Mate of the kind "touch, don't intersect"?

christoph_schmitz

Hi,

I'm pretty new to assemblies. As a first example, I tried to model a situation where a workpiece is clamped between two fixed cylinders using wedges:

https://cad.onshape.com/documents/27cc274378a7403689e51950/w/5ef048db33a54ab49fdb9d16

The idea is that the wedges can slide against each other and the workpiece, until the workpiece is fixed when the outer wedge and the workpiece both touch the cylindrical bench dogs (as they are called in woodworking).

I found it easy enough to add sliding mates between the workpiece and the wedges, and planar mates to keep everything aligned, but is there a way to generally express "these parts should touch, but not intersect"? This would apply to my workpiece touching the bench dog, or to wheels rolling on a surface etc.

I found an elaborate discussion about the concept of mate connectors that seems to suggest that it isn't possible to express this, but I'm not sure I understood that correctly. It seems "tangential mate" would be a way to describe the aforementioned constellation, right?

Thanks and regards,
Christoph

brucebartlett

Not there yet with mates that can do what your describing. If limits were available on the slider mate that could be a possibility to control parts. 

What your really after is a stop when parts intersect when dragging an assembly, not sure if this is on the cards or not. 

billy2

Christoph-

Not sure its here yet.

Seems like we need a physics environment with gravity, collisions & torque. Balls bouncing down steps and a virtual pool table to help kill time. What about cams, RPM & dwell settings? 

I think you're on to something Christoph, let's make it real.

andrew_troup

Hmm - physics, introduced in Solidworks circa 2003 ... very exciting ... seldom used though, even now, AFAIK, with modern, uber-fast machines. One of those things which demonstrates really well on simple two-body problems, but does not scale up very usably to the complexities of real-life mechanisms. Mostly superseded for many practical purposes by judicious inclusion of limit mates and other cruder techniques.

I'd be happy to be contradicted though, because I am out of touch on this particular branch of practice.

christoph_schmitz

I'll second Andrew's opinion. It ocurred to me too that this sort-of sounds like physics, but that would seem to be out-of-scope to me. A tangential or contact or limit mate would still be useful within OS, I think.

PS. Sorry for the redundant discussion, I hadn't seen the earlier one titled "contact mates". Seems to be a popular topic, though ;-)

Christoph