The Journey of an Injection Plastic Mold Maker: From Design to Manufacturing

Bubble Injection Molding: What It Is and How to Prevent It

Welcome to the world of injection plastic mold making, where you can learn about the process, costs and the expertise involved. In this comprehensive article, we’ll dive into the differences between plastic molding and injection molding, the cost of building a plastic injection mold, the key players in mold manufacturing, and the complex process of creating an injection mold.

First, we’ll break down the differences between plastic molding and injection molding. Although both methods are used to manufacture plastic products, their working principles and application fields are different. Plastic molding is a common manufacturing process that involves heating a plastic material to a liquid state, then injecting it into a pre-designed mold, where it cools to form the desired shape. Injection molding is a more complex process. It requires the use of a specialized injection machine to heat and inject the plastic material into the mold. Through high-pressure and high-speed injection, the plastic material can fill every corner of the mold, thereby obtaining more precise results. and complex products.

Next, we’ll discuss the cost of building a plastic injection mold. This cost will be affected by many factors, including the size and complexity of the mold, the materials used, and the equipment and technology required in the manufacturing process. Generally speaking, large and complex molds will cost more, and the use of advanced materials and technologies will also increase costs. However, given that injection molds can be reused, their long-term costs may actually be lower than disposable plastic molding.

There are many key roles involved in the mold manufacturing process. These roles include designers, engineers, operators, quality control personnel, and more. Designers are responsible for designing molds that meet product requirements, engineers are responsible for converting designs into actual manufacturing processes, operators are responsible for performing actual operations during the manufacturing process, and quality control personnel are responsible for ensuring the quality and performance of molds.

Finally, we’ll detail the complex process of creating an injection mold. This process includes multiple steps from design to manufacturing to testing. First, the designer needs to design the structure and shape of the mold according to the requirements of the product. Engineers then select appropriate materials and manufacturing processes based on the design. During the manufacturing process, operators are required to use specialized equipment and techniques to process and assemble molds. Finally, we need to conduct rigorous testing on the mold to ensure that it can work properly and meet the requirements of the product.


The journey of an injection plastic mold maker is filled with precision, expertise, and dedication. From the initial mold design to the final manufacturing process, every step requires meticulous attention to detail. Injection molds are an integral part of plastic molding and injection molding processes, enabling the mass production of high-quality plastic products. In this article, we will explore the world of injection plastic mold making, delving into the process, costs, and the professionals who bring these molds to life.

Understanding Injection Plastic Mold Making

2.1 What is Injection Plastic Mold Making?

Injection plastic mold making is the specialized process of creating molds used in injection molding. These molds are custom-designed to shape molten plastic materials into specific forms, allowing for the production of a wide range of plastic products. The precision and complexity of injection molds make them indispensable in various industries, including automotive, electronics, packaging, and consumer goods.

Injection plastic mold making is a process of creating a mold that can be used to produce identical plastic parts from molten plastic material. It is a common method for mass production of plastic products with complex shapes and high quality. The process involves the following steps:

  • Clamping: The two halves of the mold, called the core and the cavity, are clamped together in a machine press.
  • Injection: The plastic material, usually in the form of pellets or granules, is melted and injected into the mold under high pressure.
  • Dwelling: The molten plastic fills the entire mold cavity and is held under pressure to ensure that no air bubbles or defects are formed.
  • Cooling: The plastic solidifies as it cools down in the mold.
  • Mold opening: The mold is opened and the plastic part is ejected or removed.

Injection plastic mold making has many advantages, such as:

  • Uniformity: The parts produced by injection molding have consistent dimensions and features, as they are formed by the same mold.
  • Cost-effectiveness: The unit cost of injection molded parts decreases as the production volume increases, as the initial tooling cost is amortized over many parts.
  • Speed: Injection molding can produce hundreds or thousands of parts per day, as each cycle takes only a few seconds to minutes.
  • Variety: Injection molding can use a wide range of plastic materials, colors, and finishes to create different products.

2.2 The Importance of Injection Molds

Injection molds play a critical role in the manufacturing of plastic products. They determine the final shape, texture, and quality of the end product. Injection molding molds are designed to accommodate the specific dimensions, features, and intricacies required for each plastic component. With the use of injection molds, manufacturers can produce high-precision and consistent plastic parts with efficiency and repeatability.

