What is Large Part Injection Molding? A Beginner's Guide

Today, we will delve into the core elements of large part injection molding, from the details of the technology to the selection of materials, from the customized demands of the medical industry to the design and production process of large parts, as well as cost-effectiveness and compliance with industry standards. We will also peek into the future trends and innovations of injection molding technology and look forward to how it will impact the manufacturing industry in the future.  

1. What is Large Part Injection Molding?

Large part injection molding, we define large part injection molding as the manufacturing of large, complex plastic parts using large injection molding machines and specific mold technologies. Unlike standard injection molding which produces smaller parts, this process involves using larger injection molding machines and tooling to produce parts with dimensions that exceed the capabilities of conventional equipment. This technique is commonly used to manufacture products such as automotive body panels, industrial containers, and large consumer goods. Key characteristics of large part injection molding include the use of high-performance materials, advanced clamping forces, and specialized cooling systems to ensure precise dimensional control and consistent product quality. Additionally, the process often requires more complex mold designs and longer cycle times compared to smaller part molding.

2. What Large Parts Can Be Produced by the Injection Molding Process?

Large Parts Injection Molding is widely used in many industries to produce a variety of large plastic parts due to its high flexibility and customizability. These parts usually have complex geometries, large sizes and high performance requirements.

Automotive Industry:

• Body Panels: Including hoods, doors, trunk lids, etc., these parts need to have good weather resistance, impact resistance and surface finish.

• Interior Parts: Such as dashboards, door interior panels, etc., these parts usually need to have complex shapes and high surface quality.

• Structural Parts: Including bumpers, side panels, etc., these parts need to have high strength and rigidity.

Industrial Field:

• Large Containers: Such as storage tanks, reactors, chemical containers, etc., these containers need to have corrosion resistance, high temperature resistance and pressure resistance.

• Equipment Housing: Including the housings of large mechanical equipment, these housings need to have good protective performance and beautiful appearance.

• Molds: Molds used to produce other products, such as rubber molds, metal casting molds, etc.

Consumer Goods Field:

• Large Appliance Housings: Such as refrigerators, washing machines, air conditioners, these housings need to have durability, beauty and good thermal insulation.

• Furniture parts: Large parts such as tables, chairs, cabinets, etc., which need to have high strength and wear resistance.

Medical device field:

• Large medical device housings: Such as the housings of MRI machines and CT scanners, these housings need to have good shielding properties and corrosion resistance.

• Medical device trays and containers: These devices need to have high temperature and high pressure sterilization resistance.

Large component injection molding can also be used to produce the following types of products:

Building materials: Large plastic sheets, profiles, etc.

Aerospace: Large composite components.

Electronic products: Large electronic equipment housings.

Sporting goods: Large amusement facility components.

3. What are the Types of Injection Molding Processes for Large Parts?

There are several types of injection molding processes specifically designed for large parts. Some common types of injection molding processes for large parts include:

Multi-component injection molding:

Two-shot injection molding is a typical example. By sequentially injecting two different materials, the color and function of the parts can be layered to improve the aesthetics and performance of the product.

Multi-component injection molding can inject multiple materials into the mold simultaneously or sequentially to produce parts with more complex structures and functions.

Structural foam molding:

By injecting chemical foaming agents into the molten plastic, the plastic is foamed and expanded in the mold cavity to form a closed-cell foam structure. This process is suitable for producing parts with thick walls and complex inner cavities. It has the characteristics of light weight, good rigidity, and excellent thermal insulation.

Gas-assisted injection molding:

During the injection molding process, high-pressure inert gas is injected into the mold cavity to force the molten plastic to flow to the wall of the mold cavity to form a hollow structure. This process can produce large thin-walled parts with uniform wall thickness and precise dimensions, and can improve the surface quality and mechanical properties of the parts.

Reaction injection molding (RIM):

Two or more liquid components are mixed and reacted in the mold cavity to generate polymers and form solid parts. The RIM process is suitable for the production of large and complex-shaped parts, such as car bumpers, bathtubs, etc., with the advantages of short molding cycle and small shrinkage.

Long fiber reinforced thermoplastics (LFT):

Long fiber reinforced materials are mixed with thermoplastic resins to prepare composite parts through injection molding. LFT materials have excellent properties such as high strength, high modulus, and high temperature resistance, and are suitable for the production of automotive parts, industrial machinery parts, etc.

4. What are the Benefits of Using Injection Molding Services to Produce Large Parts?

Large-part injection molding services have become the preferred process for manufacturing large parts due to their advantages of high precision, high efficiency, material diversity, design flexibility and cost-effectiveness.

• The advantage of large-part injection molding services is that they can achieve high-precision and high-consistency production of large and complex parts through precision injection molding technology, and significantly improve production efficiency.

• Large-part injection molding services can provide a wide range of material selection and complex geometric structure design capabilities to meet the customization needs of various large parts.

