We get a lot of email from people who ask us if they can use recycled plastic in the Noztek filament extruder and the answer is yes. There are a few things that you need to bare in mind before grinding down all the scrap from your dustbin.
There are a lot of different types of plastics on the market such as PET (usually beverage bottles), HDPE (soap, shampoo containers) and PVC (more household related products). Due to the different melting properties of the different polymers it would be advisable to use the same plastic in the preparation phase.
Once you have ground down the scrap plastic into pellet sized granules add a small amount to virgin plastic and with trial and error you should produce usable filament for your 3D printer.
Here is a working home made plastic recycler and you can download the CAD files for free: http://www.facebook.com/FilaMaker
Good luck and let us know how you get on.
http://www.youtube.com/watch?v=13y7R7L8H_0