Denford Software & Machines

Hi all I have recently purchased a 1994 Mirac, the machine is completely standard running Dos.
I am a mechanical engineer but when it comes to the electrical side of the machine I am very weak so I kindly request your support.

When tool changing the auto toolchanger would stop and need a ‘push’ to complete the tool change so I decided to strip the toolchanger and check for wear or lack of lubrication. The internals of the toolchanger were found to be in good condition so I removed the old grease and lubricated with oil as specified in the manual. I operated the toolchanger manually on the bench and found it to operate as expected.

I re-assembled, and tested and found the same issue!

I then re-soldered the wires to the rotary switch which were not great - result same issue.

I checked the retract limit switch and found no problems.

I then checked the motor. I removed it and selected a tool position, the motor would make a noise but would not spin. I ‘spun’ the motor shaft and then it would go with good torque. I hit reset on the machine, the shaft will then spin in the opposite direction for a second or two and the machine will then register the tool I selected - I’m guessing this suggests the logic diode array is working.

Now the main spindle will not run. Again, I’m guessing this may be a result of the fault condition of the toolchanger, or points toward the KEB Combivert?

Does the auto tool changer need a ‘kick’ from a capacitor to start moving? Is the problem likely to be with the KEB Combivert?

Sorry for the long post, I have run out of talent and I am completely in the dark on how to fix the machine so I’m desperate for your help.

Thank you Darren.

Hi Darren

As you say all the logic seems to be correct.

Are you able to check the resistance on the motor wires in the electrical panel. I would guess you should get 1 to 2 Ohms resistance if it is good but open circuit if its faulty.

Well, after a few discussions with Martin he pointed me in the right direction and he has solved my problem with the motor.

The problem was traced back to the tool changer motor contactor. The contactor was found to have dropped a phase to the motor, so with the machine totally isolated from the electricity supply a few pokes and prods with a screw driver I managed to free up the contactor and a quick check found continuity to all three motor phase wires.

Thanks to Martin at Denford the problem was found.

Thank you Martin, terrific service from Denford considering the machine is 25 years old. Without the help from Denford I would have never diagnosed the problem……….

Just one further request……….

The motor turns the turret but it is very slow, can I increase the rpm’s to the motor to increase the inertia to avoid any stalling issues? If I can what would be a safe max limit and which inverter parameter would it be.

Does anybody have a full parameter listing for the Combivert So I can check all of my settings?

Thank you Darren.