Dimensioning Philosophy

[dr_gallup]

"First of all, the guy is a f** for trying to modify the part (noticed I said "part") in a drawing. Lame. You never modify a part in the drawing. The drawing is the LEAST critical aspect. All tooling is created from the solid model. Therefore, you modify from the solid model. Modifying a drawing tells me that he has never designed any parts and is just a drafter.
"Capturing design intent is a f**king myth. When you design something, between ID changes and everything in between the design intent literally changes about 10
times. This is fact from all of my projects starting from scratch to finish. You'd have to be a dickhead to go back and redefine all the features to show design intent. And for what benefit? So you can do "show dims"? Haha. That's a waste of f**king time right there. Just like how you guys dimension every f**king feature. WASTE OF TIME. The
only thing that matters is that the model regenerates cleanly and makes logical sense if someone were to try and modify it.
"Model cleanly and do drawings with only CTF dims. DONE!"

Boy does this guy have anger management issues! I've designed fuel injection systems that are running all around the world in BMWs, Jags, SAABs, Vettes, etc. Safety & emmissions critical components, not pastel cell phones. Obviously he has never worked in the automotive industry. Drawings and specifications are the only deliverables a design engineer produces and are legal contracts. Screw it up & your company could be sued or worse, people die. All the part definition between our company, suppliers and customers is in drawings or specs. Only the plastic parts get sent as CAD files, but there are still detailed drawings with every dimension necessary to create the part supplied.

People, please try to keep things in perspective. We are discussing design philosophy, not religion. If you can't/won't/don't want to show a part dimension then make a drawing dimension. The sun will still rise tomorrow.

 

[AHA-D]

But there's some sanity in not changing parts from the drawing level. We design in context. Parts are not free-living things but work in the context of an assembly for 99.9999 % of the cases. When a dimension needs changing, then you go to the part in its assembly context and change it there AFTER checking that this change works out. When you return to the drawing level then the dimension is updated, whether it is a part or draft dimension.


Alex

 

[pmack009]

I would like to see one of your fully dimensioned drawings.
Edited by: pmack009

 

[BigJoe]

not religion your right it

 

[newjack]

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20-30 even 50 years ago, how did designers & engineers convey the design intent? Was it by using

 

[BigJoe]

My
goal is to getrobust models and I have not seen any examples of a
fully detailed part that has ONLY model dimensions.

C'mon now newjack. I sent you a 14 page drawing with ONLY model
dimensions. Nothing created in the drawing. Want me to send
you anohter one?

 

[newjack]

C'mon now newjack. I sent you a 14 page drawing with ONLY model dimensions.

I stand corrected. You did indeed send me an example. That is the only example out of a lot of PE users. Besides, I would like to see a part with more then 8 features...

 

[scottm]

Newjack,


I wasn't ruffled - I thought it was a good question - I just wasn't sure if it was rhetorical or not. Definitely a worthy discussion - although people clearly do take it a little too personally.


Linux sucks and Batman could kick Spidermans a**. Sorry - just trying to distract people a little.

 

[BigJoe]

Linux sucks and Batman could kick Spidermans a**. Sorry - just trying to distract people a little.

You could always mention how much better macs are than pc's, too.



And to kinda keep on topic, the drawings I'm doing are for components
that end up inside of an implantable medical device. All of the
detailed features are critical to fit and almost all of the dimensions
are used in a tolerance analysis. A few of them are referenced in
high-level Risk Analysis documents. Sounds a lot like the
automotive parts that were mentioned earlier.



Overall I get the feeling that use of model dimensions vs. use of
created dimensions depends heavily on the part application and the
consequences of part failure. Pastel cell phones: create the CTF
dims in the drawing (if it fails, the phone might not work or might not
look good). Automotive, aerospace, and medical device
parts: model dims (if the part fails, people might die).



In my business management expects long design cycles. They expect
it to take some time for parts to be designed, analyzed, and
tested. The stories I hear of the consumer products business are
totally different. Like on a Friday, "have this mess of changes
done by Monday."



Newjack is bustin' my balls about the 14 page drawing of the 8-feature
part. That part was modeled with one protrusion and about 80
cuts. Dr_gallup would fire me in an instant if it took me 14
pages to detail 8 features.



Newjack, you should have told us that 4 of those 8 features were datums

 

[burnsp]

I'm in the same boat as BigJoe. I mostly use model dims but sometimes have to use created dims to detail the drawing appropriately. Yes, in many of those instances (not all) I could redefine the sketch and add the necessary dims but I usuallydon't deem it necessary. Sometimes after designing a part that has many features(usually inan evolvedorder), I may go back and compeltely redo the part with fewer and more organized features - I can then dimension the sketches as required for the drawing. Often times, the dims used to get the design correct are not the ones you need on the drawing becasue during design, you're not sure what dims are critical -only after all components are mostly complete are you really sure what dims you need or don't need.


BTWwhy does it take 14 pages to detail 8 features (actually 4)?

 

[BigJoe]

BTWwhy does it take 14 pages to detail 8 features (actually 4)?

burnsp, Newjack was just bustin' my balls. The part actually had
about 80 features. And I kinda stretched the truth, there were
only about 9 pages of details. The remaining pages were just
isometric views rotated about a vertical axis. The machinist
requested these so he could more easily visualize the part.

 

[burnsp]

I can understand about the different views - been to that town before.


This sure has been fun to watch - even without the popcorn.

 

[newjack]

BTWwhy does it take 14 pages to detail 8 features (actually 4)?

Baha ha! Oh man, stop the press folks! I was only bustin' BigJoes stones a little. All in good fun. His work wassolidand had a lot more then 8 features. It served as a very good example too!

burnsp, your points are well recieved too! Thanks for the reply!

 

[fletchtim]

Then i suppose that the procedure of making the Pro/E drawing as only a step to transfer it to AutoCAD for detaling doesn't follow the design intent?

 

[BigJoe]

Then i suppose that the procedure of making the
Pro/E drawing as only a step to transfer it to AutoCAD for detaling
doesn't follow the design intent?

Correct. And making changes to the part is a bitch.

 

[scottm]

Then i suppose that the procedure of making the Pro/E drawing as only a step to transfer it to AutoCAD for detaling doesn't follow the design intent?

Blasphemer..

. That wouldmake detailing far too simple. Hold thy tongue and pray for mercy...

 

[BigJoe]

yeah, I know. I'm going to burn for that one even though I never claimed to be a saint.

 

[donha]

I forgot what the question was

 

[dr_gallup]

Then i suppose that the procedure of making the Pro/E drawing as only a step to transfer it to AutoCAD for detaling doesn't follow the design intent?

Hey, we had to do that for years before Pro/Detail. Kind of screws up the single model, associativity thing.

 

[scottm]

I'm going to show my newness to Pro-E when I say,


Whaaaaa? Pro-E didn't even used to have a detailing module?

And it used to cost how much? Maybe I'm misunderstanding cause I saw demos of T-Flex and Unigraphics and IDEAS 15 years ago that had fully associative drawings built in.