The machine intermittently stopped and its Z axis lowered. This was the reported fault when a Yaskawa AC Servo Motor SGMGH-44ACA6E arrived at industrypart. The customer suspected a brake problem. Our examination confirmed that the brake lining was completely worn away and wear debris had contaminated the motor interior.

Customer report and confirmed workshop findings

The worn brake explains the inadequate holding action. The report alone does not establish whether it also triggered the preceding machine stoppage. No specific alarm code or machine-control fault log was supplied for this case.

Replacing the RNB4.4G-13-C brake and removing debris

We replaced the defective RNB4.4G-13-C brake in its 24 V DC version. Cleaning the motor interior was part of the repair because the worn lining had left debris inside. Brake replacement alone would not have removed those deposits. The brake designation comes from the workshop record for this case; it is not a general replacement approval for other motor variants.

Bearings, seals and encoder

The bearings and seals were renewed during the overhaul. The UTSIH-B17CK encoder was cleaned and overhauled. It provides feedback for servo control, a different function from the mechanical holding action of the brake. The encoder was overhauled in this case, rather than documented as a complete replacement.

Why a Z axis needs a reliable holding brake

Gravity acts on the moving load of a vertical axis. A holding brake maintains the position of a stationary drive when active motor torque is removed. Yaskawa describes the integrated brake of the relevant SGM□H variants as a de-energization holding brake. It is intended to hold an already stopped motor, not to perform regular motion braking. Source: Yaskawa Sigma-II, SIEPC71080001, section 6.5.2, page 6-39.

Motor control, shutdown sequencing and mechanical holding serve different purposes. A motor may rotate during a test even when its worn brake has insufficient holding capacity. Rotation visible in a video alone therefore does not establish brake torque.

Cleaning, industrial paint and final testing

The motor was cleaned and the old paint removed. A new industrial paint finish was then applied. After completion, the motor was adjusted and tested. The repair process therefore covered mechanical components, feedback, exterior refurbishment and a final functional test.

Interpreting fault indications

No specific alarm number was supplied. Alarms are generated by the connected servo amplifier or machine control. A numbered list cannot reliably be assigned without identifying that equipment. A lowering Z axis calls for examination of the holding function. The preceding machine stoppage also requires assessment of the alarm history and shutdown conditions. Encoder faults or bearing noise were not explicitly reported as customer symptoms.

Request a repair and find the motor in our shop

Please send the full motor designation, a nameplate photo, the fault description and any available alarm history. If an axis lowers, specify whether this happens during movement, after a machine stop or at power-off. industrypart supports you with diagnosis, repair and preventive overhaul of industrial servo motors.

Yaskawa SGMGH-44ACA6E AC Servo Motor in our shop.

For more information about our Yaskawa drive repairs, visit our Yaskawa repair service page.

SGMGH-44ACA6E model reference in our shop

The linked shop reference for this model lists 200 V, 4.4 kW, 32.8 A, 28.4 Nm and 1,500 rpm. These are model reference data. The installed motor nameplate and complete configuration determine the suitability of a replacement.

Video: testing after repair

Photos after repair