Part numbering etc.

I have some parts that are specific to one product, only, but many that are used in several. I try to reuse parts already used on one product on others, that's better for inventory.

I have spreadsheets that can compute how many of part X are needed to build so many of board Y. I just have to do inventory to figure out how many parts are in stock now.

Some of the more common parts like voltage regulators and differential drivers/receivers that are used a lot I just buy by the hundred, anyway, as I know they will get used in the next build. I'm more careful with expensive parts to order just a couple more than needed.

This all works well for me.

Unless your operation is quite a bit bigger than mine, just keeping work in progress together in one box works fine for me. Whenever I need to see how many of a particular board are available for final (through hole) stuffing, I just look in the box.

Jon

Yes. That's sort of how we did it when I worked at a little start-up years ago. We would produce 10 finished instruments a month, but you don't buy pa rts in monthly increments. We would buy six months of bare pcbs. Stuff them 3 months at a time with the cheap parts. Blanket order the expensive parts to be delivered monthly and installed just before testing and shipping to keep down inventory costs. Part numbers would look something like this. Project code: 123 Assembly number: 456 Revision letter: A Engineering Change Note: 01 Build code : 0

Bare PCB: 123456A Schematic and Assembly instructions: 123456A01 Different builds(BOMS): 123456A01-0, 123456A01-1, etc here is where you wou ld indicated partial builds or different builds for using the same board in different devices.

Engineering change notes were written on the back of red line schematics an d indicated part changes and cuts and jumps so you could use up all the bar e pcbs. A 123456A06-1 could be functionally equivalent to a 123456B01-1 and both would be allowed in the top level BOM. Back in those days everything was done on paper and kept in binders. Today you have to keep track of sche matic changes and cuts and jumps electronically.

The bigger companies I've worked for had more complicated systems.

We have...

Drawings: 28A450 rev A is an assembly drawing

Parts made from drawings: 28A450-1A is a part made from the drawing.

A variant of that part could be 28A450-2A.

The BOM would be file 28A450.2A

Stocked things: anything in the stockroom has a bin and a stock number. Only one type of thing can be in that bin. Different revs or dash numbers get separate bins.

The stock numbers are of the form 123-4567, and we have a document (SACRED.txt) that tells how to assign those numbers. Some things in bins are our manufactured things, some could be subassemblies, some are purchased parts.

This is our second-generation stock numbering system. We used to use

5-digit stock numbers, and that eventually got all tangled up, so we had a zillion meetings and came up with out new 7-digit numbering system and the associated software.

It's ugly, but it's great to use. I can search, see data sheets/notes, find where-used, see BOMs, all sorts of engineer-friendly stuff.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

I used a database system called Parts And Vendors for quite a while. You have to assign the part numbers, but they can have cross-links to manufacturers part numbers for stuff you buy in. Seemed to work ok. As usual, setting it up, and getting a consistent set of part numbers for in-house stuff was the hardest part.

Link:

--
Regards, 

Adrian Jansen

Trilogy Parts&Vendor was a very popular system for small manufacturing operations, but they withdrew from the market a couple of years ago.

If you google parts&vendor you'll see a lot of alternatives trying to pick up their customers (by offering P&V data import).

I use P&V and might check out some of the alternatives myself (the price of miniMRP looks nice so I'll start with that..).

Don't get hung up on part numbering systems, these days there isn't a need to code a part type, location or value into a part number.

Having worked in the production sector for a number of years I would recommend several things.

1. Be cautious of boards populated offshore, unless it is a company with a good track record. One company I worked for had an on-site PCB Dept. They decided to outsource. Overnight they went from 1% failure rate to 60 % failure rate. After many months they settled the failures down to about 25%. For a small company that would be devasting.
2. Do not go with a JIT reordering method. Even on large scale that bogged down production tremendously.

As far as part numbers for assembly stages, you might just go with a (Part #) -A, (Part#) -B...or some other numbering method so as not to confuse them with version numbers.

It is convenient to have all parts of a type, like 0603 resistors maybe, together and in order by value.

Some people assign the next 12-digit number to the next anything that needs a number: a part, a drawing, an assembly, even an employee. You're just another part in the machine.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

I'm not sure how important a part number system is either. (For us, A new part gets a new sequential number. It is then put into an instrument, (organized by a two letter code, a partially stuffed pcb for optical pumping might be OP-01-07.) I think you want a good data base program. (but it's not something I know much about, I used access MS database in the 90's.)

For us each part/piece is connected to both where it's going and where it came from. (The history of where some part has come from in the past can be important.)

Our data base is also used by purchasing, so there is all sorts of vendor information.

Keep it flexible. George H.

