If you want to make mass produced parts you will reach a limits of your 3d printed very quickly both technical and economical ones. For any serious mass production of plastic parts you must use injection molding which can be expensive in the beginning since the initial mold is costly but the parts are cheap afterwards.
Is there a middle ground? A device you can build yourself?
There is a possibility to make a DIY home workshop injection molding machine from a hacked press drill with Gingery attachment and a CNC milled metal mold.
You can use various types of thermoplastics like: PETE, HDPE, PVC, LDPE, PP, PS and ABS.
Scorch from Scorchworks documented his experience with it.
Here is a construction video of Gingery injection molding tool for a simple drill press:
Here is a demonstration of injection molding plastic parts into CNC milled molds:
For more info on his project see:
For a simple DIY drill press injection molding apparatus you can check out this PDF guide:
Injection molded objects and the mold: