use part orgin axes for mates

[dgiy]

sw2003 sp3.1

Is it possible to use the individual axes on parts to set assekmbly mates.
I can't seem to select the individual axes but maybe I am going about it wrong.

I am trying to assemble/constrain two disks that dont have holes that I can use a concentric mate on. I can constrain the two pieces with a concentric mate (on the bodies) and a face mate but the parts can still rotate and I want to eliminate the rotational degree of freedom.

All help appreciated.

Thanks,
DG

 

[dgiy]

Along the same lines.

Does anyone know, or has Solidworks ever said anything regarding "dangling" mates.

More specifically, if you have an assembly that has a lot of parts and many of these parts do not have all of their degrees of freedom eliminated via mates, does this affect performance?

Intuitively I would think that a lot of unaccounted for DOFs would mean a lot more calculations that have to be iterrated, meaning more loading down of the system.

Anyone wanna take a stab?

Thanks,
DG

 

[MadMango]

You can constrain round parts by adding a Parallel mate between the part plane and the origin plane (or another part plane).

Many times, the rotational freedom of parts like these will not effect the over-all assembly in a negative manner. Adding mates to fully constrain these types of parts will make rebuilds slower, as the software has to solve for these extra mates.

MadMango
"Probable impossibilities are to be preferred to improbable possibilities."
Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[SBaugh]

For your first post:

Use the concentric mate that you have already. To stop the rotation you can use 2 planes mated together as coincident, parallel, perpendicular or angle. They don't have to be in the same location as the hole just as long as the are a part of the part your mating, and another part or personal favorite the assembly planes.

Dangling mates? What about them? You can repair them fairly easy. If you are using faces to mate with then you will have more of a chance of getting dangling mates, if you make lots of changes to your models. If you change a face you will most likely lose a mate some where in the assembly. That's why I use Planes on all my parts. Yes it is a bit of a pain or can be, but my assemblies hold together better than if I were to use faces. Planes are forever, unless you remove them yourself, unlike faces that can be removed or replaced without you realizing it.

The more DOF's you have the more chance you have of losing the functionality of the assembly. The more mates you have might slow it, down but not like geometry. It's worth it to add the mates to your assembly than it is to lose the functionality. If you can always try to fully define your assemblies.

How did I do at the stabbing?

Regards,

Scott Baugh, CSWP
3DVision Technologies

http://www.3dvisiontech.com

http://www.scottjbaugh.com

faq731-376
When in doubt, always check the help

 

[dgiy]

Well stuck

It still seems to me the less degrees of freedom each part has the faster regens should take. Maybe I am wrong, but if the software knows where each part is supposed to be relative to all other parts then it doesant have to solve/guess on where or how the part should be oriented.

Just pondering....

DG

 

[MadMango]

If you add Mates, you are adding data that the program must solve for. If you exclude data, the program doesn't have to solve for it.

It take 3 mates to fully constrain a cylindrical part. If you do not care about the axial rotation of a part, then you only need 2 mates. Less data, faster solving.

MadMango
"Probable impossibilities are to be preferred to improbable possibilities."
Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[SBaugh]

t still seems to me the less degrees of freedom each part has the faster regens should take.

With extremely large assemblies and not using large assembly mode, I can understand how this can make a difference. But for medium to smaller assemblies, it's not that big of a deal IMO. I can open fairly large assembly (500 give or take some) not using LAM and it will open in a good amount of time...like maybe 30+ sec. That's an educated guess.

Maybe I am wrong, but if the software knows where each part is supposed to be relative to all other parts then it doesant have to solve/guess on where or how the part should be oriented

Yes but what if you change one of your parts and lose a face...do you think the software is smart enough to solve/guess where you want to locate the part? I won't assume that, just give you an error. If you can get by without fully constraing and assembly your doing good...but if something changes you may see a larger problem than you want or maybe not...depends on the way the files were designed and assembled. SW recommends to fully constrain your assemblies to prevent files from moving. There can be no guarentee that when you open the assembly next time that the files will be were you placed them before because things can change...At least that's the way I see it...


Regards,

Scott Baugh, CSWP
3DVision Technologies

http://www.3dvisiontech.com

http://www.scottjbaugh.com

faq731-376
When in doubt, always check the help

 

[sirmick]

I may be mistaken, but I believe every part or assembly happens to have an origin and a 3 dimensional orientation. This data is stored with every part/assembly.

When you drag a part into an assembly it gets assigned a position and orientation in space relative to the new assemblies origin and orientation.

