Design & Drafting Check Procedure

[ddelaiarro]

Hi all -

Bottom Line Up Front: I want to develop a design and drafting check procedure.

I manage a small engineering team that designs electronic modules for the communication industry. We have been spending a lot of money on ECNs lately. It seems that the root cause is drawing errors. Our engineers design and draft their own drawings with very little oversight during the release process.

Does anyone have experience developing a similar check process? If you do, would you be willing to share your process? I am a big believer in not reinventing the wheel and would be eternally gratefully if one of you were willing to assist me here.

Thanks!

 

[KENAT]

Do you really mean check process, which has merit, or do you mean a checklist which tends to be problematic?

First, your 'checkers' need to be suitable qualified thread1103-193286, thread765-194599 just having peer checking doesn't add as much.

These couple of links have some general ideas.

http://www.cad-portal.com/articles/art_details.php?ID=17

http://www.roymech.co.uk/Useful_Tables/Drawing/Checking.html

Back when I got given the checking task I started a few threads such as thread1103-216008 which might be worth a look.

My color scheme of choice is

RED - delete/change
Yellow - OK
Blue - calculations, questions, non mandatory suggestions...

Posting guidelines faq731-376

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(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[MintJulep]

I'd suggest that the root cause is a step further back. That your engineers and designers are not sufficiently familiar with drawing standards and the information required on a good drawing.

On a top level:

Is the drawing complete?
Is all the information necessary to make what is intended to be shown on the drawing actually on the drawing?

Do the interfaces match what the part has to interface with?

Have the designated tolerances been engineered, or were the default tolerance on the drawing title block applied blindly?

Does the dimensioning scheme support and reflect the design intent of the part, or did you just use the dimensioning shotgun tool?

Is the drawing unambiguous?
Is there any conflicting information? Redundant dimensions? Anything "open to interpretation"?

Is the drawing compliant to whatever drawing standard you claim to be working to?

 

[KENAT]

Done right, the checking process can be a very effective way of teaching how to draft.

Perhaps more so than a few days GD&T training session.

People get feedback on the actual work they're doing, a good checker will be open to questions and knowledgeable enough to educate less experienced folk. Heck, a checker worth his salt could do some 'lunch & learn' type sessions on specific points to help educate the masses.

However, Mints point is valid. Many engineering schools give little or no real drafting training. In many courses the focus seems to be on learning a specific CAD software rather than learning what you should be doing with that tool. Many Engineers see detail drafting as below them.

The combination leads to some real bad prints.

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[drawoh]

ddelaiarro,

Banish the word "procedure" from your vocabulary. Design, drafting and checking are jobs for trained, experienced professionals, who ought to be able to work out procedures on their own. Too many people in industry are rigidly procedure driven.

What you need is standards. You need to be able to examine any given complete task and determine whether you should accept or reject it. You need the standards to be backed by management. When the checker says it does not conform, management makes the time and effort to do it again, and they monitor and deal with people who persistently fail to meet standards.

GD&T training to ASME Y14.5 is a good start.

I claim that fabrication drawings should be inspectable. I should be able to inspect the part and verify that it conforms to the drawing. This is a composite requirement that accounts for a wide range of design and drafting offenses.

At the design and assembly level, you should require clear instructions for putting it together and making it work. You should be able to see how it does work. The requirements it must meet should be documented, so that you can manage ECRs without trashing functionality.

In your industry, there is almost certainly all sorts of design practise that your designers should not each learn by trial and error. There should be prefered fasteners, prefered connectors, prefered materials and finishes, etc. All of this should be written down, and reviewed periodically.

JHG

 

[DraftingMan]

ddelaiarro,

This is by no means perfect but is a good starting place as any other I have found for a Drawing Checking Standard.

Take or leave it. Good Luck.

John H. Dunten, CD
Certified Drafter

 

[KENAT]

I think that's the same as my first link, it's certainly something I used to help me initially.

I thought there had been other threads about similar, maybe the OP can find them. I seem to remember listing some of the steps I typically took.

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[ddelaiarro]

Thanks to everyone for the replies. I suppose some clarification on my part is in order:

1. I probably misrepresented myself when I included the word design in my initial post. I am simply trying to check drawings for completeness and clarity. We are using design review to confirm the designs. As such, the actual fitment of parts is not the problem.

2. My engineers are pretty well versed in ASME Y14.5M 1994 so the fundamentals of the drawing are present as well.
The big problem we are seeing is sloppy drawing practices such as incorrect notes, spelling mistakes, missing dimensions, notes that do not correlate with the drawing, etc.

A checker will help catch these types of errors. He will also help identify the biggest offenders (for lack of a better word). This information will allow us to work on the root of the problem. We will also be tracking the reason for EC's in an effort to show a reduction in EC’s for non-design related issues.

I will be using my Manufacturing Engineer as a checker. He has over 20 years experience running CNC machines, 10 years designing/building prototypes and is intimately knowledgeable on drawing practice. However, he will need to come up to speed on certain issues that other posters have presented.

This whole adventure comes down to identifying where there is a lack of attention to detail and correcting it. I believe that the information posted by KENAT, MintJulep, drawoh, and DraftingMan will be very helpful.

As always, I would very much appreciate the feedback if any of you see any flaws in my approach. I would definitely appreciate any other feedback as well.

 

[ShaggyPE]

Another thing to note. Fixing a typo should NOT require an ECN. It afterall isn't really an Engineering Change... simply an oops that has no impact on the resulting part.

-Dustin
Professional Engineer
Pretty good with SolidWorks

 

[MikeHalloran]

However, the small probability of making another oops while fixing the first oops demands that _some_ formal record be made of _any_ change, _and_ that if _any_ copy has left your direct control, the revision level must be bumped.

I.e., fixing a typo probably will require an ECN.



Mike Halloran
Pembroke Pines, FL, USA

 

[PeterStock]

If any change is made to a drawing requires a revision level change. If the only change is a spelling correction, that must be recorded. If a bunch of changes are made, one of which is a spelling correction that is not important (i.e. you spelled "THE" as "TH" and it makes no difference in the part requirements), that change may not need to be recorded. You should err on the side of caution, if you are not sure that nobody needs to know that the spelling of a word has been corrected then record the change.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net

 

[drawoh]

...

I.e., fixing a typo probably will require an ECN.

I agree.

Consider the fabricator who receives a newly revised drawing. He has to figure out what you changed. If your revision blocks states explicitly that you corrected the spelling of "DISCOMBOOBERATE" on page_4, he knows he does not have to change his process.

If your revision block shows nothing, your fabricator must search the drawing for your changes. If he cannot figure our what you did, then he must re-write his CAD program or rebuild his tools from your drawing.

Vendors do jack up prices for people who submit crappy drawings.

JHG

 

[MintJulep]

Any change to a drawing needs some type of control. Even an inconsequential typo.

That is not to say that you should necessarily revise a drawing solely to change a typo.

thread1103-224245

 

[MikeHalloran]

In 2D CAD documents, I have on occasion left notes to my successors on non-printing layers. 3D CAD systems typically have a memo field that you can use for internal information, such as a description of the typos that should be fixed at the next formal revision.



Mike Halloran
Pembroke Pines, FL, USA

 

[ddelaiarro]

I absolutely believe that, if a drawing is touched and changed in any manner, an ECN is required. I've worked for companies that have been burnt in the past on this issue and will not have it happen to us.