Drawing Quality 4

[drawoh]

This is a question for fabricators, inspectors and manufacturers. thread1103-265767 is drifting off topic, so I am starting this thread.

How good are the drawings you are being sent? Do they make sense as per drafting standards? Are you willing to promise to meet the dimensions and tolerances?

JHG

 

[11echo]

fsincox ... I have a personal story to tell you. ...Back in 1976 after I had gotten out of the Army, I already had a Jr. College degree in drafting and I had gotten my first job as a piping draftsman. I had a very formal drafting education, and part of that were afew graphic design courses. One of my first job as a piping draftsman was to detail out a tank appurtenance drawing …this tank wasn’t more then an over sized trash can. But I was trying to do a good job, and in my "infinite wisdom", decided I could make this drawing better by adding shading under each nozzle! It looked GREAT! I wanted to take it home and hang up on the wall! But then I handed it to my boss he told me to set down and we’d go over it. …So with a large red ink marker he proceeded to X out every bit of shading I had done! With red ink on the original it ruined the drawing. I didn’t say anything; I was disappointed because in my mind I was trying to do “good”. He could see I was alittle upset so he took the time to explain. He told me what I did looked great, but it wasn’t per any drafting standard, and that if any body else tried to use this drawing after me, that he couldn’t be sure if they had the talent to do as well as I did. He went on to explain that drawings needed to follow standards and accepted convention, but they needed to be as SIMPLE as possible so it could be assumed that the next draftsman down the road would have no problems using the same drawing to add or remove any modifications required. To be honest that “lesson” took afew years to sink in, but I never tried to shade anything again.
The lesson, that it seem almost everybody has lost, is drawings STILL need to be as simple as possible to insure that just about any body can use them down the line! Two axioms that just about says it all are as follows”
“NOTHING is make better by making it more complicated”!
The other lesson written between the lines here is…
”IF good work is not recognized, then poor work will follow!”

 

[KENAT]

11echo, you actually bring up a point that is perhaps even more relevant with CAD. CAD, or at least the 3D packages I'm even vaguely familiar with, get more complex all the time.

Much of it is adding capabilities that some people will find very usefull. However, often for most situations it just ends up with more than one way to achieve something, some of these ways are very complicated.

I've certainly opened files made by others that I needed to change and found it a real pain to do so, some because of bad practices, some because of complicated practices.

At our place the situation is complicated because we have a lot of 'part time' users, and a lot of interns who typically haven't used our CAD package before.

So, KISS rules to help future users, but it does sometimes limit how much advantage we can take of the CAD's capabilities, and yes, even I occasionally get carried away.

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[drawoh]

11echo,

Yes, for the sake of other users, you have to keep things simple. On the other hand, you can dumb things down well below the minimum level to do actual design. CAD is user friendly enough that dull, stupid people can perform most operations. That does not mean that they can make design decisions, or understand assembly requirements well enough to communicate requirements on the documentation.

There is a minimum level of intelligence and knowledge for someone to be able to do drafting and design.

Whining and crying about how things used to be so much better, definitely can be tracked back as far as Socrates. Perhaps someone will dig up a Mesopotamian tell and find a cunieform tablet complaining that today's makers of machines are idiots. The point of my post is that I am curious about what sort of average drawing the fabricators and inspector here are encountering. The older guys can comment on what it looked like thirty or forty years ago.

JHG

 

[ewh]

I'm sure that KENAT will be able to appreciate this ;-)

The rise of CAD coincided with the fall of the drawing checker. After all, CAD makes things so easy to do, anyone can do it! And that led to the downsizing or elimination of entire drafting departments, leaving drawing creation to the engineers. This could have worked out well, if they had kept the drawing checker, but he was part of the drafting department and had to go.
Engineers need to see their drafting mistakes, omissions and poor practices in red. Handing the drawing off for a peer check does little as far as good drawing practice is concerned (just re-inforcement of poor habits), and (in my experience) engineers often self-check because "it will get the parts out the door" quicker. Proceedures in many places have become more lax, and drawings are often signed off and released without anyone skilled at drafting having any input.
Yes, there were poor board drawings back in the day, but there were also many more good drawings, depending on the company cuture. It was a hell of a lot harder to correct your mistakes then than it is now on CAD, and those lessons tended to stick.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[KENAT]

Don't get me started ewh;-).

Anyway, there's no room for Checkers in the modern commercial world, what value does preventing errors in advance while educating folks have? The engineers just need to be trained properly; we can rely on their professionalism to self-check and do it right. Then rely on Scrap & Rework to speed up product development. That’s the way forward.

As to the OP, I do occasionally get actual drawings from vendors and generally they are pretty woeful, rarely enough info on them to do a tolerance check against for instance.

