Issue - Pad error (Bug?)

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Batucada
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Re: Issue - Pad error (Bug?)

Post by Batucada »

Bance wrote: Wed Oct 05, 2022 9:11 am In terms of contact, there is a well known problem in OCCT that occurs in certain situations, we refer to this as the Co-planar issue.
Ok, I understand. If I apply this to my own experience, it opens up previously unknown possibilities. In my first case, I "subsequently glued" a pad based on the same plane, positive in the initial case and reversed in the "glued" case.
This usually manifests itself where solids are tangentially connected, overlap is the most secure way.
In my second test attempt I had used a symmetrical pad, adding a second pad on the "positive" side did not cause any problems, but on the "reversed" side it did. Now I learned at some point that the solver performs an adjustment against convergent conditions. And this is based on floating point arithmetic. I guess that went just fine on the positive side, while it led to a problem on the reversed side. As a solution, I would suggest not to negotiate the necessary offset for such manipulations to the decimal place, but to take into account a small deduction, which should then guarantee the overlap.
Bance
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Re: Issue - Pad error (Bug?)

Post by Bance »

This problem is in OCC not FC, there is nothing FC dev's can do about it.
chrisb
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Re: Issue - Pad error (Bug?)

Post by chrisb »

If you want any parametric in your model, there is no advantage in limiting a body to a single pad. Instead of creating a second body with another single pad and finally joining both together you can almost always do the same in a single body. If it ever fails, you can still look for a workaround, but starting right away with unnecessary workarounds, makes models unclear, which I would rate as worse instead of better.
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Batucada
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Re: Issue - Pad error (Bug?)

Post by Batucada »

chrisb wrote: Wed Oct 05, 2022 1:46 pm If you want any parametric in your model, there is no advantage in limiting a body to a single pad. Instead of creating a second body with another single pad and finally joining both together you can almost always do the same in a single body. If it ever fails, you can still look for a workaround, but starting right away with unnecessary workarounds, makes models unclear, which I would rate as worse instead of better.
I think that I have gradually understood the system. It just took a little time. Unfortunately, your explanation is a bit abstract and not always immediately understandable for a newcomer like me. On the other hand, the second-last statement by @Bance confirmed my assumptions; I have already been able to apply this several times by deliberately causing the overlap by a deviation of 1/10000 mm. The workaround is therefore not even noticeable.
lordsansui
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Re: Issue - Pad error (Bug?)

Post by lordsansui »

onekk wrote: Wed Oct 05, 2022 8:39 am
lordsansui wrote: Sat Oct 01, 2022 8:54 pm check also this attached image to see some influence in the length
EDIT: But your final design shown has not 90 degree angles, so probably the example is not done for the image you have shown.

Regards

Carlo D.
Hello Carlos,

There are two posts with images, the first one you can see a flared horn (cone) folded 90 degrees where I highlighted that the cross sectional are will be different and the beginning and at the end of the fold, and the second one the image refers to a straight flare also folded at 90 degrees, but it shows different lengths for the same thing.

While folding you need to guarantee the progression of the flare, so, the angle should be constant at the same time the folded horn must have the same path length as an equivalent unfolded horn. In this way you improve accuracy reducing the error between CAD software, Acoustical Power Response Simulation and real loudspeaker measurement with microphone.

So to combine both things in a sketch that automatically do things for you, it needs a lot of constrains. I wish I could use less constrains for all the benefits it brings.
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onekk
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Re: Issue - Pad error (Bug?)

Post by onekk »

lordsansui wrote: Sat Oct 22, 2022 2:56 pm ...
Probably I would use a different approach, but if you have to use woods you are limited to "planar faces", so it could not be feasible, but using a "tube" operation (I misel using scripting so I don't remember the exact GUI name BREPAlgomakePipeShell in Python not exactly this name but on mobile I can't remember the exact name now.) and using the appeopriate transition with and angled path something similar could be achieved.

You have to use a sketch for the section and probably another sketch or a wire fir the path to follow.

Interesting challenge, if I found some spare time I will try to make an example.

Regards

Carlo D.
GitHub page: https://github.com/onekk/freecad-doc.
- In deep articles on FreeCAD.
- Learning how to model with scripting.
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Blog: https://okkmkblog.wordpress.com/
lordsansui
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Re: Issue - Pad error (Bug?)

Post by lordsansui »

onekk wrote: Sat Oct 22, 2022 3:27 pm
lordsansui wrote: Sat Oct 22, 2022 2:56 pm ...
Probably I would use a different approach
I might wanna check the link below to better understand what I'm doing.

https://freeloudspeakerplan.rf.gd
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onekk
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Re: Issue - Pad error (Bug?)

Post by onekk »

lordsansui wrote: Tue Oct 25, 2022 10:01 pm ...
I might wanna check the link below to better understand what I'm doing.
...
Very interesting, I will note down the link for future reference.

If you have to design specific things that have to be build out of wooden panel (or similar panel material) you have to model them in a specific way.

I see that maybe using the technique I have cited would not be an option, as then you have to split the continous form in pieces to permit to build them using panels.

Sorry for the nuisance.

Regards.

Carlo D.
GitHub page: https://github.com/onekk/freecad-doc.
- In deep articles on FreeCAD.
- Learning how to model with scripting.
- Various other stuffs.

Blog: https://okkmkblog.wordpress.com/
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