Kodak Trendsetter800 Speed Error and Brake Stall: Real Cause Was Servo Motor Demagnetization
Problem Summary
While servicing a Kodak Trendsetter800 CTP, we encountered a fault that is both typical and easy to misdiagnose. The device reported Speed Error and brake stall, and the root cause turned out to be servo motor demagnetization.
The device starts and runs normally, but shortly after the drum motor is started, it reports Speed Error. At the same time, the drum motor brake behaves abnormally, and the machine cannot work.
Many engineers would first suspect:
- Encoder failure
- Damaged servo drive
- Lost parameters
- Control board communication fault
None of these were the actual problem.
Field Symptoms
During operation, the following abnormalities appeared:
- The drum motor speed could not stabilize after startup;
- The system reported Speed Error;
- Braking effect weakened noticeably, stopping time increased, and even stall occurred;
- The fault was somewhat random and appeared more frequently at higher machine temperatures.
Because speed detection and brake faults occurred simultaneously, diagnosis was more difficult.
Diagnostic Path
Following the service procedure, we first checked the entire servo system.
Phase 1: Encoder Check
Encoder output signals were tested:
- A/B/Z signals normal;
- Waveforms stable;
- No missing pulses.
Encoder failure was basically ruled out.
Phase 2: Servo Drive Check
The drive was checked next:
- Input power normal;
- Drive parameters correct;
- Control signals normal;
- No obvious overcurrent or overvoltage alarms.
Note:
If the drive power module is aged or output is abnormal, speed errors and brake faults can also occur. Therefore, the drive remained a key suspect.
Phase 3: Motor Check
After continuous run testing, we found:
Motor temperature was noticeably high.
Further disassembly revealed:
The motor's permanent magnets had demagnetized.
This was the true cause of the fault.
Why Demagnetization Causes Speed Error
Many people think:
Demagnetization simply means “less power.”
In fact, for a high-performance servo system, the impact goes much further.
When permanent magnets demagnetize after long-term high-temperature operation:
- Motor back EMF drops;
- Output torque becomes insufficient;
- Acceleration/deceleration capability drops significantly;
- The speed loop cannot maintain stable control;
- Braking torque is insufficient;
- Encoder feedback may not match the actual mechanical state.
As a result, the drive concludes:
The motor can no longer run at the commanded speed, so it triggers the Speed Error exceeded alarm.
At the same time, because braking torque is reduced, the following can also occur:
- Longer stopping distance;
- Brake stall;
- Reduced positioning accuracy.
That is why “speed error” and “brake fault” appeared together in this case.
Final Solution
After replacing the drum servo motor with a new one:
- Speed Error completely disappeared;
- Drum motor operation returned to stable;
- Braking returned to normal;
- Continuous long-running operation produced no alarms.
The machine returned to normal production.
Engineering Lesson
When a Trendsetter800 reports Speed Error exceeded, do not focus only on the encoder or drive.
We recommend checking in this order:
- Verify encoder feedback signals;
- Check drive parameters and output state;
- Check whether motor temperature rise is abnormal;
- Test whether motor braking torque has dropped;
- If necessary, test the motor for demagnetization.
Especially for machines that have run for many years, magnet demagnetization is not uncommon after long-term high-temperature, high-load operation. This fault can easily be confused with drive damage, so it should be judged by combining temperature rise, output torque, and running state.
One more reminder:
Drive damage can also cause similar speed errors and brake faults. During repair, analyze the drive output waveform, current, and motor state together to avoid misdiagnosis.
Related Services
Shanghai DTP TECH specializes in Kodak CTP complete machines and core component repair, including servo systems, laser systems, and control circuits. With extensive field experience on Trendsetter, Magnus, and Achieve series, we can quickly locate the root cause and provide reliable repair solutions.
Facing a similar Speed Error on your Trendsetter? Contact us for a fast on-site diagnosis.