Thermoformed plastics are crucial in nearly every industry. The thermoforming process shapes everything from the sleek aerodynamic shells of jet skis to the compact blister packs of allergy medications. Creating these finished parts involves molding flat thermoplastic sheets into 3D forms using heat and pressure.

The two primary production methods are vacuum forming and pressure forming. Let’s explore the fundamentals of both thermoforming techniques, how the machines work, and their wide range of everyday applications.

The Power of a Vacuum

Vacuum thermoforming, considered the simplest form of thermoforming, stands out as a highly favored method for producing plastic parts. The invention of the vacuum forming production method cannot be credited to a single person. However, modern day vacuum forming became mainstream in 1938 by C.B. Strauch with the invention of the roll-fed thermoforming machine.

The process involves four simple steps.

1. Heating Up the Canvas: The machine is fed a sheet of thermoplastic like PET or ABS. Radiant heaters soften the plastic, making it pliable and ready for transformation.
2. Fitting to a Mold: The heated plastic sheet is positioned over a mold of the desired final form. Next, the machine creates a seal between the sheet and the mold to trap the hot air.
3. Forming the Part: A powerful vacuum is applied beneath the plastic sheet. This vacuum sucks the softened plastic material down onto the mold, creating a precise replica of its intricate contours.
4. Holding its Shape: Once cool, the plastic retains its molded form. The final product is trimmed and removed, ready for its destined use.

Vacuum forming is best used in low- to medium-volume production runs. It’s a relatively simple and cost-effective process, capable of producing detailed parts like:

• Food packaging: Blister packs for pills, clamshell containers for fruits and vegetables, and drink cups are all common applications of vacuum forming.
• Point-of-purchase displays: Eye-catching displays for products in stores are often vacuum-formed.
• Prototyping: Due to its affordability and speed, vacuum forming is frequently used to create prototypes for product design.

Under Pressure

Pressure forming flips the process on vacuum forming, using air pressure differently. This alternative to injection molding uses compressed air instead of a vacuum. Developed after vacuum thermoforming, the pressure forming process was not widely used until the late 1950’s.

Here’s a look at the process:

1. Heating the Sheet: Just like vacuum forming, the plastic sheet gets heated until pliable.
2. Rotate the Sheet: The softened plastic sheet is flipped over the mold cavity.
3. Pressing Down: Compressed air pushes the plastic sheet down into the mold, forcing it to conform to every detail with much higher pressure than a vacuum can achieve. This results in sharper details and thinner plastic parts.
4. Solidify and Separate: Once cool, the thermoformed part is separated from the mold and trimmed for use.

Pressure forming is a champion for high-volume production runs and applications demanding intricate details. It can achieve near injection-molding quality finishes, making it suitable for complex, high quality parts like:

• Automotive parts: Interior trim panels, dashboards, and even some aerodynamic components can be pressure-formed.
• Medical devices: Sterile trays, disposable medical equipment housings, and even some prosthetic components often utilize pressure forming.
• High-detail packaging: Blister packs with complex compartments and intricate electronics packaging frequently rely on pressure forming for their precise features.

Choosing the Right Tool for the Job

So, which method works best? It depends on your needs!

• For cost-effective, low-volume projects with moderate detail requirements, vacuum forming is a great choice.
• Pressure forming is better suited for high-volume productions with superior detail and thinner parts.

Thermoformed plastics play a pivotal role in various industries, shaping diverse products. The vacuum forming and pressure forming methods are essential in this process, each offering distinct advantages. Both techniques offer a cost-effective way to create a wide variety of plastic products.