Introduction to Vacuum Forming

Several modern conveniences that we enjoy every day are made possible thanks to vacuum forming. Without this versatile manufacturing process, life-saving medical devices, food packaging, and automobiles might look very different. 

Read on to learn how the low cost and efficiency of vacuum forming make it a great option for commercial manufacturers, independent craftsmen, and DIYers alike.

In this guide, you will find an in-depth introduction to vacuum forming, including:

• An overview of the vacuum forming process.

• How to create molds for vacuum forming.

• The benefits and limitations of vacuum forming.

• How vacuum forming is used both commercially and independently.

• A short case study on vacuum forming and 3D printing.

What Is Vacuum Forming?

Vacuum forming is a manufacturing method used to shape plastic materials. During the vacuum forming process, a sheet of plastic is heated and then pulled around a single mold using suction.

Vacuum forming is used for a wide range of manufacturing applications, ranging from small custom parts produced on desktop devices to large parts manufactured on automated industrial machinery.

What are the Differences Between Vacuum Forming, Thermoforming, and Pressure Forming?

Thermoforming is a manufacturing process where a sheet of plastic is heated to become pliable, then shaped or contoured using a mold, and trimmed to create a final part or product. Vacuum forming and pressure forming are two of the most popular types of thermoforming processes. The main difference between vacuum forming and other thermoforming processes is the methods used to form the parts and the number and type of molds that are used.

Vacuum forming is the simplest type of plastic thermoforming, that uses one mold and vacuum pressure to obtain the desired part geometry. It is ideal for parts that only need to be precisely formed on one side, such as contoured packaging for food or electronics. 

There are two basic types of molds—male or positive (which are convex) and female or negative, which are concave. With male molds, the sheet of plastic is placed over the mold to contour the inside dimensions of the plastic part. With female molds, the thermoplastic sheet is placed inside the mold to form the outer dimensions of the part precisely.

In pressure forming, a heated sheet of plastic is pressed (hence the name) between two molds instead of being pulled into place around a single mold using suction. Pressure forming is ideal for manufacturing plastic parts or pieces that need to be more precisely shaped on both sides and/or require a deeper draw (they need to extend farther/deeper into a mold), such as appliance casings that need to look aesthetically pleasing on the exterior and snap into place or fit a precise size on the interior side.

How Does Vacuum Forming Work?

The step-by-step vacuum forming process works as follows:

1. Clamp: A sheet of plastic is placed in an open frame and clamped into place.

2. Heat: The plastic sheet is softened using a heat source until it reaches the appropriate forming temperature and becomes pliable.

3. Vacuum: The framework containing the heated, pliable sheet of plastic is lowered over a mold and pulled into place via a vacuum on the other side of the mold. Female (or convex) molds need to have tiny holes drilled into crevices so that the vacuum can effectively pull the thermoplastic sheet into the appropriate form.

4. Cool: Once the plastic has been formed around/into the mold, it needs to cool. For larger pieces, fans and/or cool mist are sometimes used to speed up this step in the production cycle.

5. Release: After the plastic has cooled, it can be removed from the mold and released from the framework.

6. Trim: The completed part will need to be cut out of the excess material, and edges may need to be trimmed, sanded, or smoothed.

Vacuum forming is a relatively quick process with the heating and vacuuming steps typically taking only a few minutes. However, depending on the size and intricacy of the parts being manufactured, cooling, trimming, and creating molds can take considerably longer.

What Are the Advantages and Disadvantages of Vacuum Forming?

Many manufacturers, designers, and other professionals choose vacuum forming because it offers a blend of design flexibility at a relatively low cost compared to other manufacturing methods. The benefits of vacuum forming include:

Affordability

Particularly for smaller production runs (250-300 units per year), vacuum forming is typically more affordable than other manufacturing methods, such as plastic injection molding. The affordability of vacuum forming is largely due to the lower cost for tooling and prototyping. Depending on the surface area of the parts being manufactured and the dimensions of the clamp frame, tooling for injection molding can cost two to three times more than the amount for tooling for plastic thermoforming or vacuum forming.

Turnaround Time

Vacuum forming has a faster turnaround time than other traditional manufacturing methods because tooling can be made faster. Production time for vacuum forming tooling is typically half as long as the amount of time required to produce tooling for injection molding. When 3D printers are used to create molds, turnaround time can be even faster. By increasing production process efficiency, vacuum forming enables businesses to get new designs in the hands of consumers faster. 

