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Many items that we use daily have undergone some stages before reaching the market. Most of these items are usually plastics, metal, glass, rubber, and so on. Most consumers are unaware of what it takes for these products to reach them. One of the methods used to manufacture items is molding. Molding is a manufacturing process that involves the use of a mold to form products.
Molding companies are advancing their techniques to deliver above-standard products to the markets. The major types of molding processes are discussed below.
Injection Molding
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Injection molding is a manufacturing process of producing plastic (most common), metal, glass, or rubber. The process is utilized in the mass production of similar parts. Injection molding has several types: plastic injection molding, die casting, cube molding, silicone rubber molding, reaction injection molding, etc. All these processes use the injection molding concepts to make products.
The injection molding process starts by making a mold. The standard mold is usually made of metal, preferably steel, due to its properties. The final product takes the shape and size of the mold. It is the most critical step in injection molding as any mistake will reflect in the final product. After the mold is ready, the chosen material is put in a heater and melted. The operator then injects the molten substance into the mold cavity under pressure, taking the shape and design of the mold.
It is then left to cool and solidify to produce the final part. Injection molding is applicable in many industries from medical, automotive, packaging, appliances, etc.
Pros;
- Ability to produce a large number of parts fast.
- Production cost is lowered due to reduced labor.
- There is consistency in the manufacturing.
- Injection molding allows variation in the material used, like different colors simultaneously.
Cons;
- It becomes expensive when producing small quantities of products.
- Injection molding is costly to start since the machines are expensive.
Casting
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Casting is an industrial process where the hot liquid is poured into a mold to form a product. Unlike injection molding, where there is pressure used, casting utilizes gravity. Casting usually involves metal, but sometimes, manufacturers can use other materials like clay, concrete. The mold is made in the shape of the desired part, and it is very useful when it comes to complex designs.
Manufacturing commences by carefully designing and making a mold cavity where the operator will pour the liquid. Then the molten material is poured into the mold and left to solidify. The casting process seems simple; however, dealing with molten metal is an uphill task. The casting process can either be expendable or permanent. Expendable means the mold is demolished to let the cast out, while permanent process means the mold is made so that the cast can be ejected without destroying the mold.
The material used to make the expendable mold is usually plaster, ceramic, or sand. For permanent molds, metals are the best choice.
Pros;
- With casting, you can realize any complex design.
- There are no size restrictions in casting.
- Cooling is uniform, making the final item consistent.
Cons;
- Casting needs a lot of labor.
- It may be difficult to achieve precision.
- In casting, some mold materials like sand can cause many defects since they retain moisture.
Blow Molding
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Blow molding is a manufacturing process for making hollow products like bottles and pipes. The process begins with heating the raw material, making it a parison, and placing it on the mold. Air is then blown onto it, making the material stretch and take the shape of the mold cavity. A hollow space is left due to the air pressure. Blow molding has three types; extrusion blow molding, stretch blow molding, and injection blow molding.
- Extrusion blow molding: the parison is dropped into the cold mold, and once closed, they blow air onto the mold cavity making the parison take the shape of the cavity, leaving a hollow space.
- Injection blow molding: this process blends blow molding and injection molding. Injection molding is used to form the preform, which will then be transferred to another mold for blow molding.
- Stretch blow molding is similar to injection blow molding; the only difference is that the preform is transferred into the other mold and stretched out a bit using a rod. Then, they blow air to complete the process.
Pros;
- Blow molding facilitates the production of various plastic products.
- It is a cost-effective process.
- It is flexible as you can choose different methods for blow molding.
Cons;
- Blow molding harms the ecosystem as it depends on petroleum.
- Blow molding can only be utilized for hollow products.
Compression Molding
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Compression molding is a type of molding process that uses compression pressure to form products. The compression process begins when melted plastic is poured into an open mold then closed with another mold. Hydraulics are then used to compress the top plug, ensuring the molten plastic fits in all the spaces of the mold cavity. Compression molding has two types; sheet molding compound and bulk molding compound.
These two processes differ in the material used. For sheet molding compound (SMC), the sheets are approximately five millimeters, with the material put between polyethylene films. On the other hand, the bulk molding compound’s pellets are thicker than SMC, approximately 20 – 50 millimeters.
Pros;
- Compression molding permits the production of large products.
- It is an economical process.
- Compression molding produces strong parts.
Cons;
- There is a wastage of material during compression.
- The process is slow.
- It is labor-intensive.
Rotational Molding
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Rotational molding, also known as roto-molding, is a manufacturing process that produces hollow parts. A plastic powder is added to a mold in rotational molding, then rotation and heating are done simultaneously. Due to the heat, the powder melts, and the liquid starts to take the shape of the mold. Cooling then occurs, and the final product is complete. The process does not require any pressure, meaning the material used can be cheaply sourced.
Rotational molding is applicable in producing various tanks (water, fuel, storage, septic, etc.), toys, traffic signs, furniture, and containers. Even though rotational molding does not require any pressure; other factors can impact the final product, such as the mold, temperature, humidity, and powder quality. The materials used in this process is polyethylene (HDPE, LDPE, LLDPE, and PEX)
Pros;
- Rotational molding tools are affordable, making it an easy process to start.
- The parts produced are durable, stable, and with uniform consistency.
- Minimal wastage of materials.
Cons;
- The labor needed increases the production cost.
- The designs are regular.
- The material option is limited.
Conclusion
Molding is a process used in the manufacturing of necessary items that we use daily. The most popular type is injection molding, where plastic is the primary raw material and end product. All these methods are essential in our economy; hence, you need to work with an experienced manufacturer as an entrepreneur. RYD Tooling is a good example; we are a world-class company dealing with the design and manufacturing of goods. We value our clients and always keep them in mind during operations.
Reach out to us for any inquiries, information, or comments. We are eager to work with you to realize your dreams.
