topic Re: Joint Question in Fusion Design, Validate & Document Forum

Joint Question

richardsalzman — Fri, 24 Jan 2025 14:29:12 GMT

I am trying to use a rigid joint to join the together an assembly to a part. When I do, the assembly breaks apart. See below. I did select the entire assembly when appying the joint.

Any thoughts on this one?

Thanks... Richard

Re: Joint Question

bwalker145 — Fri, 24 Jan 2025 14:47:14 GMT

I'm only seeing one joint to the central disk for the forks on the sub-assembly file. How were the other forks located/constrained?

Re: Joint Question

bwalker145 — Fri, 24 Jan 2025 14:56:30 GMT

Ah, I see. The other forks are "pinned".

Unpin and use joints to locate to the central disk. Can either do individually, or quickest would be a rigid group to the first fork that already has a joint.

Edit: Or if you don't want to mess with any of it, just unpin all the forks & central disk, and use "ground-to-parent" in the sub-assembly instead. Would recommend Joints though.

Re: Joint Question

richardsalzman — Fri, 24 Jan 2025 16:22:23 GMT

Thank you. I am a bit new to these sub assemblies. I sketched most of this part but not the fork assembly. I increased the size of the disk (green) but I do not see how I move each of the forks. They seem to be pinned and joints. I would prefer to use a joint for each fork location.

Re: Joint Question

bwalker145 — Fri, 24 Jan 2025 16:46:08 GMT

Yeah if you want everything to update appropriately with parametric changes, definitely use joints and try to stay away from pinning/grounding.

First thing I see is there are two bodies/components associated with the Central Disk (Purple and Blue). The fork assemblies currently line up with the Purple disk. Which disk is correct one for your assembly?

Re: Joint Question

richardsalzman — Fri, 24 Jan 2025 16:56:03 GMT

The purple was the original disk. I replace it with the blue. Ideally, I would like the forks to be jointed to the blue disk. I tried unsuccessfully to make some changes so here is the updated version.

Re: Joint Question

bwalker145 — Fri, 24 Jan 2025 17:23:17 GMT

Try this out, file attached.

Not the cleanest, since I didn't want to re-do certain parts of the design, but the fork/disk assembly should be correctly constrained, and the forks should adjust location with disk size updates. I didn't touch anything else. Looks like there's some interference with that green backing plate.

Re: Joint Question

richardsalzman — Fri, 24 Jan 2025 18:03:26 GMT

You made my day. That worked pefect!

Quick question. When I brought in the file, it brought in all the associated files as well. Thankfully I uploaded into a separate folder. I ONLY "Inserted into current design the file for the "Fork Disk Assembly" that you were nice enough to fix. I am I correct that I still need to keep all the other associated files that are in the folder with the revised Fork Disk Assembly or can I delete them?

Re: Joint Question

bwalker145 — Fri, 24 Jan 2025 18:22:41 GMT

Great!

If all you did was insert the Fork Disk Assembly, I think you'd have to keep any of the files associated with the new Fork Disk Assembly (assembly, central disk, fork assembly, etc.), but would be able to delete any of the others (stepper motor, main block, etc.), as well as the old Fork Disk Assembly files. Then you should be able to move the new files back into your main folder.

Might be worth duplicating your main folder as a backup just in case this doesn't work like we expect 🙂

Re: Joint Question

TrippyLighting — Fri, 24 Jan 2025 20:08:38 GMT

@bwalker145 wrote:

Yeah if you want everything to update appropriately with parametric changes, definitely use joints and try to stay away from pinning/grounding.

I would stay away from pinning. Many Fusion users don't understand that pinning is local to the specific design only. When inserted into another design ,as in this case, the pinning is NIL

On the other hand, the GTP (ground-to-parent) feature can make assemblies much easier and is very powerful when used properly. I've linked to the documentation here.

Edit: while I am going through this, there are several other things I would not recommend. I would not expect a single position-capture feature in a mechanical assembly like this. The purpose of the position capture feature is NOT to locate components for assembly.

Re: Joint Question

bwalker145 — Fri, 24 Jan 2025 20:12:27 GMT

Trippy,

Just curious, what's an example of a good use-case for GTP vs a standard joint?

I could see using it for the initial component in an assembly, but I typically just use standard joint to constrain to the origin anyway. Or is GTP just a faster/easier way to accomplish the same thing in this example?

Re: Joint Question

TrippyLighting — Fri, 24 Jan 2025 20:55:44 GMT

I am going to create a screen recoding as this much easier to explain in words.

One of the powers of the GTP attribute is that it really helps with component patterns.

Also, it's not a feature but an attribute, meaning it is applied at the creation point of a component. It's timeless as there is no feature for it in the timeline.

It can replace many rigid groups and as-built rigid joints.

Re: Joint Question

TrippyLighting — Sat, 25 Jan 2025 02:34:14 GMT

Here's the screencast with the model attached:

(view in My Videos)

Re: Joint Question

bwalker145 — Sat, 25 Jan 2025 17:58:09 GMT

Hi Trippy,

Great, I really appreciate the screencast, that helps a lot.

I know we deviated a bit from the OP, but I rebuilt the central disk assembly (file attached) to test joints vs GTP. I can definitely see how GTP can help streamline, especially larger assemblies.

I noticed with joints, I received a warning to redefine the rigid group for all the forks when the "num_forks" parameter is changed to a value less than the previous definition. Not a huge deal in this case, but I can see how effects like that could compound into a lot of time lost for larger assemblies.

Re: Joint Question

richardsalzman — Sat, 25 Jan 2025 18:27:48 GMT

Thanks guys. This project started with an assembly that was created by someone else, so I had a hard time making it right. I am new to assemblies and joints so this was very helpful. Here is a screen shot of the finished part. Thank you very much!

Re: Joint Question

richardsalzman — Sun, 26 Jan 2025 03:19:58 GMT

Sorry to bother you again with all these questions. All was going well, until it wasn't 😞

I was making some final tweaks when suddenly I noticed that one of the joints is not working as it was earlier. When I created the joint below, the top of this bushing (red arrow) was flush with the bearing (purple arrow). I don't know why it is no longer flush. The only thing I did was use the "Edit in place" feature and somehow this joint is no longer working. Any ideas on this one?

Thanks again for all your help... Richard

Re: Joint Question

davebYYPCU — Sun, 26 Jan 2025 04:15:05 GMT

if the spacer should remain at the bearing, after the Edit in Place, you edit the Joint, (Rev 35) by the same amount.

Might help....

Re: Joint Question

richardsalzman — Sun, 26 Jan 2025 04:58:05 GMT

Thank you very much. I must be missing something. If I used the joint to place it flush with the bearing face, why do I need to offset it an additional .188"?

Re: Joint Question

davebYYPCU — Sun, 26 Jan 2025 07:46:28 GMT

My guess,

you said you Edited in Place, moved the sleeve top face, but not the Joint, the Joint is not updating because it has nothing relevant?? to the new top face.

I couldn't find where the Joint lives, but was able to lift that whole assembly by the offset.

Might help...

Re: Joint Question

I_K_H_ — Wed, 05 Feb 2025 11:33:13 GMT

I like the way you assemble this. It is the almost the way I would do it. I do have one issue with it though. In the parts list its going to show two components, Disk & All Forks. It would not show the correct amount of forks.