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February 16, 2023
3 min read time

Putting It Together: Plastic Assembly Services & Secondary Operations



Plastics technician performing plastic assembly services and secondary operations.

The Full-Service Processes That Finish the Job Right

When an injection molded component is cooled and ejected from the machine, it's finished, right? Not always! The truth is most plastic parts need a little finishing work before they're ready for their end use. Automated machines and skilled specialists perform plastic assembly services and secondary operations to ensure that each part is precise and market-ready. Let's take a closer look at finishing plastic components the right way.

What's the Difference Between Manufacturing and Plastic Assembly Services?

Great question. Many people think these two processes are the same, but there is a difference between plastic manufacturing and plastic assembly services. Manufacturing involves taking raw materials (in our case, high-quality resins) and turning them into finished plastic components. Assembly is putting together different components to make a complete product. For example, the completed parts of an injection molded toolbox must be assembled to create a finished, functional product. 

The type of assembly needed depends on the material, design, end-use, and more. Often, plastic assembly services are an integrated part of the manufacturing process. However, there are occasions when assembly services are outsourced. When you're searching for the right partner for manufacturing and assembly services, it's essential to consider whether you need a company that can get it all done in one place or if you're open to outsourcing the assembly process. 

Secondary Operations and Custom Injection Molding

Assembly is part of a more extensive suite of services known as secondary operations — operations that are done after the primary manufacturing method is completed. Custom injection molding projects frequently require finishing work before they hit the market. Secondary operations enhance and protect manufactured plastic parts and help ensure that each component is completed according to spec. These jobs may be automated, performed by hand, or combined. At Houston Plastic Products, we provide a full roster of custom assembly, secondary operations, and value-added services, including but not limited to:


A basic subtractive machining process that uses a cutting tool to smooth and shape plastic components.

Tapping of threaded features

The process of cutting a thread inside a hole so that a cap screw or bolt can be threaded into the hole.


Using an abrasive material to superficially clean and even out uneven parts on a plastic surface. It helps remove minor dents and scratches.

Ultrasonic welding

This technique melts thermoplastics to join with dissimilar materials like metal using the vibrations generated by high-frequency ultrasonic energy. It's quick and efficient. 


The process of forming plastic parts around other non-plastic parts, like a metal thread or rod.

Hot stamp foil printing

A printing process that uses heated image molds or stamping dies to transfer metal foils or pre-dried inks onto a surface.

UV-cured adhesive assembly

Using quick-curing acrylate- or epoxy-based resins that cure in seconds when irradiated by unique UV light sources.

Cost Effective Finished Products Made Easier

Nearly all manufactured plastic components require some kind of secondary operation. Be sure to consider the added cost of plastic assembly services and secondary operations early in the product design process. Choosing a complete plastics manufacturer that provides secondary operations instead of outsourcing your finishing needs will save you time and money. Products designed with both manufacturability and assembly in mind are generally more cost-effective, higher quality, and quicker to market.

At Houston Plastic Products, we specialize in end-to-end plastics manufacturing and secondary operations. Through the combination of our automated processes and experienced hand-work specialists, we provide a host of finishing work. Our in-house tool room and fabrication capabilities mean that we can take care of the small but vital details each component requires. Let's get started today on your custom injection molding project!

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