What is Vacuum Forming?
Vacuum forming is one of the oldest and most common methods of shaping plastic materials into permanent objects or recyclable products. In a vacuum-forming process, thermoplastic sheets are heated until soft and then forced against the mold by a vacuum to form desired shapes.
Vacuum forming offers cost-effective forming of plastic materials for various applications, ranging from food packaging and protective covers to large automotive parts and agricultural components.
Throughout the 20th century, vacuum forming was adapted for use in plastic manufacturing and remains increasingly relevant even today.
What are the Differences Between Vacuum Forming, Thermoforming, and Pressure Forming?
Thermoforming is the process of heating plastic sheets to make them pliable, then shaping or contouring them with a mold and trimming them to create the final product. Both vacuum forming and pressure forming are types of thermoforming processes.
Vacuum forming involves a single mold and a vacuum pump. In this process, a vacuum is applied to the plastic sheet to place it properly into the mold of the desired shape. Vacuum forming is the simplest form of plastic thermoforming. Compared to injection molding and compression molding, vacuum forming costs less on molding and requires shorter production periods. It’s ideal for parts that only need apt molding on one side or partial moldings, such as packaging material for food and consumer goods.
On the other hand, pressure forming involves more than one mold. Instead of employing suction from the vacuum pump, the sheet is placed within one mold and then pressed by placing the other mold on top of it. This approach allows precise and visually pleasing molds, such as appliance and machine casings. Pressure forming is best for producing bezels, bases, covers, and equipment panels.
What are the Materials Used in Vacuum Forming?
- Acrylonitrile Butadiene Styrene (ABS)
- Acrylic (PMMA)
- Polyethylene (HDPE)
- Polycarbonate (PC)
- Polyethylene terephthalate glycol (PETG)
- Polypropylene (PP)
- Polystyrene (HIPS)
- Polyvinyl chloride (PVC)
The Process of Vacuum Forming
The first step is clamping, in which a plastic sheet is placed in an open frame and clamped into place, and for this, the clamps should be strong enough to control the material in position. Ideally, the clamp should hold and form the thickest material from 6mm with a single heater to 10mm with a twin heater. If the machine is automatic, all the moving parts must be linked and safeguarded to avoid accidents. You also need to make sure that there are no holes or tears in your material so that it will stay secure during this process.
One of the most important parts of the vacuum-forming process is maintaining a consistent temperature across the entire plastic sheet. Even minor deviations in temperature could ruin the output of the process.
Any type of material can be used in this process, but care must be taken to ensure that the sheet is evenly heated throughout its thickness. More sophisticated quartz heaters are available which have less thermal mass and allow for faster response times. Dual heaters are also recommended when molding thicker materials, as they facilitate more even heat penetration and faster cycle times. These heating techniques help ensure consistent heat in a precise and cost-effective manner.
In this step, a photo-electronic beam is projected into the gap between the heater and the plastic. When the plastic sheet sags and breaks the beam, a small amount of air is blown into the lower cavity to lift the sheet and prevent it from sagging. It works like the molten sheet sags, and the beam breaks, then a small amount of air is blown into the sheet to lift it without letting it fall back.
Once the sheet has been adequately monitored, a vacuum is introduced to aid in the formation of the film. To remove the air between the film and the mold, a dry vane vacuum pump is employed. The vacuum pump will then be turned on. The vacuum vessel is used in conjunction with a high-capacity vacuum pump on larger equipment. This enables the use of a two-stage vacuum, ensuring the quick production of the heated film.
Plastic molds are transferred to a cooling process before de-molding. Cooling is necessary because it gives the molten plastic time to settle. Otherwise, it will be deformed. Fans are installed in the machine for cooling purposes, supporting the cooling process. In addition to the fan, the fan is also equipped with nozzles that spray cold water directly onto the plastic film, which together with the fan speeds up the cooling process by 30%. To aid in the cooling process, temperature controls are in place to regulate the cooling temperature of these particular polymers as they come off the machine. When the formed plastic sheet has cooled, it is removed from the machine for the next step.
After cooling, the molded sheet is trimmed with the help of different types of trimmers. Cuts, holes, or slits are formed within the sheets to meet the requirements of the product. Finishing includes decoration, ornamentation, or strengthening. Different products require different trimming procedures. That depends upon many factors like size, cut type, the thickness of the material, etc.
Today, it would be hard to go around without touching at least one vacuum-formed product. Vacuum forming provides manufacturing of a wide variety of products in various fields, including:
Vacuum forming has become a pivotal part of the production of interiors and exteriors of various types of automobiles. From lightweight parts of various aircraft to agricultural vehicles, cars, and trucks, vacuum forming offers affordable solutions for them all. It broadly benefits manufacturers and buyers to save money without sacrificing quality.
