Hi
Just recently built a machine but was not cheap. Works awesome, similar to extractionteks machine but I've used ptfe lined braded hoses, and a catch pit complete with molecular filter to remove water before the refrigeration pump. I'm not too sure if theirs has really been thought over. If you dont do this i've read that it combines with oil under pressure to create an acid that destroys the pump not to mention contamination ( this came from Roger Day who makes the RDA caresaver, he also declined to give a guarantee). Took the pump to bits first (cos i'm like that) and found it to be quite simple(by the way the pump i'm using is the caresaver as its sealed and has a built in oil trap). I'm not completely happy with it as its full of copper pipes which needed to be purged of solder flux and swarf and also I'm not happy with using copper due to possible reactions (although I havent had any problems). The best extraction machine and most knowledge by far has come from skumpharmresearch. big thanks to graywolf.
The machine i have now was my second prototype as the first was a bit industrial looking, just trying the principal really as I'm into extracting all sorts of essential oils.
I also use a stainless gauze sock as this makes filling simpler.
Next plan is to modify this prototype to speed up, automate the process, change a few pipes and add anther spool. The big problem no one tells you about is any material you use is soaking wet after its been flooded and drained and requires considerable temperature controlled heating and time to completely clear of residual gas. so this is why there will be two chambers and only 1 evap pot. plus you need a decent amount of heat(not temperature) to counteract the boiling off of the gas oil solution.
I am also building a small version for those at home (or in their shed) This isnt too far away.
If your in a hurry then get your wallet out but I'm telling you now that the pump alone is £1k, the 316 stainless spool, valves and catchpot/evaporation chamber vac pump filter housing all pressure tested built onto a frame, will set you back a small fortune. I've spent £4k pissing about but could have done it for under 3. I got the valves for 35 each from a mine in aus otherwise they would have been £275 each. Saying that you can use a basic new ss valve in 304 for £20., its just i didnt want to cut ANY corners (boom).
My new device I'll be lucky to make it singly to sell for under 1k and it will only do 200cc volume at a time. the upside will be the target time of 3-5 mins for a complete purged extraction. Thge hardest bit is removal of any residual gas without heating your concretes to lower the vicosity. Only mass production will get it down under £500 and thousands of machines would have to be made to get it same price as a coffee machine.
I dare say I'm not the first to build or own one in the UK as there are a number of companies who make extraction machines based on the SOXHLET process (1870 something) and have been doing so for years. Any messages of patents will be ignored.
I do have the advantage of being a time served engineer and have access to machines of all kinds. Even so its an extremely dangerous piece of kit in the wrong hands. The hardest part will be making this machine safe for joe bloggs who just want to get stoned. Saying that, If your careful its totally safe unlike the open systems which in my opinion are downright crazy and not really helping the ole ozone or the cause
init!.