Thermoforming vs. Injection Molding: Choosing the Right Process

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In the ever-evolving world of plastic manufacturing, two distinct techniques exist, thermoforming and injection molding. Having a discussion around thermoforming vs. injection molding often shows that these two methods have significantly transformed the plastic production process. 

R Series Right Front thermoforming roll stock vacuum MAP and skin packaging machine by VC999

However, thermoforming entails the melting of plastic sheets until malleable and then molded into shape employing vacuum pressure or molds. In contrast, injection molding solely depends on injecting molten plastic into mold cavities to attain its desired form. 

As beneficial as both methods are, our aim in this article is to uncover the mysteries that surround both methods, while assisting manufacturers and enthusiasts in making informed decisions on which to apply in their respective endeavors. 

thermoform plastics

1. Understanding Thermoforming

1.1 Overview of Thermoforming Process 

Thermoforming is a resourceful and unique technique that allows plastic parts manufacturers to produce efficient and reliable components. 

As briefly mentioned above, thermoforming entails transforming plastic sheets into three-dimensional shapes. The way it works starts by meticulously heating the plastic material until it reaches its maximum temperature. At this point, the material becomes bendable into any desired form. 

Furthermore, the melted plastic is spread over the mold where its intended design is readily crafted. Beyond that, a vacuum pressure rids the mold of any air and allows the melted plastic draped over the mold to fill up the spaces in its nooks and crannies. This ensures malformations are eliminated, and the part formed turns out to be aesthetically and functionally sound.

The simplicity that comes with thermoforming permits finesse, excellent performance, and unbeatable precision in manufacturing complex parts. Thermoforming creates meticulously detailed components, reflecting the intricacies of a beautifully crafted mold. 

With thermoforming, the use of complex machinery is not necessary and high pressures are not required, hence the seamless crating of parts. This is a notable advantage thermoforming offers, and that is our next point of discussion. 

1.2 Advantages of Thermoforming 

Thermoforming is embroidered with a host of benefits, especially in plastic part manufacturing. A common benefit is its ability to mold large components with no trouble, particularly with high-quality mold manufacturing. The effortless crafting of plastic parts sets thermoforming apart from other types of part production. One of the major reasons manufacturers consider it a top choice in plastic part production.

Following its comparative ease of creating large parts is its low tooling cost. Economically, thermoforming assists the manufacturer’s budget size by adopting cost-effective tools. This low-cost tooling is beneficial in producing custom designs and shorter production runs, and that’s a massive economic advantage in comparison with other manufacturing techniques.

Moreover, the time taken to complete a production cycle is way less when placed side-by-side with other processes. This means the production cycle using thermoforming ensures your parts are readily available in record time. No manufacturer wants time wasted in producing a set of components, and for that reason the best time-conscious process of manufacturing parts is thermoforming.

On that account, if your project requirements correspond with larger components being produced in a short time frame with budget-friendly tools, look no further than thermoforming. Let’s dive deeper by understanding its contemporary technique in this thermoforming vs. injection molding piece.

pressurized plastic forming process

2. Understanding Injection Molding

2.1 Overview of Injection Molding Process 

Injection molding in the world of plastic component manufacturing is the epitome of precision and cost-efficiency. As its name implies, it involves the injection of melted pellets into mold cavities at high pressure to achieve its desired outcome. In addition, once the injected materials in the mold cool and solidify, a masterpiece is born, and the awesomely designed part is revealed. 

In a fast-paced manufacturing realm, versatility and the ability to produce complex geometries and intricate dimensions are very crucial. Injection molding is a widely applied plastic part production technique that’s useful in many industries. 

Users of injection molding processes typically are in the automotive, electrical, and healthcare sector. 

2.2 Advantages of Injection Molding 

Injection molding possesses qualities that leave manufacturers satisfied with their products. One such quality is the capacity to manufacture high-volume plastic components with unimaginable consistency in the parts produced. This is a result of the high pressure and precision it requires to form parts. Additionally, injection molding thrives with complex geometries and designs, making it a preferred choice for complex designs. 

