Part numbers vs. Drawing numbers 12

[jstanczyk]

Good day everyone. This site has been a very nice resource for me in the five days that I've been a member. I hope that I can receive a little schooling here by some of you folks. This is a question about Engineering theory, I believe.

I am reading "Bill of Material, Structured for Excellence", by Dave Garwood (found it on the APICS website). He insists, in the book, that your part numbers, and the actual drawing number for that part, should be different. Currently, all of our part numbers use the same identifier for the drawing of that part.

Our manufacturing company designs and bulids it's own line of capital equipment for the HVAC industry. We are looking to go to an MRP system. We use a program called MAX, by Kewill. I am a Cad operator, and the data controller for our BOMs.

Is it worth modifying our structure? Is is it necessary? I'd like to find out what others in the industry are actually doing.

Thanks a bunch.

 

[ggarnier]

If I have a drawing numbered 12345, then even if there is no possibility that there will ever be variants of this part (i.e. dash numbers), the part is entered in the MRP system as 12345-1.

So in this sense, the drawing and part numbers are different. Providing for the possibility of variants within a drawing is the only reason I can think of for a prohibition on having identical numbers for part and drawing.

 

[solidfriend]

Sometime is easy for customers to decode a simple part number, but for engineers is neccessary to use drawing number that describes exact variant of part, even if this variant not concern to customer. excuse me for my bad english, did you get it?
I mean shaft with center holes on both ends and without cener holes is the same for customer. but for turning (machining) sometimes must have holes.

 

[jdsewell]

jstanczyk,
not fully understanding your system, i would pose this to you. if you rev the part, would you have to rev the drawing number and the part number creating more documentation?
in our system we have an assembly number, an outline drawing (basic overview of the part) and a assembly reference drawing. 3 different part numbers to keep track of.
i don't like our system.

 

[jstanczyk]

The theory, I think, points to a situation where multiple parts relating to an assembly are all detailed on one drawing. He points out in his book that a company may have the same basic design envelope (needing only one drawing to show the design) with the opportunity to have variants within that design (different part numbers). I think you guys apply to this, ggarnier.

solidfriend...When we have variants on a part, we generally apply a new part number.

jdsewell...If we revise a part, we up the revision level on the drawing and check stock to update anything on-hand. The part number stays the same, if it is interchangeable with the old design. Our software - when used correctly - allows us to track the old designs in the field with an effectivity date.

Thank you for getting involved.

 

[jstanczyk]

jdsewell,
Thinking about your situation more...If I understand correctly, you have three different drawings to change when one part number changes. Sounds like us. That is why we are also looking to upgrade from AutoCAD 2000 to Pro-E or Inventor. Change one drawing, and all other prints fall in line.

TGIF

 

[Hush]

The drawing is only one part of the product. We make the drawing part of the BOM. Our part number is the dwg number followed by a dash number like ggarnier. If we rev the drawing the part number gets revved but, if we rev the part number for say a material change we don't have to rev the dwg, saves alot of work in the long run.

 

[MadMango]

It also depends if your company uses Significant or Non-significant part numbers. Review: Significant part numbers means that the part number helps to identify the detail part, while non-significant numbers do not.

Take a metric Garlock DU Bearing, the part number is MB0606DU (very significant).
MB= metric bearing
06= bearing bore
06= sleeve length
DU= identifies the material

My company uses non-significant part numbers, and relies on our PDM and MRP system to give us descriptions of our parts. Our part numbers and drawing numbers are identical. No dashed prefixes or sufixes. Through ECO, we rev parts if required or if FFF changes (fit, form, function) we will assign a new part number which is also the drawing number.

I worked for a medical device manufacturer, and they used Significant part numbers, and different numbers for drawings and parts. It seemed that everytime there was an ECO, there was 2x or 3x the work.

I think if you already use the same number to identify drawings and parts you should stick with it. I do recommend getting rid of Significant part numbers if you use them though. "Happy the Hare at morning for she is ignorant to the Hunter's waking thoughts."

