Fanuc backlash parameter

[Hertz]

Good morning guys. I'm looking to correct some backlash in my CNC lathe and was looking at parameter 1851 and 1852.
Looking for guidance on how to adjust. I have .0023 inches of backlash in my X axis.
Fanuc 21i-T
Any recommendations?
Do I need to be in a program to measure the compensation or can I do it with the handwheel and a dial? That's how I'm finding out there is a couple thou backlash in the X but I'm not sure if that's the proper way.

 

[dandrummerman21]

Thats how I've always done it.

Is it that much everywhere along the x? That's a pretty big amount, but not unheard of.

I'd be suspect of the thrust bearing(s), but could be wear in the balls/nut, or a badly worn spot in one part of the screw.

 

[DouglasJRizzo]

That sounds like quite a bit.
1851 is backlash.
1852 is Rapid backlash.

What are the settings now?

 

[angelw]

Looking for guidance on how to adjust. I have .0023 inches of backlash in my X axis.
Fanuc 21i-T

Hello Hertz,
Are you testing the amount of Backlash with the amount of Backlash compensated for via parameter set to Zero? The Total Backlash is what you're measuring, plus whatever is set for compensation in the parameters.

Compensating for Backlash via parameters doesn't get rid of the Backlash, its still there mechanically and when excessive, it should be address mechanically.

Regards,

Bill

 

[Hertz]

I have 0 in both x and z right now in the parameter 1851. There is .002 backlash in the X when I use a dial and the handwheel. I was just wondering if the compensation in the parameter would compensate for it if I put 2 in there.
And then I was just wondering how I would verify that it's adjusted or compensated. I realized that I may have to fix it physically, but in the intern, I was wondering if I'm forced to run it like that or if there's somewhere I can help it compensate. I appreciate the answers guys, thank you. I guess I'm still right where I was before I posted this LOL

 

[angelw]

I have 0 in both x and z right now in the parameter 1851. There is .002 backlash in the X when I use a dial and the handwheel. I was just wondering if the compensation in the parameter would compensate for it if I put 2 in there.
And then I was just wondering how I would verify that it's adjusted or compensated. I realized that I may have to fix it physically, but in the intern, I was wondering if I'm forced to run it like that or if there's somewhere I can help it compensate. I appreciate the answers guys, thank you. I guess I'm still right where I was before I posted this LOL

Hello Hertz,
Although your machine may be configured for Imperial operation, the Backlash Compensation is in a number of 0.001mm units, specified without a period. Accordingly, for 0.002", you would input a value of 50 (50 x 0.001 = 0.05mm = 0.002")

You can check that the figure is correct using the Hand-wheel and dial indicator.

Regards,

Bill

 

[BT Fabrication]

ive got a machine with 18M, it has a comp for every "1" value you add to it, it changes it by a tenth.

 

[aj]

I have 0 in both x and z right now in the parameter 1851. There is .002 backlash in the X when I use a dial and the handwheel. I was just wondering if the compensation in the parameter would compensate for it if I put 2 in there.
And then I was just wondering how I would verify that it's adjusted or compensated.

The beauty of the 1851 parameter is it takes effect immediately. None of that Fanuc 'power on/power off' nonsense. So you can change it incrementally and see the changes.

 

[aj]

Hello Hertz,
Although your machine may be configured for Imperial operation, the Backlash Compensation is in a number of 0.001mm units, specified without a period. Accordingly, for 0.002", you would input a value of 50 (50 x 0.001 = 0.05mm = 0.002")

The same is true for grid shift (1850) , correct? That one always gives me grief.

 

[Vancbiker]

Hello Hertz,
Although your machine may be configured for Imperial operation, the Backlash Compensation is in a number of 0.001mm units, specified without a period. Accordingly, for 0.002", you would input a value of 50 (50 x 0.001 = 0.05mm = 0.002")

You can check that the figure is correct using the Hand-wheel and dial indicator.

Regards,

Bill

ive got a machine with 18M, it has a comp for every "1" value you add to it, it changes it by a tenth.

Determined by whether the machine has metric or inch (imperial) pitch screws.

 

[angelw]

Determined by whether the machine has metric or inch (imperial) pitch screws.

Yes.
Regards,

Bill

 

[Hertz]

Hello Hertz,
Although your machine may be configured for Imperial operation, the Backlash Compensation is in a number of 0.001mm units, specified without a period. Accordingly, for 0.002", you would input a value of 50 (50 x 0.001 = 0.05mm = 0.002")

You can check that the figure is correct using the Hand-wheel and dial indicator.

Regards,

Bill

Ok thanks alot. I tried putting 2 yesterday and it didn't move at all. Those makes sense why it didn't. I'll take a look again in the morning.

 

[angelw]

Ok thanks alot. I tried putting 2 yesterday and it didn't move at all. Those makes sense why it didn't. I'll take a look again in the morning.

Hello Hertz,
If your machine has an Imperial Pitch Lead Screw, the number you would have to register for 0.002" is 20. Unless you're using a dial indicator with a resolution of 0.0001" you may not see any result when entering the number 2 only.

Regards,

Bill