The spruee is where the machine injects the plastic into the runners, then the runners carry it past the gate to a cold well, the when the cold well fill, it forces it through the gate, and into the mold cavity / cavities. There will also be some say .5 width x .005 deep slots to let air out of the mold cavities. For a brake light lens you will need to have a ejector pin setup. (Dont want to have to pry out part from the mold, could ruin the polish).
Tonnage differs between people. some say 2 sqin per ton, other say 1.5 or The 2 can be done with certain materials, but most use the later two to have a saftey margin to insure they can clamp the mold properly.It also can make a difference if you are using a toggle locking press or a hydraulic press (about 50 tons max). I would guess a tail light mold would be roughly say 12x8" which would require roughly 144 ton machine for a sinlge lens.
The shot size would be the total part size+ all gate runners, coldwells, spruee. Basically everything that plastic would fill in the mold. My machine has a 3 oz shot which limits it to small parts.
The parting line on tail light molds can get very complex, (and relativley deep). I would double / triple / quadruple check the parting line. Not so much that you will mill and under cut, but you may not get the part you want if not done corectly.
I would say that aluminum would be a poor choice for you mold application, as it will last for the required number of parts, but the parts would most likeley have a optical degrading effect, as the aluminum may loose some of the polish as the cycles run. I have never tried a mirror polished aluminum tool, but all I use is aluminum for my molds, as it is so much easier and faster to mill, and actually pulls heat away great and (in my small pres) negates having to setup my chiller.
I have posted a picture of my molder in my photoalbum if you want to take a look. I will try to get a few better pictures of it.  |