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With custom injection molding, you can achieve efficiency, craft intricate and complex designs, and significantly reduce material waste. This process allows for consistent, high-quality results, enabling you to meet tight tolerances and exact specifications.
Whether you’re looking to produce thousands of identical parts or require flexibility in design modifications, custom injection molding provides the versatility and precision needed for various applications.
In this article, we’ll explore the basics of injection molding processes and review some of the best custom injection molding companies to help you find the right partner for your needs.
What is Custom Injection Molding?
Custom injection molding is a manufacturing process in which molten material, typically plastic, is injected into a mold to create custom-shaped parts. This process produces a range of parts, from final-use parts to rapid prototyping.
Custom injection molding uses various plastic materials, including polyethylene (PE), polypropylene (PP), acrylonitrile butadiene styrene (ABS), and polycarbonate (PC). During the process, the chosen polymer is heated until it reaches molten form, after which it is injected into the cavity of a mold under high pressure.
The polymer is left to cool in the mold, where it takes its shape, after which the newly formed part is ejected and taken for further post-processing. By manipulating heat and pressure, this method can reliably mold a variety of products with speed and accuracy.
How Does Injection Molding Work?
Let’s take a look at how injection molding works:
- Mold design and creation: The process begins with designing and creating the injection mold tool, which typically consists of several components, including the cavity and the core. The cavity and the core fit together to form the part’s shape and internal structure. Molds can be made from various materials, such as aluminum, metal, ceramic, or plastic. During the creation of the mold tool, the mold might undergo additional processes, such as nibore coating.
- Material heating: A plastic material, often in pellet or granular form, is fed into the injection molding machine. The machine is made up of three parts: the feed hopper, the screw, and the heated barrel. The feed hopper collects the plastic material and then uses the frictional action of the screw to create heat. This heat generated melts the plastic material into liquid form.
- Injection: Using a heated barrel injection, the machine forces the melted plastic into the engineered mold under high pressure.
- Cooling: The plastic cools inside the mold, taking on the shape of the mold as it solidifies.
- Ejection and post-processing: When the newly formed three-dimensional part has cooled and fully taken shape, it’s ejected from the mold and taken for additional finishing processes. These may include processes such as gate trimming to achieve a smoother finish or painting to improve the part’s aesthetic value.
Custom Plastic Injection Molding Materials
Plastic is the most common material used in injection molding processes. The type of plastic used determines the final product’s properties and performance, affecting features such as durability, strength, and thermal conductivity.
Some common plastics used in custom plastic injection molding.
- Nylon: Nylon is the generic name for the family of synthetic polymers that are based on semi-aromatic polyamides that are typically made from petroleum. These plastics have impressive electrical properties, excellent strength, and good resistance to heat and chemicals. The most commonly used nylons for injection molding are nylon 6, nylon 6/6, nylon 66, and nylon 6/66.
- Acrylonitrile butadiene styrene: This plastic is typically used to make products that do not require chemical, ultraviolet (UV), or electrical resistance. ABS is an amorphous, high-strength, general-purpose engineering plastic. It is flexible and lightweight with good impact strength. ABS is often used in custom injection molding to create toys and automotive parts.
- Polycarbonate: Polycarbonate is a term for high-performance plastic materials made up of a group of thermoplastic polymers containing different carbonate groups as part of their chemical structure. This plastic is known for its heat resistance, with a relatively high melting point of 155°C. As a result, PC is typically used to make parts used in demanding environments.
- Polypropylene: Polypropylene is a robust plastic with a high melting point, good stress resistance, and high impact strength. It is typically used as a good-grade polymer in food and packaging companies.
- Low-density and high-density polyethylene (LDPE and HDPE): Low-density polyethylene is a flexible, lightweight plastic known for its low melting point and is commonly used in plastic bags and film wrap. High-density polyethylene is a tougher, more rigid plastic with a higher melting point, making it ideal for containers, pipes, and heavy-duty applications.
- Thermoplastic elastomers: Thermoplastic elastomers generally possess the processability of thermoplastics and the elasticity of vulcanized rubber. Manufacturers use TPEs in car parts, medical devices, and consumer goods like grips and seals.
- Thermoplastic vulcanizate: Thermoplastic vulcanizate is primarily composed of polypropylene and EPDM rubber. The EPDM rubber within the polypropylene matrix is vulcanized, which provides good compression set resistance. Manufacturers use it in automotive seals, hoses, and gaskets.
