adhesive materials in BOM? 9

[bxbzq]

Hi there,
Do you include adhesive materials, like glue, thread lock, welding rod, solder, tapes, stickers etc. into BOM? If not, where should these materials go in your materials management system?

 

[tbuelna]

Yes you should. These "bulk materials" are normally called out in general notes that describe the process where they are applied. And in the BOM their quantity is usually listed "A/R" or as required.

 

[bxbzq]

Is this company specific? Or if there is any standard out there supports this, I would love to know.

 

[MadMango]

The more accurate your BOM, the better forecasting, planning, and financials.


"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[rb1957]

what's the value of controlling stock ? standard low cost items can efficiently be controlled with min/max ordering.

another day in paradise, or is paradise one day closer ?

 

[Tunalover]

Small point, but "AS REQUIRED" is properly abbreviated as "AR" not "A/R". This is per ASME Y14.38 and MIL-STD-12.


Tunalover

 

[looslib]

The only standard that I know to check would be ASME-Y14.34-2013.


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

Ben Loosli

 

[Tunalover]

Beg your pardon. You're right. Should be Y14.34 which was created from MIL-STD-12.


Tunalover

 

[Tunalover]

looslib,
I should have looked it up. I just did. Y14.34 covers how to construct a parts list among other things. Y14.38 is Abbreviations and Acronyms which was born from MIL-STD-12. That's where the abbreviation AR comes from. I'm pretty sure that if Y14.34 gives the abbreviation for AS REQUIRED that it's the same as from Y14.38.


Tunalover

 

[ctopher]

We also always have it in the BOM, with AR as qty.

Chris, CSWA
SolidWorks 14
SolidWorks Legion

 

[MikeHalloran]

If your company is using some variation of ERP, consider estimating and using actual quantities, e.g. 3 microliters, since "as required" will not generate a purchase order for something like Loctite without repeated manual intervention, which fails to work every time you get a new ERP clerk.

Mike Halloran
Pembroke Pines, FL, USA

 

[berkshire]

Also If you are kitting parts for later assembly, check expiration dates On things like glue and thread-lock.
B.E.

You are judged not by what you know, but by what you can do.

 

[tbuelna]

Small point, but "AS REQUIRED" is properly abbreviated as "AR" not "A/R". This is per ASME Y14.38 and MIL-STD-12.

Thanks for the correction.

berkshire also makes a good point about checking shelf life of bulk materials like adhesive or primer/paint.

One difficulty you encounter when specifying "AR" in the BOM is that many materials like adhesives/sealants/primers/paints are multiple components that require mixing and preparation before being applied. And usually there is a minimum amount of the material that must be prepared, which is often far more than is needed for a single application.

 

[Sparweb]

Sometimes these materials are contained in "standard practices" documents, like process specifications for application of adhesives or labelling etc.
This takes some of the responsibility away from the part designer for calling up these items, though they'll be required on the finished part eventually.
In these cases, there may be nothing but a little note such as "finish per PS101" to tell production that the part shall be etched, alodined, primed and painted according to a very specific set of processes.
In my current work environment, it's reduced even further, where there is only a little "X" in a box within a long list of standard practices to indicate that a process will be required. Then it's up to manufacturing to decide what consumables will be required, but no knowledge of what the designer had in mind.


STF

 

[MikeHalloran]

Using 'AR' in the BOM assumes that every supply chain person reading the BOM has some feel for a reasonable rate of consumption and a reasonable order unit and quantity.

In all but the tiniest outfits, the supply chain staff has absolutely no idea what you make or how you make it.

The product design engineer(s) and the manufacturing engineer(s), working together, are the only people who can make a reasonable guess about appropriate order and issue units and quantities.

If you can't be bothered to do a little math to get the BOM exactly right, then you deserve to have your phone ringing all the time with silly fire drills about BOM issues. ... and you will.



Mike Halloran
Pembroke Pines, FL, USA

 

[3DDave]

The other side of the AR problem is the manufacturing process. What goes onto the engineering drawing is a description of the finished product. This is not a description of all that is required to go into the manufacturing process.

For example, before prime and paint, one needs to clean and degrease. I've never seen any drawing telling manufacturing how many gallons of water, cleanser, or degreaser they will need for a part, nor lint-free rags to to wipe it down. And, as has been mentioned, there are times when the prep for consumables is a noticeable portion of the material required. Sometimes there are problems as simple as minimum order quantity; estimating complains the .03gms of material should cost $X, but the factory is spending $1000X, because the minimum qty for making one part is 1000 times the required qty.

And even this varies - a lot - when running a single part or running 100 or 1,000,000.

There is also loss. I see this from time to time. An assembly drawing calls out 100 fasteners, so procurement orders 100 fasteners, and the assembler drops one and can't find it. So the entire assembly process is halted for a few days to order a replacement. My favorite is polysulfide rubber sealant. The shop always wanted the 30 minute cure and then whined about how much they wasted because it set so fast. And, if moved to the 24 hour version, would whine the parts were still wet hours after assembly.

Some see the engineering drawing as the basis for all work, but in fact it is a final inspection document, not a process planning document.

 

[Tunalover]

You're absolutely right 3DDave. The engineering drawing is first and foremost an engineering and inspection document used to depict the end-item, not every step required to get there.


Tunalover

 

[tbuelna]

I have also worked on large production projects where even items like rivets were listed "AR" on the BOM since there were often a fair number of rivets rejected/lost/scrapped during assembly. For ongoing production (or sustaining) programs inventories of bulk materials are usually replenished on an as needed basis.

While we have discussed the situation regarding bulk materials and the manufacturing process, there is also the issue of how bulk materials are handled when it comes to cost accounting. Consider the problem created when you have an inventory of a particular bulk material that is used for more than one contract. How do you account for the cost of material used for each contract?

 

[bigTomHanks]

At some point somebody is going to have to manage these materials by working with operations to setup a system to ensure the right materials and levels are maintained. The BOM will never contain everything that the workers will need to complete their job but it will enable over 90% of items to be automatically ordered/maintained by computer. As others have stated when the materials person who has the system setup and working leaves things tend to fall into chaos until management realizes a problem and assigns someone to pick up the slack. Good management will know this problem is going to occur and will be on top of it before operations is negatively impacted. Problem is there is a lack of good management and many times instead of knowing from experience that it just takes a person to manage certain material supplies they try and blame engineering for every little detail not being on the BOM. This is where engineering leadership needs to back the engineers and explain the reality to the material manager.

 

[tbuelna]

As an engineer I appreciate what you are saying. But sadly things are never this simple.

Another problem I would point out with bulk materials is the waste produced from cutting pre-preg composite materials. These materials are usually quite expensive, and there is often very significant amounts of scrap material produced when the pieces are cut from the roll stock. The material can easily cost $50/lb, and when the estimates are made for materials required to manufacture these parts the scrap rate is often 100% of the material required for producing the part.