Revolute und Mate Performance

vafanoy800_datakop

Hello all,
I am building a model with 30 revolute mates. The movement in the assembly when I interact with the model is very slow and no longer usable for me.
There are 5 mates with limits and 2 gears. Is that already the limit or am I doing something significantly wrong?
I have seen gear models that seams much more complex.
Maybe the limit is also due to my 10 year old CPU i7 K2600? GPU is around 30%

Does anyone here have a hint?

This is the document: https://cad.onshape.com/documents/01cc2cc4f5ab3b5e024bd1d6/w/cb130cd9d419e00c6ac2501b/e/39fe6283fbd3d98dd81728b1
From the idea you can pull the parts, but due to the lack of power....

eric_pesty

Limits are generally slow and if you have gear relations you are already having thins "over constrained" might also be part of the problem so I would look at switching a bunch of the revolutes to cylindrical so the don't "fight each other".

I can't seem to move your assembly but I made a copy and changed most mates to cylindrical and it seems much better:
https://cad.onshape.com/documents/29b7c7256525bbd5c94c9b1a/w/9f6635ebdf2aebb4fb4eccc7/e/1012933339f1ba7b08ca0f15

steve_shubin

@vafanoy800_datakop



https://cad.onshape.com/documents/30dd9e01cf70daeb42799234/w/dbbf763646a4ad2df040ec4c/e/0ccd7b3642426c20b455d26c

If you like the way things are moving in the GIF, read on.

By the way, the movement you see in the GIF is real time. Nothing is sped up. Nothing was edited.

The round circle that surrounds the cursor, is an indicator that the mouse button is pressed down or in my case, the trackpad Is being pressed down upon. There’s a few times where I lift my finger off the trackpad and the circle goes away.

Now — I noticed in your document that you have a number of assemblies, and something like 27 different mate features under the INSTANCES section

With this in mind, If your objective is to learn how Subassemblies work, then @john_mcclary might be able to give you a tip or two. John is a Pro user — not an employee of Onshape, but a pro user that does amazing things with assemblies. Somethings are just absolutely mind-boggling

But — if you simply want to get things to move well, then you might take a look at my simplified document. Although I wouldn’t be surprised if John were able to greatly simplify what I’ve done

Though I did use the same amount of mate features that you used under INSTANCES, the difference is, that the 27 mate features I used, were all under the MATE FEATURES section

Basically what I did was I used revolute mates on the arms at the bottom of the nearest side. And then used linear pattern to duplicate those arms 15 inches directly above

And more or less did the same thing on the other side. Except instead of using one revolute mate on one end of an arm and another revolute at the other end, this time I replaced one of those revolutes with a cylindrical

Other than that, it was a matter of -
4 planar mates
2 fasten mates
1 parallel mate
And a limit on the very first revolute mate

I also have two hidden parts that I used the planar and fasten mates on

This way of doing it was quite straightforward. I only ran into one thing that wouldn’t work. Using linear pattern to copy parts from one side to the other, made everything freeze. So there is no linear pattern from side to side

S1mon

Given that these are all parallelograms, and the sides theoretically will always follow one another, you want to tie all that together in a way that requires less effort for the assembly solver.



I started by adding parallel mates to the four links ("strebe") that are between plates. This made it possible for me to get it to move, but it's still very sluggish. I'm guessing that maybe getting rid of some of the revolute mates and treating parallel pairs of links as locked together would help (use a fasten mate with an offset distance, based on the size of the plates). Then I would either use gear mates or parallel mates with the top and bottom sets of links. 

Basically you want to cut down on the complexity and number of mates that need to be solved. In general, a four-bar linkage can describe all kinds of crazy movements, but because this is really a bunch of parallelograms, you should be able to cut down on the effort that Onshape needs to solve the positions.

It also seemed like the limit mate on one of the revolute mates added a lot of complexity to the solver. I'm not sure what's the best way to address this, but perhaps keep any limits closer to the part that is fastened to the origin.

I also wonder if this would be better with all of the parts in the same level of assembly.

eric_pesty

Limits are generally slow and if you have gear relations you are already having thins "over constrained" might also be part of the problem so I would look at switching a bunch of the revolutes to cylindrical so the don't "fight each other".

I can't seem to move your assembly but I made a copy and changed most mates to cylindrical and it seems much better:
https://cad.onshape.com/documents/29b7c7256525bbd5c94c9b1a/w/9f6635ebdf2aebb4fb4eccc7/e/1012933339f1ba7b08ca0f15

vafanoy800_datakop

Hello S1mon and Eric,

thanks for your advice

@S1mon - I will test the idea with all parts in the same plane.

@ Eric The solution with the cylindrical connections will definitely help me here.

Thanks a lot

steve_shubin

@vafanoy800_datakop



https://cad.onshape.com/documents/30dd9e01cf70daeb42799234/w/dbbf763646a4ad2df040ec4c/e/0ccd7b3642426c20b455d26c

If you like the way things are moving in the GIF, read on.

By the way, the movement you see in the GIF is real time. Nothing is sped up. Nothing was edited.

The round circle that surrounds the cursor, is an indicator that the mouse button is pressed down or in my case, the trackpad Is being pressed down upon. There’s a few times where I lift my finger off the trackpad and the circle goes away.

Now — I noticed in your document that you have a number of assemblies, and something like 27 different mate features under the INSTANCES section

With this in mind, If your objective is to learn how Subassemblies work, then @john_mcclary might be able to give you a tip or two. John is a Pro user — not an employee of Onshape, but a pro user that does amazing things with assemblies. Somethings are just absolutely mind-boggling

But — if you simply want to get things to move well, then you might take a look at my simplified document. Although I wouldn’t be surprised if John were able to greatly simplify what I’ve done

Though I did use the same amount of mate features that you used under INSTANCES, the difference is, that the 27 mate features I used, were all under the MATE FEATURES section

Basically what I did was I used revolute mates on the arms at the bottom of the nearest side. And then used linear pattern to duplicate those arms 15 inches directly above

And more or less did the same thing on the other side. Except instead of using one revolute mate on one end of an arm and another revolute at the other end, this time I replaced one of those revolutes with a cylindrical

Other than that, it was a matter of -
4 planar mates
2 fasten mates
1 parallel mate
And a limit on the very first revolute mate

I also have two hidden parts that I used the planar and fasten mates on

This way of doing it was quite straightforward. I only ran into one thing that wouldn’t work. Using linear pattern to copy parts from one side to the other, made everything freeze. So there is no linear pattern from side to side

vafanoy800_datakop

He thats gread, many thanks!