770M Spindle Won't Turn

Background

The spindle is the rotating assembly that holds the tool/tool holder. It’s powered by a motor that can either be integral or – like most of our machines – external, relying on a belt and pullies to transmit the power.

Tools

• Multimeter

• Adjustable wrench

• Screwdriver set

Verify speed was commanded properly

Reason: Commanded speed did not execute.

To command a specific RPM in PathPilot, you enter your desired speed, and then you MUST press ENTER for the machine to accept the commanded speed. Then proceed to hit FWD or REV.

Inspect and/or re-tension the belt

Reason: The belt is loose, worn, or damaged.

1. Open the spindle motor door and visually inspect the belt to ensure there is not excessive wear or damage.

2. Firmly push the spindle belt between the pulleys. If it is properly tensioned, the spindle belt should move between 3 mm (0.125 in.) and 6 mm (0.25 in.). If it's not properly tensioned, continue with the following steps.

3. Unclamp the motor mounting plate: Loosen the clamp handle.
   This allows the spindle motor plate to pivot.

4. Tighten the spindle belt: Push the pivot handle backward (toward the machine column).

5. Secure the motor mounting plate: Tighten the clamp handle.

6. Firmly push the spindle belt between the pulleys. If it is properly tensioned, the spindle belt should move between 3 mm (0.125 in.) and 6 mm (0.25 in.). If it's not properly tensioned, repeat Steps 3 through 5.

7. Close the spindle motor door.

The Variable Frequency Drive (VFD) isn’t getting power

Examine the spindle door and its switch

Reason: The door is open or the switch is malfunctioning.

1. Examine the spindle cover door to verify that it's closed, being held closed, and the switch is being depressed.

2. If your mill is equipped with door safety switches, make sure your enclosure doors are closed.

Reset the brake resistor’s thermal switch

Reason: The thermal switch tripped and needs to be reset.

1. Reset the thermal switch (TS1) as follows:

   1. Power off the machine.

   2. Allow the brake resistor to cool.

   3. Press the reset button (between the thermal switch’s two terminals) to reset the thermal switch.

Verify that the spindle run/start is working

Reason: The spindle start signal from the control board isn’t working.

1. Examine wires 434 and 436 for 24 Vdc on wires J10.1 and J10.3, respectively.

   

2. Start the spindle and listen for a soft, audible click on the control board. If you hear this click (from a relay contact on the board), the machine control board is functioning properly. If you don't hear the click:

   1. Verify that there's 24 Vdc measured from wire 400 to wire 434. Make a jumper wire and, carefully,
      momentarily jumper wires 434 and 436.

      1. If contactor K2 pulls in (you will hear an audible clunk) while you have the jumper on but drops out as soon as you remove the jumper, review the previous solutions to inspect why the K2 isn’t holding.

      2. If K2 stays powered on, the control board is not passing the run signal to the circuit. The control board passes 24 Vdc from wire 434 to 436 via a relay to create the start pulse. Measure wire 434 for 24 Vdc power. If present, the control board or wire 436 connected to J10.3 is defective. Power off the machine, and jumper J10.1 to J10.3 Power on the machine and check the VFD for a display. If the VFD reads rdy, the control board is defective. If not, wire 436 may be broken. Lift the connections of wire 436 at the control board and K2 and measure continuity.

Verify that the VFD is getting power

Reason: The VFD is defective.

1. Using a multimeter, confirm you have power getting to the VFD between L1 and L3.

   1. If there is power but nothing on the display, contact Tormach Technical Support.

   2. If there is no power, review the previous solutions to try and re-establish power.

2. If there is a trip or error code that does not clear after power cycling the machine, contact Tormach Technical Support.

Measure the motor resistance (Ω)

Reason: The motor has an internal short and is malfunctioning.

1. Power off the machine.

2. Wait 30 seconds, and then remove the U, V, and W wires from the VFD terminals.

3. Measure the resistance between the following wires to see if it is approximately 2-4 Ω:

   1. Wires U and V

   2. Wires U and W

   3. Wires V and W

4. Measure the resistance between the following wires to verify that it is >1M Ω or OL, indicating that there is no short:

   1. Wire U and Ground (bare exposed metal or a green and yellow wire with a PE label)

   2. Wire V and Ground (bare exposed metal or a green and yellow wire with a PE label)

   3. Wire W and Ground (bare exposed metal or a green and yellow wire with a PE label)

5. Numbers outside of the specified range indicate that the motor or its wiring is bad and needs to be replaced. Perform the same test on the motor cable connector, if applicable.

Identify the VFD code and solution

Reason: The VFD is tripped and showing an error.

Inspect the VFD program

Reason: The wrong program has been loaded or is running on the VFD.

1. Identify your specific VFD in the table below, and follow the instructions to identify what program it is running.

2. If the program does not match your machine and machine configuration, contact Tormach Technical Support.