It appears that you want to injection-mold with thermoplastics, which is not a trivial thing to do on a small scale. There are small tryout presses and simple presses made for educational use in schools, but they aren't production machines.
Much small-scale plastic work is done with room-termperature-cure thermosetting plastics (polyester resin, epoxy resin, vinylester resin, polyurethane resin), which are a lot easier to work with. Working with them also is a lot slower, and the materials are MUCH more expensive, however. But they generally have better mechanical and physical properties. They are used a lot for prototypes of parts that will be injection-molded in production.
But building a machine and molds that will give you the heat and pressure needed to injection-mold thermoplastics is a big job, or an expensive job, or both.
What kind of plastic parts are you trying to make, and in what quantities?
-- Ed Huntress