OMG, searching our database is a night mare. We do the sequential number thing... only 4 numbers. We're at about part 5,000... you can do a lot with 5,000 parts!

George H.

We have about 6000 different parts in stock, almost 3 million pieces, and the 7-digit numbers keep them in logical and physical order. Our database program does nice searches in a fraction of a second; once we search and find a close-fit part, we can cut over to sequential list mode and see similar nearby parts. Search for 0603++3.3K and you're in the block of resistors with nearby values.

It would be interesting to randomly mix, say, SOT23 opamps and transformers and rack panels and tie-wraps.

I have learned where to walk in the stock room for catagories of parts, then I can browse the bins, like being hungry at Safeway.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Passives and many semiconductors are crazy cheap by the reel, so it's OK to buy a 4-year supply. That's the opposite of JIT.

We do work at keeping the number of different parts down, both in stock and one any one BOM. It's impressive what you can do with 1-cent quad resistor packs.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

We do that too. Up to part ~2300. Searching the database is not a problem, there is a dropdown that is ordered alphabetically so you get all RES 0603 1% together to pick from, for example. The descriptions can be tweaked after the fact to make this easier.

The main problem I have found is that suppliers can be confused. A bare PCB and assembled PCB have unrelated part numbers.

It is nice just having to type 4 digits though.

We did that too (well not for employees). We used to have separate unrelated numbers for drawings, since there could be several drawings for the same end product (pneumatics diagrams, layout drawings, electrical schematics say).

If we had to to it again I would look at something like JL describes.

--

John Devereux

It does sound sensible to me, but I have no experience in assigning part nu mbers.

I would suggest that the part number with no dash number be the completed a nd tested item. And the completed but not tested be the dash one. If you number with the dash one being say the pcb and the dash two being the stuf fed board , you will not know if a dash 4 is the complete and tested or whe ther that is the dash 5.

If some one says this is stupid, it probably is. Like I said, I have no ex perience.

Dan

Yeah I'm always going in and tweaking the description so that it contains whatever search term I thought should be there. (data base is only as good as what is entered.)

Hmm drawing and such don't get numbers here. But all sorts of consumables do... tapes, glues, IPA, solder etc...

Yeah I would like it to be different, but it's pretty much baked in to how we do things now.

George H.

I've always wanted to see a system where the PART NUMBER was = to the human readable description...

ie the ____PART NUMBER____ would be

RESISTOR 100 Ohms 1% 1/16 Watt CFilm SMT0805 Allan Bradly

Fields more to the right are optional additional information.

There is no reason with the computing power we have in this day and age to limit the part number fields to a fixed number of numbers. m

I've always wanted to see a system where the PART NUMBER was = to the human readable description...

ie the ____PART NUMBER____ would be

RESISTOR 100 Ohms 1% 1/16 Watt CFilm SMT0805 Allan Bradly

Fields more to the right are optional additional information.

There is no reason with the computing power we have in this day and age to limit the part number fields to a fixed number of numbers.

m ==================================================================================

And then you qualify a second manufacturer so the "Allan Bradly" is no longer correct, and then you have the misspelling buried in there to deal with, and then you have to find and dictate the part number to a customer who needs one as a replacement part who then has to pass it to his purchasing agent who has to type it into a PO, all without typos, and ... :-) There's a lot to be said for part numbers no longer than phone numbers.

----- Regards, Carl Ijames

Could be bad. When you say "failure", do you mean stuff like solder bridges that show up at incoming inspection, or field failures?

Yup, plus I use a lot of single-source parts that might go away, such as BF862s and BFP640s. I now have 5 reels of BF862s in stock, so we should be good for awhile even if they do go EOL. I'll stock up on BFP640s, SKY65050s, and ATF38143s as soon as we start selling stuff that uses them.

We might allow dash numbers to be alphanumeric too, so that a bare Rev A board would be -A0, or something like that.

Thanks

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

If you are dealing with Digikey, don't they handle that for you? I'm not sure how easy they make it to upload the BOM, but they will handle the multiplier thing. However, normally for production of any size, extra parts are ordered and the overage varies with the price of the part. Will your spreadsheet handle that or will that part be done by hand?

Why hand assemble the "expensive" parts? Is it to limit the cost of inventory? Or are you concerned about counterfeit chips which may be more likely with more expensive parts?

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Rick C

Oh yeah, I would mention that I turned over all my fab to a turnkey assembly house and I have never once regretted it. I get a PO from the customer, I send a PO to the assembly house, I invoice my customer and write a check to the assembly house keeping the very significant difference. The only time I need to get involved is when the test fixture craps out which it has been doing lately.

--

Rick C