Need Help!- Y-axis not homing.

[hotrob1]

Have a Awea machine with Fanuc O-M controller. Z homes, X homes, when homing Y - it travels lenght of the dog and errors out (overtravel) before homing. I can activate the limit switch by hand when Y is moving and machine will home. Any suggestions on getting machine to home in Y?

-Hotrob1-

[memoryman]

is your soft limit setting parameter correct? What error do you get?

[fanucman]

the dog switch is the problem try to adjust it..

[Ozemale6t9]

Make sure PWE is set to 0, then reboot machine while holding down 'CAN' & 'P' buttons. Hold until full boot up, then rehome machine

[hotrob1]

What parameter do I go into to override the software limits? I assume I will need to change them to 999 then move the Y-axis to re-establish the new home position. Does this sound like the fix? If I adjust the dog, then I got the tool changer position to contend with. Thanks for the info.

-Hotrob1-

Re: Fanuc O-M controller

[fanucman]

Originally Posted by hotrob1 What parameter do I go into to override the software limits? I assume I will need to change them to 999 then move the Y-axis to re-establish the new home position. Does this sound like the fix? If I adjust the dog, then I got the tool changer position to contend with. Thanks for the info. -Hotrob1- Re: Fanuc O-M controller

y do you want to change the soft limits.. what error do you get when this thing overtravels?

if it goes all the way and reaches the end of the ball screw and crashes, soft limits will not help you..

like i said you probably need to adjust the position of the switch..

[andra]

Sound you machine is cnc Milling machine ( X,Y,Z axis), but in my machine (cnc lathe)
#700 = X axis, #701= Z axis, so if you can trace where parameter for Y axis, you can try to change to 999999 and re home , after that you change again to original value.

[Dan Fritz]

The axis is supposed to rapid until it hits the zero return cam switch (where the switch turns on), then it's supposed to creep at a slow feedrate until the switch drops off the cam (switch turns off again), then it's supposed to continue creeping until it gets to the "one turn per revolution" signal on the pulse coder. That means that the cam must be adjusted so that the switch drops off the cam at least 1 turn of the encoder from the overtravel limit switch. If you have an 8mm pitch ballscrew, and the pulse coder is directly coupled to the screw (maybe inside motor), then you'll need at least 8mm of travel between the zero-return switch drop-off point and the overtravel switch.

Remember that the zero-return switch might also be sticking, and when it drops off the cam it has to reliably turn off.

Fanucs all have parameters for setting the direction of zero-return, the creeping speed after it hits the cam, and for zero-return "shift" (Grid shift). When adjusting the switches, I've found that it's better to zero out the grid shift parameter, then adjust the switches by moving the axis in jog/handle mode, and watching the diagnostics to see when the switches turn on and off. As a last step, you can fine-adjust the zero-return point by putting a number in the grid shift parameter. You can adjust the zero-return point + or - one turn of the encoder with the parameter.

[hotrob1]

Thanks for the info. From memory (not w/machine) it is a 502 error. When watching the switch, it hits the dog - slows down - travels the lenght of the dog (approx) 4 - 5", then errors out before it drops off the dog. So the switch is still activated. Like Fanucman said I thought about adjusting the dog but there is not alot of play up there. So.............I thought I'd try to re-establish home by going into the software limits and moving the axis. The P/Can fix worked short term but error came back.

Thanks.

[fanucman]

Originally Posted by hotrob1 Thanks for the info. From memory (not w/machine) it is a 502 error. When watching the switch, it hits the dog - slows down - travels the lenght of the dog (approx) 4 - 5", then errors out before it drops off the dog. So the switch is still activated. Like Fanucman said I thought about adjusting the dog but there is not alot of play up there. So.............I thought I'd try to re-establish home by going into the software limits and moving the axis. The P/Can fix worked short term but error came back. Thanks.

ok then 502 is soft limit overtravel.. there should be a parameter that disables the store stroke check at start up..

there is no other way of setting home when you have these incremental encoders..

[Ozemale6t9]

And all of the above is why I said hold down Cancel and P until machine has booted. Maybe it does not work on O series controls, I haven't had much to do with them, but on Oi series controls, Cancel/P bypasses soft limits until the machine has been successfully homed, then they become active again. From what you are describing, the machine is hitting a soft limit, not a hard limit, before it has reached the marker pulse. The proof of this would be if you can move the machine in the opposite direction without having to use overtravel release. If you can, you are hitting a softlimit. Maybe someone else has knowledge of whether Cancel/P works on O series controls?

[stevo1]

IIRC the Cancel and P work on the Oseries control. If the soft limits are set before the switches fall off the cam then this will only work on this power up. Once the machine is powered up again this will be the same issue. There are 2 things that can be done.

-The easiest way is to change the soft limits via parameters. I believe on the Om control it is parameters 700-703 for positive direction and 704-707 for negative. First check to make sure that your reference switch is not right on your hard limits. As Fanucman said if you move the soft limits beyond the hard limits then the machine will go straight to hard overtravel. Dan has pointed out the distance you will need once the switch drops off the cam.

-If the cam switch is too close to the hard overtravel then you have to physically move the cam switch as fanucman has said. You are worried about the tool change but it will depend on how your tool change is set up. The tool change position should not be built right at your hard limits. There should be room for adjustment.

My guess is you need to adjust the soft limit settings then you should have no problems.

Stevo