Cuts are perfectly undersized

[woodandtwine (Rod)]

I have a really strange problem. When i cut a rectangle on my Shapeoko Pro XXL it comes out perfectly proportionately undersized, every time. Strange… so i was thinking that my belts were stretching so i ordered new ones and installed them, same problem. I checked for loose grub screws on my stepper motors and they were all tight. I tried different end mills, same problem. So i was thinking that maybe it was happening only if my rectangle was being cut in the x orientation so i rotated it to the y and tried cutting it in that orientation and same problem. I made sure that my geometry is correct in Create and that i am cutting on the outside. I tried cutting everything in inches and also mm. I tried oiling my machine. I verified that my machine is square. My feeds and speeds are extremely conservative. My cuts are perfect. they are straight, they are consistent but they are consistently too small. I know that i can adjust my GRBL for the x and y travel but to me this is just masking the real problem. Also if i adjust the GRBL i can’t use my bitsetter. Anyone having this issue?

[cheu (Charles)]

Is the cutter that you are using on the machine the exact same geometry as the one in your tool database? Are you cutting outside, on, or inside the vector?

[woodandtwine (Rod)]

Yes, i checked with my calipers and it’s .249. so to me that’s perfect.

[WillAdams (William Adams (Carbide 3D))]

Disable the BitSetter, then calibrate for belt stretch as shown at:

Calibrating the machines over long distances

The typical technique for machine calibration: https://carbide3d.com/hub/faq/belt-stretch/ depends on precision measuring tools, and is limited by the reach of the tools in question. EDIT: It also depends on access to the MDI — if using Carbide Motion v6 it will be necessary to enable this in Settings | Options: [image] It should be possible to cut strips from a suitable blank of material, one along each axis — so we set up a square file which matches an available blank of material: [im…

then re-configure the BitSetter position, but don’t send the Grbl configuration.

[woodandtwine (Rod)]

@WillAdams

then re-configure the BitSetter position, but don’t send the Grbl configuration.

ok i was able to adjust my x and y travel based on that article and things are coming out correctly. but how i re-configure the BitSetter position? the only option that i know of is to “Set Up New Machine”

[woodandtwine (Rod)]

ok i got it. i didn’t realize that i can reset the bitsetter position by clicking “Set Up New Machine” and not send the GRBL settings in the process. Honestly this is a little confusing. i was expecting to see a setting under “Settings” to change the bitsetter. After making these changes my machine is working as expected! thanks for your replies