Making Assembly Mates Stable 2

Yeah, that's pretty much how it is. Have you used configurations? Also, depend on SW Animator?

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA

Ouch, good luck! Your big problem will be having your sub-assemblies set to flexible. Whenever I have 2 or more of a simple sub-assembly (such as a hinge) set to "flexible" instead of "rigid", it's a bear to deal with.

Sometimes I have to make a "cheat" configuration. For example, I will mate 1 half of the hinge to 1 part, and 2nd half of the hinge to the other part. This is for a simple hinge assembly. For more complex assemblies, flexibles are a headache.

SW07 SP2.0

Flores

How "large" is large, as far as part count? How many tops level mates do you have (~300 is max)? I have several assemblies with over 800 parts, no troubles.

Mate plane to plane
Stay away from angle mates
Save and save often


"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of Eng-Tips Forums?

I'm with MadMango on this (but I've been using SW a LONG time). I've lots of huge assemblies and typically never experience problems with the mates or other things--and often mate things such that moving one thing will cause several other parts/subassemblies to move.

The biggest essential hint I stick with is to mate things one to another based on something that won't change in the part/subassembly. Hence, the suggestion to mate using planes above--your primary three planes don't change or disappear, so they'll be where you expect them no matter what you do to your part. You can apply this to other stable/non-changing geometry--whatever isn't subject to being altered along the way, and therefore crashing your mates. A prime example of weak things to mate with is surfaces, edges, sketch entities (unless used as a geometry-driving skeleton sketch), holes, etc.

In my experience, most of the trouble doesn't come from SolidWorks, per se, but from slight logical faults in building up geometry or assemblies. Of course, knowing how SolidWorks "works" is necessary to get the logic rules down properly--but can save huge amounts of time.



Jeff Mowry
Reason trumps all. And awe transcends reason.

Have you tried checking the box in the Mates property manager labeled "Make Mate Stable"?



Sorry, I know it's evil, but it hit me as funny in a weird way.

Right--the Make Mate Stable option. Make sure you check that.



Jeff Mowry
Reason trumps all. And awe transcends reason.

Why do you need this assembly to move? I used to think I needed mine to move. But they don't move on drawings... messes up the dimensions. If you're creating an animation... that's one matter... but just to check the design. See if you can't make little assemblies to test certain parts with other parts & check your fit/function. Then mate everything in your "real" assembly the way you'll show it in your big drawing. Assemblies that "move" are way overrated... IMHO.

Thanks all for contributing. I am impressed with this forum regarding the number of responses; two other forums have given zero.
I do not need to animate the machine, just check part clearances, linkage interaction (double hinges, four bar, etc.) and actuator stroke requirements at different positions. Configurations may be the best approach, but that seems to have its limitations and I have some questions about that function also.
What I have learned:
1. Keep an eye on flexible subassemblies. I will see if reducing them will help.
2. Try mating to planes, especially ones defined off the 3 main sketch planes. However, many times that is hard to do and mates should simulate how parts actually align.
3. Still looking for the "Make Mate Stable" option. Send that one to SolidWorks, I hope they find it more than funny!

Bob Davis

Hi Bob,

Hope all is great. I am actually working with some large assemblies and here is a few things that have helped me with mates:

1) There is a Best Practices for Mates on the SolidWorks 2007 Help (e.g. avoid long "chains" and mate "loops" of components)
2) Avoid redundant mates
3) Do not mate to a component that has been patterned
4) Limit mates and flexible subassemblies take longer to solve
5) Try to mate everything to one or two base parts or a layout/skeleton sketch
6) If possible fully define the assembly as TateJ said "motion is over rated"
7) Submit an enhancement request for a make mates more stable option

Cheers,
Joseph

OK... here is an obvious tip to avoid mate issues, "use subassemblies" (it may seem obvious, but I have overlooked this one many times)

R2D2LAD, an additional thing to be VERY careful with is two identical "flexible" sub-assemblies. For instance, say you use two identical hydraulic cylinders to lift a platform. Logic would say place one cylinder flexible, and mate it as needed. Copy the flexible assembly and mate it to the opposite end of the table. Drag the platform, and it moves.

The problem with this is that SW tries to solve for the first, and then apply its solutions to the second cylinder, which isn't really at the same place it thought it was. SW rapidly goes south at this point.

The solution to this problem is to make a second, identical configuration in the hydraulic cylinder sub-assembly. By placing two distinct configurations of the hydraulic cylinder in the main assembly, SW must solve for both of them separately, even though the configurations are identical. This process solved a very aggravating persistent problem for us.

TJ McDermott
Formost Packaging Machines

TJMcD,

An excellent tip... A star for you.

Regards,

Anna Wood
SW07 SP2.1, WinXP
Dell Precision 380, Pentium D940, 4 Gigs RAM, FX3450
WD Raptors, 1 Gb network connection

Anna, I cannot take credit for this idea, and to my chagrin, I forget who originally posted it here. I'd credit them if I could remember.

I'll take credit though, for spreading the idea far and wide. This is something that needs to be taught in the class provided by the VARs. It took TWO YEARS of flexible assembly frustration before we learned of it here in this forum.

TJ McDermott
Formost Packaging Machines

TJMcD,
Thank you for spreading the idea. Another Star for you.


Bradley
SolidWorks Professional x64 2007 SP2.2
Intel(R) Pentium(R) D CPU
3.00 GHz, 3.93 GB of RAM
NVIDIA Quadro FX 3400