RX8,
What drove you to in-house P&P? Is the cost of doing small runs on the outside so high that this is a much more economical solution? I'm not questioning your decision, just curious. I've not had to walk this path on my own yet, but its coming.
I know you didn't ask me, but if I may just horn in with a real world example.
I used a Chinese based PCB assembly service in years past. The cost of assembly is always hard to quote without looking at the board because there are so many variable, but anyway, this particular PCB house has a standard base rate of $0.0125 per pad (regardless of single or double sided, or large or small parts). So 1.25 cents per SMD pad.
I have one product that just has a bunch of PLCC-4 LED's on it, some passives, a couple of chips and associated regulation. 30 individual parts in total. There are 100 pads total on the board (SOIC-8 is 8 pads, for example). So that board would cost me $1.25 to be assembled. There is also a setup fee of something like $150 or thereabouts.
I used perhaps 5,000 of these boards per year. Based on the setup fee and assembly price, it makes sense to order around 1,000 of these assembled boards at a time. That entire production run will use a half reel of some parts, 2 reels of other parts, 10 reels of LED's.
With all due respect to the Chinese, I don't trust them sourcing parts for me at all. Even when I have specified (for example) a National Semi branded 7805 regulator, I've had staggeringly high failure rates and do not believe the chips were genuine for a moment. And passives are so cheap that it is absolutely foolish to try to save $4 on a production run using Chinese sourced parts. So long story short, I would buy reels and ship them off to the fab in China. That means the $2,000 I spent on a reel of 2,000pcs SOIC-8 microcontrollers will only get half used... and it will be sitting in a factory in China for 2-3 months until my next production run.
Net/net, my run of 1,000 PCB's will cost me $4k or $5k when you add in the cost of all the parts, setup fees, assembly fees, shipping both ways, etc.
I have three Quad 4C's that I paid around $6-8k each for. In the course of a single year, the cost of the machine is more than paid for just by what I would have spent on those 5,000PCB's - which would have been over $6k, before setup fees, shipping costs etc.
The additional benefit I get is that I can buy my reel of $2,000 SOIC-8 microcontrollers and leave it on the machine - and if I need to do an emergency run of 50 PCB's, it's easy. If I need to grab 5 of them to repair PCB's that were bad, it's easy. If I have another product using the same parts, I don't need to inefficiently have thousands of them sitting on a shelf in China while I am hand assembling other boards with more of the same parts I had to buy separately.
And it's not just high value parts like MCU's... even "cheap" parts like power inductors at $0.25/ea get expensive when they come in reels of 3,000pcs and there are several equally expensive parts on a board.
So in a nutshell...
-Saves money
-More flexible to your needs
-Allows you to buy parts "just in time" vs warehousing dozens of reels of parts