Flexibility

Vacuum forming gives designers and manufacturers the flexibility to test out new designs and build prototypes without massive overhead or lag times. Molds can be made out of wood, aluminum, structural foam, or 3D printed plastics, so they can be changed out and/or modified more easily compared to other manufacturing processes.

Dick Teal used vacuum forming to test out prototypes of John Deere snowmobile parts in the late 1970s and early ’80s, largely because it made tooling inexpensive. In the book, John Deere Snowmobiles: Development, Production, Competition and Evolution, 1971-1983, the authors explain that “a win-win situation was created with lower cost parts and less investment in manufacturing tooling.”

Vacuum forming also gives designers the ability to offer more color options and customization to customers. This gives many businesses the freedom to offer one-of-a-kind designs and produce custom products, such as dental retainers, to clients at an affordable price point.

Manufacturing Sterile and Food-Grade Materials

Manufacturers often use vacuum forming to produce food-grade containers and parts for the medical industry because it is compatible with plastics that can be sterilized or kept free of contaminants. For example, high-density polyethylene (HDPE) is frequently used to vacuum form food storage containers.

HDPE’s resistance to acidic compounds makes it a viable material for vacuum forming cleaning product containers as well. Medical-grade plastics are used in vacuum forming to create parts that can withstand sterilization processes and meet stringent medical and/or pharmaceutical guidelines.

The Limitations of Vacuum Forming

While vacuum forming offers a number of benefits, it does have some limitations. Vacuum forming is only viable for parts with relatively thin walls and simple geometries. The finished parts may not have a consistent wall thickness, and concave parts with a deep draw are difficult to produce using vacuum forming.

In addition, while vacuum forming is often the most cost-effective choice for small to mid-range production quantities, other plastic manufacturing processes can be more affordable for very large production runs.

Applications of Vacuum Forming

In modern society, it would be a challenge to get through an entire day without coming into contact with at least one part that has been made through vacuum forming. This manufacturing process is used to produce a wide variety of parts in a huge cross-section of industries, including:

Automotive and Transportation

Manufacturers use vacuum forming to create a number of pieces and parts in cars, buses, boats, and airplanes. In cars, everything from bumpers to floor mats, and even truck beds, are manufactured using vacuum forming.

See the world’s largest rotary vacuum forming machine at work.

Vacuum forming allows car companies to produce various color and detail options for consumers and gives designers the freedom to test out new prototypes in the development process.

Industrial

Manufacturers also use vacuum forming to produce many industrial crates and contoured containers for machinery.

See how acrylic signs or skylights are produced with vacuum forming,

Vacuum forming is a great manufacturing process for parts primarily used outside or ones that may come in contact with a heat source because industrial manufacturers can use a variety of flame-retardant and UV-resistant materials. For example, fire-retardant UL 94 V-0 polyvinyl chloride (PVC) and UV filtering acrylic (PMMA) can both be vacuum formed.

Packaging and Displays

If you buy a product that comes in plastic that’s fitted to that product’s design, there’s a good chance the packaging was made through vacuum forming. Razors, toothbrushes, electronics, makeup, and cleaning products often come in packaging that was vacuum formed.

This display tray was made using vacuum forming. (source)

In addition, marketing displays, point-of-purchase (POP) displays, and grocery aisle end cap fixtures are often manufactured using vacuum forming.

Food Packaging

Vacuum forming is often used for food packaging because it is compatible with food-grade plastic and can produce parts that are easy to sanitize.

These ornate chocolates were produced in vacuum formed molds and are resting in a clear vacuum formed tray. Read our guide to learn how to create custom chocolate molds with 3D printing.

Fruit containers, plastic egg cartons, and cracker trays are often vacuum formed.

Consumer Goods

The list of consumer goods made using vacuum forming is extensive. Manufacturers can create products, including children’s toys, travel accessories, and home decor, all using vacuum forming. 

Watch this video to see how hard-case luggage is produced using vacuum forming.

Medical

Medical parts and components that need to be antimicrobial or have resistance to contaminants are often manufactured through vacuum forming.

These vacuum formed trays secure medical components. (source)

This includes medical packaging, the pharmaceutical trays pills are packaged in, components of hospital beds, and MRI and CT machine exterior pieces.

Custom Parts and Special Effects

Vacuum forming is used in various industries to create custom and one of a kind parts, such as props for special effects.

Watch this video where Adam Savage explains how vacuum forming works and created a custom prop.

Types of Vacuum Forming Machines

Vacuum forming machines vary greatly in size, cost, complexity, and capabilities, which means independent designers, hobbyists, and commercial manufacturers of all skill levels can find the right fit. Vacuum forming machines range from small tabletop models that cost a few hundred dollars to industrial machines that cost thousands.

