Reliant Sourcing Solutions: Injection Molding
Injection molding is a manufacturing process that injects molten material—typically plastic or rubber—into a mold to produce custom designed and shaped parts in high volumes. Manufacturers frequently employ injection molding to fulfill customer orders that require thousands or millions of repeated operations.
Injection molding machines consist of three main components: the feed hopper, the screw, and the heated barrel. A typical injection molding operation would proceed as follows:
- The operator places materials, usually in powder or granular form, into the feed hopper.
- The feed hopper feeds the material into the heated barrel. Within the barrel, the friction from the motion of the reciprocating screw, in combination with the heater bands, melts the material.
- The molten material is injected through the machine’s nozzle into a specially designed mold cavity mounted onto a movable plate. In the mold cavity, it cools and hardens into the shape of the enclosure.
- Once the part has completely hardened, the movable plate opens, and ejector pins eject the finished piece.
Hot vs. Cold Injection Molding
There are two basic categories of injection molding systems: hot runners and cold runners.
- Hot runner molds are comprised of two plates heated by a manifold system. Heated runners act as both a delivery system and a heat conveyance system.
- In contrast, cold runner molds feature two or three plates contained within the mold base. These runners act solely as a delivery system.
Each type of system offers its own unique advantages.
Cold runner systems provide:
- Superior cost savings in comparison to hot runner molds
- Comparatively low maintenance expenditures
- A high level of versatility, and the capability to handle a range of commodity and engineered thermoplastics
- Greater flexibility that allows for design adaptations and upgrades
While hot runner systems provide:
- Overall faster cycle times than cold runner systems
- No manual separation of the finished part required
- Increased production efficiency and reduced wastage
- The ability to fabricate larger parts than most cold runner systems