Vacuum Forming Plastic: The Quiet Start Of A Powerhouse Industry

Odds are good that you will purchase some kind of consumer product today. It might be anything from a package of new AA batteries to a toy for your child. Whatever the item is, it will likely be ensconced in vacuum sealed plastic. Indeed, a large majority of today’s products all over the world are sealed and made sale-ready in some form of plastic packaging.

Have you ever wondered how companies wrap products in such form-fitting dress? The process is called thermoforming, which is a plastic molding manufacturing technique that heats thin plastic sheets to a pliable temperature, at which the plastic is easy to manipulate and form over a mold. Vacuum forming is a simplified sub-process of thermoforming, where heated plastic is stretched onto a mold and forced against the mold via a vacuum force.

Vacuum Forming’s Inspiration

Innovative people have used natural rubbers and cellulose to accommodate many different life needs for thousands of years. The development of synthetic plastics, however, didn’t really get its start until the 19th century. Celluloid was the world’s first highly-usable plastic, developed by inventor John Wesley Hyatt. His cellulose creation was an improved version of parkesine, a plastic created by Alexander Parkes, one of Hyatt’s English inventor colleagues. In addition to improving celluloid, Hyatt also patented the first injection molding machine.

When it comes to vacuum forming, we salute a trio of innovative minds. The first thermoforming machine patents were filed by H.L. Helwig of the Rohm & Hass Company, and R.E. Leary, an engineer at DuPont. These crafty inventors employed a variety of methods to heat plastic, such as convection and radiant heat, or using hot oil or steam. In 1947, along came G.W. Borkland from Indiana, who filed a patent for a “vacuum forming” machine. Borkland would go on to make many other improvements in the world of vacuum thermoforming, and his influence introduced the world to a new form of product sealing.

Vacuum Forming In Action

The vacuum forming concept is relatively simple: A vacuum is used to produce an even distribution of pressure on a material’s surface to allow the material to conform to the shape of a mold. Thin sheets of plastic are fed into a vacuum thermoforming machine and heated until they are malleable, and then forced onto the mold in a very precise process.

In addition to sealing everyday items, vacuum sealing is also used to create intricate and incredibly strong products such as road signs, boat hulls, and an array of protective covers.

The Origin Of Vacuum Forming Molds

While most of us are unfamiliar with vacuum forming, the process is responsible for the packaging surrounding millions of everyday products. Vacuum forming is actually a simplified version of thermoforming, in which a thin sheet of plastic is heated to a high temperature so the plastic can be stretched onto a mold by use of a vacuum.

The process offers a wide range of benefits to manufacturers with its high-volume capability and simplicity of storing large quantities of plastic sheets. High quality, high volume, and low cost are all attractive to customers as well.

Vacuum Forming At Work

Left to its own devices, vacuum forming is only capable of producing shallow products such as plastic signs, covers, and product packaging for small items. Ubiquitous blister packs and clamshell packaging use this process.

To obtain three dimensions, manufacturers combine vacuum forming with line bending equipment, making it possible to create everyday products like TVs, speakers, point of sale displays and plastic containers. In fact, vacuum forming has proven to be highly adaptable and is used today for a variety of display marketing and promotional items. It’s fast, low cost and easy, making for reliable turnaround.

Vacuum Forming Mold Material

The first step of the vacuum-forming process is to create your mold, also known as “tooling.” This is usually the most in-depth step of the process. The most commonly used plastic in vacuum forming is acrylonitrile butadiene styrene (ABS). Other plastic will work, but keep in mind that the thicker the plastic is, the more heat and vacuum pull you need.

There are several ways to create vacuum forming mold; the one you use ultimately depends on your end goal, available resources, and how long you need the tool to last. Molds used in vacuum forming are made of an array of materials including: cast, plaster, clay, resin, wood, aluminum, and polyurethane.

