Quantities in Parts List on Drawings 7

[mdombovy]

Hello All,

New here. I came in hope of getting some feedback on an issue I am having at my company. In the assembly process of some of our devices, we use lubricants and adhesives which are necessary to the design. They are called out on the assembly prints in the parts list, but my question is how would you denote the quantity? For instance, our lubricants and adhesives usually come by the bottle, so a QTY of 1 would not make sense as we do not use the entire bottle for the application. Is there a standard phrase for using something "As needed" or "As required"?

Thanks for your help in advance!

 

[ctopher]

We use AR (as required).

Chris, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

 

[MintJulep]

"AR" for "as required" is common.

However that is not helpful for inventory management.

Mililiters, or ounces would be fine.

If you use a 1/4 bottle, then 0.25 would work.

 

[ctopher]

The drawing should indicate the qty used in the assy, not what is purchased or stocked.

Chris, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

 

[MintJulep]

The drawing should indicate the qty used in the assy, not what is purchased or stocked.

Yes.

But the BOM drives purchasing.

If an assembly needs 5 bolts and I am making 20 assemblies then I need to buy 100 bolts.

If that assembly needs 5 feet of wire then I need to buy 100 feet of wire.

If that assembly needs 2 ounces of goo then I need 40 ounces. If goo comes in 10 ounce tubes I need 4 tubes.

 

[ctopher]

I agree. But, call out on the BOM what the assy uses, purchasing figures out what is needed total.
I have seen errors numerous times where the quantities have been multiplied based on how many assemblies are needed. Stock is tripled, cost is up.

Chris, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

 

[3DDave]

Ah, the slippery slope of using the engineering BOM to perform factory floor ordering control. It all seems so easy when you need 1 engine in a car. But when there comes fumble-fingers with #2 washers getting dropped and one finds the factory consumes 105 washers for each 100 called out, it starts tilting a bit. When it calls out 1 drop of adhesive because the factory workers won't be allowed precision dispensers to get exactly 3 cubic millimeters it tilts rather rapidly because no one can agree on how big a drop really is.

And when the procurement staff starts noticing that there is a shelf-life and the minimum buy is far in excess of the potential consumption it all starts a big fight. This is especially true when the material is conveniently dispensed by volume but is sold by weight.

What is unfair is to make the factory figure out just how to determine just what is required. Engineering should provide some end result that confirms the required amount is used. Failing to do that led to Sun hydraulics returning a failure report with the notation that the valves would not fail if our factory would not dip them in locking compound before installing them. I guess "AS REQUIRED" on the body threads was interpreted as make sure every exposed surface got coated. For the same factory we got a report on a detonated diesel engine that the cooling jacket works better when not filled with shop rags. Sigh.

 

[TheTick]

Possible solutions:

Add a “units” column to parts list for fluid volume, weight, piece, etc

Separate table for fluids

Each fluid “dose” gets its own part number with quantity controlled on its own drawing.

 

[SwinnyGG]

This is what a robust ERP system is for.

I'm sure I'll catch flak for this but purchasing is not an engineering design function.

 

[CheckerHater]

Agree with jgKRI

The standard is pretty clear:

"When the exact amount of an item is not known, one of the following methods may be used.
(a) Enter "AR" (as required) with no expression of amount.
(b) Enter the numerical amount with "EST" (ESTimated) in this or the unit of measure column, or by a note on the parts list"

Engineering responsibilities stop after giving fair estimate (possibly including reasonable spillage or other losses)



"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[tbuelna]

In the aerospace industry, bulk materials like adhesive, lubricant, primer, paint, etc. are listed in manufacturing process specs. The manufacturing process specs are typically called out in the drawing notes. These bulk materials often have a limited shelf life, and the manufacturing process spec usually requires verification/documentation that the bulk material has not exceeded its shelf life.

 

[Sparweb]

Just to amplify what Tbuelna says, having a process specification also points the designers in engineering to supplies of consumables that are regularly stocked by production. This simplifies the selection process for the designer, and reduces the need to buy small quantities of many items for production.
I have been pushed by purchasing to enter package/order quantities in the BOM and usually resisted.

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

 

[MikeHalloran]

In order for an ERP or similar system to not cause more trouble than it's worth, BOM quantities need to reflect the amount used, accurately; no A/R allowed.

Some say the BOM itself should be in the ERP system, not on the face of a drawing.

The BOM should include the units of measure for the quantity specified.

I have used ul for microlitres on BOMs, e.g. 3 ul for Loctite on a small screw.
New units or new employees often require a little training; cost of business.

I have heard strong suggestions, bitches really, that a material control system should include separate fields for
unit of measure at use point
unit of measure in inventory
unit of measure at acquisition
... with appropriate conversions built in to minimize math errors.
Not that I have seen such a thing, but it would be nice to reduce confusion on items like rtv silicone,
which is used a couple ml at a time,
and bought in drums, or in cases of caulking gun tubes, or in cases of squeeze tubes,
depending on the use rate vs. its real finite shelf life.



Mike Halloran
Pembroke Pines, FL, USA

 

[swertel]

Mike, the ERP system that we use has everything that you mention regarding quantities, including an AR flag.

Units of Measure (UOM) are probably one of the more complex aspects of ERP.

The Item Master has the UOM that is used on the assembly. And yes, I can have mL as the UOM and still check the As Required flag.
I also have another tab to fill in other UOM: order, inventory, sale. That means I can buy goos and glues in 1 UOM, store it in another, use it in a 3rd, and sell it (if that's what you do) in yet another UOM. And there is a 3rd tab where I input the conversion factors between each UOM. Oh, by the way, those 4 different UOM are out-of-the-box. I can create as many UOM as I need and as many conversion factors.

The AR flag works with the inventory and MRP side of the ERP system. Ideally, the MBOM would have the actual quantities used, but that's not always practical nor necessary. If the Loctite, for example, is a floor stock item and I always keep a minimum amount on hand, I don't care about how much is used on each assembly. It's As Required. When I'm on my last bottle on the shelf, I order a dozen more bottles. The bottles get issued to the production floor when requested. The quantity is not planned therefore I don't need to define the actual quantity used on the MBOM.

--Scott
www.aerornd.com

 

[SwinnyGG]

A star for swertel, because that last paragraph is pretty much exactly what I was going to say

 

[3DDave]

A minor hijacking and soapboxing -

One company I was at decided that a number of upper level assembly components needed to be sourced from their electronics cabinet maker. To "simplify" things they decided that those upper level components would be best included on the cabinet drawing as "not shown" items; in the on-drawing BOM.

Then, on the upper level drawings, those items were called out again.

The trick was, they wanted the drawing BOM to be driven as a tabulation of the items in the related CAD assembly.

And the twist - some of those items are detoured to other intermediate assemblies.

So A => (is used in) B (because that's how A is ordered,) but is removed from B on the factory floor, and also A => C, but then B and C => D. So how many of A are in D? CAD model says 2. On the factory floor the cabinet only has room for 1. ERP uses comment lines to list the items to make the BOM roll up work out right.

Why did they do that? Because the engineering drawing was held as the driver for ordering and production.

As one might expect, when I looked at the assembly process, ERP, the CAD models, and the previous changes, there were hundreds of mismatches between them because they spent so much time papering over the inconsistencies. But they never audited it because, reasons.

 

[swertel]

3DDave, we've all been there.

--Scott
www.aerornd.com

 

[dgallup]

While we are hijacking... We have an ancient MRP system that shall remain nameless to protect the idiots that picked it. It has very limited unit capabilities and only 4 decimal places in the quantity field so certain items have a quantity of zero on the BoM. No one had been able to fix it.

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