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Problem with Tolerance

Posted: Tue Jun 15, 2021 2:33 pm
by mcsteve
Hello all. Recently I've been experiencing some errors in dimension. Normally I am doing projects that I just rough dimension on the CNC and then finish with other processes. Projects like crib boards and such I typically use the sander to bring caps to the correct radius dimensions.

A most recent project is to place a small watch face in a cell phone stand to act as a desk clock when the cell phone is in use. The hole dimension was to be 1.275" but the actual pocket created was 1.222". This has caused me to create a tolerance test for my machine that I could check with a miter gage. The machine appears to be under sizing almost every entity in the project. Before I start messing with things I thought it best to check with those who have experience to gain your thoughts. My system is a Shark Pro Plus using the latest version of V Carve (10.514) for code creation.

I have attached the CNC files as well as representation of what was actually cut.

Any thoughts on where to start with trying to correct my issue?

Thanks in advance.

Re: Problem with Tolerance

Posted: Wed Jun 16, 2021 10:57 am
by Kayvon
I've experienced the same issue when cutting gears for clocks. The arbor holes don't precisely match what I expect, so I go back and use a drill press to get the precise hole size I want.

I've never investigated it closely enough to fix it, but I suspect the problem lies between bit sizes not perfectly matching and some small amount of flex in the plastic gantry.

Re: Problem with Tolerance

Posted: Wed Jun 16, 2021 12:53 pm
by mcsteve
My first thought has been that it was flex in the gantry as well, but this would not explain why I am getting differences in the horizontal and vertical line distances as well.

I try to keep an eye on my bits as well considering that many are not "top of the line" brands. In this case I was using a Frued 2 flute spiral .25 bit with an actual of .244 so I had actually oversized the hole but that didn't help as the size difference was significant. My current thinking this may be an encoder issue. Do you know if there is a way to see the encoder settings in the Shark control panel so I can match those against the actual specs for steppers installed?

Steve

Re: Problem with Tolerance

Posted: Thu Jun 17, 2021 11:20 am
by Kayvon
Try CTRL+E or CTRL+G in the Control Panel.

Re: Problem with Tolerance

Posted: Thu Jun 17, 2021 12:21 pm
by mcsteve
I’ll give that a try. Thx.