topic Re: Any idea on how to drive/constrant this? in Inventor Forum

Any idea on how to drive/constrant this?

lch — Mon, 29 Sep 2025 11:02:06 GMT

Hi.

I want to drive this but i cant figure out the right constrant.

3D drawings are enclosed.

Any ideas?

Re: Any idea on how to drive/constrant this?

dan_inv09 — Mon, 29 Sep 2025 13:45:36 GMT

use that for the pin in the slot and then you probably just want a regular mate constraint that you will drive to move the parts.

Re: Any idea on how to drive/constrant this?

swalton — Mon, 29 Sep 2025 13:57:02 GMT

Thanks for posting models. I'm at work and can't download them, so here is some general purpose advice.

Try a transition constraint. You may have to add some work surfaces or points as "helper" geometry. https://help.autodesk.com/view/INVNTOR/2025/ENU/?guid=GUID-CD8AE8A0-03F0-468A-BE85-D7C5B989BA0B

You may need an axial mate constraint too.

Re: Any idea on how to drive/constrant this?

SBix26 — Tue, 30 Sep 2025 01:52:13 GMT

Before trying the transitional constraint, you must fix one of the components to 'ground'. As it is, the whole assembly is free to move in any direction, making constraint calculations unnecessarily difficult, if not impossible. The shaft seems like a logical part to be fixed. You can start over, placing the shaft first and, while placing, right click and choose "Place Grounded at Origin".

Then you'll need a couple of Insert constraints for the mounting bracket, an axial mate and a face mate for the pin, and an axial mate for the slider to the shaft.

Now that it's all locked down, use a Transitional constraint, picking first the pin face and then an adjacent slot face. This works pretty well, except for the transition to the short vertical section-- on my system it won't go around that corner, probably due to imperfectly perpendicular faces, or maybe not a big enough radius. I didn't spend the time to figure that out.

As @swalton pointed out, you might want to consider creating a surface in the slider part that is slightly offset from the slot faces and which you will use for the transitional constraint (and then turn off the visibility). That will keep the pin in the center of the slot instead of staying attached to the perimeter.

Then a constraint to drive the slider back and forth, or else just a mate constraint with limits so it doesn't jump off the pin when you drag it too vigorously.

Sam B

Inventor Pro 2026.1.1 | Windows 11 Home 24H2

Re: Any idea on how to drive/constrant this?

lch — Tue, 30 Sep 2025 07:42:44 GMT

Hi and thanks for all your reply.

I have tried using a transitional constraint, but it does not work.

Therefore, I created a new helix with a very precise and smooth transition from the helix to the vertical section.

This also does not work with the transitional constraint.

It is very unstable and either refuses to move or jumps to an incorrect position.

I have attached the new helix and hope you might be able to resolve the issue.

Lars

Re: Any idea on how to drive/constrant this?

johnsonshiue — Fri, 03 Oct 2025 01:19:57 GMT

Hi Lars,

By creating an offset surface on the groove and two small spheres on the rod, I am able to use Transitional Constraint to get the desirable movement. Please take a look at the attached file.

Many thanks!

Re: Any idea on how to drive/constrant this?

lch — Fri, 03 Oct 2025 04:21:59 GMT

Thanks a lot - I get the idea.

But its still to erratic.

I can't drive the shaft from the bottom to the top with a mate constraint.

I makes an error on it.

But thank for trying!