Have a look at this page:
Directory: Blest Machine recycles plastic back into oil - PESWiki
It is about Japanese commercial devices. But those cost so much that almost no one considers using this tech at home. Japanese put all kind of LCD's, sophisticated power management systems and monitoring devices in their units that really does nothing except increase the price. This is easy, cheap and almost anyone can build one without taking out a second mortgage on his house
The way we do this is not the only way nor the best, after you know the process, there is lots and lots of room for improvements.
You could build a small table top device for around 300-500$ maybe even less. But I wouldn't use a pressure cooker as they have a heat resistant rubber seal around the lid, it is good for food cooking temperatures, but wont hold 400 degrees celsius, it will melt and leak. Also you need a custom heating element, because ordinary heating coils that are used in water boilers, tea pots or electric stoves wont last long, because of their thin resistance wire. You need nichrome or kanthal resistance wire with diameter around 1.5mm, this will do well. The seal between the reactor and the lid is very important, it must be hermetic and heat resistant, we have tried many ways before and no seal material lasted long, all eventually fail and let the hot plastic vapor seep out, this is not acceptable. We tried heat resistant silicon for use on chimneys and other commercial stuff, not good enough. Eventually we found that the thing that works best is conical groove and a wedge that fits inside that groove around the lid, like you can see in the CAD drawing. When the lid is bolted to the reactor chamber, the fit is airtight and hermetical. The pressures in the system are very low, only such to be sufficient to bubble through the bubbler, this makes it very much safer than commercial flash pyrolysis devices that are also very expensive and affordable only by large companies.
In our case the bubbler at the end is just as a flashback arrester that prevents fire going into the reactor, but the gas really burns so slow, that it is not really needed, but better to leave it in, safety is never too much. Also the bubbler can be used to eliminate the need of condensing tanks, because the vapors cool sufficiently when bubbling through the water to turn into liquid fuel, that can the be poured off as it does not dissolve in water but floats above it. The produced gas should be burned or vented outside.