Can someone explain to me the tab suffix for a part number

[JRNICO]

Hello everyone, I have been developing a part numbering scheme for a start-up light manufacturing company. From all the wonderful discussions I have read here, I have decided to go with a non-significant part numbering scheme. In the book "Engineering documentation control handbook" Watts highly recommends a "tab suffix" as the post-fix on the part number. I don't think I full grasp this concept. For example, say we manufacture a light with part number 10101-XX (xx being the numeric tab). He describes it as "The Tab is a form of significance, although minimal. It is used to delineate similar items on the same document." Can you explain this to me? Maybe an example?

 

[MikeHalloran]

I think the reference is to a tabular drawing, as is commonly used for MS screws, where the dash number is an index into a table. The first field in each row of the table is a dash number. The second field might typically be a length, so that one drawing defines part numbers for dozens or hundreds of screws, varying in length and/or head style and/or thread size. The field of the drawing shows but one screw, with shared dimensions specified literally and with differing dimensions referring to columns in the table, which contains the dimensions for each dash numbered part.






Mike Halloran
Pembroke Pines, FL, USA

 

[MikeHalloran]

I.e., it's silly to waste an entire part number on each and every different pan head machine screw; much easier to use a number in the form of <basic part number>-<dash number>. That also handily groups similar screws together in the company part numbering system, and usually in the physical storage area as well.





Mike Halloran
Pembroke Pines, FL, USA

 

[ptruitt]

Indeed, it is complex. According to Watts, the prefix is the document designation and is under revision control. To create a 'Watts-style' part number that is married to a document, a part number is created by using the document number as the prefix and a suffix which is used for establishing design configurations. As Mike said, the different configurations may be screws that are all the same except for length. But the multiple configurations might be used to facilitate concise 'effectivity' (a specific term in the book) implementations where 123456-01 signifies the initial design which is only backward compatible and 123456-02, which is backward and forward compatible. That way, the document accurately represents two very similar parts in two different stock locations which, nevertheless, are not interchangable.

Many companies are now getting away from the Watts approach and purposely have separate and distinctly different document number (revision controlled) and part number formats. Relationships between documents and parts are database-linked using 'effectivity'.

The differences between the two are really important to understand. In either case, formal policies are required if design configurations need to be managed.

Peter Truitt
Minnesota

 

[ptruitt]

Here is another example contrasting Watts and Garwood:

Watts - A company makes an electrical panel (Doc. No 123456, Rev. C, married to P/N 123456-03) that gets a circuit breaker in a rectangular hole. The breaker is discontinued by the supplier. The replacement breaker takes a D-shaped hole. Using detail views or notes or whatever method works best, the document is revised to show two configurations: It becomes Doc. 123456, Rev D and is now married to P/Ns 123456-03 and 123456-04. One way to do it on the drawing would be to have Detail A show the rectangular hole and note that it represents P/N 123456-03 and have Detail B show the D-shaped hole and note that it represents P/N 123456-04. So with one document, we can maintain a design history to support service requirements, especially if the implementation included accurate recordkeeping. Even companies that use tabulations (suffixes) often fail to change the part number. (123456-03 stays at 123456-03.) They just bump the document revision, as if a document revision controls interchangeability. (A very poor practice.) In this case, traceability is lost and the service department is embarrassed to ask the customer if they have the rectangular breaker or the round one. Service folks should know which breaker the customer has as soon as the customer tells them the serial number.

Garwood - A company makes an electrical panel (Doc. No 12345, Rev. C, married to P/N 234234, which appears nowhere on the document) that gets a circuit breaker in a rectangular hole. The breaker is discontinued by the supplier. The replacement breaker takes a D-shaped hole. Using detail views or notes or whatever method works best, the document is revised to show two configurations: It becomes Doc. 12345, Rev D and is now married to P/Ns 234234 and 414141. One way to do it on the drawing would be to have Detail A show the rectangular hole and designate it 12345-01 and have Detail B show the D-shaped hole and designate it 12345-02. But this method requires that recordkeeping (database relationships) includes a link from the document designation (suffix included) to the part number, including the dates where this match is 'effective'. (The document revision might give a clue to help establish traceability, but that would not be a proper way to handle it.) So with one document, we can maintain a design history to support service requirements, but only if the implementation included accurate recordkeeping.

I'll guess that most companies that have their act together use the Watts approach properly. But don't give up on the Garwood approach until you understand it well, because there is the opportunity for lean bills of materials and other efficiencies that can really please folks downstream of the design group. Operations folk will probably vote for Watts (because it is a mature and well-known methodology) when it is entirely possible that Garwood would serve them better.


Peter Truitt
Minnesota

 

[looslib]

A couple of other reasons to use tab numbers.

1) You have an automobile airbag cover for a unique model, but it needs to be in 7 colors to match the interiors. Use the tab for color control, since all the parts made to the same drawing.

2) You have a welded assembly, with no intention of selling the pieces of that assembly. Use tab numbers for the components of the assembly to show that they are all required for the weldment. I worked for one company where we treated each component as an individual part, which allows more flexibility in part reuse.


"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

 

[KENAT]

The ASME drawing standards briefly cover 'dash numbers' as many know them. I forget if it's 14.100, 14.35 or one of the others though.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[ptruitt]

Ben,

Watts would agree with example 'A', but not 'B'. I am not saying that "B' could not work, but it has a different logic that conflicts with example 'A'.

Peter Truitt
Minnesota

 

[looslib]

Peter,

I agree that my example B may not be in aggreement with established conventions, but I have seen it. We do that where I work now. At other companies, the components were treated as just another part number, which would agree with Watts.

Company philosophy and heritage has a lot to do with existing schemes. For a new company, there are many books, techniques and standards to reference when setting things up. The company product can also influence how you may number your parts.

Someone who makes yearly changes, may want the model year in the part number for quick reference.

I saw a video of the Dallara DW12 IndyCar and they imbed RFID chips in the parts to be sure that the race teams are using legal parts. Might be extreme, but when dealing with a spec chassis rules, it does prevent unauthorized changes.


"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

 

[ptruitt]

Thanks, Ben. I agree.

Can you recommend any books that bring addition insight into configurations, document numbering, and part numbering that is not covered by Watts and Garwood?

Peter Truitt
Minnesota

 

[truckandbus]

The usage I've seen for tabs or suffixes is for parts with identical geometry but different material and/or finish. Often the tab is added as part of a production or manufacturing BoM so that parts for example can be bought with a primed finish so that the customer required topcoat can be added as part of manufacturing.

Parts with simular geometry, that can be manufactured with common tooling, or that are 'made from' other parts (adding a hole, cutting off a tab) should be cross-referenced in both directions to each other with drawing notes to assist Purchasing in selecting vendors/reality checking pricing and to assist engineers in following revisions through affected parts/ parts families - I've seen this attempted with tabs but not successfully - the differences are usually such that a new part number makes sense.