@herbivore21
Electric griddle, Vacuum Chamber, Vacuum Pump. That's all you need to get a cheap but effective setup going.
Griddle example:
http://www.amazon.com/Presto-07211-Liddle-Griddle/dp/B00006IUWL/ref=sr_1_1?ie=UTF8&qid=1400971918&sr=8-1&keywords=mini griddle
Vacuum Pump example:
http://www.amazon.com/Robinair-15310-VacuMaster-Single-Stage/dp/B005CO9GX6/ref=sr_1_4?ie=UTF8&qid=1400971889&sr=8-4&keywords=robinair vacuum pump
Vaccum chamber example:
http://www.amazon.com/ProVac-vacuum-chamber-gallon-size/dp/B00E0BG8R4/ref=sr_1_2?ie=UTF8&qid=1400971942&sr=8-2&keywords=vacuum chamber
These are just examples. I'm not necessarily recommending any of these products (although I do own the pump and griddle and would recommend them).
Now, like I said this is a great basic and relatively cheap setup, but it's not perfect. The problem with using a griddle is it doesn't actually heat to a certain temperature; it'll turn on for a period of time and then shut off, so the temperature never remains stable. With that said, I'm able to maintain a temp range of +/- 5 degrees when heating my oil.
Basically, you turn the griddle on to your selected heat level (practice, experimentation to find the temp for the consistency you desire) and place your vacuum chamber on top. Once your chamber has been heated up, place your oil inside the chamber (I like the little slick pads for this). If you have an IR temp gun that comes in handy here to make sure your oil is at your desired temperature. Once your chamber and oil are heated and ready to go, you simply put the chamber cap on, connect the hose to the pump and turn the pump on. From here, it's up to you. Some people like to do multiple vacuum pulls, some like to just run the pump for the entirety of the process until there is zero reaction at your desired heat and max vacuum, etc. I personally just leave the vacuum running until I get zero reaction. When your concentrate looks good (no bubbles, no movement/reaction at full vac) you're probably done. If it looks like shit under the vacuum, it's not done. I like my oil to look crystal clear even when under full vacuum and at about 100-110 degrees F. Keep in mind, larger amounts of oil and oil that is not spread thinly will take much more time to purge than a small amount or a thin film of oil.
I just typed this up really quick so hopefully it helps a little bit. I'm not an expert on concentrates and purging but I've been making my own pretty steadily for a little while now. Once you start messing with different strains and different purging temperatures it gets really fun to see what you can come up with.
Also, as a disclaimer I've read that these chambers should never be heated or used in conjunction with an electric griddle. But that's kind of the point when purging a concentrate. I've never had any issues, but just throwing it out there.
There are resources out there to help with temperatures and purging and whatnot. A lot of it, though, is dependent on the strain and quality of weed. Those are the two most important characteristics when it comes to consistency and yield, imo.
