Cut/chamfer from one edge to another?

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DejitaruJin
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Joined: Thu Jul 29, 2021 12:46 am

Cut/chamfer from one edge to another?

Post by DejitaruJin »

I've spent several hours just trying to get this one corner knocked off, but have gotten absolutely nowhere. This is supposed to be an angled support for 3D printing, but because of how FreeCAD works it had to be extruded at a right angle, and as the result of some history sequence instead of an isolated object. The only thing I need to do with it, is connect two edges. They are non planar, but this would usually not be an issue. Right now it has a chamfer applied as best I can, but that exposed face is enough to be a problem for my printer. Incidentally, if you make it close enough it makes the program crash!

If I try to chamfer it fully, it breaks when the value exceeds the length of the shortest side edge, instead of just, like... doing what it can. If it worked, this would result in a curved or angled face between the two nonplanar edges, which is fine.

If I try to use a subtractive box, there doesn't seem to be a way to make that box only subtract from this pad. If it worked, it would end up moving the upper edge down along the vertical face at an angle, which is fine.

If I try to reorder my pads so there's nothing else in existence when the subtractive box hits, it just screws everything up completely.

I thought I might be able to make a Subtractive Loft from one edge to the other, but it seems Lofts can not use edges.

This is an extremely simple, extremely common action when drafting for manufacturing. But how do I handle it here?

OS: Linux Mint 19.1 (XFCE/xfce)
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Word size of FreeCAD: 64-bit
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OCC version: 7.4.0
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jmaustpc
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Re: Cut/chamfer from one edge to another?

Post by jmaustpc »

Welcome to FreeCAD.

Sounds like there may be something non-valid in your file for some reason. If you can post the file we could have a look at it.

One tip regarding chamfer and fillet, they are limited in so far as they can not fully consume a face or they will be considered invalid. That is actually an OCC thing (the CAD kernel used by FreeCAD), not exactly FreeCAD.
DejitaruJin wrote: Thu Jul 29, 2021 1:15 am This is supposed to be an angled support for 3D printing, but because of how FreeCAD works it had to be extruded at a right angle, and as the result of some history sequence instead of an isolated object.
If I am understanding your comment correctly, that is not true. Are you saying that you only want to model just that bracket and not the entire object? If so it must be a separate "Body" object if you are using PartDesign. You can in effect extrude or similar, in many different ways not just at right angles. But I am not sure what exactly you mean.

Jim
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papyblaise
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Re: Cut/chamfer from one edge to another?

Post by papyblaise »

Is that what you want
you make a triangle on each side and a subtractive Loft
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DejitaruJin
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Re: Cut/chamfer from one edge to another?

Post by DejitaruJin »

Oh wow, it looks like a Subtractive Loft between two triangles is exactly what I need here, based on tests I did at work. Quite a bit of extra effort to go through for a chamfer, but at least my model only has four such supports.

Note for anyone who finds this through Google, if the support is up against a curved edge (as in my test) this method will leave a bit behind, as one would expect. The greater the arc length (or technically, more arc degrees) taken up by the support, the more geometry will be left behind. In my case, the difference between radius vs support width is great enough that the amount left behind is too small to consider.
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freedman
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Re: Cut/chamfer from one edge to another?

Post by freedman »

Sometimes when there are complex angles it's easier to make your support short and then model in the last angled portion as a separate pad. This way you work with adding material instead of trying to be accurate at cutting it away.
GeneFC
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Re: Cut/chamfer from one edge to another?

Post by GeneFC »

DejitaruJin wrote: Thu Jul 29, 2021 4:42 pm Oh wow, it looks like a Subtractive Loft between two triangles is exactly what I need here, based on tests I did at work. Quite a bit of extra effort to go through for a chamfer, but at least my model only has four such supports.
I am not completely clear about what you are trying to do, but one thing to consider is to "bury" the end of the support strut inside the mating piece. It can make dealing with exact edges and small gaps a lot easier.

In Part Design everything in a single body ends up as a single solid. Overlaps generally do not cause any problem and they can work to solve some tricky alignment issues.

Gene
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papyblaise
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Re: Cut/chamfer from one edge to another?

Post by papyblaise »

so you prefer that, (it's a method)
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Shalmeneser
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Re: Cut/chamfer from one edge to another?

Post by Shalmeneser »

Something like that ?
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papyblaise
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Re: Cut/chamfer from one edge to another?

Post by papyblaise »

chick that SHALM offers a potatoid hole :lol: :lol:
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