Internal Assembly WB: Cylindric Langth limit also limits the revolution. about freecad

[pierreporte]

I think it would be better to have a checkbox for each line, and remove the “Limits” one. There are cases when there can be a minimum but no maximum, and vice-versa.

[PaddleStroke]

I meant the property could hold special value to mean empty, while the UI shows empty. But yes it's not ideal anyway. Checkboxes and boolean properties are better.

[maxwxyz]

I guess because the angle limit is 0 on min and max?
@PaddleStroke can you confirm?

We discussed this briefly in #13850 (comment)
I guess either we need to handle 0 better but we cannot just ignore 0. Or make a new checkbox for the rotational limits (if a joint has multiple limits) or even a checkbox for each field (min/max), so you could define a min limit but don't limit max...

@FreeCAD/design-working-group any other ideas?
@FEA-eng how is FEM handling different limits?

[Panda631]

Why not handling 0 in min and max Input field as not constraint?

[FEA-eng]

@FEA-eng how is FEM handling different limits?

Do you mean handling of Assembly joints? FEM doesn't see and use them at all. It has its own constraints defined independently.

[maxwxyz]

@Panda631 0 as not constraint is not good. How could you limit a joint between 0 and 10 if 0 is ignored?
@FEA-eng no not joints but also regarding constraints. I think you can freeze or limit movement for certain directions in the FEM constraints. Can you specify a range in FEM and how is 0 in a ranged handled?

[Panda631]

@Panda631 0 as not constraint is not good. How could you limit a joint between 0 and 10 if 0 is ignored?

The Idea was 0 in min and max field. This ist the default setting and makes no sense as constraint. Just an Idea, a Check Box ist OK as well.

[FEA-eng]

Can you specify a range in FEM and how is 0 in a ranged handled?

No, you can only fix the displacement/rotation at 0 or prescribe a non-zero value. There are no such inequality/range constraints in commercial FEA software as well. To model something like this you usually have to include contact with rigid surfaces.

[PaddleStroke]

I thought I have done as Panda mentioned : Ignore if both min and max are equal to 0. But apparantly no.

Checkboxes are fine. That would mean that we need 4 boolean properties, one for each limit. Unless we use special values (like 123456) to mean disable in limits but this is a bit hacky.

[pierreporte]

The problem of special values is that the user must know them, while checkboxes are easily recognized, especially if coupled with disabling fields with an unchecked box.