Drawing Number System - Do you still indicate dwg sie in the code? 2

[TZellers]

I'm working on developing a new (and significantly improved, hopefully) drawing number system. Many of the systems I've seen in the past included a character within the drawing number that indicated the drawing size (either small, medium or large or A, B, E, etc). Is there any reason to do this anymore? I can't see the reason for it now or even before CAD, except if drawings were stored by size. This is a moot point for CAd systems, I would think.

 

[ctopher]

The dwg format still needs the size listed, but not the file name or part number. I have never worked for a company that list the size in a part number. But every company is different.

Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP0.1 / PDMWorks 05
ctopher's home site

 

[TZellers]

ctopher: In my experience, the part number and drawing number are different. The way I see it, this is a must in manufacturing, as often times there are multiple materials involved for a given part and maintaining two drawings for each is unconceivable. For instance, we manufacture pumps in both polypro and Noryl and the housings are identical in layout, drawing and tool design. However, each requires a unique PART number.

Having said that, I've never seen the drawing size indicated in the PART number either, but have seen it in the DRAWING number. I think you agree that the drawing size needs to be in the TITLE BLOCK, but what abuot the drawing number?

 

[ctopher]

The part number and the dwg number should always be the same. If a part is made with different mtls, they are each assigned their own part number and dwg. You can have dash numbers in a tabulated chart for the part on it's dwg. I personely have never seen it any other way...aerospace,oil/valve,sensor industries.
Sorry if I'm not much help.

Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP0.1 / PDMWorks 05
ctopher's home site

 

[TZellers]

Not very helpful in my case, but interesting none-the-less. Help me understand the systems you are used to. If you design a valve body for 3 materials: carbon steel, 316L and C20, each part would have its own unique p/n, but all would call out the same drawing number, which makes sense so far. But would the drawing number be the part number of the primary or first part?

As a side note, are the part numbers you are used to significant (i.e. they tell you something about the part)?

Thanks for the input.

Troy

 

[MintJulep]

TZellers,

With your system, how do you link a part to a drawing?

If the part number is not the drawing number then it seems a cross reference of some sort is needed.

Back to your actual question. Other than cases where paper drawings are filed by size, I don't see any reason to include the drawing size in the drawing number. One reason not to. What if you originally check out a "C" number, but your part gets complicated and you need more sections and details then you originally thought. If the sheet size is not part of the drawing number you are free to simply blow away your C size border and put in a D or E size border. If "C" is part of the number you have no choice but to go to multiple sheets.

Very few companies use significant part or drawing numbers. There are always exceptions to the rules used to assign significance.

 

[ewh]

I am more familiar with the method stated by ctopher. The drawing number is the base number and the part number is the drawing number with a dash number attached. This allows for unique numbers to be assigned to the parts while only having to maintain one drawing.
While I have seen companies attempt to use significant part numbers, this almost always leads to problems later (when the product line expands, for example).
As for signifying the format size in the number, I have never seen this done, and don't see any advantage of doing it with CAD drawings.

 

[ctopher]

Every company has their own numbering system. But, for most there is a system that makes sense to them and their customers. If you have p/n's that are certain digits and you just take out the next number, an example would be 0001 and the dwg number would be 0001. The next number would be 0002 and it's dwg number would be 0002, etc. If you make this part again with a different material, alum vs steel, it's p/n would be 0003 and it's dwg number would be 0003. This system also helps make it easier to get government jobs and be ISO cerified because it is easier to follow and understand.

Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP0.1 / PDMWorks 05
ctopher's home site

 

[TZellers]

Thanks again for the input, which substantiated my view that drawing size does not belong on the drawing numbe, which I have seen with at least 3 other pump companies (pre-CAD, however).

MintJulep: I have been thru the analysis of significant PART numbers and agree that insignificant PART numbers are the way to go for many reasons. In my opinion, there needs to be a cross reference for drawings somewhere anyhow. For example, the system I saw with Worthington had a letter signifying the paper size followed by a sequential number (5 digits I think). There was no way to determine if a pump casing drawing had been made without drain taps, for example, as no cross reference existed. Most manufacturing companies utilize some MRP or similar computer system, which becomes the backbone of information for the company. Each separate list or cross reference creates problems in maintaining and/or linkning the databases. The natural draw towards significance (part or drawing number) is for indexing w/o having to always go to a x-ref.

Again, perhaps my fears are pre-CAD based, but I shudder to think of maintaining 5 separate drawings of the same mold/pattern/part made from 5 different materials. Sounds like a sure way to create a descrepancy at some point.

Help me get over this hang-up: the 1:1 system doesn't seem any better than the one I've seen, which btw the way works like this: a drawing number coupled with a material code must equal one unique part number. (Ingersoll-Rand).

 

[MintJulep]

The important thing is that you have "a system" that is documented, and is followed. That is the minimum requirement to satisfy the auditors.

