Behavior different between QCAD CAM & Linuxcnc

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JSRoy
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Joined: Fri Sep 22, 2017 9:28 pm

Behavior different between QCAD CAM & Linuxcnc

Post by JSRoy » Wed Oct 04, 2017 10:46 pm

Hi,

I'm relatively new in the world of CNC.

I'm working on carving a number on wood. To do so, I drew a number, "exploded" it, created a CAM path and exported it. But when I load it from LinuxCNC I see the that the cutter path is different from what I expected. In QCAD/CAM, my path is on the outside of my number "2". But when I load my exported path inside linuxcnc, at some point, but only at a specific point, it is actually cutting inside of my number "2".

I'm hoping that someone could explain why this happened so I can learn from this. Also, how can I fix this?

Thank you,

JSRoy
Attachments
mince_2.nc
(7.71 KiB) Downloaded 52 times
path_In_LinuxCNC.png
path_In_LinuxCNC.png (15.96 KiB) Viewed 2226 times
path_I_Expect_QCADGenerated.png
path_I_Expect_QCADGenerated.png (6.49 KiB) Viewed 2226 times
test228.dxf
(364.08 KiB) Downloaded 52 times

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andrew
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Joined: Fri Mar 30, 2007 6:07 am

Re: Behavior different between QCAD CAM & Linuxcnc

Post by andrew » Thu Oct 05, 2017 9:16 am

When using G41/G42/G40, it is possible that a controller interprets things differently than QCAD/CAM does, especially when the path intersects itself as is the case here. You will likely just have to clean up your path in that area to create a clean corner (use Modify > Trim Both):
Screen Shot 2017-10-05 at 09.12.55.png
Screen Shot 2017-10-05 at 09.12.55.png (8.27 KiB) Viewed 2220 times
Screen Shot 2017-10-05 at 09.13.02.png
Screen Shot 2017-10-05 at 09.13.02.png (6.62 KiB) Viewed 2220 times

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Husky
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Re: Behavior different between QCAD CAM & Linuxcnc

Post by Husky » Thu Oct 05, 2017 8:41 pm

Hi,

I'm not a QCAD/CAM or LinuxCNC guy but this first screenshot captivates me .... :shock:

You are sure that LinuxCNC is using the same Mill diameter? If this solid white circle in the screenshot represent the tool diameter then it looks way to big and will mill INTO the Number 2 ....

And the milling start point is also correct? I assume you are using a 3/8" mill. If so then the start point should be somewhat around x 0.1875, y 0.1875. Regarding the screenshot it's much less than 0.1875. That would lead to a milling INTO the Number 2 ....

And the dxf drawing has mostly up to 6 identical stacked lines ....

Just loud thinking ..... :wink:
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