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[11echo]

drawoh ...Did you "see" my last axiom I posted? …"IF good work is not recognized, then poor work will follow!" …If you don't know how things are done properly, how do you make the judgment call that things are better now? I’m guessing that because computers make things easier that they do a better job? I’m here to tell you that’s not the case! A computer is nothing more then a fancy pencil and paper, even with a fancy 3D program. IF you don’t clearly know what should come out of that computer to accomplish the job …the same job that was done years ago on the board with pencil & paper, then it and the operator aren’t doing their job! No matter how “pretty” it looks in 3D with shading! I believe that if you ask just about anybody that has done this on the board for a living (us “old guys”), they’d agree!?
Now that you got me pegged as some “old Fart” that has computer phobia you are wrong again! I don’t think anything has come along in this industry that has so much potential! However it has come with growing pains.
…People in positions without a “proper” education for that position.
…No national standards or conventions on how a computer makes the presentation.
…The number of different drafting programs that have divided up the work force.
…The fact that the major emphasis now is to up grade your computer skills as apposed to up grading your designer skills.
…AND the one that really causes me heart ache is as KENAT pointed out (and what I was hinting with my story about shading nozzles), computer guys like to go overboard on how they generate drawings! Because it’s “fun” for them to intricately weave computer programs/commands/X-ref.s to generate a drawing …so complicated that it takes the I.T. department or the original author to un-ravel it so some lesser qualified employee can use the file on another job! This is where the KISS principal needs to be implemented! …AND where I point to on the first axiom I stated…” "NOTHING is make better by making it more complicated"!
All this goes hand in hand for the computer age, as it has done for the “old days” on the board with pencil and paper …like it or not.

 

[ewh]

...No national standards or conventions on how a computer makes the presentation.

Well, there has been an attempt made at standardizing some CAD practices... ASME 14.41.
I'm not at all claiming that it is a perfect standard (neither is Y14.5 though), but it is a starting point.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[KENAT]

Except...

It seems more telling the CAD programmers what to develop rather than so much telling CAD users what to do. Also it doesn't really define modelling best practices so much as how to apply anotation in a model to replace a drawing and or how to have a model/drawing pair.

I agree it's a start point but there's a long way to go.

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[fsincox]

I wish the 3D CAD companies would concentrate on a way to section view radially patterned features (ribs, vanes bosses) that when sectioned would look like proper sectioning practice, any ideas??
I started around 1980, am left handed and a perfectionist. Drafting was a chore for me as I always rub my hand accross my printing and got bad hand/arm cramps from it. I was really excited about CAD now my drawings could look like everyone elses. I love the information I can get too.
Frank

 

[KENAT]

I wish the 3D CAD companies would concentrate on a way to section view radially patterned features (ribs, vanes bosses) that when sectioned would look like proper sectioning practice, any ideas??

Is what I was referring to. Not sure what being left handed has to do with that, and who says I'm not a lefty anyway?

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[fsincox]

Are you?
Frank

 

[fsincox]

Kenat,
When you cut a section on CAD it cuts through ribs, impeller vanes, bosses, etc like a saw. That is not the correct representation according to the old standard drafting manuals, mil or ASME standards rules on section projection. I have yet to find an easy way around this, yet it is so basic to drafting practice and I felt may contributes to some of the “bad practice” mentioned here earier.
You don't have that?
Frank

 

[Belanger]

Frank, I think what you are referring to is called an "aligned section." All the goodies about section views are labeled in ASME Y14.3.

I don't know about specific CAD systems, but I remember that section views can be cut from a "cutting plane line" that is not always straight across -- it can zig zag, or turn on an angle as in the aligned section that I mention. However, when you see the section view, it makes it all appear as if it's in the same plane; you have no sense that the saw turned a corner.

Not sure if that's what you are referring to...

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[KENAT]

If you're talking about something like fig 43 or fig 44 of ASMe Y14.3-2003 then yes, my CAD system can be made to do it.

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[fsincox]

Thanks, Guys
I guess I am not describing this very well.
Kenat,
Sorry, I am not at work now and I do not happen to have a copy of that standard here in my pdf collection.
Take a section through the center of a 5 spoke pulley wheel, I can cut the section so the spokes roll down into proper opposing places, but, the spokes then are also not supposed to be shown as cut through/sectioned.
Frank

 

[PeterStock]

See the attached file for a example of what Frank is talking about. Of course there is also the fact that the tangent lines in the main view would not be what whould be shown in a classic manual drawing.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net

 

[PeterStock]

Note the section view on the left is how most cad systems would show the rib. The section view on the right is how it should be per drafting standards.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net

 

[fsincox]

PeterStock,
Thanks, Yes, that is right except in the old days and per ASME Y14.3-2003, as Kenat has kindly provided above, the other rib should be rolled into place but not "sectioned".
They used to refer to it as true view vs. sectioned. To my OP they really need to work on sectioning or more likely the standards must be changed, I would hate to see the later though it may be more likely.
Frank

 

[KENAT]

Actually, looking again, my CAD might struggle with it.

Though, looking in the standard it appears use of true Geometry is allowed, or am I misunderstanding the intent of the last para of seciont 4.2.1 and figure 45?

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[ewh]

I can only refer back to the '94 version, and thin sections should not show section lines.
It would be good if the latest made that a sugestion instead of a mandate. While the CAD system I use can be cajoled to meet the '94 standard, it is much more involved than a simple section. As for rotating into plane, I don't even try. The cutting line would have to reflect exactly where the section is taken, no feature rotation.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]