drawing numbers

[greg2835]

Can someone please explain the following. I am looking at what exactly drawing numbers are and why they differ from part numbers. Most things that I have seen say something along the lines of "part number is 12345-01 and drawing number is 12345." I understand the dash number in the part number, but how can you have a drawing number with just the base number? What would the drawing number be for 12345-02?

Thanks,

Greg

 

[MikeHalloran]

It depends on local custom.
If you are lucky, it is documented somewhere, and you can find the documentation (or you can find a cranky old girl who can run the system with her eyes closed, and has been doing it so long that she can't do it with her eyes open, because the screens just confuse her).

A search of this site should produce a LOT of discussion about part numbering and related issues, with no clear consensus except that everyone does it differently, and every system you might encounter has advantages and disadvantages.

Also note, it's fairly common to have part numbers and drawing numbers that bear no relation whatsoever to each other, so you might need computer help to translate from one to another. ... and there may be more than two identification numbers to correlate.


My last employer, an engine dealer who also blundered into generator rentals and some manufacturing, ran its business on a circa 1972 POS system (I mean that both ways). They used whatever part number was on the box that the parts came in, without necessarily keeping a record of who manufactured the part. Because of limited fixed field widths, part names and descriptions had to be severely abbreviated, and how and how well that was done depended on which low wage untrained clerk entered the part for the first time, or maybe for the third time, because the POS search function couldn't always find the parts that were in the system, and often could find a particular part by searching on a description, but couldn't find the same part when you queried by part number, using the same part number it had just found. That was partially rooted in a limited character set used by the ancient mainframe software that was in fact being executed on multiple levels of simulation, all hosted on modern IBM hardware running Linux or something similar.

... sorry for the rant; you hit a nerve there.



Mike Halloran
Pembroke Pines, FL, USA

 

[greg2835]

I want you to know Mike, that your post put a big smile on my face (especially the part about the cranky old lady).

Yeah I kind of figured at times there would have to be no real correlation between drawing number and part number. Every place I have worked uses equivalent numbers for both and I never bothered to ask if there was suppose to be a difference. I will be teaching a class in CAD for the Fall semester and am putting notes together for drawings, particularly title block information. I did search this site for some clarity on drawing numbers but I don't think I fully understand what is being said. I'll try thinking about it a bit more.

 

[3DDave]

Typically the base number is the drawing number. The drawing details -all- the various configuration dash numbers. The drawing for any 12345-XXX is 12345.

Some places use unique numbers for every part, but when there are variations that can get stupidly expensive. For example a drawing of a screw may have hundreds or thousands of possible dash numbers with codes for length, thread, and material. It would be expensive to create thousands of drawings when a few sheets of notes can cover all of them.

Check the datasheet PDF on this page

https://www.digikey.com/product-det...efense-and-marine/1757819-1/A34120-ND/1123896

 

[greg2835]

Well now your just making all sorts of sense

Ok I see the point for the using the base number as the drawing number. I guess the way my company issues dash numbers isn't what is done by most of the people on this forum. The reason we create dash numbers goes something like this. "Hey, Greg. Remember that load bearing part you made last week? Turns out the load is actually 5X more than we thought. So your going to have to completely change the geometry to get the right stiffness. Probably going to have to change the hole sizes for larger bolts too. Oh and maybe make it out of SS rather than aluminum. Go ahead and change the part number to -02." To which I say, "Are we ever going to use the -01 number in the future?" And then he says, "No that part is just a very expensive paper weight now." And then I say, "Okie dokie boss."

So we just use identical drawing and part numbers. The company I worked at before would have just told me to make that part a Rev B to which I would have said whaaaaat?

 

[MikeHalloran]

Most here would agree that when a part changes _that_ much, it should have a different number.

And we have all had a boss who defied logic and overruled us on that.

Yessir, yessir. (three bags full)

Mike Halloran
Pembroke Pines, FL, USA

 

[3DDave]

Mike,

I've only agreed once with keeping the number; the logistics TDP had already been shipped to the customer** and all of the affected prototype parts were being recalled and replaced. QA was maintaining a serialized list. I only agreed because the QA guy was on board and he was a picky person who would hassle everyone, continuously, if there was any hint the old parts weren't coming back and scrapped.

**DoD - they needed to do provision planning and changes to the part structure would have really ticked them off. All changes were overseen by the customer rep and they always wanted everything over-explained, so they understood what was happening. For those not familiar - swapping stuff out without the DoD knowing about it can get you fined or jailed.

OTOH, late in the program the DoD replaced the guy who had been signing the drawings with a new guy. The first incorporation that went to him resulted in a complaint about the way the drawing was done, followed by demanding that all the drawings be re-done, and the product should be restructured to get rid of logical drawings for subassemblies. It would have resulted (aside from redoing ERP, the hand-drawn drawings, the manufacturing instructions, and who knows what to any affected QA/QC documentation) in going from a 10 sheet J-Size to a 20-25 sheet J-size top assembly drawing with all detail parts going into it, so every minor change would require touching and republishing. Most of the sheets were between 5 and 6 feet long.

The drafting department head pushed this back to program management. I don't know what happened to the new DoD guy, but the drawing package didn't get reconfigured and the drawings continued getting signed.

 

[truckandbus]

There does not need to be a correlation between drawing number and part number. 12345-01 need not necessarily be tabulated on 12345. It may be tabulated on a chart drawing 6789 with other similar parts. Hoses, cables, lengths of angles

 

[drawoh]

greg2835,

Are you generating the drawings, BOMs and POs, or are you reading the drawings, BOMs and POs?

If you are generating the documentation, using drawing numbers to generate part numbers, is simple, efficient, and widely recommended. A lot of relationships between drawings and part numbers are elaborate because the departments that set up the systems did not talk to each other, and efficiencies were not recognized and implemented.

If you are using documentation and part numbers somebody else generated, you will have to ask them for the explanation.

--
JHG

 

[truckandbus]

there are many text books that can give background to the topic; Frank Watt's Documentation Control Handbook seems to be good. My BoM supervisor went to one of Watt's lectures and got a copy of the book and used it to establish our tab-number parts lists/drawings