Assembly3: Why redundant constraint? How to fix turning parts?

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DBA
Posts: 1
Joined: Fri Aug 13, 2021 7:32 am

Assembly3: Why redundant constraint? How to fix turning parts?

Post by DBA »

Hi all,

I'm using FreeCAD Link Daily 2021.07.17 for this construction. I encountered this issue in a larger, more complex construction so I created a demo file which is attached.
Basically I'm trying to simulate the use of a screw to fix two parts together.
screen1.jpg
screen1.jpg (74.63 KiB) Viewed 1017 times
In a real application, the pressure of the screw would fix the two surfaces against each other due to friction. Aseembly3 doesn't provide such a constraint (for good reasons), so I've tried to think about how I could emulate this and I came up with using a PlaneCoincidence constraint on the two holes (upper and lower circle of the holes of each part). That basically simulates a "loose screw". The parts are fixed together but can turn against each other.
screen2.jpg
screen2.jpg (52.7 KiB) Viewed 1017 times
Now I thought I will just add another constraint, like here in this example a SameOrientation constraint on two surfaces, or fixing a point onto another point (two corners that align) or onto a line.
screen3.jpg
screen3.jpg (50.34 KiB) Viewed 1017 times
This works in a way and aligns the parts as expected, but all of these create the issue that I get a warning that reads

09:25:57 20.916616 <asm3.sys> sys_slvs.py(66): redundant constraints

First of all I don't understand why they would be redundant (is this a bug?) - they seem to do two different things in my view.

Second, if this is not the right way to do this: what's a better or correct way to do this?

Thanks a lot!
Attachments
RedundantConstraintDemo.FCStd
(35.72 KiB) Downloaded 9 times
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