The Process of Making Injection Molds

3.1 Designing the Mold

The process of making injection molds begins with mold design. Skilled mold designers utilize advanced computer-aided design (CAD) software to transform product specifications into a mold design. During this stage, various factors such as part geometry, material flow, cooling channels, and ejection mechanisms are taken into account. The mold design serves as the blueprint for the entire mold-making process.

3.2 Material Selection

Once the mold design is finalized, the appropriate materials for mold construction are selected. Common materials used for injection molds include hardened steel, aluminum alloys, and pre-hardened tool steels. The choice of material depends on factors such as production volume, mold complexity, and budget considerations. Each material has its own advantages in terms of durability, heat transfer, and cost-effectiveness.

3.3 Mold Manufacturing

After the design and material selection, the mold manufacturing process begins. Skilled mold makers employ advanced machining techniques and precision equipment to transform the mold design into a physical mold. This involves operations such as milling, turning, drilling, and grinding to shape the mold components. Additional processes like heat treatment and surface finishing are carried out to enhance the mold’s durability, longevity, and performance.

The Cost of Building a Plastic Injection Mold

The cost of building a plastic injection mold can vary depending on several factors. The complexity of the mold design, size of the mold, material selection, and level of precision required all contribute to the overall cost. On average, the cost of building a plastic injection mold can range from a few thousand dollars to several hundred thousand dollars. It is essential to consider the long-term benefits and return on investment (ROI) that a well-crafted injection mold can provide.

The Experts in Mold Making

Mold making requires a team of highly skilled professionals with expertise in various areas. Mold designers utilize their technical knowledge and experience to create efficient mold designs that consider factors such as part functionality and manufacturability. Mold makers possess the precision machining skills necessary to bring the mold designs to life. Additionally, mold engineers and technicians play vital roles in the assembly, testing, and maintenance of injection molds, ensuring optimal performance throughout the manufacturing process.

Exploring Plastic Molding vs. Injection Molding

Plastic molding and injection molding are often used interchangeably, but they are distinct processes. Plastic molding refers to the overall manufacturing technique of shaping plastic materials into specific forms. On the other hand, injection molding is a specific method within plastic molding. It involves injecting molten plastic material into a mold cavity, allowing it to cool and solidify before ejecting the final product. Injection molding offers greater precision, complexity, and efficiency compared to other plastic molding techniques.

The Cost of Injection Molds: Why So Expensive?

Injection molds can be relatively expensive due to several factors. The intricate design and precise manufacturing requirements contribute to the cost. Mold materials, typically hardened steel or pre-hardened tool steel, add to the expense. Moreover, the expertise and labor involved in mold making, including design, machining, assembly, and testing, contribute to the overall cost. However, the cost is justified by the quality, efficiency, and durability of the injection mold.

How Injection Molds are Made

8.1 Mold Base Preparation

The process of making an injection mold begins with mold base preparation. The mold base provides a solid foundation for the mold’s components. It is typically made from high-quality steel or aluminum alloys and is carefully machined to create the necessary channels and spaces for the core, cavity, cooling system, and ejection mechanism.

8.2 Core and Cavity Machining

The core and cavity are critical components of an injection mold. The core forms the interior geometry of the desired plastic part, while the cavity defines the outer surface. Skilled mold makers utilize precision machining techniques such as milling, electrical discharge machining (EDM), or computer numerical control (CNC) machining to create the intricate shapes and details of the core and cavity.

8.3 Heat Treatment and Finishing

After the core and cavity are machined, they undergo heat treatment processes to enhance their hardness and durability. Heat treatment techniques like quenching and tempering are employed to optimize the mechanical properties of the mold components. Finally, the mold undergoes finishing processes, including polishing and texturing, to achieve the desired surface finish and texture of the final plastic product.


The journey of an injection plastic mold maker involves expertise, precision, and dedication to create high-quality molds for injection molding. Injection molds are integral to the manufacturing process of plastic products across various industries. From the initial mold design to the final production, every step requires careful consideration and skilled craftsmanship. The knowledge and experience of mold makers contribute to the success of the mold-making process, ensuring the production of precise and consistent plastic components.


10.1 How do you make plastic injection molding molds?

The process of making plastic injection molding molds involves several steps, including mold design, material selection, and mold manufacturing. Skilled mold designers use CAD software to create a mold design that meets the desired specifications. The selected mold material is then machined and shaped into the core, cavity, and other components of the mold. Heat treatment and finishing processes are applied to enhance the durability and performance of the mold.

