VMC 760/22 toolchanger problem

Hey all,

I've got an issue that started the other day. My VMC 760/22 stopped changing tools - the carousel won't come forward to the spindle, and it alarms out with a "Tool Arm Timeout".

I took the motor that drives the tool arm off and it appears the brake is stuck on.

There is 230VAC at the pins for the brake all the time; is this supposed to be the case? I would assume the brake would be deactivated with this power present, which indicates I have maybe two separate problems - the brake does not disengage when energized, and the machine is attempting to disengage the brake constantly.

Does anyone know what the proper behaviour is? Is anyone with one of these machines willing to measure some voltages for me (eg on the TLAUF card, measure AC volts between JP11-3B and JP11-2B, wires 112 and 113, with the drives on and the machine homed)?

Thanks for any help,

Isaac

The relays on the TLAUF or LCTLAUF are solid state and typically leak or short. They are the row of black devices maybe 1/4 inch by 1 inch by 2 inch.
I have seen the arm back short and thus the arm could not come out. And it does overcome the brake. I have seen the brake wear out and then the arm drops after the power shuts off losing the arm back proximity switch. Also check the arm shock absorbers. They are small mechanical devices. You can refill them but if the seals are gone, the oil leaks out.
Take the board out, turn it upside down and measure the resistance of the two output pins. Check them all. Usually they will measure over 3 mega ohms. You may find one with a lot lower resistance. Replace that one.
You will need a solder sucker to get it out. These relays are available in a 3 and 5 amp variety. Of course get the 5 amp.

George,

Thanks a bunch for the reply.

I actually had to replace a couple of those triacs in the past; I had an issue with the tool carousel just constantly rotating and found two that were failed closed. I have checked them and none are showing continuity now, so I think they're all still OK. That was my first thought, actually.

I haven't seen any shock absorbers in this machine, although it's possible I just haven't taken things far enough apart.

With the brake removed from the motor and the motor just held in your hand, if you issue a Load Magazine command, the motor spins as it should; the brake never seems to disengage, though. I'm a bit suspect of the capacitor that's inside the motor connected to the brake coil, but as it has four leads I'm not sure how to check it; it also has no markings so I don't even know where to source a replacement.

Other than a shorted triac, can you think of any reason why there would be 230VAC at the brake pins all the time?

Thanks again, it's really appreciated!

Isaac

If anyone's following this.. it turns out what I thought was a capacitor inside the motor is actually a rectifier for the brake coil. That should have been obvious but I guess I looked right past it.

I reinstalled the motor with the brake removed and everything works as it should, so the problem is definitely something to do with the brake circuit. I'm not sure what, though.. maybe a short in the coil?

George, if you're reading this, do you think there are any long term issues with running with no brake on the toolchanger motor? It seems that the only problem would be movement of the tool arm with vibrations, which could of course be a disaster, but this machine is in my home shop and never runs unattended, so it might be ok.

Just to finish this for future reference: the problem was the two resistors behind the TLAUF; one of them was blown open (but didn't show any outward signs of burning or anything). The resistors are needed to keep the triac turned on because the coil doesn't draw enough current, so with the resistance removed the brake wouldn't disengage.

I know this is an old post but do you have any details on testing the triacs and or replacement part numbers?

I have a carousel that wont stop on my Torq-cut 22.

Soldering and replacing components is no issue for me but if they are solid state I want to e sure of the testing procedure (ie does power need to be applied, pinout, etc)

Richard

Quote:

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Originally Posted by DarkStarMedia

I know this is an old post but do you have any details on testing the triacs and or replacement part numbers?

I have a carousel that wont stop on my Torq-cut 22.

Soldering and replacing components is no issue for me but if they are solid state I want to e sure of the testing procedure (ie does power need to be applied, pinout, etc)

Richard

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Richard,

The triacs are Grayhill 70M-OAC5A or something similar (should be printed on the side of the part). I checked them with the board on the bench, no power applied - just measure continuity on the switched pins on the triac. If you have continuity they're shorted closed and the triac is blown. I think I had two of them shorted, the replacements were a few bucks at Digikey and the soldering was quick and easy.

The datasheet for the replacements I bought is at http://www.grayhill.com/assets/1/7/IO_Mod_AC_Output.pdf; you want to test across the VAC Load pins.

Let me know if you need any more help.

Cool. looks like one was already replaced with a NTE product (I think I might change that out in case).

I might just replace them all... I was thinking of energizing each one using a 5v power supply and checking the contacts for excessive resistance, but I am concerned about frying the PLC/CPU chip thing. There seems to be a resistor before each one i would imagine to drop the voltage before hitting the triac that I could remove to protect the board.

Not sure. Tomorrow I will take a lot of pictures and then pull the board for inspection. I don't suppose you have a schematic for the board?

Richard

Quote:

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Originally Posted by DarkStarMedia

Cool. looks like one was already replaced with a NTE product (I think I might change that out in case).

I might just replace them all... I was thinking of energizing each one using a 5v power supply and checking the contacts for excessive resistance, but I am concerned about frying the PLC/CPU chip thing. There seems to be a resistor before each one i would imagine to drop the voltage before hitting the triac that I could remove to protect the board.

Not sure. Tomorrow I will take a lot of pictures and then pull the board for inspection. I don't suppose you have a schematic for the board?

Richard

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As I say, no need to energize them - if your carousel won't stop then one is shorted closed, just measure continuity between the load pins and replace the ones that show any continuity at all.

Pulling the board is very easy, the terminals are all two-piece and labelled so you just pop them all out and remove the 4 screws. No need to remove individual wires.

I don't have a schematic, I wish I did.. I'd really like one for the BMDC card, too!

Good luck,

Isaac

Yup, one of them is shorted. one other (the NTE one) seems to have some different readings so I might replace that one too. It could be that the different brand is made differently. I'll order an extra too just to have.

Richard

They're cheap enough and a common enough failure it can't hurt to have a few extra as spares.

Glad you got it going again.

Well... not yet... Hopefully the parts arrive by Friday so I can run the machine this weekend. :)

Richard