Opinions: Drawing Dimensions - best practice

I've not come to a decision yet - as different clients seem to each
have their own ideas so, here are some alternatives I've had to deal
with recently:-

A) Add all dimensions by manually inserting into each drawing

B) When building model check or uncheck "mark for drawing" and use
"inset model items" to add dimensions. If more dimensions are needed
go back to the model and add dimensions here - then re-insert model
items.

C) When building model leave "mark for drawing" checked (default) and
use "inset model items" to add all dimensions, then delete unwanted
dimns.

D) Have a stab at the dimensions needed by checking/unchecking "mark
for drawing" then delete any dimns not needed, then add manually any
other dimensions.

I'm sure its horses for courses and depends on what the drawings are
going to be used for - as my clients all have good reasons for doing
it their way - but what do you guys think?

Kev

 

I tend to use option D:-

I find it's better to hide rather than delete unwanted dimensions, because
if you add further dimensions to the part which you need to show on the
drawing, you will have to do another "insert model items" again which would
re-create all the deleted ones again.

There are times when the most suitable driving dimension for the model is
not the one you'd chose to show on the drawing, so I also add "superfluous"
driven dimensions to the part which I mark for drawing.

The reasons I tend to use model dimensions is:-
a) They are less likely to lose associativity to the model than drawing
dimensions.
b) It's useful to get in the habit at the modelling stage of considering the
dimensions that will be used on the manufacturing drawing.
c) When modelling the part, you often have to think about / look up / decide
upon tolerances etc, and it's easier to add this info when modelling for
recall on the drawing, rather than looking it up a second time later.
d) SWX is crap about not letting you dimension to all sorts of silhouette
edges, so you the model dimensions can be vital.

John H

 

Using model dimensions in a drawing is overrated. So is the ability
to change models from drawings. More trouble than it's worth.

The important thing about a dimension is that it tells what it
measures. As long as the dimension is associative (changes with
geometry), it does not matter.

Most of my projects end up being dimensioned manually on the drawing.
The reason is that the dimensions used to construct the model are not
always consistent with the design methodology. Parts with lengths
controlled by assembly context are better dimensioned manually.
Locations of holes that are dependent on context often need to be
dimensioned differently on the drawing for manufacturing purposes.

 

Tick,

I'm with you. I've run into people who insist on using model dimensions,
and who in fact have made it company policy to do it that way, but I
never saw the point. I know "theoretically" its a great idea, but in
practice it never works out that way. The way I model never has anything
to do with the way a machinist or part checker wants to read a print,
and I'm not going to try to model that way because an important feature
might not be modeled until last for some reason.

Besides that, by the time you get done shuffling the dimensions around,
and realizing that they aren't all there or that something is
dimensioned twice, you might as well just put them on manually anyway.
In fact, I'm just as likely to use the "Autodimension" to get things
started because its more likely to be right for certain kinds of parts
than using model dimensions.

 

I also almost never use model dimensions. They just don't often match
the dimensions needed for manufacture, and I find it much quicker to
add only the dimensions that I need rather than take the time to check/
uncheck the "mark for drawing" box. And I always miss a few and have
to go back and find them or add them manually anyway. It would be
nice, however, if the dimensions added in the drawing could be
reassociated when the links break. UG has this feature and it makes
fixing broken links a snap. I wonder if anyone from SW ever reads
this newsgroup to see how users really feel (the SW forum seems to be
primarily SW apologists).

 

Kev,
If enough people reply, you'll probably get answers to agree and
disagree with A - D. I too agree with some of the comments so far and
I also strongly disagree with many. Either way, here is my 2¢:
Because of the types of parts we predominantly create (machined) and
the type of assembly modeling we use (bottom-up), we strive to use a
vast majority of the model's dimensions. As a matter of fact, I teach
& preach to model parts with manufacturing intent in mind. This is
referred to as DFM (Design for Manufacture). We also employ DFA
(Design for Assembly) for similar reasons. This goes back to the days
when I was on a drafting board. You could not gain status as a
designer, senior designer without knowing what manufacturing is all
about. If you didn't know or learn manufacturing, you were a drafter.
Machine & machine shop capabilities are key to a good design and
therefore the manufacturability of parts. Additionally, ease of
assembly and in some cases, only being able to assembly parts one way
are also good design practices, When our drawings are complete, they
are dimensioned with 95% model dimension. Reference and/or draft
dimensions are used only when necessary. This methodology allows us to
dimension once versus twice, make changes at the drawing level and it
provides models (drawings) that are manufacturable.
Does this work for everyone? No. Do we see it any other way? No.
Eddie

 

I generally go with method A, adding the dimensions myself; part of
the reason that I've never really thought about doing all my
dimensioning in the model is that at both of the workplaces where I've
used Solidworks, ordinate dimensions were standard practice. I'm not
aware of a way to use ordinates when inserting model dimensions, and a
quick look around didn't turn up anything obvious; does anybody know
of one?

 

I too am all of the above. We very seldom model a part like it needs to
be dimensioned. Some holes that are in context usually have no
dimensions to them. The only time I ever import model dimensions might
be for a round shaft that only has 1 or 2 dimensions but usually just
put them in when doing the drawing.

 

I'm convinced that the ONLY reason it was put in was it's a really
cool demo feature. I'm with you, I don't ever use the model
dimensions.



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Chris

 

i always use model dimensions

one of the reasons is I dont like to do the work twice
if ive dimensioned and tolerenced a model i dont then want to
redimension the drawing it produces
i kind of agrees with information "input"reuse

and i can pretty much do a drawing in half the time

If