Good drafting practices, GD &T, and culture shock 12

[mmakm]

Hi all, I'm a lead engineer for a medical device manufacture that has a long history in the automotive and consumer products industry. I have a good background and understanding of GD&T and have been through many coarses. With that being said, the company I'm currently with does not practice GD&T and does not have good drafting standards & many untrained designers (Untrained in good drafting proactices). I'm making an attempt to create standards based on ANSI Y14.5.1 and also instill good drafitng practices in the designers. The questions and issues I have are these:

1. I'm trying to make a good arguement for complete manufacturing drawings because I'm constantly getting resistance to this because we supply 3d cad data and the parts are typically produced from this data. Other than incoming inspection, if the parts fits, the drawing rarely gets looked at. What are other arguements?

2. Does anyone have a good approach to driving GD&T and good drafting practices into a culture?

I was going to add more but if I could get some resolution to these issues, we've taken a huge step. Any input is appreciated, & based on what I've read in these forums we have a great knowledge base.

Thanks,

 

[JohnNabors]

Mmakim-

First I want to give a big 'heck yeah' to Kenat's comments. I also want to say that implementation of ISO 14.41 would be absolutely impossible with my company's suppliers given that several of them could maybe produce about 10 teeth per capita from their workforce but those suppliers give us the best PPM's of all our suppliers because they know what we need. They know how to read our drawings.

Don't forget to cite ANSI/ASME screw thread specifications on your drawings and/or purchase orders!! Does your inspection process measure minor diameter of internal threads or major diameter of external threads? Functional go-no/go pitch gages are relieved beyond maximum material condition and won't tell you if you have a wallowed out internal minor diameter resulting in a weak thread. Also, it's not a bad idea to let your suppliers know which ASME screw thread inspection system you are going to use to inspect their product. We use System 21 (actually the most lenient system) and have communicated that to our internal and external suppliers. Everyone knows precisely how we will inspect so that they can inspect their own work with the same inspection criteria.

Kenat- I'm doing the checking because nobody else will, but I'm pushing for a random 'peer review' system. Pray for me. ;>P

Regards -John

 

[KENAT]

Regarding Drawing Checking,

I threw my 2 denari worth in a thread a while back.

thread1103-151962 (12th June)

For starters I believe in 100% checking. In fact I prefer 300+% checking, ie there are 3 signatories in addition to the drafter/designer, my last place was aerospace/defense, every drawing be it new or an amendment got signed by Checker, Stress Engineer & Chief Engineer/Technical Director. While in theory the Checker was the only one doing a detail drawing check the others would spot things, especially our chief stress engineer.

First preference dedicated checker(s).

Second preference one designer designated as the primary checker (ie everyone else’s work goes through him, this is perhaps most applicable to small companies).

Third preference checking each others work (inexperienced staff should be excused from this duty except as learning experience)

Last, and a poor last is self check.

I don’t count design reviews as drawing check, they are good for the big picture but not much use at detail drawing check from my experience.

Just my opinion for what it’s worth. Drawing check is the best way to enforce standards/good practice that I can think of.

 

[KENAT]

Forgot to say,

Good luck John, I'm not sure I agree with random peer checking (by this do you mean only some get checked at random or the checker is picked at random?) but something is better than nothing.

 

[ctopher]

Kenat,
I 300% agree.

Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 06-21-06)

 

[JohnNabors]

I just posted on this subject yesterday and walked in this morning into a classic case of pathetic drawing control.

I'm the QAE for a manufacturer of water pumps. There is a simple part we have made by a supplier for which there was never a drawing. It's a radiator cowling spacer for a John Deere diesel engine that powers several of our pumps. All the guy does is cut 7/16" schedule 80 pipe 1-1/4" long on a chop saw.

I mentioned to the design folks about a year and a half ago that there really should be a drawing for this part in case we ever gave it to someone else to make. 500 of these parts came in today and the inspector found the following: a drawing appeared out of nowhere sometime between the last delivery in May and today; the drawing date was 3/3/05; the drawing shows a length, 1.29 ± .01, that is not the length we need and has a tolerance that God couldn't hold on a chop saw; and a .41 ± .01 diameter on the ID that actually is the 7/16 pipe 'as bought'. The drawing has the name of the person who drew it, but no initials for the engineer or the checker.

I called the supplier to find out when he recieved the drawing. His answer was: "Yesterday."

Lord help me.

