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Spindle will not unclamp tool, DAH-LIH MCV 1500, fanuc 0m control


Aug 13, 2020
After a series of issues we are finally starting to get our Dah-Lih MCV 1500 back running, but we are facing one last problem (it seems) that we cannot figure out.
The machine has a fanuc 0mc control.

To give a bit of a back story we had a shorting in the cable for the 4th axis (round table) causing all sorts of problems.
We had an alarm 950 FUSE BREAK (+24E: FX14). Replacing the fuse did not work (it just blew again), so we identified that the power unit for 24V was at fault. We replaced the power unit and got rid of the alarm 950 FUSE BREAK.

At this point we only had an error for the disconnected 4th axis, but by setting parameter 19.1 to 1 we disabled the 4th axis and got rid of all errors.

Everything seems normal with the machine EXCEPT the tool change procedure, and this is what we need help with:

we have a side mounted 25 post tool turret. When Z-axis is zeroed/homed we should be able to call M6 in MDI to change tools.
The arm rotates to take a hold of the tool in the turret and the tool in the spindle. Pressurized air goes ON. Then the procedure stops.
We discovered that the clamp that holds the tool inside the spindle does not open during tool change preventing the arm to move down.

The command M6 is a series of M-commands. We have tried to run then separately by using:

M19 - orient spindle
M81 - Arm advance
M82 - Arm down
M83 - Rotate arm 180 deg
M84 - Arm up
M85 - Rotate arm back

However it did not work. M82 - arm down does not finish and i have to press reset and move the arm back by using M85.

On the machine we have a button to open the spindle for mounting tools. When pressing this spindle air goes ON but the spindle clamp does not open, preventing us from mounting or releasing any tools.

But there is one very strange thing:
When starting the spindle THE FIRST TIME after power on the CLAMP OPENS while spindle is rotating. When pressing reset to stop the spindle the clamp closes again. The spindle also ignores the set spindle speed and rotates very slowly.

If i start the spindle a second time the clamp does not open and the spindle speed is whatever i programmed it to be.

We see that the clamp is hydraulicly controlled with a solenoid so we measured when it gets a signal. The solenoid for the clamp DOES NOT get a signal during tool change but it does get a signal when starting the spindle the first time after power on.

The hydraulic valve has an override button, and if i press it at the right time during tool change the tool changes successfully.

Because of this strange behaviour we suspected that something might be wrong in the plc or parameters so we wiped everything using (reset+delete) during startup and reloaded the original parameters and diagnostic parameters, but the problem still persists.

Sorry for the long post,
Hope anybody can point us in a direction.



Jan 6, 2007
Bergen County
Can you post your tool change program. There might be an M Code to unclamp the spindle. You also stated the spindle turned on and the unclamp initiated once. You do know you should NEVER run the spindle without a tool in it. Depending on the style of clamping, it could damage the clamping mechanism.


Aug 13, 2020
I did not know about not starting the spindle without a tool in it. Never heard about this before so thank you for the information. The first time we started it a tool was inserted, but since the machine unclamped it the tool fell out (while rotating)

Would you know where i find the program for tool change? it is not in the program list.