Plastic items are present everywhere in the world. They are the most used items compared to metals, glass, ceramic, and others. Many people opt for plastic products due to their properties like durability, lightweight, easily accessible, quality, and above all affordability. Plastics are manufactured in different styles depending on what the company is capable of and their preferences.
The most common methods of plastic production are injection mold making technology and thermoforming. These manufacturing methods are widely used in various companies. Although they both produce plastic items, they are very different in terms of production, time, cost, complexity, and so on. In this post, we are going to discuss injection molding and thermoforming including their differences to get a better understanding of the two processes.
Table of Contents
What is Injection Molding
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Injection molding is a process of plastic manufacturing. It involves the injection of molten plastic pellets into a metal mold under high pressure. The plastic then cools via the cooling system in the mold and solidifies to form a product of the desired shape. The mold is usually the heart of the whole process. Any defects or dysfunction on the mold results in low-quality products and wastage of both time and resources.
The mold is built using different metals but the most preferred one is steel since it is durable. Aluminum is also used. Plastic also comes in various types like ABS, polyethylene, polycarbonate, polyamide, polypropylene, polystyrene, and many more. Each of these plastics has its features that contribute to the choice of plastics used. Plastic injection molding was started by two American brothers Isaiah and John Hyatt.
They were attempting to create billiard balls out of plastic instead of the normally used material ivory. From there, their machine gained immense popularity. The injection molding machine was later improved by two German scientists. The benefits of using the injection molding process are;
- Allows mass production of goods at a fast pace
- The products obtained are very detailed and high-quality
- Proper utilization of resources with minimal wastage
- Permits the production of a high number of similar parts.
What is Thermoforming
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Thermoforming is the process of forming plastic products by heating plastic sheets at a very high temperature and stretching it out across a mold. The mold is usually single-sided, it is left to cool down resulting in the shape of the mold. The methods used to ensure the plastic forms according to the mold shape are pressure forming, vacuum forming, and mechanical forming. Thermoforming has several advantages such as;
- It is cheap compared to injection molding
- It is flexible and easier to modify
- The process is faster
- Permits texture and bright color options.
Even with all these benefits of using thermoforming, it is not suitable for a large production. It can handle production of up to 3000 parts annually. Thermoforming can be applied in several industries such as auto molds for Automotive, office equipment, medical, aerospace, public transportation, and construction.
Differences Between Injection Molding and Thermoforming
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Although both injection molding and thermoforming are processes of producing plastic parts, they are very different when it comes to cost, the process, the products formed, and many more.
Cost
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The cost between the two methods is very different and depending on which method you settle on, the spending will vary in every step of manufacturing.
Injection molding cost: injection molding is generally a bit expensive compared to thermoforming. The cost of building a mold is high since the mold must be built using steel to improve the quality of products. In the long run, producing parts in the injection molding is cheap because the mold is durable hence facilitates the production of thousands of parts faster.
Thermoforming cost: it is cheaper than injection molding especially when starting the process. The mold used here does not require steel since the production runs are minimal. This lowers the cost of production. However, producing parts is a bit costly than injection molding but the overall cost is still lower.
Process
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The approaches taken between injection molding and thermoforming are different. They vary in this way;
Injection molding:
- Plastic pellets are put into an injection molding machine
- The plastic pellets are then heated until molten
- They are injected into a metal mold (steel)
- High pressure is used for injection
- They cool and solidify after passing via a cooling system in the mold
- The part is then ejected out of the mold
- The mold used is double-sided
Thermoforming:
- Heating of a plastic sheet in high temperatures
- The sheet is spread over a mold
- It is left to cool down and form the shape of the mold
- Pressure is used but not as high as injection molding
- The mold used is single-sided
- Uses methods like a vacuum, pressure, and mechanical forming
Products
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Both injection molding and thermoforming manufacturers plastic products. The variation comes in terms of the size of the items, design, and usage.
Injection molding products are:
- Small since it has the capability of producing small size products (side actions and pick outs)
- Their designs are complex
- They can be applied in several industries
- 3D products are formed unlike in thermoforming
Thermoforming products are;
- Larger in size(more than 4 by 4) since it is incapable of forming small items
- Their products have simple designs
- They are used as packaging, housings, and enclosures
- Their products are one-sided, they are more of profiles and not 3D
Production Size
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The volume of production varies between these two processes as they already differ in the process, products, techniques, and the machines/equipment used.
In injection molding: the production volume is higher than in thermoforming. The machining capabilities in injection molding allow the production of many parts in a short period. The cycle in injection molding is much shorter and this also leads to low cost in production.
Thermoforming: The process of placing the sheets on the machine to be heated and then pulling it out takes longer making hence reduces the volume of production. Thermoforming is suitable for small productions.
Time
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The time taken from the commencing of a project to its termination is different in the two techniques. Before deciding on the method you will use, ensure you know the urgency of your project to avoid any delays by using the wrong method.
Injection molding: even though the production rate in injection molding is faster, the whole process from mould designing, mold making to the production of the parts takes way longer. The mold needs to be precise according to the specifications and hence more time and resources are allocated toward it.
Thermoforming: the time taken from start to completion of projects is faster compared to injection molding. Tooling in thermoforming does not require a lot of time hence the project will be completed faster.
Conclusion
When choosing the best manufacturing method for your plastic products, remember to keep in mind the cost, process, products, the volume of production, and the time taken for the project to be completed. These aspects are important for both the manufacturer and the client. Our company, Fow Mold offers the best plastic injection molding services you will ever get access to. We ensure we serve our clients beyond their expectations to promote a good relationship.
For more information on plastic injection molding, visit our website to get a beginners’ guide on injection molding to prepare you for future endeavors.
