topic Re: Stumped by revolute joint behavior in Fusion Support Forum

Stumped by revolute joint behavior

spm_no — Tue, 10 Oct 2017 18:09:19 GMT

Hi,

I am getting the hang of Fusion 360, but am stumped on a few items in this model (http://a360.co/2y93jNK).

1) When I try to rotate the revolute joint (box hinge), I'd like the box to be stationary and have the lid rotate back and forth. Currently, the lid remains stationary and the box rotates. I'm not sure how to fix it.

2) I am concerned that the joint icons do not coincide with the actual joint locations. Am I doing something wrong that is causing this?

3) There is a component called 'Right Side Top:1' which has a rigid joint. As expected, when I double click the component in the tree view and then try to move the component, it will not move. But if I right click on the component and select Parent->Top, I find that I can move this component anywhere I want, thus violating the rigid joint. What am I missing?

4) Is there a way to get the wood grain to wrap around the box?, i.e. when actually making the box I would start with a long board and then cut the 4 panels from it. Thus, at the box corners, I should see the continuous grain pattern from the original single board.

Thanks!

Ron

Re: Stumped by revolute joint behavior

innovatenate — Tue, 10 Oct 2017 19:02:21 GMT

Hi Ron!

1. Which component is fully defined to the origin of the root component? It's probably related to the number of degrees of freedom. I'm guess you have too many open!

My guess is that you need to create a rigid joint between the root origin and one component that you don't want to move. You may also be able to use ground, but you should understand that ground can be tricky if you don't understand how it works.

If you create an As-build joint between a component of the box base and the root component's origin that will remove the degrees of freedom from the base. Then try dragging the lid, that might help.

The below class has a bunch of great information about assembly techniques. I'd recommend watching this if you haven't.
Master Assembly Class

2. The design is a timeline based design and positions can change. Are some components not visible? Are you using As-built joints? It's hard to tell from the screenshot. If you want to share the design, I might be able to explain further. There's a lot of reasons why the joint icon might be seemingly "out-there" in space. It doesn't necessarily indicate an issue.

Why not toggle the visibility of the joints off (see light bulb in the browser)?

Hint: Use shift + select in the browser and the keyboard shortcut V to quickly select and toggle visibility for browser items.

3. Are you activating a component? What is happening with the timeline when you activate a component? Does that rigid joint remain in the timeline when you activate the component?

4. Have you tried using the Texture Map Controls command? It should be available on the right click menu when you right click on a component/face. I think this can help you to align the wood grain.

I hope that helps!

Re: Stumped by revolute joint behavior

spm_no — Tue, 10 Oct 2017 19:10:07 GMT

Hi Nathan,

Thanks for the response. I have included the link to the project in my initial post. Are you not able to download it?

-Ron

Re: Stumped by revolute joint behavior

spm_no — Tue, 10 Oct 2017 19:15:01 GMT

http://a360.co/2y93jNK (the link)

Re: Stumped by revolute joint behavior

innovatenate — Wed, 11 Oct 2017 01:02:12 GMT

Oops, I overlooked the share link earlier.

There are a lot of different ways to accomplish this. When I look at your timeline, I have difficult time understanding how you are approaching this design. It seem like you are creating a lot of capture positions so that you can add a joint to a component. If so, there may be some better ways to approach this particular design.

Is the design going to get much more complicated than this?

If not, using some sketch skeleton + multi-body modeling techniques => convert to components
=> rigid groups, joints and as-built joints all you to make a fully parameterized version of this design. While the attached version isn't bullet-proof, it's a pretty good start. You'll note that I can quickly change the overall dimensions by editing the parameters. You'll see that the timeline is way more clean and much shorter. I'm only using 4 joints to assemble the design together.

I think in this case it may be easier to model with some skeleton sketches. Create Bodies from the skeletons sketches and then convert those to components. Although this doesn't quite follow rule number one, create a component first, I think this may be simple enough where you could get by without it. If it is going to get more complex, I might rethink this approach. One cool thing about this approach is you'll notice that all of the origins of the components are in the same place when the lid is closed.

Note that in the case Rigid22 is an As-Built Rigid joint between a base component and the root origin which "fixes" it to the origin.

I hope this example helps. Please have a look and let me know what you think.

Re: Stumped by revolute joint behavior

TrippyLighting — Wed, 11 Oct 2017 01:21:14 GMT

This design includes a few mistakes, but it is also very inefficient.

I've attached a re-designed version for study. It uses only three sketches for the entire design.

The are no position capture features in the timeline and in general they are also not needed in your design.

Re: Stumped by revolute joint behavior

spm_no — Wed, 11 Oct 2017 02:34:37 GMT

Thank you, Nathan! Obviously, I have a lot to learn about efficient design. I appreciate the time you spent putting together an example for me to learn from. It is a great learning tool for me.

-Ron

Re: Stumped by revolute joint behavior

spm_no — Wed, 11 Oct 2017 02:35:09 GMT

Thank you, Peter! I am embarrassed to say how many hours I spent on my complicated and obfuscated design. I appreciate your elegant approach and will study it in detail. Thanks so much for your time.

-Ron

Re: Stumped by revolute joint behavior

wilburg — Sun, 24 Dec 2017 01:32:20 GMT

Ron,

I'm also starting to get the hang of F360. I have been helped by Autodesk personnel in solving some problems, and have found some working solutions on my own. I have no idea why the placement of joint icons are so disconnected from the actual components being joined, but I think I have an easy answer as to why your box, which should be the stationary component, is moving while the lid is remaining stationary instead.

When you select two components to be joined in a moving joint, the first component selected is the moving component, while the second is the stationary component. I could be missing something, but I have found that this has worked for me in all the situations in which I have tried it.

Wilbur Goltermann

Re: Stumped by revolute joint behavior

spm_no — Sun, 24 Dec 2017 02:23:30 GMT

Thanks, Wilbur, for your suggestion. Some time has passed since I built the original model, however I believe I tried to construct the joint in multiple ways including the one you suggested -- all to no avail. What ultimately worked was to use the model which Peter provided. I was able to dissect each step in his model and understand how to proceed with a logical plan of attack.

Thanks again for replying to my query.

-Ron