Here is a look at the most common mold material options:

  • Wood or MDF. Best for smaller production runs or teaching the basics of the technology as opposed to producing usable parts.
  • Cast Resins. Ideal for larger production runs because resin tools can be sanded to a very smooth finish.
  • Cast Aluminum. Cast aluminum tools may require extra finishing but the end product is very strong and this option is ideal for large production runs.

Other mold materials can also work well, depending on your project needs. To determine which mold is best suited to an application, you’ll want to analyze the inherent details and select a mold material that results in the highest quality with most efficient resource use.

Getting to Know Forming And Molding

In the manufacturing process of plastic, two common techniques are often used to form the plastic into a desired shape: molding and forming, or thermoforming. Each process requires the manipulation of molten plastic, followed by a setting period. Each technique offers unique features and benefits, making them ideal for specific applications.

What’s the Difference?

Several key differences separate plastic molding and thermoforming. Each process can accommodate different production volumes. Plastic injection molding is generally used for large, high-volume production runs, while thermoforming is used for smaller quantities. Another variable is the molding process produces finished pieces, while thermoforming often requires secondary finishing processes.

Injection molding can accommodate difficult geometries and tight tolerances, making it great for creating smaller, intricate, and complex parts. Conversely, thermoforming accommodates simpler geometries and larger tolerances, which works well for larger parts with more basic designs.

Molding can be used for a wide variety of plastics, whereas thermoforming is more limited in terms of what types of materials can be worked.

Thermoforming

Simply defined, thermoforming is the process of applying a heated plastic sheet to the surface of a mold. Common types of thermoforming are vacuum forming and pressure forming. Depending on the scope of a project, thermoforming offers several distinct advantages:

  • Lower tooling costs
  • Speedy product development
  • Ample color and texture options
  • Adaptable and easy to adjust
  • Good choice for small production quantities

Molding

Injection molding and related processes require significant upfront engineering to create detailed molds. Molds made from stainless steel or aluminum are injected with molten liquid polymers at very high pressure, and later cooled to create a final plastic product. Advantages of molding include detailed tooling and mold options, precise processing for large product volumes, and efficient material use.

Types of Molding

Casting: A basic molding process. Plastic is heated to a fluid state and then transferred into a mold to cool.

Injection Molding: Used to create three-dimensional products. Plastic is melted in a hopper and the injected into a chilled mold.

Blow Molding: Plastic is heated until molten and then injected into a cold mold. Air is blown into the plastic to form it around the mold.

Compression Molding: Molten plastic is poured into a mold and a second mold squeezes the plastic into the desired shape.

Which Process is Best?

For some industries and applications, both processes may be used to manufacture plastic parts. Many industries select a specific method based on project need. To determine which process is best for you, carefully assess your project’s characteristics and requirements.

The Basics Of Thermoplastic Production

Thermoplastics are one of two main types of plastics on the market today (with thermosets comprising the other major category). Thermoplastics are unique in that their polymer bonds allow them to be heated and remolded indefinitely, making them highly recyclable, while thermosets feature permanent chemical bonds that harden after a single heating, more or less preventing heating and remolding.

There are several different types of thermoplastics. You’re probably familiar with thermoplastics like acrylic, nylon, PVC, and Teflon, for example. How are the plastics in this category made? Are there differences between how one type of thermoplastic is produced versus other varieties?

How Are Thermoplastics Made?

By their very nature, thermoplastics can be heated and remolded again and again, depending on their chemical makeup, which means they can be “made” in a variety of ways. These plastics have to come from somewhere, however, and they typically start as components that are combined to create granules, which can be manipulated with heat and molded into products.

Thermoplastics can come from both natural and synthetic sources. For example, some thermoplastics are made from cellulosics, or cellulose fibers found in wood and cotton. Nylon, acrylic, and polyester come from petrochemicals, including petroleum- and plant-based materials.

