topic Re: Apply multiple joints to objects in Fusion Design, Validate & Document Forum

Apply multiple joints to objects

rapiddsol — Tue, 29 Aug 2017 01:16:13 GMT

I am hoping someone can direct me to a resource that can show me the best way to apply joints for this specific application.

Seen screencast. I simply would like to put the bolt in the hole and place the underside of the head on the bracket.

First to admit I don't get these types of joints. Any guidance is appreciated. Thanks for your time.

http://autode.sk/2vmESMV

Re: Apply multiple joints to objects

TrippyLighting — Tue, 29 Aug 2017 01:24:17 GMT

Is there any reason a simple rigid joint would not work ? What you are describing is not a speciffically special case.

Re: Apply multiple joints to objects

Anonymous — Tue, 29 Aug 2017 10:20:03 GMT

Tutorials to learn about assemblies and joints are available on youtube and autodesk websites.

For example you can try this video.

Take a look at this screencast to get a basic idea of applying joints between two components.

Re: Apply multiple joints to objects

rapiddsol — Tue, 29 Aug 2017 16:58:53 GMT

Thanks for the reply Mandy.

I have sat through that tutorial and unfortunately it does not address my specific issue.

I appreciate your screen cast also, but the situation I displayed is a bit different.

The hole I am trying to mate with the screw is separated by a bracket with a slot in it.

So the bolt body needs to be mated with the hole (concentric) and the underside of the bolt head mated to the top of the bracket (planer) with the slot in it.

I realize I can make the concentric joint and off-set the bolt the thickness of the bracket, I also know I can create a joint origin where I need it...but I shouldn't have to... I believe there should be a better way.

I tried making a concentric joint in one step, then a planer joint in another but they conflicted.

Thanks again for the effort.

Re: Apply multiple joints to objects

TrippyLighting — Tue, 29 Aug 2017 17:06:28 GMT

You could create a cylindrical or slider joint between the bolt and the hole in the bottom part and then a slider joint to planar joint between the underside of the bolt and the bracket.

IF that does not work, your assembly has geometric problems.

In a mechanical design such as this I'd only go through that effort in very special circumstance. Adding joints with degrees for freedom is only going to put unnecessary burden on any system having to evaluate such a joint. A rigid joint with a offset is all I'd do.

Re: Apply multiple joints to objects

Anonymous — Tue, 29 Aug 2017 18:00:37 GMT

Sorry that I misunderstood the question.

As you already mentioned, the easiest solution for this is creating a rigid joint between hole and bolt and offsetting it by slot thickness.

But if you don't like to do that then you can try this.

As shown in the screen cast if you have the sketch for the slot you made, you can get a joint origin at the center.

But if you don't have the sketch of the slot it is always better to just create a joint origin

Re: Apply multiple joints to objects

rapiddsol — Wed, 30 Aug 2017 23:06:52 GMT

Thanks Mandy,

As you stated the "easiest" solution was for me to create a joint origin. I used between two faces and the top surface of the bracket, then had to adjust the axis (direction the origin was facing).

Seems crazy the "easiest" solution requires the fabrication of an origin, or creating rigid joints with multiple dialogue boxes. what are the chances the joint origin is parametric and will update if I change the thickness of the material....hope I don't have to find out.

Thanks again.

Re: Apply multiple joints to objects

Anonymous — Fri, 14 Aug 2020 12:52:50 GMT

How robust is the approach of offsetting by the flange thickness to changes in that thickness. Surely if there is a way to mate to a face (which I can't find in 360 because it insists on using snap points) that is much more robust to changes in geometry of the other parts?

Re: Apply multiple joints to objects

ritste20 — Fri, 14 Aug 2020 13:09:36 GMT

If you tie the flange thickness to a parameter and use the parameter as your offset distance in a rigid joint, I would consider it very robust to changes.

If you increase the thickness too much you will run out thread engagement but the model won't break.

side note - you have to use the snap points to locate the joint origin but you can use a planar joint between two faces regardless of the snap points you select.

Re: Apply multiple joints to objects

Anonymous — Fri, 14 Aug 2020 13:14:13 GMT

Yep ok get that.

Is it not possible at all in Fusion 360 to do the two degrees of freedom with seperate mates?

In this case would be a mating the bolt to the hole and then a separate mate to from face of bolt to face of flange...

PS can 360 mate faces? or do you have to use the somewhat arbitrary seeming snap points?

Re: Apply multiple joints to objects

TrippyLighting — Fri, 14 Aug 2020 13:14:27 GMT

You could use a slider or cylindrical joint between the bolt and the thread and then a planar joint between the underside of the bolt and the upper face of the bracket.

Re: Apply multiple joints to objects

TrippyLighting — Fri, 14 Aug 2020 13:18:05 GMT

@Anonymous wrote:

Is it not possible at all in Fusion 360 to do the two degrees of freedom with seperate mates?

Not separate geometric mates as Fusion 360 does not use the concept of mates.

But as described in my last post, you can use 2 separate joints. Not sure I would recommend using that technique very frequently in a single design but for occasional use it should be fine.

Re: Apply multiple joints to objects

Anonymous — Fri, 14 Aug 2020 13:24:33 GMT

Ok I think I'm getting there.

Last Q is on Planar joints.

I would expect it to only constrain motion in one Axes. However it only gives you the ability to slide in a single axes.

That, almost by definition is not planar. Is there a way to achieve true planar?

Re: Apply multiple joints to objects

TrippyLighting — Fri, 14 Aug 2020 13:28:44 GMT

It would probably be helpful if you share your design or a screencast of what you are seeing. What you describe ids not the default behavior of a planar joint.

Re: Apply multiple joints to objects

Anonymous — Fri, 14 Aug 2020 13:33:49 GMT

This dialogue for a planar joint only allows you to specify a single axis it can slide in as far as I can see?

Re: Apply multiple joints to objects

TrippyLighting — Fri, 14 Aug 2020 13:38:01 GMT

Click OK and then see how the joint behaves.

Re: Apply multiple joints to objects

chrisplyler — Fri, 14 Aug 2020 14:52:48 GMT

You could do:

1. Pin-slot Joint between bolt and slotted bracket, such that the bracket face was up against the back of the bolt head.

2. Cylindrical Joint between bolt shaft and hole, such that the bolt is lined up with the hole but free to move in/out.

3. Planer between back face of slotted bracket and the face with the hole.

This would pull everything into place, and would adjust properly with changes to thickness of the slotted bracket.

Re: Apply multiple joints to objects

ritste20 — Fri, 14 Aug 2020 14:53:16 GMT

That is a bit of a misnomer. Planar joints act as you would expect a mate or flush constraint from inventor or solidworks.

UNLESS you have other joints that would create conflicts with the additional degrees of freedom.