Last revolute in a chain overdefines the assembly.

kees_bijker

Hello all,

I tried looking for this question but somehow non are actually the same and I cannot make sense out of this right now.

In this document I am trying to construct a cable chain from 3 unique parts. One end is fixed, the loose end has a slider mate with offset relative to the fixed end. And then many revolute linked center parts to fit between the two ends.

file is here:   https://cad.onshape.com/documents/36a2a3a1b4fc985b5f779dd6/w/cb8bfbfeaa242c42f7c4eda9/e/2e136d1ca8949cfcde5584a7

Every mate works on its own, and combined with each other UNTIL I make the last link of the chain to the other end.

Before this I can rotate each part within its limits, other parts follow as they should. I can slide the second piece as well. Then when you link the loose ends the whole thing turns red with over definitions in all the mates.

I cannot for the life of me figure out why this should be wrong, so I kindly ask for one of the more versed engineers here to look at it for me and hint at what it is that I am doing wrong?

Thanks in advance.

Kees

NeilCooke

Change the last one to a Cylindrical mate - there will be a planar offset tolerance issue somewhere in the chain.

NeilCooke

Change the last one to a Cylindrical mate - there will be a planar offset tolerance issue somewhere in the chain.

kees_bijker

NeilCooke said:

Change the last one to a Cylindrical mate - there will be a planar offset tolerance issue somewhere in the chain.

So to understand for future, you mean an offset in the plane perpendicular to the movement, so that the mates cannot reach each other?

This makes sense because I did offset some to match the middle, and indeed it made it work.

I made a mistake in the link, my apologies. The file is here:

https://cad.onshape.com/documents/44a768e3c68f6c30f22bd989/w/cb14b5ab338d7582091dc0ac/e/22a32a2573ad9fabd29d893f

Even though the last joint now moves too freely, I suppose I can limit that just the same. What a silly mistake unless it came from rounding within onshape.

Thanks once again.

Kees