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Dimensioning Drafts

mlocascio
4-Participant

Dimensioning Drafts

Pete Bokma,



Thank you for the suggestion. I think that what you are referring to would be A) A FAKE dimension on a drawing (if I went that way) or B) additional geometry in the model.



Please keep in mind that this draft is outbound. That may have some bearing on how it displays. Still, I would like to see a better way to display a draft dimension.



Michael P. Locascio



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52 REPLIES 52

My 2 cents

Working in the Molding / Casting world.

One of the first features is an Extract.

An Extract has no dimensions, zip, notta, none.

You can click all day on that show dims icon and no dims will magically appear, so put down the Kleenex and wipe the tears and CREATE dims.

(Ok back to creating dims, lol)



Jeff Lippeth ▪ Mold Design Engineer

NyproMold, Inc.

▪ P 847.855.2226


rreifsnyder
13-Aquamarine
(To:mlocascio)

Actually that is not at all true. You can add annotation dimensions in the solid, and in fact many of the annotation schemes I have seen using 3d pdf’s and creo view use created annotations.

BTW, what good is any of this if you have to use STEP which does not carry model driving dimensions. We can talk when AP242 is fully supported.

Rob Reifsnyder
Mechanical Design Engineer/ Producibility Engineer / Components Engineer / Pro/E SME / Pro/E Librarian
[LM_Logo_Tag_RGB_NoR_r06]

I like those 2 cents Jeff, great point with the Pro/Mold extracts… dimensionless



Paul Mailloux ▪ Program Manager



NyproMold, Inc.

144 Pleasant St, Clinton, MA 01510 ▪ www.nypromold.com

Its fun to see this topic come up again and again.  BTW, I also work with cavities, and copy-geom features and am in the Created Dims-OK camp.

In the Words of Star Trek's Dr. McCoy: "He's dead, Jim".
I think we beat this topic to death many times.


Christopher F. Gosnell

FPD Company
124 Hidden Valley Road
McMurray, PA 15317
PH:724.941-5540
FX:724.941.8322
www.fpdcompany.com
----------
DonSenchuk
6-Contributor
(To:mlocascio)

I always browbeat my users away from created dims if at all possible. This is especially true if they’re new users.

As Agent K says in Men in Black “People are dumb, panicky dangerous animals and you know it”.

People will engage in bad modeling practices if given half a chance. Maybe less than half a chance. (The best example in this thread has been making Set Datums part of other features (locators) – or the default datums! – which then requiring all other features to be touched when moving the Datum.) It’s not their fault if they were never taught a better way, but that doesn’t excuse their insistence on continued use of bad modeling practices.

People WILL also learn what @O does. That one thing, right there, should be enough to scare the bejesus out of anyone advocating to use created dims in favor of shown dims. Once a user learns this, they WILL start using it. And, in my experience, randomly. In all the companies I’ve worked at, the rework and scrap cost so much I could likely retire off the money wasted.

All that being said, there certainly are times when it’s OK or even necessary. Merged parts (a forging model into a machining model is common) into parts may require created dims. Sheetmetal may require created dims. External References may require created dims. I’m sure there are others where it is occasionally acceptable/required to use created dims. The thing is, I’ve yet to see any example where 100% use of created dims provides only positives and no negatives. Fact is, in my experience, the benefits of heavily skewing toward driven dims far, far outweighs the benefits of created dims.



rreifsnyder
13-Aquamarine
(To:mlocascio)

A few points on your response, as well as one from David Haigh. I didn’t say I make the first 3 datums my GTOL datums. I said I model to them. They are stable and you have the least to fear about features failing which to me is a greater danger when an inexperienced user is making changes beyond modifying a dimension. As David said, that leads me to recommending that the GTOL datums be created near the end of the model in ways that they can be changed without redoing everything. Of course that brings us back to the beginning, because if you make the GTOL datums last, then they can’t be used to create geometry and thus the shown dimensions are likely not useful.

My other point is whether something like a locator should be a GTOL datum. Datums must be related to the function of the part, usually something that functionally ties other features together. In the case I cited, the locator was an extremely important feature since it tied that part, as well as the entire subsystem, together. I have no issue with the selection of the locator as a datum feature, but rather with the philosophy that all features in the part needed to be tied to it.

Rob Reifsnyder
Mechanical Design Engineer/ Producibility Engineer / Components Engineer / Pro/E SME / Pro/E Librarian
[LM_Logo_Tag_RGB_NoR_r06]

“The thing is, I’ve yet to see any example where 100% use of created dims provides only positives and no negatives. Fact is, in my experience, the benefits of heavily skewing toward driven dims far, far outweighs the benefits of created dims.”

Funny, throughout this thread I’ve been thinking that in 18 years of Proe I’ve rarely shown a dim and can’t think of a time where I thought if only I have shown the dimension, I wouldn’t have problem X. Created dims allow me to separate modeling intent from documentation intent, which are not always completely aligned.

Most of my Proe career has been in molded plastics where the shown dim is likely to not point at any geometry after drafts and rounds are added. Additionally, the part isn’t made from the drawing, it’s made from the database and the database is God. The drawing is to communicate color, finish, material and critical dims for QC.

