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PeterCharles (Mechanical) (OP)
20 Jan 05 11:22
"Parts List" vs. "Bill of Materials"

This may be just a matter of opinion but I would be glad of any responses.

Is there a difference between a "Parts List" and a "Bill of Materials", or are there differences between the two, even if only subtle in nature?

Does it depend on the context in which the two terms are used, or the area (mechanical, electrical, civil engineering etc)

Thanks

MadMango (Mechanical)
20 Jan 05 11:29
Think the term depends on the context.  We use BOMs for assembly, and Parts Lists in our service manuals to indicate repair/replacement parts.

"I think there is a world market for maybe five computers."
Thomas Watson, chairman of IBM, 1943.
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

MintJulep (Mechanical)
20 Jan 05 12:26
Same thing, different name.
Helpful Member!  btrueblood (Mechanical)
20 Jan 05 13:04
In the usage for most (if not all) of the companies I've worked for, a BOM will have all of the internal sub-assembly and processing details in it (including the type of material issued, whether certs were required, consumables used, indicates the routing of the part through various processes, etc.).  A parts list is a list of "top level" parts only, without material or "routing" information, and typically won't list consumables used in the assembly (lubricants, adhesives, etc.) unless they are supplied as part of a repair kit.
GDTGUY (Aerospace)
20 Jan 05 13:57
Per ASME Y14.34-1996, paragraph 3 "Definitions", there is no difference between the two.  It states, "parts list (PL): a tabulation of all parts and bulk matenals, except those materials that support a process and are not retained, such as cleaning solvents and masking materials, used in the item.

NOTE: Other terms previously used to describe a parts list are: list of materials, bill of materials, stocklist, and item list."

These are just two different terms for the same thing per the industry standards.  But, if does not mean that there are not companies out there who have tried to define them as differnt things as noted by some of the earlier responses.

GDT_GUY
IRstuff (Aerospace)
20 Jan 05 14:42
I don't see that ASME Y14.34 implies that the PL includes parts that go into the parts, particularly, since the parts list referred to in Section 3 can be integral to the drawing, which implies that any lower level part would have its own parts list integral to its drawing.  Integral parts lists only go down to the NLA (next lower assembly).

A BOM is often referred to as an "indentured parts list," which is consistent with the definition of "indentured data list" referenced in Y14.34 Section 3.

TTFN

GDTGUY (Aerospace)
20 Jan 05 15:54
I don't think ASME Y14.34 implies anything either; it says it straight out in the definitions.  The full definition for the term 'Parts List' taken straight from ASME Y14.34 reads as follows:

parts list (PL): a tabulation of all parts and bulk matenals, except those materials that support a process and are not retained, such as cleaning solvents and masking materials, used in the item.
(a) integral parts list: a parts list prepared and revised as part of an engineering drawing. See Figs. 2 and 3.
(b) separate parts list: a parts list prepared as a document separate from the engineering drawing to which it is associated and one that may be revised independently of the drawing. See Figs. 10A and 1OB.

NOTE: Other terms previously used to describe a parts list are: list of materials, bill of materials, stocklist, and item list.

The "top to bottom" listing is referred to as an indentured data list. A definition is provided for that as well which reads:

indentured data list (ID): a data list showing the documents for a complete system or end item in a top-down (generation tree) order. See Figs. 8A and 8B.

But, like I said, different companies have applied different means to some of these terms.  So, there will probably be a lot of people who have a different take on this one.

I'm just passing along what the industry standard says on the subject.

GDT_GUY
ctopher (Mechanical)
20 Jan 05 16:02
No difference. Depends on which discipline you talk to.

Chris
Sr. Mechanical Designer, CAD
SolidWorks 2005 SP0.1

GregLocock (Automotive)
20 Jan 05 16:20
I agree in general PL=BOM, but, in the automotive industry, in my experience, a complete vehicle has a BOM, a sub assembly has a PL.

