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Three major classifications and type comparisons of injection molds

Injection molding process

Injection molding is a widely utilized manufacturing process in which molten material is injected into a mold, solidifying into the desired shape. This method finds extensive application in various industries due to its versatility, efficiency, and cost-effectiveness.

Injection molding involves injecting molten material, typically plastic, into a mold cavity under high pressure. Once the material cools and solidifies, the mold opens, and the finished product is ejected. This process allows for the mass production of intricate and complex shapes with high precision.

Classification of Injection Molds

Injection molds play a crucial role in the injection molding process, determining the final shape and quality of the product. These molds can be classified based on several factors, including construction, application, and complexity.

1. Classification by Construction

Injection molds can be categorized based on their construction into several types:

  • Two-Plate Mold: This is the simplest type of mold, consisting of two plates that form the cavity and core when closed.
  • Three-Plate Mold: In this mold, an additional plate, known as the runner plate, separates the sprue from the molded part, allowing for easier ejection.
  • Hot Runner Mold: Hot runner molds feature a heated manifold system that keeps the material molten as it is injected into the mold cavity, reducing cycle times and material wastage.
  • Cold Runner Mold: Unlike hot runner molds, cold runner molds use a system of channels to deliver the molten material to the cavity. While less efficient, they are suitable for certain applications where cost is a primary concern.

2. Classification by Application

Injection molds can also be classified based on their specific application:

  • Prototype Molds: These molds are used for prototyping and small-scale production runs, allowing manufacturers to test designs and refine them before full-scale production.
  • Production Molds: Production molds are designed for high-volume manufacturing, ensuring consistency and repeatability in the production process.
  • Multi-Cavity Molds: Multi-cavity molds contain multiple cavities within a single mold, allowing for the simultaneous production of multiple parts in each cycle, thereby increasing efficiency.

3. Classification by Complexity

Injection molds can further be classified based on their complexity:

  • Simple Molds: Simple molds are relatively straightforward in design, with minimal features and complexity. They are commonly used for basic shapes and designs.
  • Complex Molds: Complex molds feature intricate designs and multiple moving parts, allowing for the production of highly detailed and complex products.
Injection Molding Process
Injection Molding Process

Factors Influencing Mold Selection

When selecting an injection mold for a specific application, several factors must be considered:

  1. Material Properties: The properties of the material being molded, such as viscosity, shrinkage, and thermal conductivity, can influence the choice of mold design.
  2. Part Design: The complexity and geometry of the part being produced play a significant role in mold selection, as they determine the mold’s complexity and features required.
  3. Production Volume: The anticipated production volume will impact the choice between prototype and production molds, as well as the number of cavities in the mold.
  4. Cost Considerations: Budget constraints may dictate the choice between hot runner and cold runner molds, as well as the overall complexity of the mold design.

Comparison of Injection Mold Types

Mold TypeConstructionApplicationComplexity
Two-Plate MoldTwo platesBasic shapesSimple
Three-Plate MoldThree platesEasier ejectionModerate
Hot Runner MoldHeated manifold systemReduced cycle timesModerate to high
Cold Runner MoldChannel systemCost-effectiveModerate


Injection molding is a versatile and efficient manufacturing process that relies on the use of injection molds to produce high-quality plastic parts. By understanding the different types and classifications of injection molds, manufacturers can make informed decisions regarding mold selection, ultimately optimizing the production process for efficiency and cost-effectiveness. Whether producing prototypes or high-volume production runs, the right injection mold is essential for achieving success in injection molding operations.