Best Custom Plastic Injection Molding Companies & Services
Let’s look at some of the best custom plastic injection molding companies and services.
1. UPTIVE Advanced Manufacturing
Location: Multiple locations across the United States and Mexico
UPTIVE Advanced Manufacturing is a leading provider of rapid manufacturing solutions that combine cutting-edge technology and personalized service. The company supports every stage of the production process, from prototypes to large-scale production runs, ensuring that each part is optimized for manufacturability and long-term success.
UPTIVE utilizes state-of-the-art equipment, including high-speed 5-axis CNC machines, EDM, and surface and form grinders, to quickly create steel and aluminum molds for your parts. It also allows you to design custom mold bases for intricate or high-volume projects.
By partnering with UPTIVE, you can:
- Ensure precision with customized tooling matched to the best resin that meets your design criteria
- Decrease cycle times for tool inserts with mold bases uniquely designed for fast and low-volume molds
- Meet quality expectations with inspection criteria per your industry standards, including first-article inspection reports and production part approval process (PPAPs)
- Access more design choices, such as complex geometries, undercuts, and threads (using aluminum allows for easier design changes through the tool’s life)
Additionally, UPTIVE offers an extensive range of plastics, elastomeric materials, and filled composites, specializing in two-shot and insert-molded parts to deliver the speed, quantities, and tolerances you require.
In an industry full of automated quotes, limited personalization, and faceless transactions, UPTIVE provides customers with personalized support and guidance throughout the design and production process so customers get the best service imaginable.
Top injection molding capabilities:
- Injection molding: Specializes in quick-turn injection molding, using m inserts for consistent, rapid production tailored to your specifications.
- Injection tooling: Utilizes production plastic and elastomeric materials to quickly create tool inserts from proprietary mold bases for fast and low-volume molds.
Other services:
- Sheet metal fabrication
- CNC machining
- Additive manufacturing
- Rapid prototyping
- Post-processing and finishing
UPTIVE was built for manufacturers who demand precision, accuracy, and scalability–at incredibly rapid speeds. Is that you? Get a free quote from UPTIVE by simply uploading your design file.
2. Ironwood Plastics, Inc.
Ironwood Plastics, Inc. is a plastic injection molding company that manufactures close-tolerance plastic products. The company provides various solutions, including insert molding, reel-to-reel molding, and two-shot molding.
Ironwood Plastics serves various industries, including defense, healthcare, automotive, and electronics. It also offers secondary services and engineering solutions, such as high-temperature resin molding, metrology, and mold flow analysis.
Top injection molding capabilities:
- Two shot molding
- Insert molding
- Reel-to-reel molding
- Close tolerance molding
- Overmolding.
Other services:
- Pad printing
- Assembly
- Foam in place gasketing
- Sonic welding
3. Protolabs
Protolabs is a manufacturing service offering solutions for injection molding, CNC machining, 3D printing, and sheet metal fabrication. It offers custom injection molding for plastic parts and supports a wide range of thermoplastics and elastomeric materials. Protolabs’ services include prototyping and on-demand production using two-shot and insert molding processes.
Top injection molding capabilities:
- Plastic injection molding
- Liquid silicone rubber molding
- Overmolding & insert molding
Other services:
- CNC machining
- 3D printing service
- Sheet metal fabrication
4. Plastek Industries, Inc.
Plastek Industries manufactures plastic packaging for the personal care, beauty, home care, pharmaceutical, and food and beverage industries. The company specializes in industrial design, product and package development, mold design and build, injection, injection blow, injection stretch blow molding, and value-added assembly and decorating.
Top injection molding capabilities:
- Package development
- Mold design/manufacturing
- Molding/assembly
Other services:
- Tool build and mold making
- Custom product design
- Stock packages
5. American Tool & Mold, Inc.
American Tool & Mold, Inc. is a precision mold manufacturing company specializing in mold manufacturing and engineering services. The company focuses on the design of complex, precision, multi-cavity molds tailored for use in the plastic injection molding industry.
American Tool & Mold offers two-shot molding, cold runner molding, parts manufacturing, and overmolding. They offer their services to the healthcare, packaging, and automotive industries.
