Scissor jack movement?

[nvanlaar]

I cannot for the life of me figure out how to setup the joints for this movement?

I can create a 2D version in AutoCAD no problem...

Thanks in advance for any help.

Nick

[TheCADWhisperer]

Can you attach the f3d file here?

[nvanlaar]

Sure.  I was just working on that... 😄

[nvanlaar]

I forgot a pin.  And I think it's working... Does this look right?  Why won't it collapse all of the way?

[TrippyLighting · Accepted solution]

While you are using components there is a better way to do so. Yor workflow first creates sketches. Then you create bodies from these sketches and then you create components from these bodies.

The best workflow to create components is to follow Fusion 360 R.U.L.E #1:

Before doing anything, create a component and make sure it's activated.

All objects created after activating the component such as sketches, bodies, construction geometry, joint origins, etc.  are created in that component.

This has several advantages:

1. On activation the timeline is filtered to show only those items in the timeline that pertain to that component. That will make the quickly growing timeline much easier to work with.
2. If a component is exported to the data panel with "save as" this will also export the complete parametric design history.
3. Drawings can only be created from components
4. The joints in the "Assemble menu only work with components.

When another component needs to be edited for example to add geometry, it should be activated before doing so.

Now let's address problems with your assembly:

Using contact sets in conjunction with joint usually fails at some point in time so it's best to avoid them.

The green and orange rollers can be joined to the scissor arms using revolute joints.

The center of the arms are missing something so you can create joint origins in the crete of each area and create a revolute joint with a 2" puffed between the two arms.

Then, in the attached file I cheated a little in that I created a vertical slider joint between the two rectangular profiles and set some sensible joint limits.

That'll get the scissor lift part working. I'll let you work on getting the cylinder motion to work correctly 😉

[nvanlaar]

Thanks!  Is it me, or is cylinder to plane interface/constraint options extremely limited?

[TrippyLighting]

The joint system in Fusion 360 is more than just constraints, or mates as they are called in other software packages. No, I don't find it limited, specifically for such simple designs.

It would probably be easier to do if you had all the components designed to actually make this a working assembly 😉

[CBB1962]

I tried to get my scissor to act like the example.  I could get close, but that last joint would give errors everywhere.  This is what I am trying to get to work.  Any help would be appreciated.

[Anonymous]

@CBB1962 Here is a working model. I grounded "Frame", then added as-built revolute joints between the pins Cross arms. Joint Rev12 was also giving me problems, but when I used a regular revolute joint (not an as-built) it worked as expected.

It is not always possible to lock down a mechanism like this with all revolute joints. You will often have to use a cylindrical joint in place of a few revolute joints. I think something in Fusion, like a rounding error, will move a joint origin ever so slightly so that joint origins that should all be in the same plane are slightly skewed. Then when you try to lock everything down with revolute joints, Fusion can't solve it. Adding a cylindrical joint or two adds the extra degrees of freedom needed to solve it.

[CBB1962]

You make it look easy...  THANKS!