Y axis homing problem FANUC OM-C

1990 Denford TRIAC VMC running Fanuc OM-C control.

All was working fine until one afternoon getting her to home on the Y axis was temperamental but after a few attempts she did home after which she functioned normally.

That was last weekend. Now however she will not home on Y at all. X & Z home normally. The machine hasn't been moved or messed with so I have no idea what has caused this to happen.

When homing Y the axis sets off at rapids speed until it gets close to home and then slows as you would expect. However it continues straight through zero and out the other side until the axis drive cut off switch is triggered. I don't get an over travel alarm, the servo drive relay (I presume) cuts out and I get the "Not Ready" until I use the axis override button and jog back within limits.

I have taken the front bellows off and manually triggered the two switches and diagnostic 0017 reacts changing bit 6 from 1 to zero when the proximity switch is depressed. Similarly, diagnostic parameter 0000 changes bit 6 to zero when the limit switch is triggered.

Out of curiosity / desperation I flicked through the pages of diagnostic parameters and happened to notice that 51 58, 315, 317, 320, 322, 520 & 540 are all constantly changing value with some or all bits rapidly and apparently randomly changing. No idea if this is relevant or not.

I have tried turning the control on with P and CAN depressed but it has made no difference.

Any clues what to check / test / swear at next?

Thanks!

Charlie.

Power down, power back up holding CAN and P buttons until booted.

Tried that several times already. Unfortunately it has made no difference. Any other ideas?

You get this when the machine "jumps Grid" This can happen when your reference marker on the motor pulse coder is too clause to the home switch. And yes this can happen without moving or changing anything on the machine. You can adjust your grid shift parameter 508 for the Y axis. I would try to set this to zero first and see if your axis homes OK. Another test is to make the switch while the machine is homing way before it gets to the end and see if you can make it home in the middle of the slide. (TEST ONLY) if it does home then your motor encoder and home switch are working fine. Another option is move the dog for the home switch so it makes sooner or remove the motor and turn the shaft 1/2 turn and re-install. Please note that your Y axis will not home to the exact location as it use to and adjustment will have to be made. (Grid shift parameter 508) Hope this helps

Thanks for the tips. I have had a look a parameters 507, 8 & 9 and they are all zero. Checked this in both diagnostic parameters and the main ones (didn't know which to check so checked both!)

There is no dog for the home switch on this mill from what I can see - it uses the housing for the drive nut as the surface the swich registers against.

Haven't tried dismantling the servo motor just yet - I want to exhaust other options before I risk taking it apart!

I tried you suggestion of manually pressing the proximity switch whent he table was a long way away. All that happened is the machine slowed from rapids as you would expect but continued through zero and beyond as before. Am I to infer from this that the encoder is potentially faulty? If so, how do I diagnose that?

Thanks for your help so far, most appreciated.

Remember, on fanucs the switch triggers slow down only, the switch has to release off the dog before the control looks for the marker on the encoder.

Success!!

Turns out to simply be a gummed up proximity switch - if I had looked at the diagnostic screen when the machine was homing I would have seen that the switch wasn't disengaging all the way to the over travel switch.

A quick blast of contact cleaner and some manual cycling of the switch and all is well!

Thanks for your help :)

Hello everyone,
I have the exact same problem to this as well.
quick question ?
what does " Power down, power back up holding CAN and P buttons until booted. Mention early in this thread

thanks

Further to my last message , i proved the Y encoder and switch is operating correctly as i activate the homing switch and let it off when the table was in the middle.
So thats a good thing.....

But reading from the above........ .....how do I "grid shift parameter 508 for the Y axis. I would try to set this to zero "

How do we go about doing this ???

Thanks in advanced

Quote:

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Originally Posted by jubee

Hello everyone,
I have the exact same problem to this as well.
quick question ?
what does " Power down, power back up holding CAN and P buttons until booted. Mention early in this thread

thanks

---

It cancels data/ faults and enables you to re reference the machine, if same fault occurs, you could have a defective reference switch or sticking.

Quote:

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Originally Posted by jubee

Further to my last message , i proved the Y encoder and switch is operating correctly as i activate the homing switch and let it off when the table was in the middle.
So thats a good thing.....

But reading from the above........ .....how do I "grid shift parameter 508 for the Y axis. I would try to set this to zero "

How do we go about doing this ???

Thanks in advanced

---

The grid shift enables you to electronically adjust the zero point of an axis. For example by using a centre of table bore or bung, should read x/y zero on screen if swept from an indicator mounted in the spindle. Ie. Indicator X0 Y0 when rotated should show X0 YO in absolute position on the display. Adjust 508 if not, start with 508 at zero after writing down its value.

Thanks for the info. It all worked in the end. Excellent

Now that i stuffed around withy the Z axis home switch for fault finding i need to realign the ATC.

Any ideas ?
Its a Kiwa Excel 810 VMC with Fanuc 0-MC

I read in one post taking the brake off and moving the arm .... then adjusting the Z for the height.
Just cant work out how to move the arm

Quote:

---

Originally Posted by jubee

Thanks for the info. It all worked in the end. Excellent

Now that i stuffed around withy the Z axis home switch for fault finding i need to realign the ATC.

