Mach3

[Edd259]

Hi all new here but i hope some one can help, im running mach3 on my router when i am cutting a house number if i need to cut at a deeper depth the machine starts from a slightly different location can be up to 0.5mm out. i have checked for backlash by cutting a circle and there is no change around the diameter! am i doing something wrong??

[ktb100]

Does the circle measure the correct diameter? If not, it could be step per Unit set slightly off.

Kirk

[M250cnc]

i have checked for backlash by cutting a circle and there is no change around the diameter! am i doing something wrong??

Hi that is not how you check for backlash, if you do a search for backlash there are lots of ways to check depending what equipment you have to check with.

If i understand, you re-run the program and it will start from a different place, and that sounds like missed steps.

So check your backlash first.

Phil

[ktb100]

Out of curiosity, how do you check backlash Phil? We cut a circle, square and diamond if a ball bar test is not used and when it is, you must go in a circle. Then there is the good old fashioned grab it and shake it to see how much it moves while watching an indicator.

We had installed one of our Majestic MK3's using Industry Controls (Mach Industrial) at the N.A.S.A. Goddard Space Flight Station in Maryland 2 weeks ago. We had ball bar tested it but before we did, we ran the circle, square and diamond first. It was less than 0.002" over 23" prior to putting the ball bar on and super fine tuning it. But how do you test it? If there is an easier or quicker way, I would love to know what it is.

Thanks,
Kirk

[Edd259]

Thanks for your response Phil but not too sure what you mean missed steps? i have also checked backlash and found very little to worry about when machh3 restarts the same cot it is a lot further out than any backlash i might have. any thoughts is it something in the programming im doing wrong.

regards edd

[Edd259]

Does the circle measure the correct diameter? If not, it could be step per Unit set slightly off.

Kirk

Hi Kirk yes the circle measures perfect i dont know if im doing something wrong with the programming but it restarts a lot further than the backlash is out by.

[M250cnc]

The way to measure backlash is as follows

Use a Dial Test Indicator (DTI) and fix it to some part of the Z axis and fine jog the table up to a piece of smooth steel and zero the DTI and the DRO for that axis then move in the same direction a small amount past the DTI zero

Then reverse direction and fine jog until DTI reads zero, the backlash will be what is displayed on the DRO

Now when i say you may have missed some steps that is from too high a speed/rapid feed rate or snatching of the cutter into the material can cause missed steps.

So you have lost position, you are not where the machine says it is.

To prove it halve your acceleration and velocity, and run the program again.

If you come back to the correct position then you know what the problem is.

Everyone is on this forum bragging about how fast their machine is, it's how accurate it is that's more important.

Phil

[ktb100]

I agree completely with Phil on the backlash for Z but I thought the problem was in "X" and "Y". Anyway, Lost steps can be caused from too high of an acceleration and velocity as well as a mechanical bind or with current being too low being supplied to stepper motors. Try slowing the acceleration and velocity down in motor tuning and see if that cures it. If not, please let us know and we will see if we can help.

Cheers,
Kirk

[M250cnc]

I agree completely with Phil on the backlash for Z but I thought the problem was in "X" and "Y"
Kirk

OK to clarify, put the DTI in the spindle, but if you can't do that fix it to the Z axis then you can measure X and Y

Phil

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