Non-naturally balanced feed system for an injection molding apparatus
A low constant pressure injection molding machine forms molded parts by injecting molten thermoplastic material into a mold cavity at low constant pressures of 6,000 psi and lower. As a result, the low constant pressure injection molding machine includes a mold formed of easily machineable material that is less costly and faster to manufacture than typical injection molds.
1. An unbalanced feed system for an injection mold of an injection molding apparatus, the injection mold having a plurality of mold cavities, the plurality of mold cavities receiving molten plastic at a substantially constant viscosity, the unbalanced feed system comprising:
wherein the feed system maintains a balance of 90% or greater;
a hot runner having a first feed channel that terminates at a first mold cavity in the plurality of mold cavities and a second feed channel that terminates at a second mold cavity in the plurality of mold cavities, wherein the first feed channel and the second feed channel are unbalanced in their design due to a circular cross-sectional shape of the first feed channel varying along a length of the first feed channel and a non-circular cross-sectional shape of the second feed channel varying along a length of the second feed channel and the circular cross-sectional shape varying differently than the non-circular cross-sectional shape;
a gate for receiving molten plastic, the gate being in fluid communication with one of the first and second feed channels; and
a controller that maintains the molten plastic at a substantially constant melt pressure.
2. The unbalanced feed system of claim 1 wherein the feed system maintains a balance of 95% or greater.
3. The injection molding apparatus of claim 1 that injects the molten plastic into the mold cavities such that part weights for all of the mold cavities vary by less than 5%.
4. The injection molding apparatus of claim 1 that injects the molten plastic into the mold cavities such that part weights for all of the mold cavities vary by less than 1%.