Flexible assemblies

I'll pop this question here.

Sub-Assembly (A) has two configurations.
Sub-Assembly (B) contains Sub-Assembly (A) twice and flexible is checked for
both. In addition, Sub-Assembly (B) has two configurations.
Sub-Assembly (C) contains Sub-Assembly (B) twice and flexible is checked for
both instances.

Will this work and allow flexibility of (A) or will it have problems?

 

You can if the sub assembly and sub-sub assembly are both flexible

 

Yep, exactly

 

Poor old user goes and puts this conundrum to the group:

Now suppose subassy (A) has been designed, approved, released and put in the
vault at Rev. 0. The subassy is then placed two or three levels deep in an
assembly as previously pictured and the assembly wants to be parametric as
to the number of sub-assemblies that contain (A).

Quiz question:
How many identical configurations should be put into sub-assembly (A) on the
off chance it will be used multiple times in an assembly (flexible
assumed)?

a. 100
b. 1
c. 1000
d. 2^n where n is the number of levels deep the sub-assy is placed.

How do you handle vaulting the sub-assembly with PDM?

a. Generate a new revision each time you increase the number of
configurations.
b. Stop the PDMserver and hack the version with new configuration into the
vault.
c. Turn on "Allow check in at same level."
d. Don't bother, just keep the assembly stored locally.

If the API had all the calls necessary to control assembly configs and
flexibility this wouldn't be such a problem. Last time I checked it didn't.
If it did, one could traverse the top level assembly tree, check for
duplicate subassemblies, do a little math and generate configs on the fly
much like sheetmetal drawings do for flatten pattern and alternate position
views do.

 

Dale,

Here is another PDM related Conundrum.

Suppose I want to work like this:

Create all parts and assemblies as follows before drawings:

1. All parts to contain part definition information such as dimensions, GDT
frames, centerlines, surface finish callouts, notes, etc. so that when
creating a drawing this stuff can all be imported and the draughtsman need
only position things.

2. Ditto with assemblies.

3. The part is a sheet metal part or a an assembly is a mechanism.

4. All the aforementioned parts and assemblies are created, checked,
approved and released in the vault before drawings are created.

5. Now drawings are made and for the items in 3) above flat patterns are
automatically generated or alternate position views are created as
appropriate. Both of these will create a configuration in the parent part
or assembly. But these have already been approved and checked into the
vault without those configurations.

Should the part in the vault be revisioned to accommodate these added
configurations or should it be left at its current revision level?

 

Look deeper into your PDM system's functionality. Ours (Meridian by
Cyco) differentiates between "versions" and "revisions". A "revision"
is an official change, with a rev. letter change and ECN, etc. A
"version" change is any change at all. This is used when doing things
like adding or changing configurations or minor adjustments that don't
merit a full ECN revision.

The PDM archives all versions for posterity, and allows "rollback" to
different points in time.

 

Our system (Conisio) won't let you change a file unless you lock it, it's
read-only. Therefore, in your scenario, the person doing the drawing must
lock the model file in order to save the newly created flat pattern config.
Then when he unlocks it, the version is updated.

WT

 

If I were faced with that choice, I would probably re-examine why I'm so
dead set on using flexible subassemblies. If it's gonna cost me that much
work, I would either skip it or rearrange my subassembly structure to
accommodate it better (or try to do something creative like making an
alternate structure using envelopes which would show the motion).

Again, why are you so concerned about the rev level? Why not just make the
changes and let the rev do what it will? You could overwrite the current
rev, but if you do that, inevitably there will be some problem where
something changed in another configuration that you didn't count on.

I usually manage the drawing and the model separately, and allow the
revisions to be independent. It's too much work to do it consistantly
keeping the model and drawing revisions in lockstep.

I would never recommend hacking the vault. Sometimes you can get away with
it, but I would do it as a last resort. The cost of really effing it up is
just too high. In fact, I have seen SolidWorks refuse to help people who
have hacked their vault and made a mess of it.

