Screaming Circuits: Short Cuts Don't Always Make Long Delays


Short Cuts Don't Always Make Long Delays

The saga continues. I have my parts kit. The PCBs should be here from Sunstone tomorrow. When I placed the order on our website, I estimated that I'd have the parts and PCBs today, but I wasn't really sure. I knew there would be a chance that it would be tomorrow, but I thought it would be good to see how our communications goes when something is late. Obviously, an assembler can't start building until the parts have arrived, so the Industry standard is to start the turn-time once everything is in the shop.

If a box is late and the sender doesn't know it, unintended delays can be added into the process. Knowing this, we recently did a lot of work to improve our communications, on such issues as late parts, to help reduce delays. Sure enough, I dropped on over to the website and right on the top of the home page is a note that I have an issue (late parts) with my job. Tonight at midnight, I should receive an email telling me the same thing too.

On the subject of the PCBs, I sent Gerbers to Sunstone. That works just fine, but I'm always a bit nervous about the accuracy of my layer mapping. They double check, so I've never had problems, but I still get nervous.

If I'd waited a few days, like until today, I could have taken a short cut by just sending in my CAD board file - they just started accepting native CAD files. You can still use Gerbers, but if you use Altium, Eagle, OrCAD, National Instruments Circuit Design Suite, Ivex Winboard or PCB123, you can just send in the board file and save some time and hassle.

When I get the boards tomorrow, I'll pack everything up and deliver it to the receiving folks. Then I'll see how the rest of the build process goes from the other side of the fence, and I'll see how we deal with extra parts. I did that on purpose also. With a couple of parts, I'm delivering several hundred more than I need. With a few other, just the requisite 5% over. It will be interesting to see just how I get the extras back.

Yes. I know. I work here, so I shouldn't have any doubt about how all of this stuff works. I do know how it goes, but it's always a good thing to, every now and then, check and see how well practice matches up with theory.

Duane Benson
Grip, Fang, Wolf! Guard the mushrooms!


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Hi Steve;

For our proto service, we like to see 5% (round up to five for real small quantities) as a "just in case" for most parts. 0201s should have 50% extra. ICs are fine with just one extra. For expensive parts, exact quantities will work.

As far as minimum length goes, we don't really have one. If you need one 0805 10K resistor on one board, you can send us a strip of six resistors. (one to build and the five spare). For your ten boards, you would send a strip of 15. For 100 boards, you would send 105. You can send multiple cut strips to make up the total needed.

As far as the connection between title and sign off, readers of the book should realize it. Others... Who knows?

Does Screaming Circuits require 5% overage on ALL parts? What about for ICs or connectors? Is there some minimum length for taped parts? Simple example: if I have a design that calls for one 0805 10k resistor, and I am getting ten boards assembled, do I need to provide ~12 resistors, or do I need to provide, say, 5" of resistors (~40?) This becomes more important for expensive things like tantalum capacitors ($6~$10/ea).

How many people will actually realize that your sign off is related to the post subject?

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