What Is Plastic Injection Molding?

Custom Plastic Injection Molding Services

Plastic injection molding is a reliable and cost-effective method of producing high volumes of solid plastic parts and products. The technique involves melting a polymer into a liquid state, then using high pressures to force it into a hollow mold. Once it has cooled and solidified, it is removed from the mold, and the cycle repeats. Ensuring the material takes on the proper shape and size necessitates careful design and construction of the mold and setup of the molding machine. While meeting these requirements may be challenging, partnering with an experienced plastic molding company can streamline the process.

At Plastic Design International, we have provided custom plastic injection molding services to industrial customers for over 40 years. Armed with several decades of industry experience and state-of-the-art facility molding machines that accommodate 35 to 385 ton loads and up to 16-cavity mold, we have the knowledge, skills, and tools to take on virtually any plastic injection molding challenge.

Advantages of Injection Molding

Compared to other manufacturing methods, the injection molding process offers a number of key advantages, including:

Lower Material Scrap Rates

Subtractive manufacturing processes—such as machining—form components by removing excess material from stock pieces. As such, they tend to produce significant amounts of material waste. In contrast, injection molding forms components by filling mold cavities with a precise amount of material, which results in minimal waste generation.  Additionally, for thermoplastic pieces, any excess material removed can often be recycled and reused in future production operations.

Higher Part Design Complexity

The injection molding process accommodates a wide range of part and product designs. Due to the immense amount of pressure applied to the material during the molding process, each section of the mold design is fully filled. This process quality results in greater detail in the finished molded piece, including for highly complex or intricate designs.

Greater Cost-Effectiveness

Injection molding operations require an initial investment in the design and construction of injection molds. However, once finished, the molds can be reused over and over. Additionally, much of the process can be automated to cut down on time and labor costs while reducing the potential for defects.

Comparing Injection Molding to Other Manufacturing Methods

When discussing the injection molding process, industry professionals often compare it to alternative plastic manufacturing methods such as blow molding or 3D printing. While there is some overlap in application among these methods, their best use cases are distinct.

Injection Molding vs. Blow Molding

Although blow molding and injection molding employ similar mechanisms, they remain distinct processes. The primary differences between the two are as follows:

  • In injection molding operations, the molding of the plastic occurs entirely within the mold. The end product is a solid plastic piece.
  • In blow molding operations, the molding of the plastic occurs once the mold is removed. The end product is a hollow plastic piece.

When choosing between injection molding and blow molding for a production project, one of the key considerations is part design. The injection molding process is better suited for solid components, while blow molding is more appropriate for hollow components.

Injection Molding vs. 3D Printing

Both 3D printing and injection molding add material to form the desired parts and products. However, they employ significantly different mechanisms, which translates to different use cases. Some of the main distinctions between them include:

  • The injection molding process is more suitable for projects with longer turnaround—approximately five to seven weeks for simpler part designs. While it accommodates virtually any size, shape, or complexity level, it is generally most cost-effective when used for producing final part designs in larger quantities (1000 units or more).
  • The 3D printing process is more appropriate for projects with shorter turnaround—about one to two weeks. As it does not require the use of specialized tooling, it accommodates frequent design changes with little to no additional production costs. It is typically employed for the production of small pieces in smaller quantities (100 units or fewer).

3 Considerations for Plastic Injection Molding Operations

When planning a plastic injection molding project, there are several factors to keep in mind to ensure all part and production specifications are fully met. These considerations include:

Production Materials

Plastic injection molding is a highly versatile manufacturing process suitable for use with a broad selection of plastics. The material chosen for a project depends on the part design and production requirement and influences the design and construction of the injection mold.

At Plastic Design International, we work with all thermoplastics except for PTFE, PVC, rubber, and silicone. Our material capabilities include the following:

  • ABS
  • Acetal
  • Acrylic
  • Copolymer polypropylene
  • HDPE/LDPE
  • Nylon
  • Polyetherimide (PEI)
  • Polycarbonate
  • Polyester
  • Polyether ether ketone (PEEK)
  • Polypropylene
  • Polystyrene
  • Polyurethane

Mold Tolerances

During the design of a mold, it is important to include enough clearance to accommodate tolerance variation. While it is easy to remove excess material from a piece in secondary processing operations, it is much harder to add material to a piece that is smaller than the specified part dimensions. Discussing critical part tolerances with a mold designer and maker before proceeding to full-scale production is essential to ensuring the mold is capable of reliably producing the desired pieces.

Secondary Operations

In some injection molding operations, the molded pieces may need to undergo secondary processing to conform to the part design. These processes range from machining and finishing to assembly and testing.

At Plastic Design International, we offer the following secondary services to ensure our customers receive a fully finished molded component:

  • Part assembly
  • Hot stamping
  • Machining
  • Heat staking
  • Sonic welding
  • Flushing/cleaning
  • Hardness testing
  • Leak testing
  • Moisture testing
  • Force/break testing
  • Destruct testing
  • Continuity testing
  • Part decorating

Industries Served

The injection molding process is employed to manufacture parts and products for use in various industrial operations. At Plastic Design, our customer base is highly diverse, stemming from many industries, including, but not limited to, the following:

Why Work With Plastic Design International?

Injection molding is a cost-effective manufacturing method for high-volume production projects. When planning such projects, it pays to partner with an experienced service provider to ensure operations proceed as intended.

Founded in 1977, Plastic Design International has extensive experience providing industrial customers with high-quality manufacturing solutions. While we began operations as a short-run prototype research and development (R&D) business, we’ve since expanded our capabilities to meet all injection molding needs. Our team accommodates project requests with the following specifications:

  • Construction material: ABS, acetal, acrylic, copolymer polypropylene, HDPE/LDPE, nylon, polyetherimide, polycarbonate, polyester, PEEK, polypropylene, polystyrene, and polyurethane
  • Temperature range: up to 900° F
  • Clamp tonnage: 35 to 385 tons
  • Shot size: up to 676 grams of PS
  • Number of cavities: one to 16 cavities
  • Part thickness: .020 inches and up
  • Part tolerance: ±.002 inches
  • Surface finish: EDM, Mold tech, and SPI
  • Production volume: prototype, low/high volume, small/large run, long run
  • Lead time: quotes on a job-by-job basis with options for rush, KANBAN, and JIT delivery available

In addition to our injection molding services, we also offer an extensive list of secondary services, including part assembly, machining, finishing, and testing.

To learn more information about our injection molding capabilities or partner with us on your next project, contact us or request a quote today.