I think that the constraints are values in a giant matrix and everytime a new mate is added the matrix needs to be solved in order to determine what the value of the position and orientation of each constrained part is. So additional data and work is generated with each mate.

The software doesn't calculate where an unconstrained part could be. It just lets you drag it into the assembly and all around the assembly. Wherever you drag it the software updates the position and orientation variables to reflect that. I am thinking you have got the cause and effect between variables and restraints in an unconstrained cas backwards.

 

[JNR]

You can just mate enough to fully constrain the part. Origin to origin and two basic planes (say, top and front).

I agree about "rotational" parts like screws, pins, etc where you don't really care. It would be nice if you had a "coaxial-fixed" mate which merely trapped the extra degree of freedom where it was and prevented all those damn negative signs in the tree. They are misleading and confusing and time wasting. I have asked for this enhancement several times.

3/4 of all the Spam produced goes to Hawaii - shame that's not true of SPAM also.......

 

[TateJ]

I can't add any more knowledge to this thread...
But I like SBaugh's notion about mating with planes - regarding their longevity:
If you change a face you will most likely lose a mate some where in the assembly. That's why I use Planes on all my parts. Yes it is a bit of a pain or can be, but my assemblies hold together better than if I were to use faces. Planes are forever, unless you remove them yourself, unlike faces that can be removed or replaced without you realizing it.
Question though:
I tend to create my parts symmetrically about the primary planes - ie, mid-plane extrusions and the like.
If I want to use only planes for mating, I would have to add an extra plane on the bottom of a part - for example - if I need a coincident mate in its assembly.
That would be kind of a pain, no?
Mayby I'm holding your feet to the fire over a general statement - sorry.
Perhaps you'd like to clarify?

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[MadMango]

I don't think there are any hard & set rules for mating, it's all dictated by design intent, modeling methods and corporate requirements.

I try to use Planes in mating the main sub-assys in my models. Many times, smaller components are mated using faces of the models.

MadMango
"Probable impossibilities are to be preferred to improbable possibilities."
Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[SBaugh]

Question though:
I tend to create my parts symmetrically about the primary planes - ie, mid-plane extrusions and the like.
If I want to use only planes for mating, I would have to add an extra plane on the bottom of a part - for example - if I need a coincident mate in its assembly.
That would be kind of a pain, no?
Maybe I'm holding your feet to the fire over a general statement - sorry.
Perhaps you'd like to clarify?

I did state above that it “can” be a pain ”Yes it is a bit of a pain or can be” but if you do a lot of modifying of the part in the context of the assembly or Automation then you should (IMO) take the time it takes to make the extra Planes. It pays for itself in the end, if something were to change and you were to lose a face that would totally fry your assembly. Smaller Items like Screws, Bolts etc… are made the same way Symmetrical (most of the time, if not made by the user). So you could use the default planes to control them instead of faces. You would have to have at least one if not two planes per location of the hole. You can offset more than one plane at a time now, which helps when offsetting planes. Depending on the design and the design intent. You don’t always have to use Coincident mates between planes to fully define say a bolt. You could use the default Plane of the assembly and make a mate parallel perpendicular, angular, or coincident if applicable to a plane within the bolt part. But using a face like concentric mate isn’t bad either, but if you remove the hole, then you will get errors in the assembly. If you used planes and those planes are NOT referenced to the feature you just removed, then the mates will stay. IMO - This is where the user must make notes (mental or not) how he/she has assembled their files.

Does that help answer your question or did it bring up more questions?

Best Regards,

Scott Baugh, CSWP
3DVision Technologies

http://www.3dvisiontech.com

http://www.scottjbaugh.com

faq731-376
When in doubt, always check the help

 

[TateJ]

That clarifies nicely, thanks SBaugh.
I just wanted to make sure I heard what you were saying.
I guess it's a trade-off, between time to create extra planes or re-create assembly mates if you get FUBAR.

Read my profile & make me an offer... now!
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[SBaugh]

Yea pretty much...but if you do alot of in-contexting and automation there is no substitute to building assemblies like this...IMO. I probably told you this before, but I built and Automation designed washer tank for my previous employer. It was fully automated by a few overall lengths and some options. You can see the washer at my site, but I can't pass out the actually assembly. It cut the time from idea to drawing layout by 75%. It's the one program that I'm throughly enjoyed making.

Best Regards,

Scott Baugh, CSWP
3DVision Technologies

http://www.3dvisiontech.com

http://www.scottjbaugh.com

faq731-376
When in doubt, always check the help