Is it good practice to constrain cylindrical parts?

We usally have a fair amount of cylindrical parts in our assemblies. We usually dont fully constrain cylindrical parts, and let them "spin". Our VAR said this will speed up rebuild times, as well as design time since you dont have to do an extra mate. My problem with this is, I look at my design tree at the end of a design to see if everything is fully constrained. All cylindrical parts still have a - sign next to it, so I have to check them to make sure they are defined except for spining.

Is there a better way to do this? It can be rather time consuming checking all cylindrical parts to make sure they are indeed only spining about the axis.

Suggestions/comments welcome. Thanks.

Reply to
SW Monkey
Loading thread data ...

I pretty much agree with everything you said. I too leave bolts, etc. free to spin for the same reasons. I also see the - signs, but have come to the point where I am consistent enough in my procedures that I pretty well know what's tied down enough, and what isn't. Once in a while I go pull on something to check it, but for the most part, I can recognize what still needs attention.

WT

Reply to
Wayne Tiffany

i agree that it saves a little time but if you have to look at some one elses stuff, or you theirs, trouble shoot a glowing red tree it makes it easier to muddle thru the mess if stuff is constrained completely. i almost always throw a // on the planes just to tie it down. i mean u r talking a split second to do it. if a few // mates is going to break ure system you need a bigger puter! my .02 ;0)

Reply to
3d

If it is that time consuming you could create a macro to parse the mates and make sure all cylindrical parts have a coincident and concentric mate. Or atleast that all components have atleast 2 unsupressed mates.

Corey

Reply to
Corey Scheich

Just had a mental picture. Not even sure this is viable or desirable, but what would it take to have a program that "shakes" the model to see if anything is loose? You could start at the top of the assy, go through each part and see if it can move. If so, see if the only motion is rotational. Then, some way to highlight those that go places other than the allowed cylindrical rotations.

WT

Reply to
Wayne Tiffany

good point... i only wish i was that freakin smart......drooooool..... he hehe......droooool......

Reply to
3d

=) I don't think it has anything to do with smart. Simply LAZY. I hate to do things over and over when I know I can automate it. Work the computer to death because that is what you paid for.

Corey

message

Reply to
Corey Scheich

When looking at someone else's mess (or my own), I begin by creating a working config, then suppressing fasteners and such. This marks them as checked, and removes them from further consideration and rebuild. I keep suppressing other components as I check them and get a feel for the structure of the assembly. Suppressing components also helps identify which components are making trouble. Mate diagnostics tools help to steel this process. By the time I get down to the last few components, I have a good feel for the assembly and everything is back in order. Then I can delete the working assembly of keep it for other uses.

I agree with Wayne that it's not normally worth the time to constrain the rotation of components that don't need to be oriented.

Reply to
Dale Dunn

Oh it should be viable I don't know off hand how you would determine cylindrical rotation It must be possible though. You would have to make sure that you move it back though.

Corey

message

Reply to
Corey Scheich

true dat. i fall into the catagory that i know i could 'Learn" how to do it but i can git er dun as fast and i need it right now! i'll figure out the better way later....only later never comes!

Reply to
3d

This reminds me of the Degree of Freedom symbols in MDT.

Reply to
Jeff N

Another aspect of this that no one has mentioned yet is that sometimes open degrees of freedom can mess up dynamic assembly motion. Say you have a robotic arm with loose screws in it. Moving it around unconstrained may be too much to solve.

By the same token, if you do constrain the screws rotationally, but constrain them to parts that the move relative to, then you can be causing another whole set of problems. Personally, I don't constrain them. Under normal circumstances I think it's overkill. I only constrain them if I'm having problems with dynamic assembly motion.

matt

"SW Monkey" wrote in news: snipped-for-privacy@z14g2000cwz.googlegroups.com:

Reply to
matt

What I do is to insert my first part into the assembly, on the origin and make sure that it is 'fixed'. When each additional component is added to the assembly, they are either mated to the first fixed part (usually a center plane), or to another part of the assembly.

Fasteners and other cyl. parts left spinning.

Now, as long as there are no mates to the assembly itself (e.g. planes), then all you have to do in 'un-fix' the first component and drag and rotate the whole assembly around.

You'll be able to verify any mating problems easily. You can hit undo to bring you back.

If I'm not mistaken, it is a good rule of thumb not to mate anything to the assemby planes. Maybe there are exceptions to the rule?

Mike Wilson

Reply to
Mike J. Wilson

Are you talking about when you're working on an assembly that imploded and now has a "glowing red tree"? If I'm reading it correctly it sounds like an interesting way to work.

Whit

Dale Dunn wrote:

Reply to
wc

wc wrote in news: snipped-for-privacy@chili.com:

Yeah, that was how I developed that habit.

Reply to
Dale Dunn

Hi.

I have always said that I want all part in assemblies to be fully mated because then yo know what you are working with. And the rotation mate should be a parallel to one of the three planes. That cannot take much time to solve.

I think you can use the gravity simulation to check if a part is not mated correctly.

Have a nice weekend

Klaus

Reply to
Klaus Sabroe

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.