What’s more? Injection molding presents manufacturers with flexibility in material selection, allowing the production of finely formed components. Materials ranging from thermoplastics to advanced engineering-grade materials. So, a suitable method of manufacturing plastic parts, with complex designs that can be produced in high volumes and with numerous material options is found in injection molding.

Thermoforming materials

3. Material Selection and Applications

3.1 Material Compatibility in Thermoforming 

Now here is a crucial part that decides the turn a plastic part takes in thermoforming. Material compatibility is non-negotiable to attain accurate dimensions and align with the capabilities of the process. Material properties that suit the thermoforming process must be carefully considered before making a choice. 

Consequently, thermoforming as we have already established entails heating and shaping of materials into desired forms. For this reason, the material to be used in this process must be equal to the task. This means the material of choice should be able to withstand the rigors of the process. Heat resistance, transparency, and flexibility are properties the material to be considered for thermoforming must possess. 

Few materials nonetheless meet these requirements and they include Polycarbonate (PC), ABS, and acrylic. This makes the materials available for selection quite limited when it comes to thermoforming. However, materials such as ABS and polycarbonate have the attributes necessary for the thermoforming process. 

Thermoforming is a unique plastic part manufacturing process that offers versatility in shape, size, and efficient production. Accordingly, the material compatibility should be in tandem with the process by offering flexibility, impressive heat resistance, and clarity.

3.2 Material Versatility in Injection Molding 

Injection molding on the other hand has an abundance of materials to choose from. The versatility of materials in injection molding provides it with materials suited to various application requirements. and as such, materials range from elastomers, and thermosets, to thermoplastics. This is an appreciable bonus to the manufacturing technique as it permits manufacturers to consider different material types for different production purposes. 

Injection molding is typically preferred by many plastic component manufacturers just because of the range of material choices it provides. It encourages design flexibility and innovation, especially with complex and near-impossible designs as obtainable with advances like 3D printing technology. If your project’s requirements entail components with high impact resistance and excellent thermal stability, then injection molding has got your back all day. 

Yet with all of the glorious material options available in injection molding, it is likewise paramount to understand the complexities of each material. Some materials are difficult to operate or are likely to increase cycle time when cooling is slow. Furthermore, some materials also present the possibility of shrinkage under high pressure when injected into the mold cavity.

That being so, numerous materials are compatible with injection molding, but understanding material behavior in the process is essential for excellent part production.

4. Design Flexibility and Complexity

4.1 Thermoforming Design Considerations 

Comparing thermoforming vs. injection molding in terms of design flexibility and complexity indicates the cruciality of details involved in thermoforming. Details that either enhance or diminish the structural integrity and functionality of the parts produced. These factors include

  • Draft Angles: For smooth, seamless, and trouble-free ejection of the part from the mold, draft angles take up that responsibility. The inclusion of draft angles saves manufacturers from the probable occurrence of distortions. Without draft angles, parts can be stuck and its removal becomes difficult. 
  • Undercuts: This design consideration also helps with the removal of the component from the mold. The only challenge here is that undercuts may be more detrimental than advantageous with thermoforming. It is on that note advised to be minimized or avoided completely due to its nature.
  • Part Thickness: A uniform thickness ensures the proper heating and cooling of plastic sheets. Consistency in part thickness guarantees that the heating, forming, and cooling stages allow for the production of smooth and functional components.

As wonderful as thermoforming is, some limitations accompany the process in terms of design consideration. It is agreeable that thermoforming supports design freedom, but there are certain designs it cannot achieve. Specific intricate designs and complex dimensions are way out of its league. Take nothing from it, thermoforming is special in its way.