Here are a few examples of the range of vacuum forming machines available:

Industrial vacuum forming machines, such as industrial vacuum forming machines from Formech,  Ridat, or Belovac, are ideal for commercial applications and manufacturing large parts.

Tabletop vacuum forming machines, such as the Mayku FormBox that uses a standard vacuum cleaner to create a vacuum, are great for small businesses and at-home professionals.

DIY vacuum forming machines can also get the job done, and the building process makes a great educational project for kids and teens. 

When using a vacuum forming machine, remember to always follow the manufacturer’s instructions, wear safety gear, and only use the machine in a well-ventilated area.

Materials for Vacuum Forming

A variety of thermoplastics are compatible with vacuum forming manufacturing. Some of the most commonly used plastics include:

• Acrylic (PMMA)

• Acrylonitrile butadiene styrene (ABS)

• Polycarbonate (PC)

• Polyethylene (PE)

• Polyethylene terephthalate glycol (PETG)

• Polypropylene (PP)

• Polystyrene (PS)

• Polyvinyl chloride (PVC)

How to Create Molds for Thermoforming

Designers and manufacturers have multiple options to produce tooling for vacuum forming production. Flexibility is a major advantage of vacuum forming as a manufacturing method and each type of mold manufacturing process offers unique benefits and limitations. Here are a few of the most popular:

3D Printed Molds

Many businesses are turning to 3D printing to create molds for vacuum forming, because it offers a fast turnaround time and low price point, especially for shorter runs, custom parts, and prototype designs. 3D printing also offers unmatched design freedom to create complex and intricate molds. 

Read our detailed design guide for creating 3D printed vacuum forming molds or download our white paper to learn more about low-volume rapid thermoforming with 3D printed molds.

Modeling Clay Vacuum Forming Molds

Hobbyists, DIYers, and designers who want to sculpt a quick prototype can use modeling clay to create a mold for vacuum forming. However, it should be noted that molds made from modeling clay are unlikely to last more than a few uses. The heat involved in vacuum forming can cause clay molds to crack and break down rapidly.

In addition, it is important to give clay molds ample time to dry before using them for vacuum forming. All water needs to be fully evaporated or baked out of the clay so that it doesn’t obstruct the vacuum or damage any vacuum forming equipment.

Wood Vacuum Forming Molds

Wooden molds are considerably more durable than clay molds and can withstand several hundred to several thousand runs before deteriorating. Independent designers and commercial production lines alike use wood molds to create their products. Choosing a stronger wood, such as oak, can further increase the lifespan of a wooden mold. Wood molds are a great choice for thicker molds with minimal small details.

The limitation with this type of mold is that it will expand and contract slightly during the vacuum forming process. Eventually, this can cause a wooden mold to crack, splinter, or warp. However, wood is a great choice for many mold designs, and it is easy to craft designs using this medium with a few simple woodworking tools.

Cast Aluminum Molds

Aluminum molds are more expensive and take longer to produce (turnaround time may be anywhere from two weeks to two months) than other tooling options. Because of this, cast or machined aluminum molds aren’t used as often for short runs or prototypes, but they are frequently used for large-scale production. Industrial vacuum forming machines often incorporate aluminum tooling because these molds are considered to have one of the longest lifespans of the tooling options available for vacuum forming.

Structural Foam Molds

Structural foam molds can be a cost-effective alternative to cast-aluminum molds while offering comparable durability. Structural foam parts are lighter weight than cast aluminum, which can also be a large benefit in certain production lines.

Case Study: Driving Innovation with Vacuum Forming and 3D Printing

Ashford Orthodontics, the largest specialized orthodontic laboratory in the UK, is pioneering dental appliance manufacturing using a blend of 3D printing and vacuum forming. Using both of these manufacturing methods, they have cut down their overall production time compared to competitors and enabled clinicians to provide a faster and more seamless patient experience.

Ashford Orthodontics is able to deliver retainers and other appliances to the ordering clinicians just 48 hours after receiving digital scans, all thanks to their precisely orchestrated round-the-clock production cycle. When the lab receives a new order, they review the digital scans, design the tooth movements in dental CAD software, and then send them to the lab’s mighty fleet of 3D printers for overnight printing. The next day, the printed replicas of patients’ teeth are used as molds for vacuum forming clear dental retainers and aligners.

An Ashford Orthodontics technician uses a vacuum forming machine to produce a clear aligner.