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Vacuum Forming

Vacuum forming is a popular manufacturing process used to create a variety of everyday products. It is a type of thermoforming process that uses heat to soften a plastic sheet, before forcing it over a mold via a vacuum. The part then cools and hardens into its final shape. Vacuum forming is popular due to its relatively low tooling costs, and quick turnaround times, making it ideal for prototyping and small-scale production.

In this article we look at vacuum forming, how it works, where it’s used, and the benefits and drawbacks of using it to manufacture plastic products.

What Is Vacuum Forming?

Vacuum forming is a manufacturing process that produces shaped plastic products by heating a sheet of plastic and using vacuum suction to pull it around a mold. The process uses various types of plastic, such as: polyethylene (PE), polycarbonate (PC), acrylonitrile butadiene styrene (ABS), and polyvinyl chloride (PVC).

Vacuum forming is widely used to manufacture various products, such as: plastic containers, consumer products, and automotive components. It is ideal for small-scale production, as its tooling costs and turnaround times are relatively low.

What Is Vacuum Forming For?

Vacuum forming is a manufacturing process used for producing plastic products for various applications. Thermoplastic sheets are heated and shaped against a mold using a vacuum, resulting in plastic components or products with relatively simple convex or concave geometries, such as: enclosures, packaging, or automotive parts.

How Is Vacuum Forming Used in Manufacturing?

Vacuum forming is used in manufacturing to create plastic parts. Vacuum forming is a cost-effective, versatile process with a fast turnaround time that is ideal for rapid prototyping and small-scale production. It is often used for creating durable custom parts in a wide variety of applications, from small custom components to large industrial parts and products.

How Does a Vacuum Forming Process Work?

The vacuum-forming process works by heating a sheet of thermoplastic so that it softens, before using a vacuum to pull the sheet over a mold, forming the final product.

The plastic sheet is clamped in place and heated by the vacuum-forming machine. The sheet must be heated uniformly to prevent defects in the final part. Various steps, such as: auto-leveling, pre-stretching, and plug assistance, then occur that form the plastic into the rough shape of the mold. A vacuum is then applied to suck out excess air and ensure that the plastic is formed completely around the mold. The plastic product is then cooled so that it hardens into the final shape, after which it is removed and put through post-processing steps such as: trimming, finishing, and decorating.

How Long Does the Vacuum Forming Process Take?

The vacuum forming process is relatively quick, taking a few minutes from start to finish. However, the cooling and post-processing steps especially can take much longer depending on the complexity and size of the product being produced.

How Does Vacuum Forming Differ From Other Molding Process Types?

Vacuum forming is a thermoforming process, which means that it uses heat to soften and form a plastic sheet into a product, using a mold. This is different from other processes such as injection molding which forces molten plastic under pressure into a mold to form products.

Vacuum forming uses a vacuum to draw the softened plastic sheet over the mold, which differentiates it from pressure forming, which uses pressurized air to push the sheet over the mold.

Is Vacuum Forming the Same as Thermoforming?

Vacuum forming is a type of thermoforming. Thermoforming refers to a family of manufacturing processes that uses heat to form a plastic sheet over a mold and allow it to cool and harden to manufacture products. The two main thermoforming processes are pressure forming, which uses pressurized air to force the plastic sheet over the mold, and vacuum forming, which uses a vacuum to force the plastic sheet over the mold.

What Molds Are Used for Vacuum Forming?

There are two types of molds used in vacuum forming:

Male (Positive) Mold: The male mold is convex-shaped. Male molds shape the inside contours of the plastic product.
Female (Negative) Mold: Female molds are concave, and shape the outside dimensions of the product.
Molds used in vacuum forming can be made from a variety of materials, such as: wood, aluminum, or plastic. This adds versatility to vacuum forming, to help compete with methods such as 3D printing which allow for rapid prototyping at low costs.

What Are the Plastics To Use for Vacuum Forming?

A variety of plastics can be used for vacuum forming. Each plastic has its characteristics that make it more or less suitable for certain applications. The types of plastics that can be used for vacuum forming are:

Acrylonitrile Butadiene Styrene (ABS): A thermoplastic with excellent impact resistance, formability, and weather resistance.
Polycarbonate (PC): Has high strength and impact resistance with good formability, but is relatively expensive.
Polyvinyl Chloride (PVC): Inexpensive, with good fire retardancy and chemical resistance. Thicker sheets have good impact strength and rigidity.
Acrylic (PMMA): Has excellent clarity, with medium to high strength. However, acrylics are relatively expensive.
Polyethylene Terephthalate glycol (PETG): Has excellent formability, with high impact strength.
Polystyrene (PS): Relatively inexpensive with good formability and medium strength, but it has low UV resistance. Polystyrene is not environmentally friendly and takes a very long time to decompose.
High-impact Polystyrene (HIPS): Has high impact strength while remaining relatively inexpensive.
Polypropylene (PP): Has good mechanical strength and chemical and thermal resistance.
High-density Polyethylene (HDPE): Has high strength-to-density, offering tensile strength with good chemical resistance and recyclability.