Granules are created when the base material is heated, desired additives like dyes are mixed in, and the mixture is cooled and separated into small particles that are easy to package and transport. From there, manufacturers can reheat granules, add desired chemicals, and mold them in different ways to create a wide range of products.

Differences In Thermoplastic Manufacturing

There are a few different ways thermoplastics can be molded into desired shapes or configurations, including extrusion, injection molding, and thermoforming.

  • Extrusion involves passing heated thermoplastic material through a die, or steel disk, before pressing and cutting it to create desired shapes.
  • Injection molding, as the name implies, involves injecting heated thermoplastic material into a mold and allowing it to cool and harden into the prescribed shape.
  • Thermoforming involves heating sheets of thermoplastic and forming them in or over molds, allowing them to cool, and then trimming away excess material.

In Conclusion

The type of production used may depend on several factors, including the type of thermoplastic being used, the product being created, and the preferences of the manufacturer. Ultimately, thermoplastics that remain unpolluted by chemical additives have the best chance of being heated, remolded, and made into new products during the recycling process.

An Introduction To Twin Sheet Thermoforming

To those outside the industry, thermoforming is as foreign as alien life on another planet. Ironically, this process is used to manufacture hundreds of everyday products including fitness equipment, control panels, spa shells, commercial display stands, and much more. Another fascinating element of thermoforming is that, thus far, it is not widely known or understood, even within the industry.

While vacuum forming and pressure forming have been an accepted part of the industry for years, twin sheet thermoforming is a relative newcomer. This is a technically challenging process, but can be simply defined as vacuum or pressure forming two plastic sheets simultaneously, using two molds on separate platens, or presses. The platens are then brought together while maintaining pressure while air is injected between the sheets. Resulting pressure ensures all features of the mold match and are then ready for manufacturing and finishing. At the heart of twin sheet thermoforming is plastic sheeting, but how are those plastic sheets formed? We can find the answer in the types of plastic used.

How Is Plastic Sheeting Formed?

Plastic sheeting is typically made by film casting; squeezing molten polymer through a very narrow opening. An extruder pushes the lava-like plastic through the opening and the film drifts out in a curtain, falling onto rapidly-moving rollers that cool both sides of the film.

Types Of Plastic Used In Twin Sheet Thermoforming

One strong advantage of twin sheet formatting is that most any thermoplastic can be used in the process, including ABS, styrene, TPO, polyethylene, TPU, polypropylene, polycarbonate, and PETG.

Some of these materials, however, can throw a wrench in the manufacturing works, particularly if the plastic sheet is too thin. For example, polycarbonates and PPEs like Radel and Ultem quickly lose their heat, requiring fast and accurate welds on joining surfaces. With such a short window of application time, quality and product integrity can become an issue.

The best plastics candidates in the twin sheet process have proven to be TPO and polyethylene.

Thermoforming Companies Are A Unique Breed

In today’s manufacturing world, comparatively few thermoformer companies have the technical capacity for twin sheet thermoforming. This dearth of options, however, will subside as the flexibilities of twin sheet forming are very attractive to engineers, including the ability to combine more than one resin type, which then boosts weld strength with less potential for warping.

In Conlusion

The next time you are out and about or shopping for, say, new fitness equipment; consider that many of the products you see were created through the little-known process of twin sheet thermoforming.

What, Exactly, Is A Living Hinge?

You’re no doubt familiar with hinges, which add convenience to our daily lives. Just look at any door, from your front door to cabinets in your home, and you’ll find hinges that allow these portals to open and close with ease.

Of course, these hinges are made of separate materials, typically sturdy metal, and screwed into place to connect doors to framing. What if, instead, the hinges were part of the door and frame materials themselves? It may sound crazy, but this is the basic premise behind a living hinge.

While you’re not likely to find living hinges on wooden doors, there are likely several products in and around the average home that employ this handy technology. Here’s what you should know about living hinges and why they’re so important.

What Is A Living Hinge?

