How to keep cylinders from reversing themselves 2

[PhoenixDynamometer]

Hello all,
We use quite a few hydraulic & pneumatic cylinder assemblies in our assemblies as "flexible" models for mating purposes. Many times when moving the upper level assemblies through their degrees of freedom the cylinders reverse themselves (rod & cylinder body are facine away from each other). When we build the cylinder assemblies we always have the rod body and the cylinder body concentric with each other. When they reverse themselves they maintain the concentic mate but the concentric mate should not allow them to "un-mate and then mate again". Is thee a way to prevent this from happeneing while still using them as flexible assemblies? It is really becoming counter-productive.
Thanks.

http://www.phoenixdyno.com

Home of the world's most accurate and repeatable dynamometers, dynamometer accessories, and data acquisition & control software.

 

[Eltron]

Have you tried to add a limit mate on one of the cylinder ends?

Dan

http://www.eltronresearch.com

Dan's Blog

 

[EEnd]

I would try adding a parallel mate between two planes that are normal to the axis of the cylinder.

Eric

 

[PhoenixDynamometer]

I am thinking that if the model is able to ignore the concentricity mate long enough to reverse the cylinders it will ignore the limit and parallel mates as well (just long enough to flip them.

http://www.phoenixdyno.com

Home of the world's most accurate and repeatable dynamometers, dynamometer accessories, and data acquisition & control software.

 

[Eltron]

Thinking will get you in trouble every time, especially with SW. If you give the software another reference (limit or parallel) while keeping your freedom of movement you may be OK.

Dan

http://www.eltronresearch.com

Dan's Blog

 

[CorBlimeyLimey]

SolidWorks is like a teenager. Not enough freedom, or too much freedom, spells trouble.

 

[Updraft]

Our standard practice is to make cylinder subassy files with three configs: Retracted, Extended, Stroke Limited. The Stroke Limited has a limit mate while the other two simply use coincident mates of the piston faces with the endcaps. Since limit mates can sometimes allow the bad behaviour you describe we often use one of the other mates for setting things up in the next level assembly. After that assembly is well developed and stable we'll then use the Stroke Limited config of the cylinder. Along the way there are typically additional constraints (mates) applied in the top level assembly that help to keep everything behaving. This generally cuts down on a lot of the other problems.

- - -Updraft

 

[kellnerp]

Find the mates for the cylider.

Look at the mate order.
Re-order the mates just for the cylinder.
Mates are solved in sequence one at a time. If a flippable mate is solved first that could be the problem.

TOP
CSWP, BSSE

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