Servos Fault on Fast Direction Changes


The X- and Y-Axes on the 1300PL are controlled by servos. When quick changes in direction are made, a large amount of energy is fed back into the power supply. If you are experiencing servo faults on change of direction moves, check out the troubleshooting steps below.

Table of Contents

Continuity and wire checks

Reason: Power supply not connected to backfeed clamp

Check for loose wires between the power supply and backfeed clamp (PN 39102).

  1. Power off the main breaker.

  2. Measure the continuity between the V+ terminal of the power supply and the + terminal on the backfeed clamp (follow wire 207).

  3. Perform the same check for the V- terminal of the power supply to the - terminal of the backfeed clamp (wire 208).

  4. Power on the main breaker, release the E-Stop button, and press the blue Reset button.

  5. You should see a green power LED on the power supply and an orange ON LED on the backfeed clamp if they are connected correctly.

Check the backfeed clamp operation

Reason: Faulty backfeed clamp

Check that the backfeed clamp is enabling itself.

  1. Power on the manin breaker, release the E-Stop button, and press the blue Reset button.

  2. Watch the status LEDs on the backfeed clamp. You should immediately see the ON LED.

  3. After about 1.5 seconds, you should see the Enable LED light. If you do not see the Enable LED light, your backfeed clamp is not sensing input voltage and needs to be replaced.

Check that the backfeed clamp is triggering on hard braking.

  1. Create a new G-code program with the following test snippet:

  2. Jog your machine to -X, -Y corner and ZERO both the X- and Y-axis. Then proceed to run the test program.
    Caution! The test program will run continuously until the Stop button is pressed. Make sure you are in a safe position away from the motion envelope.

  3. Watch the orange Clamp LED on the backfeed clamp when the axes are slowing down. You should see a momentary flicker (<5 ms).

  4. If you see no activity from the Clamp LED and either axis faults during the test, replace your backfeed clamp.

The braking energy is only dissipated in the backfeed clamp under very high braking situations, which is why a G-Code program is used to test it instead of simply jogging the machine back and forth.


If you continue to have problems, contact Tormach Technical Support.