Any ideas ?
Its a Kiwa Excel 810 VMC with Fanuc 0-MC

I read in one post taking the brake off and moving the arm .... then adjusting the Z for the height.
Just cant work out how to move the arm

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If the toolchnge magazine and tool arm are a single unit.The place to start is to check the pick up and deposit of tools in and out of the magazine using manual functions. Correct if required.

Next, drive all axis to toolchanging position and using a tool without a pull stud in the arm, use the manual functions to find out where the misalignments are. Then adjust toolchange position parameters and or tool arm position.

To move the tool arm you may need to press in the arm motor contactor button in the electrical panel, by jabbing it in little by little to align the arm, but only if no manual functions exist. Be super careful doing this and you will need a second person to help.

The tool arm might have adjustable dead stops and confirmation switches that may need attention for spindle position.

You may be able to move the arm using the motor fan with a bar in the brake to act as a lever to unlock the motor. Remove fan cover and find the brake lever hole. DON'T do this with power on, keep e-stop pressed to prevent motor running if off the switches.

You may need a service tech, because these procedures can be dangerous for the inexperienced. A good tech could do these adjustments in a few hours.

Quote:

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Originally Posted by jubee

Thanks for the info. It all worked in the end. Excellent

Now that i stuffed around withy the Z axis home switch for fault finding i need to realign the ATC.

Any ideas ?
Its a Kiwa Excel 810 VMC with Fanuc 0-MC

I read in one post taking the brake off and moving the arm .... then adjusting the Z for the height.
Just cant work out how to move the arm

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ussualy the motor of the arm has a hexagonal shaft on the end for a 12mm or 13mm socket key
also ussually there is a levier around the end of motor,where is the cover of the ventilator,to release the brake and be able to rotate by key the arm
Move the Z axis and rotate the arm untill you reach the perfect position where will be a gap on the upper side ,around 0.5-0.7mm like in the hand draw i made for you to understand
most of people do not know the science behind it but i willl let it here to be understand
the arm profile is smaller than the tool groove like i show in the drawing and it is need it becasue when the tool is release from spindle must drop on the arm holder and not to damage the arm by pulling it up or pushing it down
when the arm will come with the tool to the spindle ,the gap will be on the lower side and when the tool will be clamped that must have a space for the axial movement of 0.5-0.6mm for a BT40 tool and will not pull the arm up while clamping
so that is the best position for a tool change where the sequence will run smooth and with no visible movement of the arm ,up or down while clapming or unclamping from the spindle
If you do not know exactly if your arm motor can be moved by key just show us a picture from above and we will see
The pciture is for a tool in spindle already clamped and the arm that is coming to the spindle side.
Good luckAttachment 489400

Thanks so much for the detail responses , very much appreciated.

I will attach a couple of photos i took yesterday of the motor etc. I cant see any Hex shaft or with a socket key. I could of been looking in the wrong spot, on top of the motor you say ??

Heres a few photos of the motor for the tool changer. It sits at the back and on the top looks like a cooling fan. I can rotate that fan housing on the top but the tool arm doesn't move.

Again, thank you for your help.Attachment 489414


PS.... some reason the photos are shown 90 degrees ...Sorry
will try and rectify

It wouldnt let me send more then one photo....
Couple more ....hereAttachment 489416Attachment 489418

All good , found it.

Its just a small screw under the fan section that moves a small lever and takes the brake off.

It worked and now i have adjusted the arm. Wasn't that bad after all. Pretty straight forward.

Now I'm looking to see how i can adjust the tool change Macro Z height ......From a few searches looks like lots of help and details.
hopefully something i can use out there...

Thanks again guys for your help
Very much appreciated :)

Quote:

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Originally Posted by jubee

All good , found it.

Its just a small screw under the fan section that moves a small lever and takes the brake off.

It worked and now i have adjusted the arm. Wasn't that bad after all. Pretty straight forward.

Now I'm looking to see how i can adjust the tool change Macro Z height ......From a few searches looks like lots of help and details.
hopefully something i can use out there...

Thanks again guys for your help
Very much appreciated :)

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Great news :-)

Quote:

---

Originally Posted by jubee

All good , found it.

Its just a small screw under the fan section that moves a small lever and takes the brake off.

It worked and now i have adjusted the arm. Wasn't that bad after all. Pretty straight forward.

Now I'm looking to see how i can adjust the tool change Macro Z height ......From a few searches looks like lots of help and details.
hopefully something i can use out there...

Thanks again guys for your help
Very much appreciated :)

---

if you post the macro program we can see how the Z is going to reference for tool change
ther are 2 ways of doing it
1, using the second reference point with G30 and the parameter to adjust will be 737
2.if it is doing in in the reference point that will be with G28 you have to adjust the gridshift in the parameter 510

the easy way to check is if you have G30 in the macro program for tool change or you have a small value in the parameter 737 that will mach the machine position in the tool change point for Z axis
Good luck