Mostly I’m just amused that this topic still creates such a debate. If you’re model accurately captures your design intent and your drawing accurately communicates what it should to those who need it (shop floor, QC department, etc.), that’s what’s important. To some degree, who cares how you got there. (I’m assuming that the created dims are not substituted with @O here. That’s another topic altogether in my book and a big no-no in almost every situation.)

--
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Doug Schaefer | Experienced Mechanical Design Engineer
LinkedIn
DonSenchuk
6-Contributor
(To:mlocascio)

I have to revert back to the full quote: “A person is smart. People are dumb, panicky dangerous animals and you know it.”

I’ll readily admit that a person, in this case you, could potentially use 100% created dimensions correctly. But then we go to your last parenthetical, which is where I’m coming from. I do have a user in-house here that uses a lot of created dimensions. Because I know his skill level is very high and I know he won’t abuse @O, I leave my soap-box in the storage shed. When I have to address large numbers of users, shown dims is the way to go. Too many users in all my years seem to have this idea that simply changing the dimension with @O corrects all problems they can’t or won’t fix by editing the model. Even at companies that have rules to expressly forbid their use except when absolutely necessary, users being unable to figure out how to change even the simplest features fall back on “it was absolutely necessary for me to use an overwritten dimension.” Yes, it may come down to user ignorance or user laziness, but at the end of the day that doesn’t change the rework or scrap cost that could have been avoided. For quite a few people, there is never enough time to do it right [1], yet always enough time to do it over.

[1] Even if ‘doing it right’ means asking for help and learning the proper way and why of the matter.

The complexity of making unintended changes to a model is the biggest reason for using the @O option.

Back in the days of paper and pencil, this was allowed because the out of scale dim was underlined. This would be a nice feature to re-implement (I believe the ANSI/ASME specs may still allow it)

I believe Modelcheck can check your drawings to flag any @O dimensions and keep them from being checked in.

The trade-off then becomes the problems when CAD users complain that model XXX was created some time ago, is poorly documented/designed, and a change in the dim causes the whole thing to crash or turn inside-out.

BTW, although I use created dimensions I absolutely dislike @O overwritten dims. Maybe if they were underlined as noted above, and the underline could not be removed, this would be OK.



Christopher F. Gosnell

FPD Company
124 Hidden Valley Road
McMurray, PA 15317
PH:724.941-5540
FX:724.941.8322
www.fpdcompany.com
-----End Original Message-----

I’d like to propose one viable use for @O: using a dimension as a label, such as ‘Knurl this section’ (where the extents are clearly defined by geometry that is indicated by the dimension witness lines).

Of course, this may not be strictly supported by BS 8888 or your drawing standard of choice, but it can be unambiguous if used appropriately and, more importantly, won’t cause your model to crash.

Not that @O on its own can do so, as it can only be applied to a created dim…

Jonathan
DonSenchuk
6-Contributor
(To:mlocascio)

This reasoning gives me heartburn.

If one of my users makes a change to a dimension and it makes unintended changes to the model I would hope they would slam on the brakes and determine why that just happened rather than immediately resort to “I’ll just @O it and then everything will be great!” Otherwise we would end up with too many instances of the model not matching the print, leading to anybody downstream (assembly models/drawings, external refs, tool design, manufacturing, 3d capable vendors, etc.) creating bad parts. Or thousands of bad parts.

Yes, it is a real annoyance when one inherits a model with bad modeling practices. It’s also an opportunity to correct the mistakes at the source rather than just passing problems down to the next department.
mlocascio
4-Participant
(To:mlocascio)

Donald,



This is the one of the best things written on this elongated thread. It’s good to know what’s going on out there.



I like the song by Tom Petty “I Won’t Back Down.” If I had someone working for me who made it a point to create dimensions, especially if modeled dimensions were available, I would have to give him the baseball option (3 strikes and you’re out). I agree with Donald about the idea that people CAN and WILL “fake dimensions.” You cannot change free agency, but you can work around it.



Michael P. Locascio


Doug – thanks for saving me the time and consideration to type up my sentiments; they waver between yours and John Scranton’s.



I was going to let it go, but then Doug posted exactly what I have to say – except the god part – even to the 18 years of Pro/E…



There is a reason why PTC gave us both ways – and it wasn’t so we can argue about it. I believe it was so we can get the job done.



-Nate


Been on Pro/E since 1993 (no idea what rev that was).
I use and teach both created and shown as needed. Each has their time and place.

But where some of the “shown” guys lose credibility is in their insistence on referring to created dimensions as “fake.” Whatever the feeling is on created dimensions, they are not fake. They update just fine and represent the geometry dimensions. I would define a fake dimension as not representing the actual geometry or not updating when the model changes.

This is a common logical fallacy known as appeal to emotion. Defined as manipulating an emotional response in place of a valid or compelling argument.

Thanks,
Chris

DonSenchuk
6-Contributor
(To:mlocascio)

Just have to say I really love your sense of irony. A little dry, but still nicely done.