Vacuum forming has several uses within industrial sectors. Many industrial boxes and formed containers for machines are made using the vacuum forming technique. Besides that, it is also a great manufacturing process for parts mainly 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.
The plastics that are used are also excellent for packaging. They are not only cost-effective enough for huge production lines, but they are also sturdy and hygienic, with a wide range of sizes and form options. Everything from the food and beverage packaging that lines supermarket shelves to the containers used for medical supplies, cleaning items, health and beauty products, and more is likely to have been created using a vacuum-forming technique. Signs and billboards are also made using vacuum-forming techniques in display centers. Acrylic is also used for mobile phone covers.
Because of its capacity to generate bespoke goods and its long-lasting quality, vacuum forming is an excellent approach for making store displays. Vacuum forming has recently begun to be employed for creative reasons, particularly in the retail and marketing industries. Given their potential for beauty and eye-catching abilities, it’s no surprise that vacuum-forming plastic has become a popular method of making those wonderful displays you see when you’re out and about.
Vacuum-formed displays, from the grocery shelf to the cosmetics counter, allow each displayed product to have its own display space, in the shape of a pot, channel, or cutout. Vacuum-formed retail displays are frequently developed with the display goods in mind, allowing them to be custom designed to fit the object exactly.
Vacuum forming can be used to create safety guards, safety eyewear and visors, and even riot shields. Making things like this out of a single piece of plastic improves their durability. This is, of course, a tremendous advantage in these applications.
Vacuum forming is commonly used to make medical parts and components that must be antibacterial or resistant to contamination. This comprises medical packing, pharmaceutical trays in which tablets are wrapped, hospital bed components, and MRI and CT equipment external pieces. Thermoformed trays, blister packs, clamshells, CT scanner components, MRI machine components, X-ray machine components, carts, trays, heating pads, operation kits, vacuum-formed trays, etc., are a few examples of medical products produced using vacuum forming.
Vacuum-forming plastic is used to make a variety of home goods. Consider your own home: the plastic bathtub in your bathroom, the plastic cutlery and appliances in your kitchen, and the garden equipment stored in the shed. These are all popular household items that are used daily and were made through the vacuum-forming method.
As an alternative to glass, vacuum forming is becoming more common.
Vacuum forming offers several benefits and advantages over other plastic-forming processes, which include:
Because vacuum forming is faster than other traditional manufacturing methods, it has a faster turnaround time than injection molding. Vacuum forming tooling can be made in half the time required for injection molding. Using 3D printers to make molds for vacuum forming can further reduce turnaround time even more. Vacuum forming allows firms to get innovative designs into the hands of customers faster by boosting the efficiency of the manufacturing process.
Vacuum forming is a fast and efficient way to mass-produce plastic containers. You can ramp up production quickly and economically if you use a lightweight tool. This makes vacuum forming an excellent choice for product development, where incremental improvements are likely.
Vacuum forming can be a very cost-effective method of production. The decreased cost of tooling and prototyping contributes significantly to the affordability of vacuum forming. Tooling for injection molding can cost two to three times as much as tools for plastic thermoforming or vacuum forming, depending on the surface area of the pieces being created and the dimensions of the clamp frame. However, it is important to note that the cost of vacuum forming will still be determined by a variety of factors, including the design and materials required for your product.
Designers and manufacturers can use vacuum forming to test new concepts and prototypes without incurring big costs or lag times. Because of its capacity to produce thin sheets, vacuum forming can construct complicated designs that would be extremely difficult or impossible to fabricate using conventional processes. For example, you could use vacuum forming to create a curved object for a sculpture, or you could use it to create an object with no straight edges at all, such as a phone charger whose shape is determined by how air flows through the socket when charging your phone.
Vacuum forming is a fast, inexpensive way to make prototypes. It’s ideal for small-scale production runs and agile prototyping. There’s no reason why you can’t use it for large projects too, but it does come into its own with smaller jobs.
Mass production, in various forms, has been a reality since the industrial revolution. Vacuum forming uses one tool per job, but it offers a huge level of versatility in how it uses tools—for example, basic templates can be customized into new shapes and sizes. They can also be updated to reflect new developments in their area of use.
Because vacuum forming is suitable with plastics that can be sterilized or maintained free of impurities, manufacturers frequently employ the technique to produce food-grade containers and parts for the medical industry. High-density polyethylene, for example, is widely used to vacuum manufacture food storage containers.
With its resistance to acidic substances, HDPE is also a viable material for vacuum-forming cleaning product containers. Vacuum forming is the best approach for sterile and food-grade materials such as plastic food containers and medical equipment. Vacuum-formed items are the best since they can be sterilized and used for a long period while remaining clean and germ-free.
At DITAI, our vacuum-forming production engineers and specialists can design, develop and produce all elements in-house, from design and tooling/molds to forming and CNC cutting, while maintaining unparalleled quality. To learn more about our vacuum-forming products, you can contact us here.