Newbie need help, outputs are 1mm smaller

Reehtjurd · 2020-03-05

Hi folks, I have been cnc routing a lot and just realized that outputs are 1mm smaller ( X by 0.5mm and Y by 0.5mm ). Thanks in advance, Richard.

difalkner

· #2 · Mar 5, 2020

Have you measured your bit to see if it is actually 3.175mm? I had a similar problem with a 1/8" bit that should have been 0.125" but when I measured it I found it to be 0.123". Same with a 1/4" bit that should be 0.250" and is actually 0.245". So I now have those defined in the tool library with their actual size and my parts come out pretty accurate.

David

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MEBCWD

· #3 · Mar 5, 2020

Richard have you calibrated you machine? This may be your problem.

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Reehtjurd

Discussion Starter · #4 · Mar 5, 2020

difalkner said:
Have you measured your bit to see if it is actually 3.175mm? I had a similar problem with a 1/8" bit that should have been 0.125" but when I measured it I found it to be 0.123". Same with a 1/4" bit that should be 0.250" and is actually 0.245". So I now have those defined in the tool library with their actual size and my parts come out pretty accurate.

David

Looks like i need a caliper. Seller (local) said that it is 3.175mm and I think I'm using the biggest bit. Well, you know, it is from China :lol: I got set of 10 (0.8 - 3.175mm) for around 6bucks.
Well, i will update you as soon as i get a caliper.

Thanks David!

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stevenrf

· #5 · Mar 5, 2020

Sounds to me like all you need to do is account for this in your backlash settings as with MACH3 after you have verified the exact diameter af the tool.

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difalkner

· #6 · Mar 5, 2020

Reehtjurd said:
Well, i will update you as soon as i get a caliper.

Thanks David!

Glad to assist! Also, if your pocket is a flat bottom, then set your Radial Stock to Leave at say 0.005" (or 0.127mm) or some small amount and Axial to 0.0". Then make a second pass using either 2D or 3D Contour in Conventional Cut with no stock to leave. You can generate these as one file for G-code and as soon as the pocket finishes cutting it will move to the finish pass without having to do anything else. That will give you a more accurate dimension than just using the Pocket Tool.

You should still have a set of calipers but you might try this second pass with the different profile before you head out to get the calipers.

David

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Reehtjurd

Discussion Starter · #7 · Mar 7, 2020 (Edited)

difalkner said:
Glad to assist!

When i set my $100=800step/mm which is 400step/mm before and run G91 G21 X100, it stalls. Is this because of uneven screw on the coupling or because it is too much for the stepper?

*Stepper motor is Nema17, 8mm threaded rod / 2mm pitch.

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Reehtjurd

Discussion Starter · #8 · Mar 9, 2020

MEBCWD said:
Richard have you calibrated you machine? This may be your problem.

stevenrf said:
Sounds to me like all you need to do is account for this in your backlash settings as with MACH3 after you have verified the exact diameter af the tool.

difalkner said:
Glad to assist! Also, if your pocket is a flat bottom, then set your Radial Stock to Leave at say 0.005" (or 0.127mm) or some small amount and Axial to 0.0". Then make a second pass using either 2D or 3D Contour in Conventional Cut with no stock to leave. You can generate these as one file for G-code and as soon as the pocket finishes cutting it will move to the finish pass without having to do anything else. That will give you a more accurate dimension than just using the Pocket Tool.

You should still have a set of calipers but you might try this second pass with the different profile before you head out to get the calipers.

David

Hi folks,
Today, i tried cutting with easel again. pocket size is perfect but starting position is off like it was before.

With easel, i got perfect cut but starting position is off. Fusion360, starting point is perfect but the pocket is off by 1mm for each x & y axis (0.5mm each side).

Imo, this tells me that the machine itself is doing fine and i don't think that recalibrate will fix this problem.

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difalkner

· #9 · Mar 9, 2020

Reehtjurd said:
Fusion360, starting point is perfect but the pocket is off by 1mm for each x & y axis (0.5mm each side).

Did you do this? In the Pocket cut, set your Radial Stock to Leave at say 0.005" (or 0.127mm) or some small amount and Axial to 0.0". Then make a second pass using either 2D or 3D Contour in Conventional Cut with no stock to leave. You can generate these as one file for G-code and as soon as the pocket finishes cutting it will move to the finish pass without having to do anything else. That will give you a more accurate dimension than just using the Pocket Tool.

David

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Reehtjurd

Discussion Starter · #10 · Mar 9, 2020

difalkner said:
Did you do this? In the Pocket cut, set your Radial Stock to Leave at say 0.005" (or 0.127mm) or some small amount and Axial to 0.0". Then make a second pass using either 2D or 3D Contour in Conventional Cut with no stock to leave. You can generate these as one file for G-code and as soon as the pocket finishes cutting it will move to the finish pass without having to do anything else. That will give you a more accurate dimension than just using the Pocket Tool.

David

Hey, that i forgot to try. I will do that first thing tomorrow. It's getting late here.
Thanks again David!

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Reehtjurd

Discussion Starter · #11 · Mar 10, 2020 (Edited)

difalkner said:
Did you do this? In the Pocket cut, set your Radial Stock to Leave at say 0.005" (or 0.127mm) or some small amount and Axial to 0.0". Then make a second pass using either 2D or 3D Contour in Conventional Cut with no stock to leave. You can generate these as one file for G-code and as soon as the pocket finishes cutting it will move to the finish pass without having to do anything else. That will give you a more accurate dimension than just using the Pocket Tool.

David

Just did it.
X1Y1 and XiYi only with 2D contour and the outputs are 99.9% (120mm x 90mm±0.05-0.1mm & 85mm x 65mm±0.05-0.1mm)
X2Y2 and XiiYii with 2D pocket (stock to leave; radial 0.127mm & axial 0mm) + 2D contour (both stock to leave 0mm) and it is almost there.
I give it another try but this time i will do 2d contour first for X2Y2 and XiiYii then 2d pocket.

*Dimension in fusion360
X1Y1 = 90x120 X2Y2 = 75x105mm
XiYi = 65x85mm, XiiYii = 50x70mm

Y1 said:

Y2 said:

X1 said:

X2 said:

Yi said:

Yii said:

Xi said:

Xii said:

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difalkner

· #12 · Mar 10, 2020

Looking good, Richard. In the 2D Contour profile Passes tab you'll see a check box labeled Repeat Finishing Pass and if you check that it will make a second pass around the selected contour. Do that and you'll probably be at your exact dimension. And I would cut the pocket first, then do the contour pass at full depth.

David

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