Cheers

Greg Locock

rerig (Aerospace)
20 Jan 05 18:03
I agree with btrueblood.
A Parts List would not normally include sealant, adhesives, coatings, etc.
A Bill of Materials should list all materials and not just the Parts.
An Indented Parts List would list all of the Assemblies and their Sub-Assemblies, but not all of the Materials.
A Parts List is to select what parts to order, including hardware.
A BOM is a purchasing tool to get everything necessary to assemble the parts. A BOM might even list special toos required, if they need to be purchased.

Rerig
automatic2 (Industrial)
20 Jan 05 19:04
My exposure has always dictated that a parts list identifies an assembly, by it's constituents (unique elements). The bill of materials describes the constituents as a purchasable item, either generic or proprietary.
rmw (Mechanical)
20 Jan 05 22:17
A part that appears on a parts list as a single entity, a bracket, for example, might on its fabrication drawing have a bill of materials that shows a list of several components, plate, angle, bar, nuts bolts, etc., all of which when welded, and fastened together, make a bracket that appears on a parts list.

rmw
fwc (Mechanical)
22 Jan 05 9:14

parts list- A listing of all components used in the production of a parent item that does not reflect its structure or intermediate levels, and is not useful in time- phasing requirements based on lead time offsets.

bill of material (BOM)- A structured list of the items used in making a parent assembly that reflects the actual production process in terms of timing and quantities consumed. It is constructed in conjunction with the routing, which describes the individual production steps and rates used. A BOM may optionally include information relating to backflushing, use of alternate and optional components, tie between components and the operations that use them, and other data. BOMs are used by the MRP function to calculate component requirements when given a parent demand, and in building product costs. (Syn: product structure, recipe, formulation, ingredients list)

Found them in the links below;

http://www.bridgefieldgroup.com/glos7.htm

http://www.bridgefieldgroup.com/glos1.htm#B

fwc

btrueblood (Mechanical)
24 Jan 05 16:46
I guess it would have been a good idea to ask the original poster: "in what application does your question apply".  As far as the ANSI Y-standards are concerned, the terms are interchangeable, and my earlier posting should be ignored, because:  the Y-standards cover engineering drawings, which are not supposed to be process-specific.

But, the terms "BOM" and "PL" or "IPL" are quite unique when you talk to manufacturing engineering types (which I've been doing a lot of lately), aka resource planners, aka shop (production) controllers, who have a lingo of their own to sling.  These are the people who spend hours/days/years programming lots of petty little details into insufferably non-user-friendly software packages that are intended to make their lives easier.  To them, you'd better not mix your terms because the differences can be pretty significant.

Interesting posts, though.
drawoh (Mechanical)
24 Jan 05 17:52
btrueblood,

   I agree with you mostly.  We have parts lists attached to your engineering drawings.  Our MRP department has BOMs.  We could just as easily have done it the opposite way.  In house here, we do have to make a distinction.

   In addition to these, I attach "material lists" to fabrication drawings to call up everything our fabricator orders.  SolidWorks cannot tell the difference between these and a parts list or BOM, but at least, we are clear about which list we are talking about.

   All of this is absolutely arbitrary.

                           JHG
rbulsara (Electrical)
24 Jan 05 20:17
My two cents, speaking from what I see how these terms used:

BOM is usually lists the material that is being quoted by a vendor. Bill of material may include complete assemblies such as a compressor, window air conditioner, a meter.

Where as a part list could be and normally used for listing parts need, included or recommened for maintainig an assembly or system. It may say an oil filter, air filter, belts etc..which other wise may be included for a compressor (I made this example up, do not point out my techical deficiency in a comrpessor).

Another example, BOM may include a car, but parts list will include a tire, light bulbs, wipers etc..

I think, it is not what is in the list but what the list is used for.

rbulsara (Electrical)
24 Jan 05 20:19
A BOM may include some parts such as guages on compressor only to indicate adequate details so a buyer knows what he is getting or if the BOM meets the specifications.

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