Whereas traditional hinges are made from a separate material and attached to surfaces to create a stable and lasting open/close mechanism, a living hinge is made from the same material as the pieces it connects and is an extension of them, creating a seamless transition from a base to an opening/closing part.

How is this possible? The hinged portion of the material is much thinner than the parts it connects, allowing for a degree of flexibility without breaking. Often, this process is used with plastics—just look at the lid of your shampoo bottle—but it can also be applied to a diverse range of materials, such as paper, cardboard, wood, and more.

Typically, such hinges used in everyday products are designed using sophisticated technologies like computer aided design (CAD) software and produced via injection molding (for plastics), although other methods are sometimes used. The growth of 3D printing has created a new, cheaper avenue of production, but the quality simply isn’t as good as traditional methods.

Benefits Of Living Hinges

There are several reasons why manufacturers might choose living hinges over the alternative. For one thing, they’re easier and less expensive to produce, since they’re made from the same materials as the surfaces they connect and they’re already attached.

They also tend to create a more streamlined aesthetic, and you won’t have to worry about wear as much as you would with separate hinges that are attached to surfaces. Plus, a living hinge is designed to bend, with plenty of flexibility; so no matter how much you open and close a door or lid, it shouldn’t break.

In Conclusion

A living hinge made from thinned material connecting two surfaces isn’t ideal for every hinged application, but with easy and inexpensive manufacturing, flexible and durable construction, and a sleek appearance, living hinges are great options for many manufactured products.

Getting To Know Plastic Thermoforming And Vacuum Forming

In the world of plastic manufacturing, everyday terminology is thrown around like confetti and it can be difficult to discern the nuances of specific processes. These processes are described by “plastic thermoforming,” “pressure forming,” and “vacuum forming.” All three are similar in scope, but there are important differences to understand. Employing the use of the wrong one in manufacturing could lead to disaster, and marketing an errant term can be equally troublesome. Let’s look closer at these common industry terms.

Plastic Thermoforming

This term has become a generic label applied to the plastic manufacturing process involving the heating of a thermoplastic sheet to a specific temperature and applying pressure to mold into a three-dimensional shape. When the plastic has cooled, it can then be trimmed and formed into its final product form. Thermoforming machines are large, highly-engineered and complex, and typically more expensive to purchase and operate.

Thermoforming is generally cost-effective and allows the freedom to accomplish whatever you need. In addition, the cooling time for the plastic is quick, making this a great choice when producing a high volume of quality products. Thermoforming and vacuum forming can both be used to create engaging decorative looks.

Vacuum Forming

Vacuum forming is a common thermoforming manufacturing process. Vacuum forming applies a vacuum energy to transform a heated plastic sheet into a pre-planned shape. The softened sheet in placed over a mold and then sucked down onto its surface. The sheet is then removed from the mold, cooled, and prepped for finishing. Vacuum forming allows more accurate replicating of the mold shape, which boosts the end quality.

Vacuum forming can be cheaper than thermoforming, due to lower operating machine costs. It is also a straightforward process that takes comparatively little time. Custom vacuum forming can also be tailored to suit specific needs and project parameters.

Advantages Of Thermoforming

Compared to related processes, such as injection molding, thermoforming boasts several key advantages:

  • Lower tooling costs
  • Shorter tooling lead time
  • Efficient prototypes means faster product development
  • Adaptive to evolving customer needs
  • Integrated process with virtually limitless flexibility
  • Wider design scope

Products Made Via Thermoforming

Many common products are made wholly or partly through the thermoforming process, including:

  • RVs
  • Pools and spas
  • Fitness equipment
  • Store displays
  • Medical and office equipment
  • Scientific instruments
  • Control panels for an array of product
  • Product housings and covers

In Conclusion

Thermoforming prepares your company to meet its particular market goals and, in the end, you can spend more time making product sales and less time waiting for it to clear the manufacturing steps.

Can Thermoplastics Be Recycled?

