Requirements:
- Only raw resources as input (plates + plastic + sulphur gas)
- Have 4xprod4 modules in all assemblers
- Make optimal use of speed beacons
- Have as close to optimal ratios as possible
The ratios are not quite correct, but 1 green -> 2 red + 2 blue comes close. The reds are overproduced (1.4/8 > 2/15) and the greens are underproduced, but that can be compensation by adding an extra speed beacon for the green production.
Each green requires a dedicated cable, so the reds need their own cable plant, which can feed a lot of reds.
Normally I would like to have beacons on both sides of each assembler, and have the assemblers directly touching each other (no horizontal gaps). For blue circuits, I don't think that is possible as they the sulphur gas takes up the whole side, unless you use underground pipes to outside the beacon column, but that space should be free for the next rack. So, you need 3 inputs/outputs (green and red in, blue out) on the other side, which means two belts, which means there can be no beacon column on that edge. So, I decided to do a double column of assemblers around a central 'bus', which allowed me to place one extra beacon in the center are near the greens:
blueprint
This is the design copied twice, which produces 140 blue/m out of 2.1k copper and 1.6k iron. The blue assemblers have crafting speed of 3.625 and 3 (the bottom one profits from the speed beacon), so theoretical maximum is 4*6.625*1.25*(60/15)=148/m, so that's close enough. Since each blue requires 2 reds=4/1.4=2.875 greens, this requires in total 6.625 * 22.875 /15 = 10.103 from each green assembler, which can output 2*1.4*3.625=10.15/s. In total the setup above should produce 10.103*4*60=2424 green/minute, but it makes only 2.3, so the greens are not producing fully, but I'm not quite sure what the problem is.
If you add a third group on top it will be copper starved. An alternative is to add a second copper line just for the cable plants at the bottom. This allows you to place a third group, which consumes the full iron line, producing 206 blue/s (out of 222 theoretical maximum)
more circuits
blueprint
(see also my green circuit (viewtopic.php?f=202&t=33355#p210326) and green+red circuit racks (viewtopic.php?f=8&t=37859))