I would also recommend against keeping the assembly stored on your local
machine. That approach will work, but keeping track of things is why
you're using a PDM system in the first place. Multiple copies of files
will get you in trouble somewhere down the line.

matt

 

Yeah, that's an interesting question. I think there are two answers:

1) make sure that you make a flat pattern config of sheetmetal parts before
you finish with it, in the same way that you make a scaled config of molded
or cast parts.

2) if you forget to do 1), you will need to take ownership and check it
back in after the drawing has automatically created the flat pattern
derived config in the part.

If you make the drawing, but don't check the sheetmetal part with the new
flatpattern config back in, your drawing will be incorrect next time you
open it (unless it has been made as a "detached" drawing).

That's a scenario I hadn't thought of before. I'm gonna remember that.
Thanks for bringing it up.

matt

 

No, PDMW doesn't manage configurations separately, but it does make new
revisions to files that have been changed. When the sheetmetal flat
pattern drawing view is created, it automatically creates a new config in
the part, which constitutes a change, so the part should be up-revved.

There are some PDM apps that allow you to manage each configuration as a
separate document. Sometimes it has uses, but I'm not a big fan of that
either.

matt

 

See responses below:

I am faced with that choice because of the nature of the equipment I am
designing. The same assembly is repeated over and over and must be shown in
the appropriate location in each instance in the same assembly.

The point of this question is that one doesn't know apriori how many times
an assembly may need to be used in another assembly and that PDMW in
particular seems not to be able to deal with this sort of thing.

During development this is fine. Just let the rev level bump up. One of the
beauties of PDM during development is that a snapshot of the project can be
had at various stages and one can go back to a previous state if necessary.
After release to the outside world the rules change.

My current working method with PDM is that a revision level must be changed
when one thing occurs. Any change to either the model or the drawing that
effects the way the part is to be made is a revision. So changing a note is
a revision and changing a dimension is also a revision. I have to have this
definition because when I release parts for quote and production based on
revision level I must have record of their changing. For example
specifiying red paint instead of blue paint in a note on the drawing would
be a revision. Changing tolerance on a hole from +/- .01 to +.001 -.000
would also be a revision even though it occurred on the part level. Adding
a configuration to a sheet metal part for the sake of making a flat pattern
drawing would not be a revision.

They don't document the vault structure and there is limited instruction for
manually going into the vault and changing things. So, yes, vault hacking
is at your own risk.

There actually is an out in PDMW and that is to check the box for allow same
revision checkin. So vault admin can allow this to happen when appropriate.

I agree with you whole heartedly. One copy in the vault, the vault backed up
and on tape every night and everyone can sleep better.

 

Do minor revisions bump up the revision number? We use the PDM derived
revision number stored in custom properties as the revsion number on the
drawing.

 

One of the seeming difficulties in managing SW models is that SW will change
a file for its own internal bookeeping purposes without user knowledge that
it has done so. This is especially true with assemblies where the face
numbers used in mates can change due to changes in a part. When this
happens the part and assembly may have to be checked back in with the
assembly at the same rev level and the part at a new rev level.

Dale,

PDM is as much a discipline as a software solution. You have to do it one
way or the other in a production environment or you will have total chaos.
What strikes me as being rather odd is that the PDM solutions offered with
SW don't take the way SW works into consideration and put limits on how one
works. I am starting to appreciate some of the configuration management
things I saw in CATIA when I demoed it some years ago.

 

Don't do that.

In our system, all changes increment the "version" number (generated
by the PDM system) up by one. For revision (ECN) level, we use a
separate property that is not manually incremented.

 

Since the minor revision is a seperate field in the database, it is up to
the company's requirements how they wish to use this. In the case of those
who use the minor revision, it does not warrant a major revision therefore
it also does not require an ECN to add a new configuration, fix a misspell,
etc., but again it is up to the individual company.

Best Regards,


--
Bob Hanson
Centare Group, Ltd. - Custom
Software and Systems Integration
Specialists
http://www.centare.com