When it comes to thermoplastics, you might not be clear on whether they can be recycled, as there is some confusion about the difference between thermoplastics and thermosets, especially when it comes to recycling. What’s the truth? Are thermoplastics recyclable, and how do they differ from thermosets?

Can Thermoplastics Be Recycled?

The simple answer is yes. Thermoplastics are a type of plastic that become soft when heated, so they can be molded, and then cooled to restore their rigid structure. Thermoplastics are frequently used to create items as diverse as pipes, insulators, adhesives, and more, and many of these products can be recycled and turned into new, usable products. What makes thermoplastics recyclable is that they can easily be reheated and remolded for new purposes.

The polymers found in thermoplastics are strong, but feature weak bonds. This is what allows them to be reused indefinitely, which is why these materials are highly recyclable. Different applications can cause plastics to downgrade when they are recycled, making them less recyclable with every phase of reuse, but this is typically related to additives, not the polymers themselves. Chemical additives are often designed to strengthen the bonds of thermoplastics, making them harder to melt and therefore limiting their potential for reuse.

The Difference Between Thermoplastics And Thermosets

There are essentially two main categories of plastics: thermoplastics and thermosets. What sets them apart? Primarily the way their polymers are linked. As noted above, thermoplastics feature weak bonds that allow for easy reheating and molding of the plastic.

Thermosets differ in that they feature permanent chemical bonds that cause them to retain their shape, even when reheated. This makes for strong products, but it is difficult to break down such plastics for the purposes of recycling and reuse. Thermosets cannot be heated and remolded like thermoplastics. They are brittle, but heat-resistant, which is why they’re frequently used for high-temperature applications, such as insulating materials.

The particular difference between thermoplastics and thermosets lies in the bonds linking polymers. In a sense, thermoplastic bonds could be described as ties that can be cut and retied, while thermoset bonds are more like a strong weld that is virtually unbreakable.

In Conlusion

Knowing which types of plastic can be recycled isn’t easy, and there are factors beyond the polymers themselves that can affect recyclability. One thing, though, is entirely clear: thermoplastics are recyclable. Thermosets cannot be recycled in the same ways, but this doesn’t necessarily preclude some form of reuse.

Thermoplastics 101: What Are They?

Most of us encounter all kinds of plastic products in our daily lives, from plastic bags, to water bottles and food containers, to sports equipment, to PVC pipes, to insulative products, to adhesives and sealants, and so much more. Plastics are used in product packaging, building construction, electronics, transportation, and nearly every industry. Versatile, lightweight plastics are used for all kinds of applications, adding convenience and cost-effectiveness to many areas of modern existence.

What are plastics? Broadly speaking, plastics are substances made from polymers; there are two main categories: thermoplastics and thermosets. What, exactly, are thermoplastics? What separates them from thermosets? What are the different types of thermoplastics and how are they used? Here’s what you should know.

Characteristics Of Thermoplastics

To understand thermoplastics, you must first understand polymers, which are made up of linked chains of monomers. What separates one plastic from another is how those monomers are linked. Thermoplastics are characterized by weak links. What does this mean?

This property is what makes thermoplastics so versatile. Because of these weak links, thermoplastics can be heated, remolded, and cooled to resume a strong and rigid structure. In other words, thermoplastics could be recycled and reused indefinitely (barring the use of chemical additives intended to strengthen bonds, which can reduce their ability to be heat and remolded).

Thermosets, on the other hand, feature permanent chemical bonds that make for strong and durable products, but preclude the potential for heating and remolding the plastics, limiting recyclability.

Different Types Of Thermoplastics

Thermoplastics and thermosets are broad categories of plastics, and there are several types within each category. Some of the most common thermoplastics include:

  • Acrylic
  • Nylon
  • Polyethylene
  • Polypropylene
  • Polytetrafluoroethylene (Teflon)
  • Polyvinyl Chloride (PVC)

There are several other types, but these subcategories of thermoplastics are responsible for a wide range of familiar products. Acrylic, for example, can be used for windows, aquariums, and a variety of other purposes. Nylon is the basis for hosiery, carpet fiber, guitar strings, and more. Polyethylene is found in everything from milk containers to machine parts.

