From making food containers to producing blisters and car parts, the thermoforming machine finds use in many different sectors. It’s no surprise, then, that many companies are looking to invest in one (or add it to their arsenal). But what’s the machine all about? Let’s start with a comprehensive look at the typical thermoforming machinery.
What is a Thermoforming Machine?
A thermoforming machine is a piece of equipment used for the manufacturing process known as “thermoforming.” This is a process where thermoplastic or other material is heated to a point where it softens and can be formed into different shapes.
Usually, some kind of vacuum pump, air pressure, or a mechanical form is used to force the thermoforming plastic on/into a mold. Once in place, a clamping mechanism holds it together while it cools and hardens, normally with the aid of a cooling system.
The purpose of a plastic thermoformer is to produce products such as trays, blisters, containers, and bigger like automotive components and signage structures. These are used in a wide range of industries including manufacturing, health, transport, and horticulture.
Thermoforming is a major production method in today’s world, especially when it comes to shaping plastic to the desired shapes. In order to help you grasp the purpose of a thermoformer, well start with the thermoforming definition. Here’s a brief description of what’s involved in this technology.
What is thermoforming?
Thermoforming is the heating of thermoforming polymers or other material to its forming point (varies depending on type of plastic), but not enough to melt it. Once hot enough, the plastic is drawn tightly against the mold by applying vacuum or vacuum and air pressure to form it to the shape of the mold.
Types of Thermoforming
Thermoforming is usually either thin or thick-gauge thermoforming. Thin-gauge thermoforming uses thin plastic sheets and mostly produces disposable or recyclable plastic products. Thick-gauge thermoforming utilizes thick plastic and is normally suited for permanent-use products. The techniques used in thermoforming are: vacuum forming, pressure forming, and mechanical forming.
- Vacuum thermoforming– air is drawn from the area between the plastic sheet and the thermoforming mold. This causes the thermoplastic to be drawn over or inside the mold to take on the required shape. The technique is called vacuum forming, and the machine that utilizes it a vacuum thermoformer.
- Pressure thermoforming– this means vacuum thermoforming but with the addition of positive pressure above the mold, usually in the order of 50-100 Psi. The air helps to push the plastic against the mold. Pressure forming creates products with greater tolerances and textures.
- Mechanical thermoforming forming– mechanical forming uses a second mold to shape the plastic sheet in another mold. Mechanical forming is also called plug assist thermoforming and applied in making twin-walled products, in high-depth thermoforming, or when forming pipes and other closed products.
During the thermoforming process, the heated plastic must take a specific shape. This shape is made possible the mold. These molds are made from a variety of different materials through casting, machining, or even 3-D printing. Common thermoforming molds include:
- Reinforced plaster
These are the raw materials used in the thermoforming process. In a plastic thermoforming machine, the materials options are wide and varied. The type used depends on the use of the particular product. Common thermoforming materials are:
- ABS– automotive trim, the housings of electronics, refrigerator liners, and a wide range of cases
- Polypropylene– packaging products, seats, products for lab use, electrical hardware
- Acrylic– household products, bathtubs, automotive trim, roofing products
- Polyesters– packaging products like clamshells, pallets, and other products
- Polystyrene– food or drink containers, toys, housings of electronic goods, advertising structures, refrigerator liners
- Polyethylene– water pipes, thermoformed bottles and other contains
- PVC- pipes, signage products
Thermoforming Machine Parts
A simple thermoformer is a single-station device with all thermoforming processes happening in one place. In a complex unit, like the type shown in the thermoforming machine diagram above, different parts are involved. These include:
- Fixed parts that make machine’s structure: industry standards require these components to be resistant to corrosion and, if used to produce food containers, to meet set health standards.
- The moving components: these include belts or chains, cams, shafts and other mechanical components such as bearings. Like the structural thermoformer parts, the moving components must be able to withstand metal fatigue and wear.