 

[GregLocock]

Supposing you have two parts made to the same drawing, but made of different materials? Obviously the part numbers will differ, yet the drawing /could/ remain the same (depending on whether you spec materials on the drawing).

I've been round this loop once, as we set up a Design and Documentation System for a bootstrap project. The drawing number was the filename, and was partly meaningful , of the form <projectabbreviation><sequential file number>.<filetype>, but the part number was fully meaningful. The linkage betweeen the two was specified in a table somewhere handy, I think it would have been the BOM.

Cheers

Greg Locock

 

[tcampbe1]

Here's my beef with part numbers being completely distinct from drawing numbers. The connectivity of part number to drawing needs to be kept in two places, on the drawing and in the PDM (unless the drawing and the PDM are linked) and sometimes a third place, the MRP system. Having information in only one place is a huge saver of management cost, mistakes, and it promotes accuracy. Good discussion!

 

[Gianfranco]

Hi friends,

I believe is necessary to pose an essential question.

1. Why is necessary identifying a part by a number/code?

The specific activity (to coding, I mean)is not only matter of Tech. Deps: it has a lot of consequences: let think at specs for orders, Bom, physical and virtual inventories, stocks, traceability, quality records, non conformity management, disposals, assistance, spare parts, costs, etc.
BTW: We all know, the coding activity is managed with a departement logic (times/costs/troubles). Isn't true? Please, take in your mind the last consideration.

Let pose us an other simple question.

2. Why several firm (mainly tech. deps) do not accept to managing the part no./code taking into account the changes or revisions?
The changes, and revisions, are considered a big tedium and an unacceptable loss of time. Isn't true?

For the replay to the 2nd question I can say you the following facts:

a) The cost of generation of one part code/changes/revision, is ranging $100-500 /each depending on the &quot;informative/communications&quot; system and organization.

b) The cost of of misalineament of drawing numbers, part numbers or codes, I've measured it several time in my working life (as executive and consultant), taking into account the global costs, (at organizational level), can amount at dizzy/vertiginous costs of $10.000-100.000, and more.

c) The first causes of these troubles are due to the behaviour of tech. and sales deps. that create (i) by-passes during the contract reviews and, sometimes, (ii) fantasious procedures to avoiding to change the part number (including the revision in it, I mean). Why? They are all convinced that is a loss a time and money (see question/answer 1). Unfortunately these are facts not opinions.

At the end let pose us the last group ofquestions.

3. How to avoid the troubles generated by a misalineament of part/code configurations? Are the costs of these actions acceptable? What is the simple action?

An advice for an answer: please, be certain to think not as member of one departement but in firm/whole point of view.

Gianfranco.

 

[SnowCrash]

This discussion touches on some of the trickiest parts of the engineer's work in manufacturing; how to get the information into the hands of the customer and onto the manufacturing floor.
In one industry I used semi-signifigant numbers - each type of part had a series of numbers, 40000 for terminals, 60000 for plastic, 70000 for assemblies. It worked until we ran out of numbers. A drawing number might be 70000 and it would have hundreds of part numbers (as dash numbers). We liked the dash number to reflect the number of contacts, but it did not always work out that way. Too many leftover numbers. Sometimes the dash numbers just reflected the creation sequence.
We had a separate document for the customer drawing which contained critical, inspectable dimensions only.
It was possible to have a revision level for these drawings every time we added a dash number part. These drawings also reflected changes in the manufacturing process - which is not the same thing as the BOM, although manufacturing process sheets or steps or specifications can go into the BOM.
It is reasonable to have a customer part number which bears no relation to the manufacturing part number. Bearings, pumps, cylinders, and valves are common examples of this. In a job shop we can make the identical part for several customers. It has a different drawing and part number for each customer, but the CAM files are the same.
Did someone mention file names? We started with eight character file names, remember? You guys have it easy today! There is no particular reason why the file name and the part numbers have to be related or the same. I put the file name in the drawing format.
In an industry where the product has a text name we used to create in house part numbers. A catalog/customer part number would be &quot;Southern Potato Hoe&quot; but our manufacturing reference would be SPH01.
Today I think I would put the design drawing, manufacturing drawing, BOM, and customer drawing in one drawing file with different format sheets. Manufacturing specs and CAM filenames would be in a database and be shown in the BOM.
The file directory structure is one important control. Our current system is /department/softwarepackage/customer/job.
So a file might be D:/Engineering/Solidworks/Boing/23415/part1revA.sldprt

which was part of the original question, right?

