Plastic Fabrication: How It Works, Types, And Advantages
Plastic is one of the most widely used materials of modern times. It is lightweight, affordable, and versatile, and this contributes to its varied applications.
There are hundreds of plastic options, each with varied properties that make it suitable for a specific product. But how do you make a plastic part? That’s where plastic fabrication comes in.
Plastic fabrication refers to any process used to manipulate and transform raw plastic material into finished products or parts. There are numerous plastic fabrication technologies designed to cover different plastic materials, applications, and part geometries.
Every product designer and engineer needs to be knowledgeable about the plastic manufacturing options available today. In this guide, we’ll discuss common plastic fabrication methods and their applications. We’ll also cover the selection criteria for plastic fabrication processes, commonly used plastics, as well as the pros and cons of plastic fabrication.
Plastic Fabrication Methods
Plastic fabrication encompasses the design, manufacture, and assembly of products using plastics or plastic composites. As we’ve already noted, there are several plastic fabrication methods available. They all take advantage of plastic’s ability to be manipulated and shaped into any desired form.
Here is a closer look at the common plastic fabrication processes.
Compounding Plastic Fabrication
Compounding, also known as blending, is a plastic fabrication process that involves melting and mixing two or more plastics. The molten plastic mixture is then shaped using a mold, die, or other tools.
Plastic compounds may be mixed with;
Strengthening components such as glass fiber
Polymer fillers
Blowing agents
Compounding plastic fabrication can be used to create higher-quality end products. It also allows for the production of unique materials that are ideal for specific applications.
Plastic Welding Fabrications
Like metal welding, plastic welding joins two or more plastic surfaces together using heat (except for solvent welding. The plastic materials are heated until they melt, pressed together, and allowed to cool and harden. This results in an exceptionally strong molecular bond.
Plastic welding can only be used for thermoplastics (plastic materials that can be melted numerous times and assume a new shape. Common thermoplastics that can be welded include ABS, PVC, PP, HDPE, and PVDF.
Types of plastic welding processes include laser welding, ultrasonic welding, contact welding, hot air welding, radio frequency welding, and extrusion welding.
Plastic Molding, Including RIM, Rotational, Blow, Compression, and Injection Molding
Plastic molding is a common process in the plastic industry. It involves pouring molten plastic into a mold. The plastic forms a custom shape as it cools and solidifies within or around the mold. Here are the different types of plastic molding processes.
Injection Molding
In injection molding, a thermoplastic or thermoset polymer is heated until it melts. The molten fluid is then injected into a metal mold using a screw-type plunger or ram. As the molten plastic cools and hardens, it takes the shape of the mold. The final stage in the injection molding process is the ejection of the part from the mold.
Injection molding is a versatile process that allows for cost-efficient mass production. Types of injection molding technologies include;
Gas-assisted injection molding
Liquid silicone injection molding
Metal injection molding
Thin-wall injection molding
Blow Molding
Blow molding is a fabrication process that is commonly used to produce hollow plastic items such as industrial containers, bottles, and fuel tanks.
There are three major types of blow molding;
Extrusion blow molding
Injection blow molding
Injection stretch blow molding
Although there are significant differences in these three blow molding technologies, the basic principles remain the same. First, the plastic material is heated and melted. It is then molded into a parison (thermoplastic molten tube).
Next, the ends of the parison are sealed leaving a small area that allows blowing air to enter. Push air into the parison to form a hollow center. Finally, the blow-molded part is cooled, ejected, and trimmed as required.
Reaction Injection Molding (RIM)
Reaction Injection Molding (RIM) utilizes chemical reactions to produce complex and more customizable parts. Different polymers are injected into a mold where chemical reactions take place combining them. The end product is a stronger and more lightweight component.
RIM has applications in the automotive, industrial, and medical industries.
