[drumsticksplint]

Hi Guys,

I need to replace the y axis ball screw bearings on a machining centre I've recently purchased. I'm just wondering if disassembling the motor / pulley assembly will affect the referencing procedure once everything is back together? This is the first Fanuc machine I've owned, so not sure how the control handles the referencing? I'm guessing the axis travels to the reference switch then the motor slowly moves to a reference pulse, which was set up when commissioned? Or will the machine have absolute encoders?

Any tips on how to maintain the reference position or how to set it back up once the bearings are replaced would be greatly appreciated.

Thanks

[zavateandu]

you need to look for a reference dog if it is present.
if you have a limit switch and a dog where this limit switch is pressing than you have no problem for reference when you dissasemble the ballscrew and the bearings.
if you have minimum 2 limit switches it means that you have 1 for reference position and 1 for hard limit so you can start your work with any concern.
if you have only 1 limit switch it means is only for hard limit and the in this case i always put the axe on the reference and make a mark with a paint marker.
after i assembly i move the table on the mark and make the reference in the same position.
there are machines with no dogs at all.For the hard limit they use mechanical stoppers that are ussualy placed on the bearings seat.
it is easy to take out the covers and show us a picture.
let us know if you have in parameters 20 and 21 like this:00000111

[drumsticksplint]

Thanks for your reply!

The arrangement of the switches is 1 limit and one home / reference per axis with a "dog" that activates each switch. Parameters 20 and 21 on my control both read all zeros.

I guess that means that I can take apart the assembly quite easily without worrying about messing up the referencing

I thought its best checking before ripping everything apart, experience has taught me this, haha!

[zavateandu]

yes you can do your job without any problems

[drumsticksplint]

Hmmm..Ok, now I have lost my reference position for my Y axis.... Any ideas how I now restore this? I've been reading up and found something on grid shift. However, I'm not entirely sure where the actual zero position was on my Y axis before I stripped the bearings.

[zavateandu]

if you have a dog for reference i supposed you get now over travel alarm when you try to reference.
you need to make the parameter 701 from what you have(i think is around 2500-5000) to 999999.
make reference on y axis.
after reference is made you need to go back and put the old value back.

you do not need to restore it to perfect position.
you just need to remeasure the G54 position and you are done.

[drumsticksplint]

Yes I had a 'y axis over travel' alarm.

I changed the 701 parameter to 999999 from my value of 12000, ref'd the machine then set the 701 parameter back to 12000 and all seems to be good.

When you say remeasure the G54 position, this is only for pre existing programs right? The machine is new to me so I don't have any programs in the memory yet.

Thanks for your help

[zavateandu]

yes is for the existing part because for the new part you will for sure measure the new G54.
have fun with the machine!