What Are the Applications of Vacuum Forming?

Vacuum forming is used for the production of a wide variety of products for many applications such as:

Packaging: Vacuum forming is widely used for making packaging for food and medicine, as well as enclosures for medical equipment and consumer goods.
Automotive: The automotive industry uses vacuum forming for a wide variety of products, such as electronics enclosures, various covers, and interior trim items.
Signage and Display: Vacuum forming is typically used for creating display cases, marketing displays, and signage.
Custom Industrial Parts: Vacuum forming’s flexibility and wide range of plastics make it suitable for creating small batches of custom industrial parts.
Prototyping: Vacuum forming is a good process for rapid prototyping and producing small batches of products at low cost. This makes it ideal for prototyping products before switching to manufacturing processes that scale better at high volumes.
Cosplay and Costume Design: Vacuum forming can be an efficient way to create rigid costume pieces, such as plastic plates of armor and other items.

What Is the Quality of Vacuum-Formed Products?

Vacuum-formed products are high quality but suffer from a few shortcomings. On the positive side, these products are generally strong and durable. However, vacuum-formed parts generally suffer from poor surface quality and wall thicknesses that are not uniform. Additionally, vacuum forming cannot produce high levels of detail on products.

How Long Do Vacuum-Formed Products Last?

Vacuum-formed products can last a long time, depending on the geometry, type of product, type of plastic used, and environmental conditions. Generally, the plastics used to create vacuum-formed products have good strength and resistance to chemicals and environmental conditions, often allowing them good longevity.

What Are the Advantages of Vacuum Forming?

Vacuum forming has the following advantages over other manufacturing processes:

Cost-effectiveness: Vacuum forming is a relatively low-cost manufacturing process, especially for small production runs.
Fast Production Cycles: Tooling for vacuum forming is fairly simple to make, and the vacuum-forming process itself is quick, allowing for fast production cycles.
Low Waste: Vacuum forming produces relatively little environmental waste.
Suitable for Small-Scale Production: Vacuum forming is fairly suitable for small-scale production and prototyping, compared to other manufacturing processes.
Versatility: The range of plastics available, as well as the speed with which tooling can be made and changed, makes vacuum forming a very versatile process.

What Are the Disadvantages of Vacuum Forming?

Vacuum forming has the following disadvantages over other manufacturing processes:

Material Limitations: Vacuum forming is limited to using thermoplastics, that is, plastics that can soften when heated, and harden once cooled.
Design Limitations: Vacuum forming is only suitable for relatively simple geometries.
Thickness Uniformity: Vacuum forming does not always produce part walls of uniform thicknesses.
High Initial Cost: The specialized equipment required to perform vacuum forming is very expensive, which could make it prohibitive for smaller businesses.
Surface Quality Issues: Vacuum forming frequently leaves surface defects, which require additional post-processing steps to correct.

Is Vacuum Forming Cheap?

Vacuum forming has high initial costs for the specialized vacuum-forming equipment, but is relatively cheap for tooling and part production. Creating molds for vacuum forming is cheaper than for similar plastic manufacturing methods, such as injection molding. Although it is cheaper than other processes, it may still be prohibitively expensive for smaller companies.

Part production is quite cheap, especially when considering overall costs for small-scale production, including prototyping costs. Because tooling is much cheaper than other processes, the costs of prototyping and refining designs are also much cheaper. However, when production scales past a certain point, processes like injection molding start becoming cheaper per product.

Is Vacuum Forming Cheaper Than Pressure Forming?

Generally, vacuum forming is cheaper than pressure forming for medium-size production runs. Pressure forming and vacuum forming are two thermoforming processes that are relatively similar. Both processes start with a sheet of plastic being heated and placed over a mold. With vacuum forming, the softened plastic sheet is drawn over the mold via a vacuum. With pressure forming, pressurized air is used to forcefully push the sheet over the mold. When the sheet has been drawn over the mold, it is left to cool and harden.

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