- The electronic parts: in a modern plastic thermoformer, electronic components include servo motors, electrically controlled actuators, speed drives, sensors, and control displays/touchscreen controls for easier operation.
A typical multistage thermoforming machine is also composed of several sections known as stations. These sections work together to ensure a continuous production line:
- In-feed system
- Heating station
- Forming and cooling station
- Trimming/cutting equipment
- Stacking Station
- Out-feed system
The thermoformer parts in more detail, including the different options for each part.
This is the plastic sheet loading system. It’s usually either sheet-fed or roll-fed and manual or automatic. A sheet fed system uses cut plastic sheets and is most suited for thick gauge plastic (between 0.125 and 0.500 inches) or low-volume production. A roll-fed system uses a continuous roll of plastic film, and suits thin-gauge plastic (below 0.060 inches) best.
In a manual loading system, a thermoforming machine operator manually places plastic sheets into the machine. This loading system is mostly used with single station machines such as prototyping units or heavy-gauge thermoforming for large parts like automotive components.
An automatic sheet-fed thermoformer utilizes a robotic system (usually air actuated) to introduce cut thermoforming plastic sheets into the machine. In a roll-fed machine, the chain and pin system is the most used method. It essentially consists of a chain to advance the plastic and pins (or grips for heavier gauge plastic) to hold and steady the sheet from above.
Here is where the plastic sheet is heated, also called the oven. Once the sheet is pliable, it will go through the rest of the machine to be formed into the required shape. Different methods are used to heat the thermoforming plastic: through contact with a heating panel and rods, using hot air, and by infrared heating.
Some of the commonly used heat sources are resistance bars, heating wires, quartz heaters, ceramic radiators, gas-heated plates, and heating lamps. Most thermoformers use infrared heating. In terms of cost, heating wires and resistance bars are the less expensive option. However, they oxidize and lose effectiveness too quickly.
Quartz heaters are more effective (even for higher temperature processes) but cost more. For the thermoforming process to be effective, the heating must happen in a controlled way. In order to achieve that, thermoforming machine manufacturers use thermocouple-based controllers or thermistors in the heating system.
Forming and Cooling Station
This is where the sheet is pressed against a mold and forced to take on a 3-dimensional structure as it cools. The section contains several components including mold/molds, forming table, clamping frame, vacuum or pressure system and, depending on the machine’s configuration, a cooling station.
A thermoforming mold is the object that the plastic sheet will be pressed against and can be heated to level of heat that is necessary to form the sheet. It’s usually either positive/male, or negative/female. A positive mold assumes a convex shape, while a negative mold takes a concave shape.
Different materials may be used to make thermoforming molds. These include wood, plaster, aluminum, and even plastic. Aluminum provides one of the best molds. Its heating and cooling is easy to control for shorter cycle times and products of better quality. Aluminum molds are also easy to make.
Trimming and Stacking Station
The thermoforming of plastics often produces unwanted edges and other material, necessitating the use of trimming equipment to cut off the excess material from the formed piece or pieces. The trimming can be done using a variety of methods depending on the geometry, material quantity, and desired requirements.
The trimming methods include: hand knives, sawing, cutting dies, and CNC routers. In most complex thermoforming equipment, a counting and stacking unit is usually included. It consists of a robotic mechanics to stack the cut products together, ready for packaging and shipping.
This is the part of the thermoformer machine where the finished formed piece is pushed out or pulled out. It can use a conveyer or an automated system to transport the formed pieces away from the machine and into another part of the factory where they will be handled by workers.
There’s also usually a mechanism to transport the thermoforming webbing, or part of the plastic sheet that was left after cutting off the formed products. Some machines roll the webbing in a spool to be sold as scrap, while some incorporate and machine to grind it for later re-use.
The thermoforming machine is a versatile piece of equipment that can take different configurations. It can be a simple machine capable of only a few cycles every hour, or a complex, automated system for industrial use. Now that you know more about thermoforming machinery, you can see how useful it is in the manufacturing industry. In the next section, you will learn about its working process.