PolarPattern appears to work but not visible

[garya]

In the attached file, the next to last feature is a loft of two partial sections of the top rim, which is a linear pattern of the bottom rim.
The loft appears to work fine (feature "Proto_Support")
However, when I try to propagate that to the other pillars with a polar pattern, the it appears to work (no errors reported) but the additional supports do not show up. I can see the outline of the bottom sketch of the loft on each of the pillars, but the loft isn't there.
Ideas about what I'm doing wrong?

PolarPatrn_1.FCStd

(122.25 KiB) Downloaded 47 times

OS: FreeBSD 11.4-RELEASE-p6 (XFCE/xfce)
Word size of FreeCAD: 64-bit
Version: 0.20.master
Build type: Release
Python version: 3.7.9
Qt version: 5.15.2
Coin version: 4.0.0
OCC version: 7.5.0
Locale: C/Default (C)

[Shalmeneser]

There is clearly a problem.
We can see seams around the top.
The Std_DependencyGraph seems correct.
Part_CheckGeometry seems correct.

Modifying the Proto_Ssupport Loft, against coplanarity doesn't heal anything.

I don't know.

[TheMarkster]

It is a coplanar issue. I used PDWrapper macro to 3D offset the support by .1 mm and it works.

Snip macro screenshot-af422b.png (98.74 KiB) Viewed 2503 times

Usage:

1 install pdwrapper (tools menu -> addon manager -> macros)
2 Delete Supports (last polar pattern feature in tree)
3 select Proto_Support, run macro -> additive type -> follow Proto_Support in the tree
3 select PDW_Add object, set Show Offset Props to True (at bottom of property list)
4 set Tip Tool Offset property to 0.1
5 set Pattern Tool Offset property to 0.1
6 select PDW_Add, execute polar pattern feature -> 4 occurrences

This is a workaround for the real problem -- the boolean fusion fails due to coplanar faces. You haven't done anything wrong, it's just a bug in the CAD kernel that FreeCAD uses (OCCT). A better workaround is to enlarge the sketches used to create the Proto_Support object.

What the PDWrapper macro does here is uses 3D offset to enlarge the Proto_Support loft only very slightly by 0.1 mm. A smaller value might also work or perhaps even a negative value. The Tip Tool Offset modifies the original object. The Pattern Tool Offset modifies the extra copies made by the polar pattern tool, or more specifically, the shape that the polar pattern tool makes copies of.

[Shalmeneser]

Modifying the offset manually, I cannot successed.

[garya]

In an attempt to get around this, I changed the order of construction to get rid of the polar patterns.
In this simpler model, it fails to even loft the first time.

PolarPatrn_2.FCStd

(45.23 KiB) Downloaded 29 times

[garya]

If I save and reload PolarPatrn_2, it looks ok.
If I then try to create a polar pattern of the Proto_WindingRib and the Loft, it fails with the message "One transformed shape does not intersect support".
I don't understand that -- in the attached image, it looks like the top of the original upright is cut off.

PolarPatrn_2.jpg (92.87 KiB) Viewed 2443 times

[TheMarkster]

Maybe it is not a coplanar face problem then, but something else that is being corrected with the offset. I tried scaling, but that also fails.

Another workaround is to use fillets for the support structure:

Snip macro screenshot-5b85f1.png (92.64 KiB) Viewed 2414 times

[garya]

Another workaround is to use fillets for the support structure:

I was trying to avoid using fillets because they don't seem to work with transforms, so subsequent additions don't always work.
For example, if I create only the proto_post and add fillets to it, then do a polar pattern to get posts with fillets, I can't do that. Maybe I just don't know how to do that properly.
I tried making the sketches 0.1mm smaller than the rims, and also 0.1mm larger, and in both cases it fails to create the polar pattern.

[TheMarkster]

I usually save the fillets for last because they are quite fragile to topological naming and because they are fairly simple (if a bit tedious) to do. Another train of thought is to do them very early in the process.

You can use a multitransform to add the fillet, polar pattern it, and then mirror it.

Snip macro screenshot-9a5c58.png (89.4 KiB) Viewed 2352 times

[garya]

Thanks.
I tried simplifying by getting rid of the angular constraints and circular aspects of the pillar and loft, so the pillar is square and the loft sections are a square and a rectangle. I also reduced the base to simply two circles. It still fails.

PolarPatrn_4.jpg (11.98 KiB) Viewed 2326 times

PolarPatrn_4.FCStd

(32.32 KiB) Downloaded 37 times

However, if the base is a square, it works.

PolarPatrn_3.jpg (26.18 KiB) Viewed 2326 times

PolarPatrn_3.FCStd

(47.07 KiB) Downloaded 35 times