Two-Shot Injection, Overmold, and Insert Molded Products

Over the past three decades, Thumb Plastics has mastered two-shot and insert molding. Our design and engineering innovations can be found in a variety of industries including automotive, agriculture, lawn and garden, industrial, and medical. Here is a small representation of the products we’ve developed for automotive:

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Thumb Plastics is more than a manufacturer. We specialize in engineering value into your two-shot injection and insert-molded plastic parts. Moreover, leveraging the knowledge and experience of all Gemini Group companies gives us the unique ability to optimize part design, drive cost out of products, and reduce lead-times.


We’re part of a horizontally integrated network of experts and we’ll never compromise the integrity of your product in favor of a pet process or material.

Two-Shot Injection Molded Plastic Products

Using two-shot injection molding process, Thumb Plastics can produce two-component or two-color products in one machining cycle, eliminating additional assembly costs. Two-shot is the ideal process for the high-volume production of products with rigid and flexible components, multiple colors and surface grades, vibration and noise dampening characteristics, and sealing functionality.

  • Expanding Structural Solutions (Sorb Rocker & Pillars)
  • Expanding Sealing Solutions (Baffles & Carriers)
  • Air Induction Bellows/Cuffs
  • Airbag covers
  • Stone/Mud guards
  • Air guide seals
  • Spoiler strakes

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Insert Molded Plastic Products

Using the insert molding process, Thumb Plastics can mold plastic directly on to metal components and assemblies, eliminating the need for messy adhesives and fasteners. Insert molding is the ideal process for adding plastic grips and handles to metal parts, or metal fasteners, magnets, and structural reinforcements to plastic products.

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Two-Shot Molding Case Study: Active Grill Shutter Guides (AGS)

The front end of a RAM truck with the left side of the grill removed to reveal two-shot molded active grill shutter guides.

The Market:

The customer is a Tier1 international automotive supplier with an emphasis on innovation and technology. The company’s products include automotive exteriors, closures, roof systems, and seating – to name a few.


The Challenge:

The customer was having issues sealing off an Active Grille Shutter (AGS) system with the air guide seals. The innovative under-the-hood system was designed to help OEMs meet CAFE standards by re-directing air around the vehicle to reduce drag. The sealing components of the system are absolutely critical and the manufacturing process to make them – two-shot injection molding – is difficult to master. The customer was quick to realize this as the incumbent supplier failed to meet stringent quality standards. The customer had to find a supplier experienced enough to manufacture the complex part.


The Solution:

Needless to say, the customer turned to the two-shot experts at Thumb Plastics, Inc. (TPI), a Gemini Group company, for design and engineering support and innovation. The key to TPI’s success lies within its culture of continuous improvement, it’s adherence to Lean – one piece flow – manufacturing, and its commitment to delivering quality products at a competitive market price. Drawing form over 30 years of experience launching hundreds of two-shot interior, exterior, BIW, and underhood applications, TPI was able to quote the four-component, multi-million dollar program in less than a week and was awarded the program soon after. The final production design was guided by our internal design support team, optimized for DFM, and is set for production in 2019.


The Result:

The final part design exceeded the customer’s expectations, along with our highest quality and OTD standards. In addition, the efforts of TPI’s in-house part and tooling design team reduced the mold expense to our end customer with a savings of nearly $200k in tooling.

Engineering Success

An assortment of two-shot injection molded and insert molded parts manufactured by Thumb Plastics.

Got an idea for a solution requiring the innovation of two-shot? Not sure where to start? Thumb Plastics has the design and manufacturing experience to help solve your company’s product dilemma and give you a competitive advantage. We believe in proactive communication and collaboration early on in the design and engineering phase. This allows us to incorporate DFM right from the start, eliminating potential problems before they add to your cost and development time.


Want to build quality and low cost into your product? Put us to work for you!