4.2 Injection Molding Design Considerations 

Design considerations in injection molding consist of a plethora of factors that also enhance the optimal execution of the process. These factors open up a world of endless possibilities that assists injection molding in reaching admirable part production goals. They include

  • Gating: In the high-quality mold manufacturing industry, this is the entry point of the molten plastic into the mold where the part formation occurs. Even so, the proper placement of these gates improves part integrity and aesthetics. When the mold gate is appropriately positioned, the melted plastic efficiently flows into the mold regardless of its high pressure. 
  • Ejection Pins: This tool ensures the safe and smooth removal of the component from the mold. However, the lack of proper planning and positioning of the ejector pins can leave marks and scratches on the mold and the manufactured part, hence the necessity for adequate placement.
  • Mold Flow Analysis: The careful study of the mold flow is hinged on the type of material and the mold design. This ensures the flow pattern of the molten plastic is not egregious resulting in badly formed components. 

Injection molding thrives in the face of complex designs, unlike thermoforming. Nonetheless, the flow pattern determined by material properties and mold design must be meticulously understood. 

5. Cost Comparison and Volume Considerations

5.1 Cost-Effectiveness of Thermoforming 

Considering the financial aspects of thermoforming in comparison to other part manufacturing methods, including high-quality CNC machining, thermoforming stands out as a budget-friendly process. 

After every production when the books are opened, thermoforming will emerge as the significantly cheaper method of manufacturing plastic components. Its relatively lower tooling cost aids this feat. The mold thermoforming utilized in parts production is less complex, which is a reason for its simplicity and cheaper tool. 

On top of that, thermoforming perfectly meets the requirements for projects that require lower volumes and shorter production runs. It helps manufacturers disburse resources efficiently. In addition to that, shorter production runs that may not require elaborate molds further assist in economizing. 

The manageability of thermoforming provides a mode of judiciously dispensing resources when compared to other manufacturing techniques. Less elaborate molds equal the reduced cost of tooling. The ease of operation further lessens overhead costs. However, due to factors such as post-processing and trimming, extra costs could be accumulated. 

The need for post-production processes such as trimming may be required to enhance its aesthetics and functionality. This is why the cost per part produced by thermoforming is likely to increase. Beyond that, thermoforming remains your best chance at a cost-effective part production.

5.2 Mass Production and Economies of Scale 

On the contrary, injection molding takes the spotlight when it comes to its cost advantages. It is typically suited for commercial production of plastic parts, hence the investment in the tools required for it. Yes, it is true that at the initial acquisition and installation of injection molding tools, costs can be high. But the benefits lie in its economies of scale. This translates to a high yield in the long run for injection molded parts.

Confused, let’s explain further. The tooling costs of injection molding equipment are quite capital-intensive. However, the cost is offset as the volumes produced increase making up for its tooling cost. With Injection molding, the cost per part produced reduces as mass production commences complimenting the investment in the molds acquired.

Injection molding greatly benefits manufacturers of identical parts on a large scale, allowing the economies of scale to effectively flourish. Once the molds are set up, the efficiency of injection molding kicks in, and its cost efficiency is unveiled. 

It is safe to say that both thermoforming and injection molding offer cost efficiency, only on varying scales. While thermoforming is simple, utilizes fewer complex tools, and still saves costs, injection molding switches it up with its intensive machinery and its economies of scale.


Bringing this to a close, venturing into both worlds of thermoforming vs. injection molding has unveiled the diverse personalities of both methods. 

Thermoforming finds its calling in the crafting of larger parts, lower volumes, and judicious allocation of budget. While injection molding actively thrives in molding complex dimensions, mass production, and effectively activating its economies of scale instruments. 

Additionally, getting the best of both worlds entails meeting all requirements, including design considerations and material selection for optimal operation. And there you have it, we hope this serves your informative appetite as a manufacturer or an enthusiast.


Gary Liao

Gary Liao

Gary Liao is the Engineering Manager of TDL Company and has more than 20 years of mold design experience.

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