Fanuc 0MD (2000) Y axis overtravel during zero return

Jrill · Dec 17, 2019

Hi Guys,

When I start up the machine and try to zero it, the Y axis overtravels and does a 520 error at ~0.079in (2mm), but when I restart using P+can it goes all the way to ~0.103 and hits a hard emergency stop.

I've had Z axis overtravels before (usually after shutting down the day before without going into e stop first) and I always used P+can to fix it, so, not sure what to do this time?

What could be causing this?

13engines · Dec 17, 2019

Does your machine use decel dogs for home position? If so, check the physical switches for positive action, chip build up and soaked or partially trashed wiring, inside and out.

Jrill · Dec 18, 2019

I took the covers off...

It has one dog that's about 3" long, which is probably about where it stops the rapid to start feeding slowly toward zero.

I noticed today that it no longer does the rapid for the Y axis, so I guess there's something wrong with the corresponding switch or the wiring for it.

Things under the covers are damp, but the switches actuate perfectly.

Which bit can i look for to see if the switch is registering when I actuate it by hand?

ifixcnc · Dec 18, 2019

The X bit is a builder determined thing.
What control and machine is this?

Jrill · Dec 18, 2019

ifixcnc said:
The X bit is a builder determined thing.
What control and machine is this?

Looking for how to check the Y axis reference switch operation, whether that's a bit or ladder diagram or something else.

Control is Fanuc 0M-D
machine is Hardinge VMC600II (built ~2000)

Vancbiker · Dec 18, 2019

Jrill said:
Looking for how to check the Y axis reference switch operation, whether that's a bit or ladder diagram or something else.

It will be a diagnostic bit. Do you have the wiring diagram? Most builders include the diagnostic bit assigned to each switch in the diagram.

Jrill · Dec 18, 2019

Vancbiker said:
It will be a diagnostic bit. Do you have the wiring diagram? Most builders include the diagnostic bit assigned to each switch in the diagram.

It doesn't look like any of these are bits, but is this part of the ladder diagram or something I can use? Electrical stuff like this is new to me, so I'm not totally sure what I'm looking at.

ifixcnc · Dec 18, 2019

That page is the Y bits = Outputs, that turn on the indicator light.

Jrill · Dec 18, 2019

ifixcnc said:
That page is the Y bits = Outputs, that turn on the indicator light.

Like the light on the front keyboard panel? lol

Jrill · Jan 6, 2020

Update: bought a new SL1A switch and changed it out but there's no difference.

It seems diagnostic X0017 bit 5 shows whether or not the reference dog is being depressed or not (is that specific to the MTB?), and it's not changing at all so I'm guessing there's a broken wire. Should I be checking anything else before diving into the wires?

ifixcnc · Jan 6, 2020

Yes it is specific to the MTB.
If you can find the wires from the switch at the I/O board, open the circuit (pull the wire) and close it (jump the wire)
If your bit changes then check the wires.

Delw · Jan 6, 2020

More than likely your machine lost ref zero.
need to put -9999999 in each x amd y parameters then home then change them back to the Machine org parms.
one of the more tech savey guys on here can help you better as I know how to do it only on my machines but bad at explaining.
Be advised your reference zero on the part will change also so reset it before you run your tools

Other Brother · Jan 10, 2020

Jrill said:
Update: bought a new SL1A switch and changed it out but there's no difference.

It seems diagnostic X0017 bit 5 shows whether or not the reference dog is being depressed or not (is that specific to the MTB?), and it's not changing at all so I'm guessing there's a broken wire. Should I be checking anything else before diving into the wires?

Yes, X17.5 is your y-axis decel. Did you check for 24 volts on the wire when you changed the switch? Unfortunately I have had to replace many of these cables on these machines. The plastic wire tracks get jacked up and then the wires break. You might want to order all 4 cables that run together, both OT switch cables and both decel cables for x and y.

It's a nasty job but you probably need to clean the chips out from under that table anyways.

Attaching a pdf of the cable sets that I think you need, but I would verify the part numbers at Hardinge for your model and serial number so they can reference the BOM. Items 35, 36, 37, and 38 in the attached pdf. Disregard 33 and 34.

Daryl

VMC 600II Cable Sets PDF

Jrill · Jan 10, 2020

Other Brother said:
Yes, X17.5 is your y-axis decel. Did you check for 24 volts on the wire when you changed the switch? Unfortunately I have had to replace many of these cables on these machines. The plastic wire tracks get jacked up and then the wires break. You might want to order all 4 cables that run together, both OT switch cables and both decel cables for x and y.

It's a nasty job but you probably need to clean the chips out from under that table anyways.

Attaching a pdf of the cable sets that I think you need, but I would verify the part numbers at Hardinge for your model and serial number so they can reference the BOM. Items 35, 36, 37, and 38 in the attached pdf. Disregard 33 and 34.

Daryl

VMC 600II Cable Sets PDF

Thank you! This is just what I needed and I appreciate the time/effort for my obscure machine issue. It's good to know x17.5 is, in fact, the Y axis decel switch bit, and to know there are cable sets.

Since my last post I did find a wire to the decel switch had broken and fallen out of the plastic connector thing, and in moving it around I also somehow lost the X axis decel in the same way... the plastic connection has a lot of corroded metal in it and it's been damp and probably full of coolant off and on for the last 20 years, so no wonder it failed. I wish I had found the broken wire or had known to check the connectivity on the switch before removing and replacing it (altering zero and all that fun stuff).

My boss called someone in to fix the wiring, so early next week should be up and running again.

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