ABB OmniCore IRB 6740 Product Manual

7.4 Manipulator collapses on power downDescriptionThe manipulator is able to work correctly while Motors ON is active, but whenMotors OFF is active, one or more axes drops or collapses under its own weight.The holding brakes (normally one in each motor), is not able to hold the weight ofthe manipulator arm.ConsequencesFor a heavy robot, the collapse can cause severe injury to personnel working inthe area or severe damage to the robot and/or surrounding equipment.For a small robot, the collapse can cause injury to personnel working close to therobot or damage to the robot and/or surrounding equipment.Possible causesThe symptom can be caused by:• Faulty brake.• Faulty power supply to the brake.Recommended actionsThe following actions are recommended:InformationActionDetermine which motor(s) causes the robotto collapse.1See the circuit diagram.Check the brake power supply to the col-lapsing motor during the Motors OFF state.2If found faulty, the motor must be replacedas a complete unit.Remove the resolver or resolver cover ofthe motor to see if there are any signs ofoil leaks.3If found faulty, the motor must be replacedas a complete unit.Remove the motor from the gearbox to in-spect it from the drive side.4Product manual - IRB 6740 6373HAC085701-001 Revision: A© Copyright 2023 ABB. All rights reserved.7 Troubleshooting7.4 Manipulator collapses on power down