Tài liệu 2 injection molding machine

Injection Molding Machine 30 ton, 1.5 oz (45 cm3) Engel 1 Injection Molding Machine 2 Plunger injection units 3 Reciprocating screw injection molding machine 4 2-stage injection molding machine 5 Screw designs 6 Non-return valves 7 Clamp mechanisms 8 Two-plate mold 9 Two-plate mold Sprue: channel from die nozzle Into the mold Gates: restrict the polymer Flow into the cavity Runner: channel from Sprue Into the cavity 10 Three-plate mold 11 Three-plate mold three-plate mold two-plate mold The three-plate mold is typically used for parts that are gated away from their edge. The runner is in two plates, separate from the cavity and core, 12 Stack molds 13 Runner System • Runner Balancing is an essential for a balanced filling pattern with a reasonable pressure drop 14 Sprues and runners 15 Hot Runner System The ideal injection molding system delivers molded parts of uniform density, and free from all runners, flash, and gate stubs. To achieve this, a hot runner system, in contrast to a cold runner system, is employed. The material in the hot runners is maintained in a molten state and is not ejected with the molded part. Hot runner systems are also referred to as hot-manifold systems, or runnerless molding. Hot runner system types: (a) insulated hot runner (b) internally heated hot-runner system (c) externally heated hot-runner system 16 Gating systems 17 Injection Molding Cycle (1) Close the mold (3) Retract the screw (2) Inject the melt (4) Open mold – eject part 18 Injection Molding Cycle The total cycle time is: tcycle=tclosing+tinjection+tpacking+tcooling+tejection 19 Typical cavity pressure cycle Cooling time generally dominates cycle time 20