Mating Conditions vs Positioning Constraints 1

[Michel1978]

Hello,

I would like to know what the difference is between "Mating Conditions" and "Positioning Constraints".

Thanks

Michel
Mechanical engineer

 

[hudson888]

Basically mating conditions are evaluated sequentially as they are applied whereas the newer positioning constraints are not which makes them more flexible and powerful. They're able on occasion to work across assemblies and sub assemblies which was a limitiation with the older mating conditions. After some comparitive checking last year I was reasonably convinced that the newer positioning contrains would be better and more robust, which when you think about it is unsurprising after all why would the PLMS change their product for the worse.

My testing with them involved several posts back and forth on this forum whereby John Baker filled in some gaps for me. I have since tried changing over a reasonably challenging engine assembly that I had animated, and found that it worked. You might try searching the forum for those earlier posts as the exercise was worth following up.

Mating conditions by the way continue to be supported for backwards compatibility but can be translated to positioning constraints. The translation directly supports most methods, and it will advise you if you need to reapply the odd constraint. Whether mating conditions will be supported indefinitely or not is a matter for conjecture but there is as yet no threat of their demise.

Cheers

Hudson

 

[dhmtb]

Hudson,

Could you possibly find the thread that you mention? I could not find it with a search.

We are starting to find some huge problems with an assembly (~1000 components) taking minutes to apply a constraint. I have a smaller assembly (87 components, 145 constraints) which is starting to show symptoms. ie, taking 10 seconds to apply a constraint versus a simple 20 component assembly taking a split second.

Is this normal? (does more constraints = more time to compute?)

Thanks.

 

[hudson888]

Ah... I have never tried with quite such a high number. I can see the problem and hadn't thought of it. Maybe it does do that becuase they're all being processed concurrently. To be truthful I am probably not alone in that we don't choose to maintain huge numbers of mating conditions. What we do find is that for smaller numbers the contraints system offers levels of flexibility we formerly were hamstrung without.

Cheers

Hudson