repair team, updated 2026-10-01.

Real Field Case

Machine: UR UR10e (2020)

Symptom: A UR10e raised C57A1 (brake release failed) and one joint would not move.

What we did: We measured the brake supply and coil on that joint, found the brake sticking, serviced it and tested release.

Result: The brake released normally again and all joints moved; about 3 hours.

Can't find the cause? One call can pinpoint it

Tell us the alarm code, the model and what the machine was doing when the alarm appeared. Universal Robots c57a1 Universal Robots c57a1 is an everyday diagnosis for our engineers, and remote diagnosis (phone or video) costs nothing.

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Related Brakes alarms

C150 — Protective Stop — Position Close to Joint Limits C152 — Protective Stop — Position Close to Safety Plane Limits C153 — Protective Stop — Position Deviates from Path C154 — Protective Stop — Position in Singularity C155 — Protective Stop — Robot Cannot Maintain Position C157 — Protective Stop — Collision Detected
Same family: this code belongs to the Brake alarms family - the page collects all Brake-family codes we have handled, with the common inspection order and spares.
Other brands: we also keep field-fix libraries for Kawasaki · Staubli · Epson and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the Universal Robots c57a1 alarm mean?

A joint brake did not release when commanded; the joint does not move and the controller stops the motion. We are very familiar with this alarm on Universal Robots CB3 / e-Series (UR5/UR10/UR16/UR20) systems — usually the first on-site inspection is enough to confirm the cause. Universal Robots c57a1 sits in the brake family; on our work orders the highest-frequency trigger for this code is "Brake solenoid or brake coil failed".

QCan I clear a Universal Robots c57a1 alarm myself?

Whether Universal Robots c57a1 clears on its own depends on the outcome of "Listen/feel for the brake click when enabling servos on the affected joint". Finish the flow with "Replace the brake assembly or motor if the brake is mechanically dead" to confirm Universal Robots c57a1 - do not skip it. If that step is clean, the second most frequent cause on Universal Robots c57a1 is "24 V brake supply wiring broken". Two attempts and still there means stop: Universal Robots c57a1 involves a dropping vertical axis, and running Universal Robots c57a1 on can turn a repairable fault into a replacement.

QWith a brake alarm like Universal Robots c57a1, can we keep producing for now?

The commonest causes we see on Universal Robots c57a1 are "Brake solenoid or brake coil failed, 24 V brake supply wiring broken, Mechanically stuck brake from corrosion or contamination", so we stock the van against those. For Universal Robots c57a1 specifically, we carry the brand's common brake assemblies, relays and supply modules; every change ends with a static hold test. For Universal Robots c57a1, brake faults carry drop risk so we prioritise them, and after replacement we hold-test on site before handover. Before we roll, tell us what Universal Robots c57a1 shows on the PolyScope event and alarm pages; codes carry a C prefix (C15x, C5x, C7x) and what the machine was doing - phone or video triage is free.

This page on Universal Robots c57a1 was compiled from actual repair records of the Henghuan Robotics repair team. Alarm notes are our own summary for troubleshooting reference only and may vary with controller and software version — please consult Universal Robots documentation or contact us if in doubt. Henghuan is an independent service provider, not affiliated with or endorsed by Universal Robots.