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Understanding Different Types of Plastic Molds
American Plastic Molds are the basis for many everyday products. From small embryonic head screws to the shell of household appliances, they are critical for production and manufacturing.

This type of plastic molding uses injection pressure to shape the raw material into the desired shapes. It is a common method for producing high volumes of parts with exacting tolerances, and can be used to make both large and small pieces that need to be tough or rigid.
Injection moulding is a highly repeatable process that yields dimensionally consistent results. This is especially helpful for complex designs with stringent dimensional tolerances. It is also an environmentally friendly method with minimal waste; scrap plastic can be reground and reused in the process.
The process begins with the creation of a mold, which is usually made from steel or aluminum for strength and durability. This is done by professional machinists based on the design of the final part. It can take up to 20 weeks to create the mold, which must include a variety of features such as cavities, gates, runners and sprues, and ejector systems.
Once the mold is complete, it’s ready for production. The molten plastic is injected into the mold channels (sprue, runners and gates) using an injection unit. This pushes the molten plastic into the mold cavity until it is 95% filled. The injection unit is controlled to achieve a balance between injection speed and pressure. Injection pressure is affected by the viscosity of the molten plastic and its shear rate.
As the molten plastic fills the cavities, the injection pressure is replaced by holding pressure to ensure that the molten plastic stays compacted as it cools. Once the molded plastic has cooled, the mold is opened and the individual molded pieces are separated by trimming. This process can take up to four weeks, and the trimming is done using separate equipment.
There are a wide range of materials available for injection molding, including acrylonitrile butadiene styrene, polyethylene, and polypropylene. It is possible to mix these materials with other additives, such as glass fibers and chemical compounds, to produce a specific mechanical or physical property. There is an almost endless choice of colors as well, with the use of masterbatch or compound coloring.
Extrusion Moulding
Extrusion is a type of plastic moulding process that utilizes shaped dies to create long lengths of thermoplastic products. During this process, the granulated polymer is heated and melted before it is forced through the die in order to take on its final shape. This allows manufacturers to produce linear shapes such as tubes and pipes, as well as thin-walled profiles like wire insulation. The resulting product is then cooled and cut to length before it can be used.
Extruded plastics are widely used across numerous industries and sectors. From industrial piping to synthetic filaments and even drinking straws, there is no shortage of applications for this versatile manufacturing method. However, it is important to understand the benefits and drawbacks of this manufacturing process in order to select the right one for your project.
The primary advantage of extrusion moulding is its ability to create linear products in a continuous sequence, allowing for rapid production and high efficiency. This is especially beneficial for projects that require large quantities of the same essential design, such as cable and wire insulators or PVC water and sewer pipes. Furthermore, this manufacturing process is compatible with a variety of different plastic resins, enhancing its versatility and applicability across multiple industry sectors.
Plastic extrusion also offers several environmental benefits, including less waste compared to injection molding. This is because excess material resulting from the extrusion process can be recycled and fed back into the manufacturing cycle, minimizing overall waste and ensuring that the most efficient use of raw materials is achieved.
In contrast, injection molding tends to generate more waste in the form of sprues and runners, which are the channels through which molten plastic passes before entering the mold cavity. These excess materials can be ground up and reincorporated into the manufacturing cycle, resulting in reduced production costs and alignment with sustainable practices.
In addition to these environmental benefits, extrusion is often more cost-effective than injection molding, particularly for longer production runs. This is because the tooling required for this process is simpler and cheaper, and there are fewer steps involved in the manufacturing process.
Casting Moulding
A casting mould is a type of plastic mold that allows for the creation of objects with complicated shapes. It can be used to create decorative statuettes and figurines, as well as lamp bases and other decorative items. It is also commonly used to produce components for toys, especially those that require a hollow interior to reduce weight and material usage.
Casting moulds are often made from a durable alloy, such as aluminum or copper, but they can also be made from stainless steel, low-carbon martensitic aging steel, or even zinc. These materials provide excellent cutting, polishing, and heat-resistant properties. Moreover, they are less costly than other types of plastic moulds. This is especially true when compared to those that are made from hardened steel, which can be quite expensive.
When casting, the liquid that is poured into the mold must fill it evenly, or else it will not form correctly. The problem is that complex shapes can have parts where air can become trapped, preventing the casting material from fully filling those areas. This can be overcome by tilting, rocking, tapping, or otherwise agitating the mold while it is being filled, but this isn’t always effective.
Another way to prevent this issue is by using a special additive that can bind the liquid plastic together more effectively. This type of additive is usually called a flow agent, and it can be added either during the pouring process or afterwards. The additive works by lowering the melting temperature, so that the liquid can melt more easily and fill the mold.
The advantages of casting include the ability to make extremely detailed and intricate products, as well as the flexibility in design that is often impossible with other manufacturing methods. It can also be very cost-effective, making it an excellent option for production runs of thousands or more parts.
While there are many benefits to using this method, it is important to remember that it can take up to a year to build the molds required for casting. This can be shortened by working closely with the plastic molding company at the design stage to help reduce mold complexity. Choosing simpler designs and avoiding any features that are difficult to separate will also help speed up the production process.
Transfer Moulding
The transfer molding process combines the best of both compression and injection molding. It is a popular method for encapsulating delicate electronic components and can also be used for over-molded parts. This process works well with a wide range of materials, including polyurethane, natural rubber, and unsaturated polyesters. It is commonly used in the automotive, electronics, and contract medical manufacturing industries.
The process starts by preparing the molding compound with additives to achieve desired properties and aesthetics. Then, the mixture is placed in a pot or chamber and heated to a certain temperature. The hot material then passes through a hole called the sprue into the mold. A hydraulic plunger is then used to force the hot material into cavities and close the mold.
This method is more accurate than compression molding and allows for more detailed molded parts. It is also a good choice for producing complex shapes, especially those with intricate details that need to be ejected from the mold after cooling and hardening. However, this type of molding is prone to air pockets in the finished product due to the high viscosity of the plastic. This can lead to a loss of material and require extra steps to eliminate these defects.
Another benefit of this process is that it creates sharper part edges than Compression Molding. This is because the rubber enters the mold at near the curing temperature, reducing the tendency for expansion and shrink to tear away pieces of the rubber around the split line.
The transfer molding technique is compatible with thermoset and some thermoplastics, but is most popular with the use of elastomers like silicone, polyurethane, and unsaturated polyesters. These materials are known for their durability and elasticity and can be used to make seals that can stand up to harsh environments, such as those found in power generation and renewable energy. They can also withstand extreme temperatures and aggressive chemicals. In addition, the simple pot and plunger setup of the process reduces tooling costs compared to other methods of molding. This makes transfer molding a great option for projects with shorter production timelines.