Overlapping edges using PolarPattern

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RussG
Posts: 124
Joined: Wed Apr 27, 2022 11:27 pm

Overlapping edges using PolarPattern

Post by RussG »

OS: macOS 10.16 (I guess people here know that no such macOS was ever released. I’m running 11.5.2)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24366 (Git)
Build type: Release
Python version: 3.9.7
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.3
Locale: C/Default (C)

I have a question about the attached FCStd file PolarPattern_Overlap.FCStd. I looked at about 5 or 6 pages returned in my search of the forum but didn't find an answer. To make the file I used the Part Design Workbench. I made one Sketch, padded it, and then applied a PolarPattern.

In one of the screenshots, 5_petals.jpg, the PolarPattern has 5 occurrences and therefore shows 5 flower petals. In the other screenshot, 8_petals.jpg, the PolarPattern was changed to 8 occurrences and in the screenshot showing this you can see how the flower petals overlap. It is this overlapping about which I am inquiring. Specifically, does this overlapping represent a FreeCAD faux-pas or a CAD faux-pas in general? I didn’t receive any FreeCAD error messages (but it was problematic when trying to apply a fillet or chamfer to the edges of the petals; there are no fillets or chamfers in the attached file, BTW) When I output an STL of the PolarPattern with 8 occurrences and opened it in PrusaSlicer 2.4.2 it seemed OK there too, from what I could tell with my very limited experience.

So, is this sort of overlapping generally to be avoided? Is it usual and to be expected? How in general should I think about this sort of thing?

Thanks!
PolarPattern_Overlap.FCStd
(36.32 KiB) Downloaded 11 times
5_petals.jpg
5_petals.jpg (171.96 KiB) Viewed 515 times
8_petals.jpg
8_petals.jpg (198.92 KiB) Viewed 515 times
drmacro
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Re: Overlapping edges using PolarPattern

Post by drmacro »

FreeCAD executes the pattern around the axis (in this case the center) it simply copies the shape of the petal. It does not resize the petal. If the petal takes up more the 360/8 degrees, it overlaps.

360/5 does not.

It's certainly not a bug.
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
RussG
Posts: 124
Joined: Wed Apr 27, 2022 11:27 pm

Re: Overlapping edges using PolarPattern

Post by RussG »

Thanks for your reply. It seems my question may not have been made clearly enough. I wasn't asking what PolarPattern does. I know what it does. I wasn't suggesting there was a bug in FreeCAD. What I was asking is if when PolarPattern is used and it creates overlapping edges (because of the user choosing settings that created the overlaps), will that will create a problem further down the line such as when trying to 3D print the file. In other words, is there anything problematic about a FreeCAD file with such overlaps when it comes to 3D printing, or for that matter, elsewhere. I was asking if creating files with this sort of overlap should be avoided or if it is OK.
drmacro
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Re: Overlapping edges using PolarPattern

Post by drmacro »

Not necessarily. You can set the Refine property to true and it will merge the seam lines where it can. This can be necessary for some further operations.

But, the model in you images should slice ok.
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."
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Shalmeneser
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Re: Overlapping edges using PolarPattern

Post by Shalmeneser »

Refine=true will fuse coplanar faces and will suppress 'useless' lines. It's useful with fillet and visualisation.
chrisb
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Re: Overlapping edges using PolarPattern

Post by chrisb »

RussG wrote: Fri May 20, 2022 12:31 am In other words, is there anything problematic about a FreeCAD file with such overlaps when it comes to 3D printing, or for that matter, elsewhere. I was asking if creating files with this sort of overlap should be avoided or if it is OK.
It is completely ok to model with such overlaps, they occur frequently with simple pads too. 3D printing - or to be more precise - creating a mesh from such a solid is no problem at all, I have done it often.

As Shalmeneser said, Fillets and Chamfers can have problems going across vertices where more than 3 edges meet, and then a refine can help. I do definitely not recommend to do automatic refines though, because some models fail without any understandable reason then, while the issues occurring with fillets can easily be spotted with some experience.
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