As much as you dig through your CRC Handbook of Chemistry and Physics, you won’t find reference to “The law of conservation of components.” That’s because it’s my law and it relates to reels of parts being the way to go when you need a lot of PC boards built, but not necessarily so when you need smaller quantities of boards assembled. It’s just not practical to deal with a bunch of cut strips when building hundreds or thousands of boards. It is also easier to use reels than cut strips with small quantities of PC boards, it may not always be practical or economical to do so.
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Reels, though still easier, can be a bit wasteful when you just need a few PC boards assembled. But there is no need to go out and buy reels or waste those small strips of extra parts left over from past jobs. You can send us cut strips for your small quantity builds and we can still machine assemble from those strips.
Sometimes buying in strips is more about conservation of cash too. Say, for example, you need 20 2.2K Ohm, 5% 0603 resistors. You could buy a small strip of 25 from DigiKey for $0.32. That gives the 20 you need, plus a few spares just in case.
Alternately, you could buy a digi-reel ( a custom quantity reel). On the reel, you’ll probably want more parts to keep the strip long enough for the feeder. Let’s go with 250 parts for $1.39. Digikey charges $7.00 extra to create a custom reel, so that’s a total of $8.39. Still peanuts.
For a third choice, you could just buy a full reel of 5,000 for $10.64. Dry roasted peanuts, but still peanuts on a relative scale. If you’re gong to need the same part for a lot of designs, this might make sense. But, there’s more than just cost to consider. You need to store and ship it. Shipping two dozen reels gets pretty expense. Storing and inventorying several dozen reels can become a hassle too.
The beauty of DigiKey, Mouser, and other places that sell cut strips, is that they essentially become your parts warehouse. You pay the $0.32 cents and never have to worry about whether the part is in your inventory, how many are in your inventory, digging it out of wherever you stuffed the reel when you last needed it…
On the other hand (this is complex. There are a lot of hands), when parts are short and supply is uncertain, you might want to buy that reel to make sure you have parts for prototype run number two.
If you do buy and store the whole reel, you don’t need to ship the entire reel to us. Just cut a strip with the number you need, plus about 10% for that “just in case” (50% extra for tiny 0201 parts). In disrupted supply chain times like these, every little component is a potentially valuable resource, so keep the trimmings and feel free to use them for your small quantity builds.
Of course, if you need a few thousand of the parts, go ahead and send us the reel. It would make sense then.
Duane Benson
The law states that if a reel of 1,000 parts is cut into ten equal strips of 100 parts, you still have 1,000 parts
Unless you cut through a part. Then you will have less.
And don’t forget, conservation of parts or not, Screaming Circuits is always here to build your prototypes and on-demand electronics manufacturing. Visit our PCB assembly quote page and see how much this will cost.