Generate Rotate Pattern with Specific Loft

[Spindoctor]

Hello!

I try to generate a Rotate Pattern with a specific loft in FreeCAD 0.20.

FreeCAD wouln't show an error message, however, the copies of the loft do not appear.

Bildschirmfoto-20210425180405-956x818.png (101.95 KiB) Viewed 1120 times

Can you tell me, what I am doing wrong and how to do it right? Or is this a bug?

Thank you in advance!

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OS: Debian GNU/Linux bullseye/sid (GNOME/gnome-xorg)
Word size of FreeCAD: 64-bit
Version: 0.20.24693 (Git) AppImage
Build type: Release
Branch: master
Hash: e01f0d25d5f3ef9ceb66aa087212121e9f2f2e8b
Python version: 3.9.2
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.1
Locale: German/Austria (de_AT)

[Bance]

Why did you attach the sketches to datum planes?

[chrisb]

I fumbled quite a lot with this, so I finally cannot say what brought the difference (made things overlap, turned sketches to get seams out of the way, removed useless DatumPlanes, which were attached to generated geometry, attached sketches to sketches unti it worked). Then reverted some of the changes, and it is still ok. You may compare it to your model and try to change yours becoming mine.

[Bance]

The loft sketches themselves are not very well constrained, after that is sorted the easiest was just to offset from XY Std plane.

[Spindoctor]

Hello and thanks for your replies!

You are right about the planes. The way I used them in my little sketch doesn't make much sense. I trained myself to use planes whenever possible. Is this a bad habbit? What do you think?

However, back to topic:
Thanks to @chrisb's example I think I was able to narrow down the problem and make my example even more "minimal" (please find it attached).

I added an octagon to Sketch001. Interestingly, the PolarPattern works when I drag the vertical line from Sketch001 (the only left degree of freedom) inside the octagon and it fails when I leave it outside (please try it out yourself).

Bildschirmfoto-20210426211006-1890x403.png (41.06 KiB) Viewed 1046 times

In other words: the polar pattern only works when the "clones" of the Additive Loft overlap.

So I would like to ask again: is this a bug or am I doing something wrong?

By the way: With your help I was already able to solve my initial problem, so I only ask out of "academic" interest and because I want FreeCAD to get better and better

[Bance]

So I was wasting my time?

[chrisb]

The way I used them in my little sketch doesn't make much sense. I trained myself to use planes whenever possible. Is this a bad habbit? What do you think?

Always using DatumPlanes seems to be a case of personal preferences. In general I use DatumPlanes only if I have more than one sketch in the same plane, and even then I often attach one sketch to another. I do this because it keeps the model tree cleaner. Planes have the advantage, that you can make them directly visible.

So I would like to ask again: is this a bug or am I doing something wrong?

I am not sure and would like to add an additional model, where I replaced the loft with a pad. The instances don't overlap as well, but the Pattern works anyway.
I would guess that it is an OCC issue, but as I'm not sure please add a ticket.

[Vincent B]

I think sketches must go to the y axle to avoid trouble.

[Spindoctor]

So I was wasting my time?

not at all!

I am grateful for every help I can get and your hint definitely got me closer to both: a more concise minimal example and the solution of my initial problem!

[Spindoctor]

I think sketches must go to the y axle to avoid trouble.

As far as I could investigate the issue, it's definitely a way to attach the sketch to the y axis.

However, it is also enough to let the clones overlap just a little bit.

But I see no obvious reason, why the model should be invalid when the clones do not overlap - as chrisb stated, it works with pads instead of lofts.