I would be worried about the drawing + material code = part concept. Consider:

Pump casing originally designed to be cast from ductile iron. The designer looks at the pressures involved, forces on the input and output flanges, temperatures, etc, and designs a casing giving consideration to the material properties ductile iron. The foundary looks at that drawing and detrimines the actual shape that the mold (or plug) needs to be to account for shrinkage as the thing cools, where there are gates needed, and other foundary stuff. The foundary creates a pattern drawing for this.

Now a new customer comes along and says "I saw that pump you made for this other guy, I really like it, but I want it in aluminum." The same casing in aluminum will not behave identically as the ductile iron that the thing was designed for. It will be weaker. It may be more brittle. The thermal expansion will be different, which in turn will produce different stress patterns. The shrinkage in the mold will be differnt, so you can't use the same pattern to get the same part.

To me it seems like there are some serious potential problems here.

The design of a part MUST consider the material that it will be made of.

 

[TZellers]

IF the drawing contains different data, i.e. thicker walls, more gussets, etc, then it should NOT (IMHO) be a "table" drawing, i.e. a common drawing with a table of materials and part numbers. It would indeed be a different drawing and drawing number altogther. Here's an example of a p/n I've seen:

2469A010X15A001 which would be a pump casing (2469) in a 12x10x15 size (010x15) with 150 lb flanges (A) and drain tap only (001). The A is just a place holder. The same casing with 300lb flanges might be:
2469A010X15B001. or with vent and flush taps and 300lb flanges:
2469A010X15B003. drop the last three digits for a casting drawing number.

This seemed to work better than M13325, which meant medium (B- size) drawing #13325. As I said before, alot of this headache has to do with legacy drawings, and I am starting anew (or trying to) with a MCAD system so the slate is clean.

It may seem trivial to those who only do what their company has implemented (the way we've always done it mentality), but we currently have significant part numbers, which IMHO, is a joke and drawings that use the significant part numbers as the drawing number. We also have multiple materials that are similar in shrink rate, strength, etc that don't require mods or different drawings and I fail to see the attraction of maintaining two seperate but identical drawings.

Many thanks for the discussion.

 

[ctopher]

good luck

Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP0.1 / PDMWorks 05
ctopher's home site

 

[CorBlimeyLimey]

TZellers ... Do your manufacturing shops keep hardcopies of the drawings? If so, they might appreciate the sheet size being part of the drawing/part number, for their filing system.

& all the best.

 

[TZellers]

CBR: Yes, they do. However, our current drawings are mostly A size anyway. This new product line will be physcially much larger and better suited for at least C. And, most of the work will be done in-house (my hope anyway).

 

[paulyg]

This thread is over a month old now but I thought I would share my experience anyways. I am in the same boat as TZellers. My company uses separtate numbering systems for parts and drawings. Our drawings start out with the size designation (A,B,C,D,E) then a four digit sequential number. Our part numbering system is totally different. This is the way our company has done things since the 1940s. I imagine this numbering system started out of convienience, keeping all the D size drawings in order in D size drawers is easy. Unfortnatly we are stuck with this system now. Any suggestions of creating a new numbering system have been meet with resistance from management. And as much as I would like to see us move to a more modern system, I can see how such a move would turn into a mess and become an unimaginably large task for us to convert the 25% of drawing we do have on CAD (the rest are still on Mylar or Vellum).

TZellers, I'd be interested in hearing how your project turned out.

 

[ctopher]

Curious, can you show us what a typical dwg and part number looks like?

Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP1.1 / PDMWorks 05
ctopher's home site

 

[aamoroso]

A little late in the thread but here is a study on part numbers, the study is from 1986 but interesting content if you are planning on a number system.

Institute for Systems Research

It's a pdf file so you need adobe or a equal viewer.

 

[ewh]

Thanks aamoroso! Good info.

 

[paulyg]

I don't check this board too often as you can see.

ctopher,

Our drawing numbers look like:
B-5701, B-5702, B-5703 (B size)
D-7589, D-7590, D-7591 (D size)

Our part numbers look like:
19578, 19579, 19580, 19581

For assemblies we do:
A-19582, A-19583

we also do groups and material options:
19563A, 19563B (different materials, same shape)

19563-1, 19563-2, 19563-3 (same family, some dimensional differences)

A-19563-1, A-19563-2 (different assembly options)

 

[ctopher]

paulyg,
No problem with that dwg system. Having the size with assemblies is not consistant with parts, and is not needed because the size is indicated with the dwgs.
Also, I would not use the dwg size with any of the files names in CAD files. It would be easier in the future to keep track if the dwgs were to change size.
Sorry, but at the beginning of this thread, I thought you were using the dwg size within the file name, i.e. 12345D.

Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP2.0 / PDMWorks 05
ctopher's home site
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