Preface/Note

I am writing this page ( Eric ), so sorry if this gets confusing with edits/additions by others. (PS feel free to edit it, I'm not territorial)

Basics

So basically I have been researching this a bit. It is used mainly for hollow objects (3D Printing Works As Well). One easy to see application is 1 liter bottles. These start as injection molded parts. The process itself is quite similar to glass blowing, but with molten plastic. Also forms can be placed around the part to contain it's expansion. So that is the batch process, which may be of less intrest to us for final use, but I think it is useful for learning how the process works and it's complexities before moving on to other more applicable processes. The one i think is most applicable is the continous version of this technique. It works similar to a filament extruder, except it injects an air bubble down the center. This is simple in theory, but it gets quite tricky.

So I think, as stated above, that we should start with the batch process, and with the knowledge learned from that, move on to the continious

So the first step is to make an injection molding machiene (preferably the precious plastics design)
I think one option would to be bore a hole through where the handle attaches to the piston, and add a rod through there
Then it is just a matter of determening mold shape/attachment as well as the air supply (hopefully computerized), this is just speculation but a heat gun/hair dryer may work, although air compressor may offer more control
After this it is just fine tuning (putting it all together, software/control system developmen, making it look presentable, amd finally final testing + publication

I honestly don't quite know about this one
Firstly we need to research the process, and what is usually done
We could possibly modify the extrusion machiene by precious plastics (granted it would be a heavy modification)
One armchair thought I had was to have a hollow screw/axle and feed the air through that to avoid the problems of non parallel air supplies
The die/nozzle is the next main problem
Just like with the filament extruder, I expect a lot of trouble in the cooling, the control systems, and the software

Publish all the above
Refine (aesthetics + reliability + ease of use)
Make a nice cad library of molds for injection molded componets (for the batch blow molder), as well as 3d printable files that replace the parts those molds produce
Make a nice cad library of continous blow molder nozzles/dies