vmc Backlash Opinion

Hello guys!

First of all, Merry Christmas to everyone!

My thread today is about the backlash.

I have a Kitamura mycenter 1xif, it's the model with high precision contouring control option for reference... Control is Fanuc 16i mb

Anyway,I have been spending money on this machine, I have got some of the Fanuc drives refurbished as well as spindle refurbished, and x-axis ballscrew refurbished.

Now the question is I checked the parameter 1851 (fanuc backlash parameter) before refurbishing the ballscrew was 330, after refitting ballscrew , value has been adjusted to 100.

Are those values in microns, 100 microns after refitting seems huge , I have seen a thread where a guy with a Kitamura HX400 said a value of 100 equals to 10-micron adjustment which would make sense then?
I have read another thread where a guy with a Fanuc 20i control with high-resolution encoders said when the machine was new, he had on the y axis value 65 which then would seem on average compared to the values set on my machine.

Then I do still have 0.0003" on the y-axis and 0.0004" on x and Z which I would like to compensate or sort out.

I only "checked" back with the tenth clock.

Thanks in advance!

I've always thought it was set using the Least Input Increment, which for most machines would be 0.001mm, but looking in the parameter manual it says "Detection Unit." I take that to mean encoder resolution. Regardless. I have a Mori VMC with single digit backlash comps, and a well used Mori lathe with 2 digit ones. Not sure if any of this is of help, but does suggest your numbers might be high-ish.

If the machine is putting out parts that you're happy with and are meeting tolerances, I'd say you have little to worry about no matter what the numbers are.

The machines I mentioned are controlled by an18MC and 18iTA.

I've always found it kinda confusing figuring out what the units are. Best foolproof method I have found is to put a large number in and see what it plays out as on the indicator.

That said I have a machine with an 18iMa that has 0 1 and 3 for the backlash comp and it has no measurable backlash. Of course it has huge pretensioned screws.

I also have a machine with numbers around 80 and you will be there all day if you try and get it to make parts to a tenth.

My Brother Speedio has some absurdly small backlash comp increment -- I think it is .00001mm. I have settings of around 400, which manifests in something like .0002" of comp.

Regards.

Mike

Hello there,

Thank you for the answers!

The machine seems to repeat dimensions quite well, I am not too sure , it might possibly be something like 10 units equal 1 micron? 100 units 10 microns?

I will hope so

As said the backlash comp after refitting refurbished ballscrew assembly has been set to 100 , could it be that much from a regrind?

Hello there!

Not sure if this will be helpful for someone else in the future, but I just checked the original parameter sheet , and the machine when was new in 2002, had as backlash parameter 1851 0 on x, 115 on y, and 60 on z, which is pretty much then in inline I would say.

Again I suppose in my machine 10 units equal to 1 micron