Top injection molding capabilities:
- Thermoplastic injection molding
- Injection molded plastic parts
- Overmolding
- Stack molding
Other services:
- Cold runner molding
- Parts manufacturing
- Insulated runner molding
- Value added molding
6. Xometry
Xometry specializes in on-demand precision part production and prototyping manufacturing. Its services range from plastic injection molding to metal injection molding, die casting, metal stamping, metal extrusion, plastic extrusion, sheet metal, laser cutting, waterjet cutting, laser tube cutting, and tube bending.
Top injection molding capabilities:
- Insert molding
- Overmolding
- High-volume injection molding
- Gas assist injection molding
Other services:
- Additive manufacturing
- CNC machining
- Sheet and tube fabrication
- Plastic part production
- Metal part production
- Value-added solutions
7. Seaway Plastics Engineering, LLC
Seaway Plastics Engineering, LLC is a contract manufacturing company specializing in plastic injection molding services. The company’s services cover mold design, in-house tooling, cleanroom molding, and finishing operations.
Seaway Plastics Engineering is ISO 13485-certified and serves the medical, aerospace, defense, and precision industries. The company offers a wide range of industrial—and medical-grade thermoplastics and liquid silicone rubber (LSR) to meet the needs of these industries.
Top injection molding capabilities:
- Plastic injection molding
- In-house tooling
- Injection molding-thermoplastic and liquid silicone rubber (LSR)
- Cleanroom molding & assembly
- Finishing
Other services:
- Post-molding operations
- Low-to-mid volume injection molding
8. Murray Plastics
Murray Plastics specializes in custom injection molding and plastic part manufacturing. The company offers various services, including part design, in-house mold building, resin selection, and secondary operations like finishing and fulfillment.
Top injection molding capabilities:
- Plastic injection molding
- Plats injection mold building
Other services:
- Value-added services
- Inventory management and logistics
9. Nicolet Plastics
Nicolet Plastics is a custom plastic injection molding manufacturer that offers engineering services, including product development engineering to ensure manufacturability, project management using Smartsheet for real-time activity tracking, and design consultation during tool construction. Nicolet Plastics also provides insert molding, metal-to-plastic conversion, and post-molding operations.
Top injection molding capabilities:
- Plastic injection molding
Other services:
- Additive manufacturing
- Post molding and assembly operations
10. The Rodon Group
The Rodon Group offers high-volume precision manufacturing and custom plastic injection molding services to a diverse client base. The company serves industries producing windows and doors, household appliances, and food and beverage.
The Rodon Group also offers plastic injection molding, mold designing and building, toolmaking, just-in-time (JIT) manufacturing, quality control and product testing, packaging and order fulfillment.
Top injection molding capabilities:
- Custom plastic injection molding
Other services:
- Design
- Toolmaking
- Manufacturing
- Cleanroom
- Material selection
11. Extreme Molding
Extreme Molding is a custom injection manufacturer that specializes in injection molding, overmolding, and compression/transfer, among other services.
Extreme Molding offers services to the consumer and life science industries. In addition to manufacturing, Extreme Molding offers assembly, packaging, and fulfillment.
Top injection molding capabilities:
- Silicone injection molding
- Overmolding
- Compression/transfer molding
Other services:
- Color matching
- Packaging and fulfillment
- Value-added secondary operations
- CAD drawing services
Work With the Best Custom Plastic Injection Molding Company
Custom injection molding enables the creation of specialized plastic products that traditional manufacturing methods cannot produce. However, to truly harness this technology’s potential, it is important to partner with the right company with the capabilities, expertise, and materials to bring your creative ideas to life.
Choosing UPTIVE means partnering with a company that understands the complexities of additive manufacturing and utilizes state-of-the-art equipment, including high-speed 5-axis CNC machines, EDM, and surface and form grinders. These advanced tools allow UPTIVE to quickly create steel and aluminum molds for your parts, even accommodating intricate or high-volume projects–all at incredibly quick speeds.
UPTIVE systems are engineered to produce quick-turn parts that meet your standards for precision, durability, and lightweight construction while offering you more design choices, such as complex geometries, undercuts, threads, and more.
UPTIVE’s approach integrates advanced manufacturing techniques with a customer-centric focus, providing clients with:
- Expert guidance to ensure that parts are designed for manufacturability and scalability
- Collaborative, long-term partnerships that foster continuous innovation
- An extensive knowledge base to educate and support clients throughout the production journey
- The ability to visit your tool at any time so you can make any adjustments throughout the process
Experience the human side of rapid manufacturing with UPTIVE.