Plastic injection molding is a process that involves melting plastic pellets and injecting them into a mold cavity to form a desired shape. The mold cavity is usually made of metal, such as steel or aluminum, and has two halves that fit together. The mold cavity is designed to match the shape and size of the final product, as well as to allow for cooling and ejection of the plastic part.

To make a plastic injection molding mold, you need to follow these steps:

  1. Design the mold cavity using a computer-aided design (CAD) software. You need to consider factors such as the type and amount of plastic material, the wall thickness, the draft angle, the shrinkage rate, the parting line, the gate location, and the venting system.
  2. Choose the mold material and the mold making method. You can use steel or aluminum for the mold material, depending on the durability and cost requirements. You can also choose between different mold making methods, such as machining, casting, or 3D printing, depending on the complexity and accuracy of the mold design.
  3. Fabricate the mold using the chosen method. You need to ensure that the mold halves are aligned and fit together properly, and that they have smooth surfaces and edges. You also need to install features such as ejector pins, cooling channels, sprue bushings, and runners to facilitate the injection molding process.
  4. Test the mold using a prototype machine or a low-volume production machine. You need to check if the mold can produce plastic parts that meet the specifications and quality standards. You also need to optimize the injection molding parameters, such as the temperature, pressure, speed, and time, to achieve the best results.
  5. Use the mold for mass production using a high-volume production machine. You need to maintain and clean the mold regularly to prevent wear and tear, corrosion, or contamination. You also need to monitor the injection molding process and inspect the plastic parts for any defects or deviations.

10.2 How much does it cost to build a plastic injection mold?

The cost of building a plastic injection mold can vary depending on factors such as complexity, size, material selection, and precision requirements. On average, the cost can range from a few thousand dollars to several hundred thousand dollars. It is essential to consider the long-term benefits and ROI that a well-crafted injection mold can provide.

The cost of building a plastic injection mold depends on several factors, such as the size, complexity, material, and design of the mold. A typical plastic injection mold can cost anywhere from $1,000 to $100,000, depending on these factors. Some of the main cost drivers are:

  • The number of cavities: The more cavities a mold has, the more parts it can produce per cycle, but the higher the initial cost and maintenance cost will be.
  • The type of material: Different plastics have different properties and require different molding conditions, which affect the cost of the mold. For example, thermoplastics are cheaper and easier to mold than thermosets, which require higher temperatures and pressures.
  • The complexity of the design: The more intricate and detailed the design of the part is, the more complex and expensive the mold will be. For example, a mold with undercuts, threads, or inserts will require more machining and special features than a simple shape.
  • The quality and durability of the mold: The quality and durability of the mold depend on the choice of steel, the surface finish, and the cooling system. A high-quality mold will last longer and produce better parts, but it will also cost more to make and maintain.

10.3 Who makes molds for plastic?

Molds for plastic are made by skilled professionals known as mold makers. These experts have expertise in mold design, machining, assembly, and testing. They work closely with mold designers and engineers to bring the mold design to life and ensure its optimal performance.

Molds for plastic are made by specialized companies that design and manufacture them according to the specifications of their clients. Molds are usually made of metal, such as steel or aluminum, and have cavities that match the shape and size of the desired plastic product. The mold is attached to a machine that injects molten plastic into the cavities, where it cools and solidifies. The mold is then opened and the plastic product is ejected. Molds for plastic can vary in complexity, cost and quality, depending on the type of plastic, the product design and the production volume.

10.4 Why are injection molds so expensive?

Injection molds can be relatively expensive due to factors such as intricate design, high-quality materials, and precision machining requirements. The complexity of the mold design and the choice of materials significantly impact the cost. Additionally, the expertise and labor involved in mold making contribute to the overall expense.

One of the most common questions that people have about injection molding is why the molds are so expensive. Injection molds are complex and precise tools that are used to create plastic parts with high accuracy and quality. The cost of an injection mold depends on many factors, such as:

– The size and shape of the part
– The number of cavities in the mold
– The material and hardness of the mold
– The design and engineering of the mold
– The machining and finishing of the mold
– The testing and validation of the mold

All these factors require a lot of time, skill, and resources to produce a mold that meets the specifications and expectations of the customer. Therefore, injection molds are not cheap, but they are worth the investment for mass production of plastic parts.