I’m referring to pointing out Appeal to Emotion while simultaneously using Argument from Authority. In this thread alone we’ve seen variations on “I’ve been using the software since…” of 18 years, 18 years, version 6, version 9 and 1993, where that person sets themselves up as the Authority portion of the logical fallacy. The second worst Pro/E user I’ve encountered out of hundreds started on version 7. No lie.

And it’s not really the created dimension itself. Though creating a dimension on the drawing that one has already created in the model seems a waste of time, I’ve already pointed out where their use is practically required. It’s really the introduction of a process by which “errors”[1] are introduced into the product creation process.

I realize a lot of people operate on the philosophy of ‘hey, we need to get this done no matter what’. Those that do this and have the integrity not to cheat the dimensions (using @O or even sloppier methods) really aren’t operating to the detriment of that product creation process. Unfortunately, that’s proven to be a minority of users (and even dept heads!) by quite a large margin. That’s really the what and why the shown dimension crowd is generally against.

[1]While calling them errors may not be technically correct, people don’t like it when you point out they took intentional actions to introduce the problem. It’s not like they accidentally made those menu picks.

nice thread so far … and another 18 years of Pro/e are missing something.



Most important fact for dimensions is between design intention and the needs of manufacturing. Are they the same – easy doing with shown dims. But what are you doing if the basic datum’s for design are different with the datum’s for manufacturing?

- you can redefine all features and reference to the manufacturing datum’s – and waste your time

- you can redefine the features you need for drawings and add reference dims - some time my favorite with a mapkey to remove the ()

- you can create the dims in the drawing – without cheating

Do it right the first time means to know the later needs. In mechanical design may be. For real development of new design – where do you from? Maybe you don’t know the technology or you have rapid prototyping with less need of dims = dims from design intend. And then you have to redesign for later samples – now you need more dims for mechanical manufacturing …

I could write much more, but I would not waste your time …



It all depends from what you need and from the trust in the skills of your Pro/E-worker(s) – there is no silver bullet.



Uwe


StephenW
23-Emerald I
(To:mlocascio)

Wait a minute!!! You’re saying the vast majority of people who use created dimension also use the @o to “cheat the system”?? Are you sure you really mean that??
Only people who live in the shown dimension world are honest?? REALLY?? That’s a pretty high horse you’re on right there.

I usually show dimensions. I also spend the time to correct my models when I realized I can’t show the dimension as I want to detail it on the drawing as long as it doesn’t mess up my design intent. I use created dimension also. I TRY my best to have my model represent my design intent AND also manufacturing. Sometimes those things don’t mesh well.

I have never used @o to “fix” a dimension. I have used @o to make a cool dimension looking note and to denote a symbol for some reason or another. In my 19-20 years of experience (said with an air of authority, haha) I have only come across a handful of user who have tried to game the @o to shortcut the work.

I have also come across a handful of users who have SHOWN a FAKE dimension. They sketched something in the model so they could show a dimension that didn’t define the geometry so they could have their precious shown dimensions and still say they are of the high and mighty shown dimension only group.

So, they showed a FAKE dimension, do they still belong to the club??



DonSenchuk
6-Contributor
(To:mlocascio)

No. Poorly worded on my part there. I’m saying that, in my experience, giving users carte blanche to use created dimensions leads to far more use of @O dimensions than using shown dimensions. Also in my experience, users that defer to the created dimensions side of the scale that can be trusted not to screw it up are by far in the minority.



Sorry, but I disagree. In this type of discussion, I find a person’s experience relevant. Maybe not an absolute, but certainly relevant.
So it doesn’t really fit the appeal to authority fallacy. But thanks for clarifying my rank on the worst Pro/User list and which version I started.

I maintain that referring to a created dimension as “fake” is an appeal to emotion. IMHO, “fake” has a misleading, negative connotation.

If you’re having success with either or a combo or both, great job. If you’re really slow and/or making lots of mistakes, it might be time to reconsider your process.

(disclaimer – I am not an expert on anything. I may or may not have any idea what I’m talking about.)

DonSenchuk
6-Contributor
(To:mlocascio)

Oh. I thought you were trying to inject a little light-heartedness into this topic. The fact that it’s people self-establishing their authority using either years of experience or version doesn’t change the fact that’s it’s an appeal from authority. I’m also confused as to where I clarified your rank or which version you started. But oh well. Just to clarify, the best Pro/E user I’ve come across also started way back in the single digit version days (IIRC).

Fake dimensions are bad. Non-fake ones aren’t.


mlocascio
4-Participant
(To:mlocascio)

I just think that it would be WONDERFUL to have a Pro/E job where I could spend all of this time emailing.


Which then gets into the limited tools you have available in CREO, etc... to resolve failed models. I find I have to have two sessions open (one with the model pre-change, and the other with the model post-change) to get a full picture for failure resolution. Often clip-suppress is the best choice initially, as the feature that failed may not be the feature with the issue.

I agree modelling in 3D means that the model must be accurate.

"In theory there is no difference between theory and practice, but in practice there is."



Christopher F. Gosnell

FPD Company
124 Hidden Valley Road
McMurray, PA 15317

(disclaimer – I am not an expert on anything. I may or may not have any idea what I’m talking about.)

HA HA!

Awesome.



(me too…)


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