Inconsistent Auto-Tool Settings

[robb]

First - hope this year is better than the last one.

I have G3 with v4 installed. Been running a few tests after some serious maintenance/bearings replacements.

I have Auto Tool Zero and Tool Change (manual) setup. I Homed and set the X,Y,Z co-ordinates for a test job and then ran T0 M06. The process ran and there was a Z offset in F4 of -1.56996 (I use Imperial measurement). I ran T1 M06 and checked F4 offset which showed -1.57019. I ran T2 M06 and F4 showed -1.57009.

Why am I getting these, differing, offsets for Z axis each time I run the command? I would have expected each Z offset to be exactly the same.

[Incidentally, I tried to capture the F4 screen, a few times to show you folks but, the .bmp file was zero bytes and useless? That hasn't happened in previous versions.]

Thanks

Robb

 

[cncnutz]

Hi Robb,

While it is a reasonable thought that you would see the same values when measuring the tool height there are limits to this.
When you see the difference between the highest and lowest value you measured you will see that it is two ten thousandths of an inch between them and the actual difference is probably half of this amount.
It would take a very high quality Z axis with 0 backlash on an very rigid X axis rail to resist this miniscule amount of axis movement. Touching an axis is enough to move it this amount.
A stepper motor when it moves vibrates which will cause the X & Z to vibrate changing the reading.
You also need to take into account that your Z axis is belt driven so any slack in the belt will cause small amounts of backlash in addition to the actual backlash of the axis.
Microstepping is not accurate either due to the way they work. Only full and half steps are accurate.

In this instance I don't think it is reasonable to expect a heavy mill to be able to hold a tolerance of two ten thousandths of an inch or better.

I tested the screen capture using the 3 axis mill software that you are running using both CTRL+P and Print Screen keys. In each case it worked fine.
Have you tried a different USB flash drive just in case the one you are using has some corruption on it that prevents MASSO writing to it?

Cheers Peter

 

[robb]

Hi Peter,

Nice to know you're okay and not caught by the deadly Covid.

I'm sure you're correct about the 'inconsistencies'. I suppose I was being a little unreasonable in my expectations. Happy to live with that and the slight variability inherent in my CNC mill.

I will check the USB (which is quite new - but, could be the problem. Minor issue though).

Thanks for your help. Always appreciated.

Robb