Adjusted BOM, lost sleep....
I've been losing sleep over how to present the costed BOM (Bill of Materials) for the ShapeOko mill.
The most straight forward method has been shown on the downloads page over at shapeoko.com for the last couple of days. However, something just wasn't sitting right with me about the total.
When everything in the hardware category is listed with the cost of a *package* the "total" cost for that item isn't exactly transparent.
Let's use for instance a 100 pack of .125" nylon spacers.
A 100 pack of .125" nylon spacers cost $7.04 from mcmaster.com. However, the shapeoko mill only requires 8 .125" nylon spacers. Not 100. So is the cost $7.04 for the nylon spacers OR is the cost $0.56 ($0.07 * 8)
So what's the cost?
I've spoken to several people who do this for a living: manufacturing engineers, engineering managers, and accountants. They all tell me the cost is $0.56.
After thinking about it for quite a while, I've decided they know what they are talking about, and I trust their opinions on matters such as these and have changed the BOM to reflect that decision.
Now, it does makes the total "look" better. At $332.58, that's significantly lower than the previous $365.90. But, in reality your cost is going to be no different if you buy the 100 packs from McMaster.There are two thigs that makes me feel a little better about the BOM change:
- Most of you are Makers! And as a Maker, I know that I have no problem with extra spacers sitting in my "inventory" for use on a future project and hopefully you don't either.
- You could buy them in single pieces if you have access to a hardware store. All of the nuts/bolts are pretty standard pieces and can be purchased at most home improvement stores individually.
With all that said, what do you think?
Is the revised bill misleading? Should it be presented a different way? Are these blog posts explanation enough?