Rotational Molding
Rotational molding is a high-temperature, low-pressure plastic casting technique that is also known as rotomolding or rotamolding. It produces hollow plastic products such as canoes and automotive components. In this process, a hollow mold is filled with unmelted plastic and sealed.
The mold starts to rotate bi-axially and it is then heated in an oven. The rotation process continues, and therefore, the molten plastic covers the walls of the mold evenly. Finally, the mold is allowed to cool and it solidifies into the desired hollow part.
Rotational molding is often used to form larger plastic parts that require uniform walls.
Compression Molding
Compression molding is a simple plastic fabrication method. It involves placing plastic powder or pellets onto a hot metal mold. As the plastic material becomes more pliable, it is compressed to assume the shape of the mold.
This fabrication process is attractive due to its affordability for short-production runs. It is therefore used in prototyping and creating samples before mass production.
Plastic machining
Plastic machining is one of the most common plastic fabrication methods. This subtractive process involves removing material from a solid plastic workpiece to create a finished product of the desired shape and size. Plastic machining covers different processes including cutting, turning, routing, drilling, and grinding. These operations can either be done manually or using computer numerical control (CNC) machines.
CNC plastic machining generates precision plastic parts that are used in the aerospace, automotive, electronics, and medical devices industries. This plastic manufacturing process can be used for different plastic materials including acetal, acrylic, ABS, PE, PC, PEEK, and nylon.
Plastic Foaming
In this plastic fabrication method, polymer composites are manipulated to create plastic foam using physical or chemical blowing. Additives such as UV stabilizers, antioxidants, and pigments may be mixed in with the base resin to improve the performance of the part.
Foamed plastic has a wide range of applications such as producing kids’ toys, plastic boats, furniture, and air filters. Common plastics that can be foamed include PS, PEX, PP, PA, and plasticized PVC.
Plastic Lamination Fabrication
Plastic lamination creates a protective coating on the exterior surface of another material. This plastic barrier safeguards the material from damage caused by external impact and environmental factors. Also, this process enhances the appearance of the coated product.
To apply plastic laminate, the fabricator will typically use both pressure and heat to ensure that the lamination layer sticks to the surface being laminated. Types of plastic lamination processes include synthetic resin lamination and film lamination.
Die Cutting Fabrication
Die cutting is a straightforward manufacturing technique. First, the fabricator will form a custom die in the desired shape. Using this die, flat plastic sheets can then be cut to produce the required plastic parts.
Die cutting is an inexpensive and relatively fast process. It has applications in the automotive, electronics, and telecommunications fields. Common plastics that can be die-cut include ABS, PC, PE, PP, styrene, vinyl, and more.
Thermoforming Fabrication
Thermoforming is similar to the plastic molding process. However, instead of melted plastic, this technique utilizes gently heated plastic sheets.
The plastic sheet is heated to its softening point. It is then stretched over a female or male mold, manipulated, and the excess material is trimmed off. It cools into the desired shape.
Thermoforming can be further grouped into vacuum forming, pressure forming, mechanical forming and drape forming. This inexpensive manufacturing method is suitable for both small-scale and large-scale production of goods.
Vacuum Casting Fabrication
Vacuum casting, also known as urethane casting, is a fabrication process that lets you create small quantities of high-quality plastic parts. It is, therefore, perfect for prototyping, concept proofing, and function testing.
Vacuum casting involves pouring casting resin into a silicone mold. A vacuum eliminates air pockets and bubbles and this creates an ultra-smooth finish. Finally, the resin part is cured in an oven and ejected from the mold once it has cooled down.
Plastic Extrusion Fabrication
The plastic extrusion process involves melting raw plastic and creating continuous plastic shapes. First, the fabricator will melt plastic pellets by heating them using a single-screw extruder. The molten plastic is then forced into a die. As it cools and hardens it assumes a continuous profile.
Plastic extrusion is used to create thin plastic sheeting, pipes, plastic films, and window railings.