So in a complex environment you are going to need some serious MRP software to control all this.

Crashj 'try to keep it simple' Johnson

 

[MadMango]

With a nice PDM Package you won't have to place the Rev in the file name, which makes it so much easier (in SWX anyway) to update parts in assemblies.

To comment to Gianfranco:

1- Part numbers, codes, whatever you want to call them... they are just as important as the nomeclature of the part in your database. If you have a MPD/PDM system, sometimes you don't have the part number, but you know it's a welded bracket. Having standard nomenclature along with non-significant part numbers can be a great help.

2- Every company should consider the ease of changing the documented parts properly (through ECR/ECO procedures) rather than having to deal withthe parts on the assembly line. The cost saving is a no brainer if you can catch problems with the documentation (BOM, Drawings, etc) rather than the physical part.

3- The easiest way to structure your part numbers is by first creating a BOM Map of your product. You know you have to sell the customer something, that is the 1st number (a bottle of soda). Then you ask yourself, &quot;What does that contain?&quot; (bottle, cap, soda, lable, shipping box, tape, shipping lable). Assign each of these items as well, into fuctional areas or sub-assemblies.

For example, the bottle, soda, cap and lable would make up 1 sub-assembly, while the shipping box, shipping lable and tape would make up another level of your BOM Map. By covering these basics, you will maintain your numbers better, and will logically structure your BOM.

Disclaimer: There are hundreds of ways to organize your companies data, and this may not be the best for your industry or processes. &quot;Happy the Hare at morning for she is ignorant to the Hunter's waking thoughts.&quot;

 

[Gianfranco]

Hi all,

I thank very much MadMango for the replay.

Answer 1: I agree with him.
I can adding an hystorical observation about the coding activity. All tech. deps wants to identify a part with the minimum digit/characters (alfanumeric or numeric) and, at the same time, with the maximun of the information (category, class, sub-class, functional, dimensional characteristics, etc. The birth of semi-speeching, and full-speeching codes, summarized the description of the part/drawing/document, were motivated to avoiding long description and, moreover, the management of a nomenclature to be used for the generation of the code/drawing/document.
The use of PDM, and modern databases, or the use of the long description for making the queries(by substrings) should vanished the importance of the &quot;*-speeching&quot; codes.

Answer 2- I want to say that the costs - apparently generated by a lacking management of configuration - are actually generated mainly by a behaviour of a people: documents/part code are the results of the behaviour of people and not the viceversa.

Answer 3- I fully agree.
The coding procedure, whatever the choice of the part/drawing/document identifying strategies, should be classified in one of these cases:

a) hermetic code with long description
b) semi-speaking code with medium description
c) full-speaking code with short description
d) only description with nomenclature and an hidden code

comes up from the deep structure of your final/finished product, and internal culture/resources used.

I believe that:

1) there are enough matters for a FAQ on: What are the best strategies/methods to creating the code numbers for assembly, sub-assembly, parts, materials, drawings, documents;
2) our four stars friend MadMango is certainly the more qualified collegue to do this.

Thanks to all.

Gianfranco

 

[Norgrenite]

Could anyone give me a good definition of FFF (Fit, Form, function)?

We have a part number for V-packing and are replacing with U-packing. Fit and function are the same - but form? I am debating using a different dash number or not. We are replacing the part and vendor, and no longer using the V-packing.

All thoughts are appreciated.

Thanks,

Norgranite