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:

  1. The operator places materials, usually in powder or granular form, into the feed hopper.
  2. 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.
  3. 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.
  4. 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

Benefits of Injection Molding

In general, there are several benefits to employing injection molding, such as:

  • Less material waste. Compared to other manufacturing processes—e.g., CNC machining, milling, punching, or blanking—the injection molding process produces a relatively small amount of waste, which, in turn, reduces material costs and increases production efficiency.
  • High level of consistency. Injection molding operations are extremely repeatable, and the difference from one part to the next is negligible. This manufacturing quality offers a considerable advantage when manufacturers need to produce high volumes of tight tolerance parts.
  • Cost-efficiency. For facilities that regularly produce large quantities of parts, injection molding is a cost-effective manufacturing method.
  • Organizational efficiency. Injection molding offers a highly effective way to organize multiple internal parts within a housing, reducing the total number required for a finished product.

Applications of Injection Molding

Injection molding finds use in a variety of industrial applications, especially in the production of thin-walled plastic parts and components. One of the most common thin-walled plastic parts produced is plastic housings, which are containers or enclosures supported by interior ribs and bosses. These components are used in many industrial products such as consumer electronics, power tools, household appliances, kitchenware, and automotive dashboards.

Other thin-walled products commonly produced by injection molding include:

  • Open containers (e.g., buckets)
  • Toothbrushes
  • Small toys
  • Measuring cups
  • Plastic bottles
  • Valves
  • Syringes

Partnering with Reliant Sourcing Solutions

At Reliant Sourcing Solutions, we are an industry leader in providing turnkey manufacturing solutions that help our customers to see each project through from start to finish. With nearly five decades of experience in professional sourcing, we can assist you in every phase of your project, including the design phase, prototyping, tooling, production, quality assurance, warehousing, and transportation.

If you need a sourcing partner for your next manufacturing project, contact us or request a quote today. One of our experts will get in touch with you soon to speak with you about your concerns and project requirements.