 

[ctopher]

Very common. I have seen that a lot over the years.
One time I created a detailed drawing of a part that fit into another a certain way. Made an assy to show the direction it goes. All were checked and signed off by checker/designer/eng/QA/mngmt.
Later, a new assy person decided the part should go in rotated 180deg. The aay person and the mfr eng marked-up the dwg, then had more parts made, then shipped them to the customer without any checking or approval. All parts and assy's were sent back from the customer. Thousands $$ were wasted.
So, not only do you need a checker, you need a good system in place to track all drawings from drawn to release through change.

Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 06-21-06)

 

[drawoh]

KENAT (and others),

Why should the drawings be checked by a specialized checker? What should a design checker know that an experienced, reliable designer or engineer need not know?

I cannot think of a better background for a design checker than extensive design experience.

JHG

 

[ctopher]

A checker should know standards better than others and is not cought up with day to day design issues of a drawing. The checker focuses only on the drawings/documentation.

Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 06-21-06)

 

[KENAT]

drawoh,

In addition to what ctopher put:

I cannot think of a better background for a design checker than extensive design experience.

Of course his background should be in design, I can't think of any other decent way to get the skills & knowledge required probably 10+ years preferably to defense/govt requirements. Doesn't mean his current primary role need be design.

Practice makes perfect, the more time spent checking the better you'll get at it. Dedicated checkers spend more time checking so get more practice.

Some people make great designers but not such good checkers. Every checker should be a reasonable designer but not every designer is or need be a particularly good checker. Not just from a technical point of view but from a personality point of view.

Putting all drawings through a single person or small group better ensures consistency in interpretation of standards etc so leading to a common level of drawing quality.

I could probably go on about this for a while. I've worked under all the ways of checking I listed in my previous post except for the self check (I always check my work before submittal to checking but almost always miss something). From my experience and talking to other experienced colleagues independent dedicating checking is best.

If other designers are to do the checking then it should be ensured that they are adequately qualified/experienced. IMHO takes more experience to be a good checker than to be a good designer.

 

[ewh]

Bravo, KENAT, for a good post! I have mentioned in other threads about how relying on peers for checking is not the best solution, unless they have all had extensive drafting training and experience as well as design experience. It is much to easy to miss mistakes when under pressure to get the drawing out the door, and an experienced, dedicated checker is your best insurance that the drawings will be correct and consistant. It is almost always less expensive to get the drawing right the first time than to have to revise it later.
As for self checking, unless you set the drawing aside for a week or so, most of the mistakes will be invisible to you. Even then, it is much easier to miss your own mistakes than someone else's.

 

[LONDONDERRY]

I have to admit I pretty shocked to hear of a medical device company that lacks interest in documentation, espeically if they are required to be FDA compliant.
You can make your argument, but don't lose your job or get in trouble with it. I would be hard pressed to send a 3D model out to a vendor for fabrication instead of a 2d drawing. One of the problems you may be facing is the company's attitude towards drafting as being the last rung on a ladder compared to engineering. I have my drafting, design and engineering degrees and I can tell you countless times where engineers themselves are horrible drafter and refuse to do it all together because its beneath them.

If you feel like you fighting an up hill battle then you might want to call some out side ISO consultate to explain to the managment the improtance of drawing or find a new job.

 

[humanbone]

I'm a drafter/designer at a medical device company. I am the first and the only drafter/designer here. and to boot im still/kind of in college. i have learned the hard way from the FDA, it is all documents, documents, documents, then control, control and control some more. The FDA dosent care if it built right they just want to know if you have the paper work to back it up to prove it was made wrong. It sucks cause all i want to do is get the job and i have to all this extra BS paper work. so that means 3d models, sketches, drawings, pdf, training records on drafting/GD&T itself, everything is kept.

so when i send stuff out for vendors i ask them what they want to build off of. cause there is a good chance i already have what they want. so to answer the root question

1. I'm trying to make a good arguement for complete manufacturing drawings because I'm constantly getting resistance to this because we supply 3d cad data and the parts are typically produced from this data. Other than incoming inspection, if the parts fits, the drawing rarely gets looked at. What are other arguements?

Tell them "the FDA will come hunt you down, eat you and swallow you whole with out even taking a breath." luckyly i was the new guy and i told them im trying to make things right, and they let me go.

 

[ewh]

I don't know about the medical industry, but in aerospace, it is becoming increasingly common to base parts on the solid models, with the drawing serving more as a basis for ESSENTIAL inspection. If the part passes inspection, is functionally correct and meets it's requirements, why do you feel that it is necessary to have everything listed on a drawing?
Take a look at ASME Y14.41 and see where the future is headed. MBD doesn't mean that you have to completely do away with drawings, just that the drawings don't have to contain every bit of information required to make the part when your model already contains that information.