In Conclusion

Thermoplastics are all around us, in a variety of forms, and they can be made stronger and more permanent with the use of additives, although these modifications may impact the ability to recycle certain products.

Which Plastic Is Used For Thermoforming?

There are a variety of common thermoforming materials and each have their own strengths and drawbacks. Which plastic will be the best for your application really comes down to the application itself. Some of the common factors to take into consideration can include:

  • Stiffness. How rigid does the final plastic product need to be in order to fulfill its intended use?
  • Hardness. How hard does the final plastic product to be in order to withstand any chipping, cracking, or abrasions that may come along with its intended use?
  • Impact Strength. How much impact will the final plastic product need to endure before it finally breaks?
  • Heat Deflection. How much heat will the final plastic product need to withstand before it begins to distort?
  • Tensile Strength. How much resistance will the final plastic product need to handle before it is pulled apart?
  • Forming Range. How hot does the plastic sheet need to be before it can be thermoformed?

There are more, of course, but you get the idea. If you haven’t already done so, you’ll want to make note of these types of needs. Once those needs are established, they are compared to a variety of different plastics to find a fit that best matches your needs and budget. Below are some of the most common plastics used in thermoforming, as well as some basic characteristics of each.

  • Acrylonitrile Butadiene Styrene (ABS). One of the most commonly used thermoplastics. It features a good impact resistance rating. It’s available in a host of different colors and flame-retardent grades (UL94-V0).
  • High Density Polyethylene (HDPE). The advantages of HPDE are that is it resistant to cold temperatures, as well as being very resistant to impact and chemical interaction. The tradeoff is that it offers less dimensional stability than some other thermoplastics.
  • High Impact Polystyrene (HIPS). Its low cost makes it a popular option. That it is easy to form and comes in quite a few colors doesn’t hurt anything either.
  • PMMA/PVC blend (KYDEX). Another popular option, KYDEX is impact-resistant and chemical-resistant. It comes in a lot of colors and flame-retardant grades (UL94-V0). Combine all of this with a highly-cosmetic appearance and it makes for a great general-purpose thermoplastic.
  • Polycarbonate (PC). Being a clear material limits its use in certain applications, but its resistance to high temperatures and good impact strength continues to make it a popular choice.
  • Polyetherimide, Ultem (PEI). This autoclavable material has an amber-colored appearance and is quite resistant to high temperatures.
  • Polyethylene Terephthalate Glycol (PETG). This clear material forms well and is impact resistant.
  • Polymethyl Methacrylate, Plexiglass (Acrylic). It can come as a clear material or in a number of different colors. Acrylic is really resistant to abrasion and easy to fabricate. Impact-resistant grades are available, as well.
  • Polypropylene (PP). Very similar to HDPE, PP is chemical-resistant, as well as being resistant to higher temperatures and impact. Like HDPE, the flipside is that it is not as dimensionally stable as some other materials.
  • Polyvinyl Chloride (PVC). Valued because it is rigid and impact-resistant, PVC also comes on flame-retardant grades (UL94-V0). PVC, however, often has a limited availability.
  • Thermoplastic Polyolefin (TPO). From a fabrication perspective, TPO can be somewhat difficult to form, particularly if we are talking about deep-draw shapes. That aside, its excellent impact resistance and available high-gloss finish makes it an ideal material for outdoor use.

In Conclusion

A host of different thermoplastics can be used for your next project. To find the right one, start by assessing the needs and environment of your final product and work backwards from there to find a plastic with the right qualities for you.

To learn more about the best plastic to suit your plastic thermoforming needs, give Spencer Industries a call at 1-800-467-4561 today!