Path workbench, how to lay a part flat?

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derkork
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Joined: Tue Jul 27, 2021 6:45 pm

Re: Path workbench, how to lay a part flat?

Post by derkork »

Gene, thank you for outlining your process. I tried this but I really got confused by how this rotation thing works but was finally able to lay the part flat using a -60 degree angle and Y-Axis:
2021-07-30_12-57-57.png
2021-07-30_12-57-57.png (39.36 KiB) Viewed 831 times
But it is still well above the XZ-plane. So now it needs to go down to the XZ-plane. But how far? I cannot find a way to measure how far this thing is above XZ-Plane exactly. I can try to eyeball it, but that is always going to be inaccurate. My assumption (which may be wrong) is that the part (and the stock) need to lie flat on the XZ-plane (not hover above it) because that is how they would lie in the CNC machine.

As for the "missing something" part, maybe I am just overthinking this but let my lay out my problem here: In this particular file you can actually know the plane's angle because its an equilateral triangle so the plane must have been rotated by 60 degrees and the face is only rotated on one axis. But if the part happens to be rotated about multiple axes (e.g. 30 degrees X-axis and 60 degrees Y-axis) I wouldn't even know how to enter this into the rotation fields. Finally it may not always be the case that you know or can easily calculate how a part is rotated in space, especially if you just place a datum plane on a face. If I went for something else than an equilateral triangle (maybe attach something to some D20 dice face) there may not be an easy way to find out at which angle that datum plane is tilted. That's why I am looking for a simple and straightforward way to lay a part flat on a particular face. This functionality exists e.g. in slicing software for 3D printing and is super useful for quickly orienting a part into a direction suitable for printing and I think this would also work very well for the path workbench.
derkork
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Re: Path workbench, how to lay a part flat?

Post by derkork »

jamtek wrote: Thu Jul 29, 2021 2:07 am I had posted earlier in the Path/CAM forum with a link to the YouTube video that gave me the idea.
https://forum.freecadweb.org/viewtopic.php?f=15&t=59037
That is actually a very neat way of doing this, albeit with a few bit more clicks. But it totally takes the guesswork out of this and i figure it would also work for more complex parts.
chrisb
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Re: Path workbench, how to lay a part flat?

Post by chrisb »

derkork wrote: Fri Jul 30, 2021 11:18 am But it is still well above the XZ-plane.
When you hover over the face you see the position in the status line at the bottom. Move the z-component by the negative of that value.
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GeneFC
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Re: Path workbench, how to lay a part flat?

Post by GeneFC »

derkork wrote: Fri Jul 30, 2021 11:18 am As for the "missing something" part, maybe I am just overthinking this but let my lay out my problem here: In this particular file you can actually know the plane's angle because its an equilateral triangle so the plane must have been rotated by 60 degrees and the face is only rotated on one axis. But if the part happens to be rotated about multiple axes (e.g. 30 degrees X-axis and 60 degrees Y-axis) I wouldn't even know how to enter this into the rotation fields.
There is no magic in FreeCAD. Every element is precisely placed with exact numbers. They are in there somewhere. Look in the "Placement" and "Attachment" entries of the Properties panel below the Combo box.

I agree it would be extremely useful to click on a face and select "place on the x-y plane" for subsequent use in the Path WB. I do not believe this currently exists other than perhaps the camera tricks.

But in any case the numbers are there. Multiple angles can become very confusing. One way to deal with the issue is to ensure that the plane you plan to process in the Path WB is already at the correct location. I agree that may not be practical in complex cases.

Gene
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jamtek
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Re: Path workbench, how to lay a part flat?

Post by jamtek »

derkork wrote: Fri Jul 30, 2021 11:50 am That is actually a very neat way of doing this, albeit with a few bit more clicks. But it totally takes the guesswork out of this and i figure it would also work for more complex parts.
Oh, I just watched Sliptonic's recent YouTube video, It's super easy to re-orientate the Z axis, no math involved!
https://www.youtube.com/watch?v=g55hiFvq5Ns
When setting up the job I selected one of the interior vertices of your triangular holes and clicked n Z-Axis. I then set the origin to a bottom corner and refreshed the bounding box.
Peek 2021-07-30 11-17.gif
Peek 2021-07-30 11-17.gif (918.14 KiB) Viewed 775 times
derkork
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Re: Path workbench, how to lay a part flat?

Post by derkork »

jamtek wrote: Fri Jul 30, 2021 3:42 pm Oh, I just watched Sliptonic's recent YouTube video, It's super easy to re-orientate the Z axis, no math involved!
https://www.youtube.com/watch?v=g55hiFvq5Ns
When setting up the job I selected one of the interior vertices of your triangular holes and clicked n Z-Axis. I then set the origin to a bottom corner and refreshed the bounding box.
Peek 2021-07-30 11-17.gif
I think we have a winner here. That would work for basically anything no matter at which angle it is rotated. And it is very easy to use. Thank you very much for sharing this!

Also thanks to everyone else providing help and insights here, I certainly learned a lot!
GeneFC
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Re: Path workbench, how to lay a part flat?

Post by GeneFC »

jamtek wrote: Fri Jul 30, 2021 3:42 pm It's super easy to re-orientate the Z axis, no math involved!
As long as there is an edge that should be aligned with an axis that is correct.

I am not aware of any method to orient a "face". I just tried some experiments in a very recent version of FreeCAD, and I could orient edges, as you say, but not planes. Might be done with multiple steps.

In many or most cases the existing capability will work for the required orientation.

Gene
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