Vacuum Formed Plastics
Plastics are very popular as materials because of their many industrial uses. Plastic is a flexible raw material and can be molded to take on any shape or form. A manufacturing process involving plastics can create a number of articles and components.
There are different kinds of plastic raw materials used in combination to accomplish definite industrial specifications. The material is utilized for a variety of purposes, including making kitchen appliances, accessories, bags, and many others. Several industries and manufacturing companies, such as automotive companies, electronics, pharmaceutical companies, and food industries use vacuum formed plastic packaging components and products along with their main products.
Plastic thermoforming procedure uses heat on plastic covers, sheets, or materials until they are pliable enough to be molded into a specific shape or form. A usable product will then be created after molding and trimming the plastic. In mass plastic forming, a manufacturer will use a process that is completely mechanized.
A thin gauge system is popularly used to manufacture containers, cups, lids, clamshells, blister packs, disposable trays, and different other products for various industries, including retail, food, and medical industries. Meanwhile, thick gauge systems are used for producing instrument panels for aircraft, door panels for vehicles and truck liners, and many others.
Vacuum Formed Plastics - Engineered Plastic Products, Inc.
Vacuum Formed Plastics - Engineered Plastic Products, Inc.
An Overview of the Thermoforming Process
Thermoforming is a common technique for processing plastics. It is one of the oldest methods as well in which vacuum forming is among the most used systems. Vacuum formed plastics and other products are everywhere and actually play a major part in people’s everyday lives.
Thermoforming involves the use of heating a plastic sheet until the sheet becomes soft. It will then be draped over a mold. Later, a vacuum will be applied, drawing in the plastic sheet until the desired shape is achieved. The process can be used to create permanent objects from plastic. Typically, there are draft angles used in the mold design for easy removal of the part from the mold.
The plastic forming procedure usually utilizes complicated controls consisting of hydraulic, heat, and pneumatic systems. The controls enable more detailed applications as well as a speedier manufacturing process.
Virtually all kinds of thermoplastics can be used as a sheet and can be processed through vacuum forming. The following though are the most commonly used materials:
- Acrylonitrile butadiene styrene
- Polyester copolymer
- Polyvinyl chloride
Plastic forming has many industrial uses as it produces a variety of products. The typical ones include:
- Trays for baths and showers
- Boat hulls
- Turnpike signs
- Machinery guards
- Exterior shop signs
- Machinery guards
- Protective covers
- Vehicle door liners
- Vehicle cab parts
More about Vacuum Formed Plastics
Vacuum forming is simply one of the forms of the thermoforming process where a vacuum is utilized to obtain a certain shape. There are different mechanisms and steps involved to create plastic packaging products and many others:
- Clamping: The process makes use of a clamping frame to guarantee that the plastic sheet will stay in place during the process of forming plastics.
- Heating: There are radiant heaters that are typically used for heating the plastic sheets, which have been positioned on top of the aperture of the vacuum machine. Thicker sheets may require having both surfaces heated, but only sophisticated machines have this capability. They have heaters that move on top and below the plastic sheets.
- Pre-Stretching: During the process of pre-stretching the material, air is introduced to create a small bubble-like entity. The mold is then raised to the sheet that has been pre-stretched. This process is used to attain level wall thickness.
- Vacuuming: When a vacuum is applied to the sheet, it is drawn into close contact with the mold. After that, the mold detail is collected.
- Plug Assisting: In this phase, a deep draw is needed where a top plug is often used. This plug will help push the material into the mold to continue the forming process.
- Cooling and Releasing: The plastic sheet will be allowed to cool, which can take some time. This is why some methods are used, such as blown air or sometimes, water spray. Molding may be released where slight air pressure will often be introduced.
- Finishing: Any finishing job will then be performed depending on the product. This can include decorating, cutting, drilling, trimming, or polishing. The final products, whether they are blister packs, clamshells, or plastic trays, will be formed.
Mold and Mold Design
For this plastic making process, a mold can be as modest as a wooden block, but it can also be as complicated as an injection mold that has all the ancillary elements that permit mold trimming. A wide range of materials can be used in this process. However, it is important to define the type of mold material to be used based on the desired finished product.
Among the mold materials used are the following:
- Modeling clay: This material is widely used for model making and education purposes. Modeling clay enables the user to swiftly form a low-cost prototype. This prototype can be left in an oven to be cured overnight. This material is suitable only for a few designs since the heat and pressure given to it can cause the clay to deteriorate fast.
- Plaster: This material is a good option for creating inexpensive prototypes. When using plaster though, it is important that it is allowed to dry first in a warm environment for three days; otherwise, moisture can damage the vacuum aching and the pump.
