Joint Conflicts

[Anonymous]

I may have bit off more than I should have, since I'm just learning Fusion 360, but I was excited to just jump right in. 

I wanted to try and emulate a mechanical movement across 8 sections and several connection points. I tried it first with 4 sections and had somewhat success, but when I tried to expand to 8, I ran into different conflicts with the joints. I've attached the current file version for reference.

Once I tried to complete the 8 sections with joint assignments, I saw that the previous joints turned red and errors were pointed out. I tried to figure out the errors and tried to adjust the directions and trying the flip button. No solutions.

Now I have further impacted the previous joints and they will not connect to the model anymore.

Baffled!

I appreciate any direction/advice.

Martin

[Anonymous]

An additional screen shot of the 4 section version.

[kgrunawalt]

Martin,

I'll take a close look at this. Thanks for supplying the model. It could be that some small difference in planar face angles is accumulating until the joint solver fails.

To simplify, I'll try redoing this using subassemblies for repeated assemblies. I'll also try using cylindrical joints as much as possible to reduce constraints in the system. Many of these revolutes can be replaced by cylindricals without changing the motion of the system.

We could improve Fusion to handle these complex systems better.

[TrippyLighting]

While it don't think it has anything to do with the joint problem discussed in this thread , I note that you have not followed Fusion 360 R.U.L.E #1: Before doing aything, create a component and make sure it is activated.

I am sure you have noticed that your timeline is very long and it's getting somewhat tedious to manage it.

Followint R.U.L.E #1 will ensure that all objets and featiure created after activaton of the componnet, which is automatic for newly created components (so we can't forget) are created in that component. When the component is activated the timeline is filtered to show only thos features and operations in the timeline that pertain to that component which makes working with long timelines much more manageable.

Also, if you ever export (save as) a component into the data panel and you did not follow the rule you'll likely have a rude moring awakening as none of the design information is comtained in the exported component. Only the body.

[Anonymous]

I was assuming that I made a basic mistake early on and the issue compounded itself as i built further.
So all the attributes of the component should live within the component's folder, such as sketch, body, joint, etc., correct?

Would the best next step be to go back the original few parts and assure they are created correctly at the component level and then recreate the model again?
I greatly appreciate the tip and the direction.
Thank you!

[Anonymous]

Thank you for your help. From another reply to my question, it appears I started my project with some incorrect practices that led to this model going nuts.
Cheers!

[TrippyLighting · Accepted solution]

If you are not under time pressure to complete this model, then, yes, for the earing experience I'd re do part of this and build components corectly.

You should also think ahead how this can be better structured in terms of assemblies and sub-assemblies to make the browser tree shorter and the design more easy to read.

I don't think this necessarily has to do with the joint problem's you are reporting. My suspicion is that at some point something is over-constraining the system and prevening it from moving. 

[kgrunawalt]

I would approach this type of complex linkage by

1. Create an empty component that will be an assembly of parts that define the repeating part of the linkage. This assembly will be patterned later. These should not include the same part more than once.
2. Activate this component so that subsequent part creations are put in it automatically. This simplifies the time line.
3. Create a sketch that defines multiple parts that define the repeating portion of the linkage. 
4. Create parts from this sketch in place via extrusion, etc.
5. Use "as-built" joints to join these parts. As-built joints assume the current positions when the joint is intruduced are correct. This reduces complexity too and makes the whole assembly more driven from the initial sketch.
6. Minimize revolute joints by using cylindrical joints if sliding motion is already removed by other joints. This reduces constraints on the mechanism that could cause conflict.
7. Activate the top component
8. Pattern the subassembly in a linear way to create the N instances you want. Ideally, the pattern would place them in an assembled position so they can be joined together with as-built joints. This "as-built" use of patterning suggests that he pattern distance is derived from a sketch dimension so that it will react properly if the sketch is altered.
9. Add as-built joints to link together the N instances of the subassembly.
10. Ground whatever should be grounded

This is a very top-down assembly creating approach that Fusion enables. It will drastically reduce the length of the timeline and the complexity of the compute. I have not actually done this for your model. It really does require starting from scratch I think. I have used this approach with similar linkages subassemblies. There may be some gotchas with your model that I've not thought of (multiple sketches, for example).