[killersoundz]

I thought I had this figured out but since I just switched to 8x microstepping my parts are coming out marginally smaller than they should be.

200 step/rev steppers.
10mm pitch ballscrews.

I had calculated 4064 steps per inch at 8x microstepping (1600 steps/rev)

is this correct or probably not? I can't math. :tired:

[awerby]

I get the same number, but there might be something else causing your parts to come out undersized. Are you sure the tool is really the size you're assuming it is, not slightly fatter? Are you accounting for backlash? Are you using your CAM program correctly, cutting to the outside of the part boundary and not on the line or inside it?

[killersoundz]

I get the same number, but there might be something else causing your parts to come out undersized. Are you sure the tool is really the size you're assuming it is, not slightly fatter? Are you accounting for backlash? Are you using your CAM program correctly, cutting to the outside of the part boundary and not on the line or inside it?

I have a theory that my end mill is bent right now I sorta crashed it. It's cutting terribly now for sure. It's supposedly carbide so I don't think those bend they usually just snap but I stopped it just as it was crashing so it may be possible. I just went and bought a new one just in case so I'll try that.

As far as the steps per goes. The accepted inch to mm conversion is 25.4 but if you look up the long version of that there's a few more decimal spots. Actually converts to 4064.016 steps per rev in my case. That should be completely insignificant. But it is possible over a large distance it could start throwing things off a thousandth or so.

I guess I'll have to change mach3 to work with mm and just put in 160 steps per mm. But dang do I hate the DRO's reading out in mm

[ger21]

Actually converts to 4064.016 steps per rev in my case

That's .00025" in 5 ft. or .001 in 20ft
You're also assuming that your screws are exactly 10mm pitch. The pitch can be off by roughly ±.002" per foot, which is the manufacturing tolerance.

I guess I'll have to change mach3 to work with mm and just put in 160 steps per mm. But dang do I hate the DRO's reading out in mm

There's absolutely no reason at all to do this. It has nothing to do with your part sizes.


If you do some testing, you'll find that part size will change depending on the direction you are cutting. There are many factors that can affect actual part size.

[jalessi]

What actually is marginally smaller? Please post intended dimensions and completed machined dimensions.

[awerby]

If your carbide endmill is behaving as if it were bent (you're right - they don't bend), chances are it's not seated in the collet correctly, which would account for undersized parts (and bad cutting action). If you're using an ER collet system, the collet has to snap into the closer nut before inserting the tool. If you're using a Jacobs chuck to hold the endmill, that could have a similar effect - switch to collets.

[killersoundz]

If your carbide endmill is behaving as if it were bent (you're right - they don't bend), chances are it's not seated in the collet correctly, which would account for undersized parts (and bad cutting action). If you're using an ER collet system, the collet has to snap into the closer nut before inserting the tool. If you're using a Jacobs chuck to hold the endmill, that could have a similar effect - switch to collets.

I found my problem.

Attachment 383596

That's a new bit I just got yesterday. MDF did that....Bosch sucks.