Challenge: Getting this (iris type) assembly to work?

øyvind_kaurstad

I found a interesting device on Thingiverse, called the Venus box. It is an iris type design, and since the user posted Parasolid files, each part could be imported into Onshape. There is nothing wrong with the design itself, but I wanted to see if I could create a working assembly of it. My assembly skills are really limited, and I am struggling with it. The designer of this posted a video of the final printed assembly and how it works:

https://www.youtube.com/watch?v=-EtzOVkyGRA

However, I feel it should be possible to make it work as an assembly in Onshape, so I thought perhaps someone in here was up to the challenge. To save you some work, here's a public document with all the parts imported and ready to be assembled:

https://cad.onshape.com/documents/57a9b35ae4b0c89c3d4b7e10/w/066f5a8e8ce6aaad13afb85b/e/4e40e7be114d0d1b859e9df5

I have added some basic mates to get things reasonably aligned, but given I am inexperienced with assemblies, it might all be wrong.  :-)

mahir

Here you go. Just drag the knurled cam part at the bottom. The motion is a bit choppy. Too many gear mates is my guess. It would be nice if patterns didn't lock mates and actually followed them. That would've let me mate just 2 of the iris parts and pattern the other 2.

https://cad.onshape.com/documents/57ae27cce4b005c413ee4fc0/w/3f91c502d0a3b28896c6c3eb/e/60a21c838ca01d0209de2dac

mahir

Here you go. Just drag the knurled cam part at the bottom. The motion is a bit choppy. Too many gear mates is my guess. It would be nice if patterns didn't lock mates and actually followed them. That would've let me mate just 2 of the iris parts and pattern the other 2.

https://cad.onshape.com/documents/57ae27cce4b005c413ee4fc0/w/3f91c502d0a3b28896c6c3eb/e/60a21c838ca01d0209de2dac

malay_kumar

Very nice @mahir. Any feedback on assembling in onshape?  We are consistently looking into ways to make it easy to use for new users. Animation look very nice on animating 'Revolute1' or 'Revolute 2'

mahir

Thanks @malay_kumar. This was my first experiment with mating, so it took a little getting used to how OS does it with mate connectors. There are a few suggestions that come to mind. As I mentioned, it would be nice if patterned parts updated with mates. In this case, one circular pattern would have replaced 2 revolute and 2 gear mates.

Speaking of gear mates, it's not intuitive how the 2 revolute mates are synced. I had to iteratively adjust the secondary axis on several mate connectors to make sure the gear mates' starting position was where it should be. It would be nice if the UI for gear mates let you pick interactively/visually which values of the mate connectors to sync with, or let you specify the current state as the staring point. 

Lastly (for now), a more functional pin-slot mate would have been easier to implement than a gear mate with finely tuned ratio. I could see it being a way to constrain a mate connector on a prescribed surface or edge. Tangent mates can almost do this, but not quite. It's really only useful for simpler geometry like rollers in 2D slots. 

malay_kumar

Thanks for the feedback. @mahir. All of your suggestions are in plans. One advantage of locking things during pattern is that it is fast to solve  and which is what user want lots of time. We will have option to create link mates in some form.

We have plans to add UI for meshing (start position of relation) gear (and other) relations.

Also we have plans to support mate connector in tangent mate and bring other ways to bring curve/surfaces in assembly that would allow complicated pin-slot or other interesting relations using tangent mate. Tangent mate do support point on curve but it is a bit difficult to select vertex or correct curve. Thanks again for feedback.

øyvind_kaurstad

@mahir: Thanks for taking the time to do that, good work. I'll study your solution to see how it is all connected and try to learn something. I will admit that getting mates to work as I want in Onshape isn't always easy. Too much eyeballing and trial and error. Getting limits just right is often a pain.