topic Re: How to precisely set position of assembly parts incorporating multiple joints? in Fusion Design, Validate & Document Forum

How to precisely set position of assembly parts incorporating multiple joints?

midvok — Fri, 24 Feb 2023 16:33:06 GMT

I've created a cabinet hinge (overlay type) which moves on 4 pivot pins. I've used the Revolute joint type for each of them, grounded the hinge body, and it moves just fine when dragging by mouse.

But I can't figure how to do these 2 things:

1. How to move the hinge leaf precisely to the intended angle (specified by the angle between X-axis of the body and X-axis of the movable leaf)? Setting the joint angle directly is not easily possible, because there are 4 joints with 4 angles, thus the kinematics is not so trivial.

The best I was able to do is to insert a Measure to check the angle (on the picture), but while there is the Measure I'm not able to move the assembly by mouse. So I have to close the Measure and then have no feedback how it moves, which makes it useless.

2. I would like to set 2 named positions (closed=0deg and open=110deg) and then be able to force the assembly to assume them. I noticed there is the "Go To Home" option, which could be used for at least the closed position, but I can't use that either because of the problem (1) - I don't know how to put the hinge exactly to 0deg angle.

I guess I would need something what can be done by inverse kinematics in Blender, but I have no idea how it's done in CAD systems like Fusion -- I bet it must be doable somehow since CAD systems are used for modeling by exact dimensions.

EDIT: Eventually I managed to set some approximate limits manually (by 2 joint angles) and set "Go To Home" for the closed 0deg position. It's in the attached file.

Re: How to precisely set position of assembly parts incorporating multiple joints?

jhackney1972 — Fri, 24 Feb 2023 15:17:29 GMT

The answer to your first question is to right click on the joint and select Drive Joint. You can enter any angle you desire or drag the joint to the position you desire. Then you can use the shown angle in the Joint Limits dialog.

Re: How to precisely set position of assembly parts incorporating multiple joints?

davebYYPCU — Fri, 24 Feb 2023 15:24:18 GMT

Two step process,

Each Joint, gives a reading of its current position, drag the moving side to 110 degrees, (trial and error / align to a sketch, etc)

When you have that, read off the current position of any one Revolve Joint, (Hide the Bodies if you can’t see them) and set that Joint limits to those values.

Now you can click drag the hinge from Zero to 110 but will not go past it.

Once the limits are set, you can also drive that Joint to the other end and Capture Position, stepping up and back in the Timeline will then do stop to stop moves.

Might help....

Re: How to precisely set position of assembly parts incorporating multiple joints?

midvok — Fri, 24 Feb 2023 15:36:24 GMT

Thank you for the tip. I've seen the Drive joint feature, but but it's a try-error approach, because no single joint simply corresponds to the final angle of the cabinet leaf. Moreover, I can't place any "live measure" to see the exact value of the final angle while driving a joint.

Re: How to precisely set position of assembly parts incorporating multiple joints?

jhackney1972 — Fri, 24 Feb 2023 15:40:55 GMT

Attach your hinge model and let the Forum users give it a go. If you do not know how to attach your Fusion 360 model follow these easy steps. Open the model in Fusion 360, select the File menu, then Export and save as a F3D or F3Z file to your hard drive. Then use the Attachments section, of a forum post, to attach it.

Re: How to precisely set position of assembly parts incorporating multiple joints?

midvok — Fri, 24 Feb 2023 15:49:50 GMT

Thank you for the tip. It seems like the try-error approach is only possible way in Fusion while there is no inverse kinematics method implemented yet?

Re: How to precisely set position of assembly parts incorporating multiple joints?

davebYYPCU — Fri, 24 Feb 2023 16:05:15 GMT

You can do live tracking of the required measurement.

Sketch > Project the aligning data, set the driven dimension to the current angle,

Show Dimension after sketch is finished.

Drive the Joint to 110 degrees in the sketch.

Set Joint limits.

Delete the sketch.

Might help....

Re: How to precisely set position of assembly parts incorporating multiple joints?

midvok — Fri, 24 Feb 2023 16:24:19 GMT

Thank you for the suggestion to "Sketch>Show Dimension" even after the sketch is closed (I didn't know that).

However, it seems the Projected line in the sketch doesn't update live when I'm driving the join angle.... it stays where the projection was created. Is there some toggle option for live update?

Re: How to precisely set position of assembly parts incorporating multiple joints?

davebYYPCU — Fri, 24 Feb 2023 17:06:42 GMT

Not sure, I know I have done similar steps before, and I am not at the correct computer to sort out a demo.

however, change the sketch - Delete the projected link, set the angle to 20 degrees.

Drive the Joint parallel to the line.

So will get you going.....

Re: How to precisely set position of assembly parts incorporating multiple joints?

jhackney1972 — Fri, 24 Feb 2023 20:24:27 GMT

I wanted to give you a quick video on how I use Drive Joints to determine the Joint Limits to drive a hinge within its range. I used one of my models since you did not export yours.

(view in My Videos)

Re: How to precisely set position of assembly parts incorporating multiple joints?

midvok — Sat, 25 Feb 2023 00:15:48 GMT

Thank you very much for your great support and showing me the align method which really works very well 🙂

It's also great that I can simply Align the movable part to the "global" XZ plane and then adjust all joints as "Set as Home Position" which enables me to later force "Go to Home Position" and the hinge is closed.

PS: I believe I've tried the Align command previously, but I must have done it wrongly because it made the assembly stuck somehow. Anyways, now I'm using the Align command again (as you demonstrated) and it works perfectly 🙂