Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

BOM Variances

BOM Variances

BOM Variances


I'm looking to establish what is the standard way of dealing with BOM with Variances. For a simple example I have two BOMs (2 separate parts)

- Part A
- Part B
- Type A

- Part A
- Part B
- Type B

Now as you can see both top levels parts need components Part A & Part B, however at the time of ordering the customer specify whether they want a Type A or Type B (note they must pick one). I'm of the opinion that having a top level part for every possible variant is a bad idea, I prefer the idea of a single BOM which looks like this:

- Part A
- Part B
- Type

In this instance the type entry is more a generic part, the PLM system would ensure links are maintained to the possible choices.

Happy to hear peoples thoughts of what the standard accepted practice is?


RE: BOM Variances

I'm failing to see the virtue of a single top level part having more than one possible BOM. I.e., the presence of options other than the part number has the potential to lead to all sorts of expensive confusion, and costs of cross-shipping parts to make one top level part into a different top level part with the same identifier, and explaining all that crap to customers.

One virtue of a PLM system is that a single product can have multiple BOMs, e.g. a BOM for the shippable product, a BOM for top level assembly, BOMs for service FRUs, etc., without producing or maintaining expensive drawings for each BOM.

But every BOM should/must have a unique identifier, so that the intended customer's agent, possibly just out of high school, can order exactly what that customer needs, without knowing or caring about or understanding optional configurations, or the internals of the product.

Mike Halloran
Pembroke Pines, FL, USA

RE: BOM Variances

I have two examples that may be on point.

My wife always orders a Quarter Pounder WITHOUT CHEESE at McDonald's.
More than half the time, the first one served has cheese on it anyway.
Sometimes NO CHEESE is appended to the ticket that goes to the kitchen, sometimes not. It's an option that exists in the touchscreen menus at the registers, but apparently it's exercised rarely enough that it's just sort of ignored.

I used to work in a marine exhaust shop. The shop drawings we produced included a lot of detail, but no weld symbols, because the default condition was to weld everything that could possibly be welded.
One day I wanted to make some turbine parts that had to look nice, and I put on a weld symbol showing a puddle weld recessed below the surface. Instead of walking a hundred feet or picking up the phone, one of our most experienced fabricators just 'buttered up' the recess, filling it more than completely, and took the excess off with a 60 grit snag grinder. It looked like shit. Again, NOT welding every possible surface was a rarely exercised option that was just sort of ignored. Also ignored was the red magic marker notation on the shop prints to call me before starting. Experienced fabricators don't need no help from some damn engineer, after all.

It used to be that the default condition at McDonald's was a Quarter Pounder without cheese, and a Quarter Pounder with cheese was a completely separate menu item, apparently with a different ideograph on the register. At some point, McDonald's decided to combine the two, uh, BOMs, and make 'no cheese' an option. ... probably to make space for more menu ideographs on the register face. I can't support the idea.

In our exhaust shop, the welders were very talented, but they learned on the job or elsewhere, and being able to read weld symbols was never demanded of them. I suppose it made sense from some perspective other than mine.

Mike Halloran
Pembroke Pines, FL, USA

RE: BOM Variances

Part numbers are cheap. You should have a unique identification (aka part number) for every standalone item you create. Many times, these are "phantom" part numbers. In other words, no drawing may exist, no released document created to illustrate it, the part number only exists in the electronic systems used to identify and track it.

This is a classic example of Model Number vs. Part Number.
You have a Model 1 consisting of Part A and Part B with the option/variant of Type A or Type A.
The customer facing side of the identification is still Model 1, Type A or Model 1, Type B;
but the backend is going to identify those as P/N 12345-1 and 12345-2 (or 12345 and 12346 if you don't like dash numbers).

How you cross reference the model+option with the part number is the fun part of configuration management.


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close