assembly master model

[rollinsn]

Greetings,



I had a new user ask me why master model features could not be created
and live happily in an assembly. Ashamedly, I could not come up with a
compelling reason. I actually tried a couple of simple things and I
don't see why it wouldn't work - at least in theory... For a simple
assembly with a few parts, couldn't this work? Might this be a quick
and dirty top down design method? Any thoughts on this - reasons to run
away from the idea?



(why does this question make me feel like a complete newbie?)



Thanks...



-Nate

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[mpeterson]

At first thought I think you could have the Master Model as part of your
assembly, but I wouldn't recommend it.

One of the benefits to this method (Master Model) is the parts are ONLY
referencing the master model (its parent) and not needing to pull into memory
anything else. If the Master was in theassembly then the entire assembly needs
to be pulled into session when working on the part. You won't see that, but
could slow things down.

Another draw back is if you have parts in the assembly that need to move as with
Mechanism then you wouldn't be able to move parts since they are dependent on
static assembly features.

Having the Master in the assembly would also open up the oportunity to create
many circular references which can be a real headache to resolve.

In general the Master Model should be the upper control of critical geometry and
the assembly should be JUST the grouping of all the parts together and thus
where Mechansim is used. There are exceptions, but creating geometry features in
an assembly is not a good practice either.

These are just the first few things that come to mind. Even for a simple
assembly I would use a master model if there are critical things to control
between parts. If its simple enough I just wouldn't even use a master model.

Don't know if any of that is compelling enough to run away, but a few things to
consider.

Sincerely,
Mark a. Peterson
Sr Design Engineer
Igloo Products Corp
-

[BrentDrysdale]

Hi Nate,
Nice to "see" you on the exploder. Virtual is as good as it gets from this
side of the world.

As I understand it the Master Model technique was the early Top Down Design
method with ProE. Also as I understand it PTC developed Skeleton parts to
take over the Master Model function.

Mark's comments cover things pretty well though I would say that if you folk
are running the higher level license then to use a Skeleton instead of the
Master Model part. The real difference is that Skeleton parts are designed
for the job as they always assemble at the top of the tree, even before the
Assy datums and the skeleton does not show up on your BoM. If you only have
the basic licence I don't think you get that functionality so the Master
Model method will let you do almost the same things but you have to manage
its tree location yourself and it will show in a BoM.

Whichever way you go I would only use non solid features in the driving
part. In our Skeletons we use the various datum features and surfaces and
collect these in Publish Geoms for use in other parts via Copy Geoms. I
agree with Mark that you need to be extra careful with mechanism type
assemblies. I personally think that either the Master Model method or
Skeleton part Top Down Design gives very robust and easy to understand
assemblies and are easier to use that the Layout method.

Happy to comment further if you want to get back to me directly.


Regards, Brent Drysdale
Senior Mechanical Designer
Tait Radio Communications
New Zealand
DDI +64 3 358 1093
www.taitradio.com


On 8 April 2011 08:20, Nathan Rollins <-> wrote:

> Greetings,
>
>
>
> I had a new user ask me why master model features could not be created and
> live happily in an assembly. Ashamedly, I could not come up with a
> compelling reason. I actually tried a couple of simple things and I don’t
> see why it wouldn’t work – at least in theory… For a simple assembly with a
> few parts, couldn’t this work? Might this be a quick and dirty top down
> design method? Any thoughts on this – reasons to run away from the idea?
>
>
>
> (why does this question make me feel like a complete newbie?)
>
>
>
> Thanks…
>
>
>
> -Nate