Plastic is a versatile material frequently used in the medical, manufacturing, electronics, firearms, aerospace, and electronics industries. Manufacturers can use different forming processes to create the desired plastic shapes. Explore compression molding vs. thermoforming, including the pros and cons of each method, the differences between them, and when to choose one over the other.
Compression Molding vs. Thermoforming: What Are The Differences?
These two forming processes are both used to create shapes for a wide range of applications. They have some similarities: both use heat, molds, and plastic materials. However, they differ in many ways. To better understand the differences between thermoforming and compression molding, you should first know what each process entails and when it is best used.
What Is Thermoforming?
Thermoforming is a process used to create simple to moderately complex plastic parts. It involves placing a heated plastic sheet over a mold. Pressure is then applied to force the soft plastic onto the mold, where it takes the latter's shape.
You must use special thermoplastics for this process. Some of the most common choices are:
- Acrylonitrile Butadiene Styrene
- High Density Polyethylene
- High Impact Polystyrene
- Polyethylene Terephthalate
- Polyethylene Terephthalate Glycol
- Polypropylene
- Poly Vinyl Chloride
Most thermoplastics are fully recyclable, which makes it an environmentally friendly process compared to many others.
Pros and Cons of Thermoforming
Advantages of using thermoforming include its quick setup time, low cost, and suitability for low-quantity production runs. These features make it an excellent choice for one-off projects.
There are relatively low tooling and production costs with thermoforming. Additionally, it requires minimal labor, which further reduces costs.
It is also a very quick process. You can go from ideation to finished product in a matter of weeks. In addition, it is relatively quick and easy to make changes to an original design if needed.
Another benefit is that it can help companies reach sustainability targets. Many thermoplastics are recycled, and scraps can be reused for future products, reducing reliance on virgin materials.
However, there are some drawbacks to this technology. While thermoforming is great for producing simple shapes, it is not a good choice for complex products or those with internal features. It is also limited to relatively thin components, like car panels, packaging, and signs.
Common Uses for Thermoforming
Parts from tractor awnings to dental trays are made using thermoforming. Perhaps the most common use for thermoforming is in packaging and shipping trays. Most clamshells and blister packs use thermoforming. Other common products you will see made from this process include:
- Automotive panels, bumpers, fenders, and interior parts
- Commercial signage and shelves
- Medical devices, trays, and enclosures
- Shelving and storage racks
Its flexibility makes thermoforming a good choice for initial product development where changes may be needed. Designers can make minor modifications without a significant cost or loss of production time.
What Is Compression Molding?
Compression molding works differently than thermoforming and is often used when strength and detail matter most. It involves a multi-piece mold that surrounds a plastic charge that has been reinforced with fibers. You must heat both the mold and the charge to precise temperatures during compression molding.
The mold remains closed while the material cools, allowing it to chemically change into a hardened, finished product that you can remove cleanly from the mold.
Pros and Cons of Compression Molding
A major advantage of compression molding is that it can produce high strength products with relatively complex designs. This is the result of fiber reinforcement and the two-part mold used. Additional advantages include:
- High accuracy and consistent results
- Minimal waste
- No additional finishing is required
- Suitable for thicker parts
There are a few disadvantages with compression molding. For example, it is more complex than thermoforming, which results in a longer and more expensive setup process. Additionally, thermosets used in compression molding are frequently not recyclable, reducing the sustainability of the process. Finally, it is more time-consuming and costly than thermoforming.
Common Uses for Compression Molding
Compression molding is widely used to produce automotive, aerospace, and electrical components. Examples include:
- Computer peripherals such as keyboards
- Kitchen utensils and dishes
- Medical devices
- Plastic pallets and industrial bins
- Vehicle dashboards
Some thermosets have unique properties that make them well-suited for specialty applications. For example, polytetrafluoroethylene is nonstick, making it a great choice for cooking utensils.
What Are the Key Differences Between Thermoforming and Compression Molding?
When comparing compression molding vs. thermoforming, it is important to note several key differences between the two processes. The biggest difference between thermoforming and compression molding is in the type of mold and how it shapes plastic. The former uses an open mold to which you apply plastic sheets, while the latter uses a multi-part mold that closes around a heated plastic slug.
When removing a thermoformed part from its mold, you must trim and shape it during a finishing process. Compression molded pieces use a premeasured amount of plastic inside a closed mold, and come out in the finished shape.
On the surface, this results in excess material waste in thermoforming. However, materials used in the process are fully recyclable, so you can use trimmings repeatedly in new pieces. This is often not the case in compression molding.
Another key difference between thermoforming and compression molding is in the setup and forming speed. Thermoforming tends to have a much quicker setup time and a less complex process. The manufacturing process is also very quick compared to compression molding. These factors help to make it a very economical process for shaping plastic parts.
A final way that the two processes differ is in the complexity, thickness, and strength of finished products. Thermoforming is ideal for thin-walled plastic components with a moderate level of detail. Compression molding can accommodate thicker parts that require high strength.
Compression Molding vs. Thermoforming: Which One Is Right for Your Application?
Ready-Made Plastic Trays is a leader in thermoformed plastic trays for the medical, agricultural, pharmaceutical, and manufacturing industries. Our trays are ideal for storing and transporting large and small components. We use sustainably sourced plastics and recycle scraps from our thermoforming operations. Contact our team today to learn more about compression molding vs. thermoforming. Find out how our thermoformed trays can support your specific medical or manufacturing needs.
