I had such a revelation with my PI that I wanted to share it right away, even though I am probably about to make myself look dim-witted.
My CEO was already involved with it and I asked him if it was worth while. From what he told me it seemed the profit was reasonable, so I trained the skills. He also sent me an e-mail with a run-down of what to do. I then set to work. I decided I would use the PI to construct fuels for our POS. I picked five suitable worlds and built my colonies. I was succeeding in my task, but production was slower than I first thought. I ran this for many weeks.
However, recently we set up another POS in Low-Sec. So, a couple of days ago I abandoned the colonies, replenished my Crane's cargo hold with fresh Command Centres and rebuilt my PI in the new system.
I paid more attention to what I was doing this time, and I noticed that a cluster of four Extractors were excavating around 2,300 units per cycle each. Collectively, that's 9,200 unit per 30 minute cycle (give or take a few units due to the slight variations in mining quantities between each Extractor).
Now, in the instructions that my CEO had mailed me, he said to watch the input levels to Processors. He also told me that the Launch-Pad would hold all my excess materials. In the previous system, I never saw any excess on my Launch-Pad so I thought the Extractor-to-Processor ratio I used was right.
Wrong, wrong, wrong, wrong and WRONG!
It takes a Basic Processor Factory thirty-minutes to convert 3000 units of Noble Metals into 40 units of Precious Metals. But I would like to emphasise '3000 units' again. Remember I said I had four extractors kicking out 9,200 units per hour? So, if the Processor will only accept 3000 units every thirty-minutes, where do the remaining 6,200 go?
I'll tell you - thin air.
The Factories will happily accept the 3000 units they need, plus queue up an additional 3000 units as long as there isn't any already waiting. Any excess 'poofs' into thin air. And this has a knock-on effect to any processors thereafter. The thing is - this doesn't have to happen, but I had been running my PI like this for weeks.
The way I 'routed' (not linked) my PI buildings was:
Extractor -> Basic Factory -> Advanced Factory -> Launchpad
It seemed logical. But it's not, if you think about it carefully. Imagine all the lorries queued up outside my Basic Factory waiting to empty 9,000 units of Noble Metal into the Processor. The problem is they can't. The Processor and it's limited storage are already full and there is nowhere else to store the excess. Well, they're not going to hang around outside a factory for days on end waiting for there turn, so they drive off home and sell my metal on the black-market for their own gains. And I don't blame them.
In my new set-up, EVERYTHING is routed through the Launchpad. That's the trick. If the building churns something out, it goes straight to the Launchpad. Then, if a factory needs a material input it can take what it needs from there instead of being directly linked to a supply structure(s), which could be trying to feed it material when it's already full. This is what my CEO was trying to tell me, but at the time I assumed that any excess would automatically be taken to the pad. The correct way is to route Extractors and Processors to the Launchpad first, and then route the relevant materials stored on the Launchpad back to the PI structures that need them.
Storing surplus stock also allows me to monitor materials that are either excessively piling up or depleting too quickly. I can then balance out the levels by either adding or removing Extractors. This can also free up both CPU and power in my Command Centre, allowing me to run additional Factories. And more Factories means more profit.
Now that (I think) I have set up my PI correctly, I am much more involved with it in a good way. I have spent many, many hours trying to configure it right and I am still tweaking days later. I actually find it fun. I estimate it will take at least a week to get all my Extractors-to-Processors balanced efficiently. This is because I have to monitor mineral piles after making any changes. Or I could use Maths, but I hate Maths.
In only 48 hours I have already produced 24% of what I made in the 3 weeks of running my old set-up. And I expect this increase to triple once the PI is finally balanced. I hope to keep on top of stock so I don't have to start building silo's, too.
So, remember to route everything through the damn Launchpad, not just link it.