- Wood: It is easy to fabricate using this cheap mold. Compared to plaster, wooden molds have a longer life and is even used for producing more than 500 formings. The recommended material here is hardwood, especially obeche and jelutong. Both of which have a close and level grain, making them easy to work with. These hardwoods are also prone to less cracking and splitting.
- Aluminum: This material is a favorite for production because it has good surface rigidity, has low wear, and has heat conductive properties. Aluminum is lightweight and has an excellent ratio of weight and strength.
- Cast epoxy resins: Resins are widely available and they are relatively cheap. Molds using cast epoxy resins are durable and they create a forming that has a good surface finish.
The mold material is selected depending on the difficulty and the time required for the service. For instance, if only a few parts are required with the use of moderately low-temperature plastics, oftentimes plaster or wood would be used as the mold material. Meanwhile, if the quantity requirements for the finished product are around thousands and the temperatures of the material are higher, aluminum mold (or aluminum based resin) would be used.
Concerns and Considerations
Producing plastic products through vacuuming comes with a number of important considerations in order to achieve the design or form that is required for the process to function properly:
- Size: The size of the material to be used should be considered. If it is too large or even too small for the vacuuming equipment, it can lead to problems.
- Shape: While it is true that achieving different shapes is easy in vacuuming, there are certain shapes that cannot be used due to the draw ratio in specific spots. Additionally, there are times when the entire part can be too great. It is also impractical to have varying wall thickness.
- Drafting: When it comes to part design, the draft is one of the most important considerations, especially in determining whether the mold is male or female.
- Undercuts: As much as possible, undercuts should be prevented because it makes the design of the mold quite complicated.
- Radii: The size of the part and the radius are related to each other. The radius will depend on the mold type as well as the thickness of the sheet.
- Integrity and Functions of the Part: It is important that the adequate attention is given to the design process for the part so that it will be strong once completed. Additionally, mounting points should be carefully planned to help the load be distributed evenly.
- Texture: In general, the sheet used is textured, since regular patterned sheets can get distorted during the formation process. Fine graining is used as well and it should be noted that enhanced grain height can affect the thickness of the product.
- Tolerances: Another important concern in vacuuming to form plastic products is tolerance, which will depend on a variety of factors, including the type of cooling, type of material, type of mold, and the method of trimming used. In forming plastics through vacuuming, the first thing that must be done is to determine the mold material type and the expected tolerances.
Advantages of Vacuum Formed Plastics
Although the use of forming plastics through vacuuming is largely restricted to materials that are not too deep or those that do not have a critical wall thickness, the process does have a number of benefits for the manufacturer.
- It is precise. Vacuum formed products, including plastic packaging, are created with more precision when it comes to their design specifications. This is true, especially when compared to plastic products that have been created through molding together several parts. Precision is important, particularly for products that are designed to provide support to another object. For example, a plastic tray for a wrapped chocolate confectionary needs to be accurate in size, shape, and other factors. With the use of vacuum processing for plastics, error is minimized during production, while reducing the possibility of stock recall and the need to add more expenses.
- It is cost effective. Another benefit of the process is it is comparatively low in cost compared to most other methods. It makes use of low pressures, so it does not need a large quantity of sophisticated or advanced tools. This also means that molding can be created with the use of inexpensive materials. Another thing that is associated with the benefits of plastics formed through the vacuuming process is that the large parts of the material can be produced using just one sheet of plastic. This clearly reduces the quantity costs of the material. Aside from that, the discards coming from the finished products may be recycled, so that they can be turned into new plastic sheets. The low costs make forming of plastics through the vacuuming process quite attractive for small business or small production lines.
- It supports flexibility of the design. The use of molds enables this type of thermoforming process to create products that have complex designs. This is often important in a company that takes branding and logos seriously. With the vacuuming process for forming plastics, fulfilling practice requirements of various designs is not a problem. This is why the process is a popular means of production within the packaging industry as well as those that use plastic covers for their main products.
- It is a time efficient method. Everyone in the business world understands that time is of the essence because time is money. Forming plastic products using vacuum does not only involve low startup costs, but it is also a very economical production choice. It uses simple processes, so there is simply less time spent on the design and the final product. Because there is no need to spend too much time on the outcome and the design, there is extra time available to be used on more intricate details. Additionally, the products are presented to the public much quicker. There are also sophisticated machines for vacuuming that facilitate automation, thus generating products in much larger quantity without wasting a lot of time.
With the advantages above, it is no wonder that this method of generating plastic products is more preferred than others. The use of vacuum to form plastics is a good alternative to other methods like injection molding, complex fabricated sheet metal, and fiberglass procedures. There are an infinite number of applications, such as medical equipment, railcar interior seat and trim components, engine covers for aerospace and transportation industries, and much more. From cheaper plastic costs to affordable machine costs to easier production, it is no wonder this process is the chosen technique for forming parts of plastic.