3D Printing
3D printing is the process of using computer aided design (CAD) models to build an object layer by layer. During the process, the 3D printer will pile layers of plastic one after the other until it constructs the desired product. This manufacturing technique is compatible with a variety of plastics and it used in robotics, medical, aerospace, consumer products,and automotive industries.
There are different types of 3D printing such as powder bed fusion, sheet lamination, selective laser sintering, steolithography technology, fused deposition modelling, and material jetting.
Choosing a Plastic Fabrication Process
There are numerous plastic manufacturing processes, each with its unique advantages and disadvantages. Here are some of the factors you need to consider when choosing a plastic fabrication technique for your product.
Lead time
Some manufacturing processes are faster than others resulting in a shorter time-to-market. In most cases, manufacturers prefer plastic fabrication methods that reduce production time.
Cost and volume of products
Some manufacturing processes are more cost-efficient for mass production while others are suited to low-volume production.
Size of products
The dimensions of your plastic products will determine which fabrication process is viable. Some plastic fabrication methods are suitable for smaller parts while others can create large parts.
Type of plastic material
The choice of plastic manufacturing method will also depend on the specific plastic being fabricated. For example, thermoset plastics cannot be welded, and therefore, they’ll require an alternative technique.
What Are the Materials That Can Be Used in Plastic Fabrication?
Different polymers are processed into end products using suitable fabrication processes. The most common materials used in making fabricated plastic products are;
High density Polyethylene (HDPE)
Low density Polyethylene (LDPE)
Acrylic (PMMA)
Polyvinyl Chloride (PVC)
Polyethylene Terephthalate (PET)
Acetal (POM)
Polystyrene (PS)
Polycarbonate (PC)
Polypropylene (PP)
Different Types of Slip Fit
Where the press fit is extremely tight thermal expansion and contraction are more applicable. It could be thermal expansion of the material with the hole. It could also be the contraction of the shaft – shrink fitting.
What Is the Quality Level of Fabricated Plastic Parts?
Fabricated plastic parts come in different qualities depending on the type of plastic material used, the fabrication technique, and the design.
Premium quality plastics are characterized by features such as precision and accuracy, durability, and strength. Lower-quality plastic parts are prone to issues such as warping. brittleness, and a shorter life span.
Employing the proper finishing procedures can improve a product’s durability and resistance to abrasion and the elements.
What Are Examples of Fabricated Plastic Products?
Fabricated plastic products are everywhere. Reports indicate that the most common plastic products are packaging components, construction products, and automotive parts. Here are some examples of common fabricated plastic products.
Plastic packaging including plastic bottles, bags, and containers.
Construction products such as plastic pipes, windows and doorframes, floor lining, custom components, and more.
Automotive parts including bumpers, car windows, dashboards, and interior parts.
Plastic toys, kitchenware, and electronics parts.
Advantages of Plastic Fabrication
Let’s explore some benefits of plastic fabricated parts.
Cost-effective: One of the reasons for the widespread use of fabricated plastic parts is their affordability.
Versatile: Plastic is a highly versatile material that can be shaped into parts of different sizes and shapes. It has varied applications in virtually all industries.
Durable: Plastics are generally strong, resilient, and durable. Some varieties are resistant to impact and chemicals allowing them to perform well in various environments.
Recyclable: Most plastic products are recyclable. This process lowers the acquisition costs of raw materials and most importantly reduces pollution.
Disadvantages of Plastic Fabrication
Despite their popularity and advantages, plastic fabrication products come with some cons. They include;
Pollution: Plastic pollution remains a threat to our planet. Tonnes of plastic trash end up in landfills and seas and this issue needs to be addressed.
Low melting points: Plastics have a range of melting points, some high and others low. Low melting point plastics, such as polyethylene and polypropylene, cannot be used in high-temperature applications.
Breakdown caused by sunlight: Lots of plastics are not built to absorb UV radiation. Therefore, when left in the sun for long stretches, plastic products may discolor, become brittle, and even break down.
Author
Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.