• Choosing large-part injection molding services can effectively reduce production costs, shorten production cycles, and achieve large-scale production to enhance product competitiveness.

5. What Materials are Suitable for Molding Large Parts?

A variety of materials can be used for injection molding of large parts, each with unique properties.

• Polypropylene (PP) has excellent chemical resistance, good fatigue resistance, and is cost-effective.

• High-density polyethylene (HDPE) has excellent chemical resistance and high impact strength and is often used for large tanks and pipes.

• Acrylonitrile butadiene styrene (ABS) is a versatile material with a good balance of properties, including impact strength, stiffness, and processability.

• Polycarbonate (PC) has high impact strength, excellent dimensional stability, and good heat resistance.

• Polyamide (PA) has high strength, stiffness, and good wear resistance.

• Liquid crystal polymer (LCP) has excellent dimensional stability, high temperature resistance, and electrical properties.

6. How does Large Parts Differ from Standard Plastic Injection Molding?

Large part injection molding and standard plastic injection molding share the same fundamental principle of injecting molten plastic into a mold cavity to form a part. However, there are several key differences that distinguish the two processes, primarily due to the scale and complexity of the parts being produced.

Equipment and Machinery: Large part injection molding requires significantly larger and more powerful injection molding machines with higher clamping forces to accommodate the larger molds and increased material volume. These machines are designed to handle the increased pressure and temperature needed to fill the large molds.

Mold Design and Complexity: Molds for large parts are typically more complex and require greater precision in their design and construction. This is because larger parts often have intricate features, undercuts, and varying wall thicknesses that need to be accommodated in the mold. The design and manufacturing of these molds can be a more time-consuming and costly process.

Material Selection: The choice of materials for large parts may be limited compared to standard injection molding due to factors such as the availability of materials in large quantities, the ability of the material to fill large molds consistently, and the cost of the material.

Cooling and Warpage: Larger parts have a greater tendency to warp or distort during the cooling process due to their size and the non-uniform cooling rates. This can lead to dimensional inaccuracies and require additional measures, such as specialized cooling systems or post-processing techniques, to mitigate these effects.

Cycle Time: The cycle time for large part injection molding is generally longer than for smaller parts due to the increased volume of material that needs to be injected and cooled. This can affect overall production rates and costs.

Tolerances and Precision: While both processes can achieve high levels of precision, achieving tight tolerances on large parts can be more challenging due to factors such as mold deflection, material shrinkage, and cooling variations.

7. What are Some Reliable Large Part Molding Service Providers?

By carefully evaluating these factors and conducting thorough research, you can find a reliable large part molding service provider to work with on your project.

Texas Injection Molding is one of the largest custom injection molding companies in Texas, they are certified to ISO 9001-2015 standards and have a full-service tool and die shop for these extensive manufacturing requirements.

EVCO Plastics was established in 1964, and since then, it’s become a place to collaborate, inspire and create parts that push the boundaries of what’s possible. Today, they operate more than 35 large-ton plastic injection molding machines, ranging from 1,000 to 4,400 tons, at our facilities in the United States, Mexico and China.

Protolabs helps companies bring new ideas to market by providing the fastest, most comprehensive digital manufacturing services worldwide. The company is known for rapid prototyping and low-volume production, offering a wide range of materials and finishes.

PSI Molded Plastics specializes in producing small to large, aesthetically pleasing, complex molded products, providing added value in a one-stop shopping environment. They are recognized for their attention to detail and personalized service, ensuring their customers the highest quality products and services in the industry.

8. Why Choose Hing Tung for Large Part Injection Molding?

Hing Tung, was founded in December 2011, located in Shenzhen, the innovation city of China. HingTung has been committed herself to build a designed and manufactured high-tech enterprises. Our product dimension ranges from mold, hardware products, plastic products, mechanical equipment, router, set-top box, electronic products, to gear technology development. Meanwhile, our business dimension covers both domestic and international trade, import and export of goods and technologies, etc. To provide our customers with a full range of one-stop structural parts services from pre-production review, production process control, to post surface treatment and preassembly is our mission and pursuit.

In many plastic mold forming methods, HingTung focuses herself only on the injection molding method for manufacturing plastic parts, with the aim of becoming the technology leader in this field. In the field of injection molding, our expertise determines that we can offer our customers a wide selection of molds: single and multi-cavity molds, embedded-part injection molds, two-color injection molds, thin-wall molds, automatic threading molds, HASCO and DME standard molds, molds of various sizes, and molds weighing up to 10 tons. In HingTung, no matter the test mold or the mass production mold, each mold is executed in accordance with strict standard procedures to ensure the quality of mold design and manufacturing.

Final Suggestions

We encourage readers to contact HingTung for more information about our services or to discuss your specific needs. Whether it's through our website or by speaking directly with our technical experts, we look forward to collaborating with you to develop solutions that meet your requirements.

HingTung thanks you for your reading and interest. Feel free to share this article, and we look forward to becoming your trusted partner in large plastic molding.