Choosing the Molding Method to Meet Your Needs
When building a product requiring molded plastic parts, injection and blow molding are the best methods. These methods produce high-quality and cost-effective plastic products and parts, although each of the methods is used in different applications and have specific requirements.
What is the difference between injection molding and blow molding?
The differences can be looked at from three different perspectives, including different products, different processes, and different molds.
Different Products
One of the most notable differences between the parts that are made by injection molding and those made by blow molding is the fact that the injection process molds solid parts, while blow molding creates hollow ones. If a manufacturer is producing a product that needs one rigid wall, injection molding is the way to go. Some of the products that a manufacturer using injection molding create include housings for computers and TVs, hair combs, and bottle caps. If a person needs a piece that is structural, flexible, or can hold a fluid, blow molding is the method to use. The best example of a product created through blow molding is a water bottle. Most bottle manufacturers use blow molding to create billions of bottles and at a low price. Blow molding can also be used to make various industrial shapes for fuel tanks, coolers, and stadium seats, among others.
Different Processes
The second aspect to look at when comparing blow molding and injection molding is the processes used in both methods. When an injection mold is created, it is held together using intense pressure. The pressure is adequate to ensure that the interior part is filled with molten plastic resin under high pressure. The cost of making a product and the machine size is based on the tonnage pressure that is needed to hold the injection mold together. When blow molding is used, a tube (plastic) is heated and filled with air. The air is blown into the tube until it becomes a hot plastic, also known as a parison. A mold is used to clamp around the parison, trapping the blown plastic as air fills it into the shape of the mold. The size and cost of the machines and the production cost of blow-molded products depends on the weight of the material used to make the mold. It is important to note that the unit costs for blow and injection molded parts compare to the similar weights and dimensions of the components.
Different Molds
This is the last component of comparison, and the author of the article notes that the injection molds need a high precision match between the halves of the mold to ensure that the flow of material is controlled correctly. When injection molding is used, the greatest battle (90%) that the manufacturer faces is in the creation of the mold. Once the manufacturer has an error-free mold, the remaining part of the process is easy. The precision needed in making an injection mold makes the process more expensive than creating a blow mold. Blow molds, on the other hand, give the manufacturer freedom between the mold halves use since each half forms a wall shape. In this process, making the mold is only 50% of the hassle, although variables such as flash, streaks, wall thinning, and air leaks need monitoring. It is also essential to understand that wall thickness variation is crucial in designs. Quality is essential as well, and it is needful that the supplier of the products has a quality team that is trained in measuring, monitoring, and improving the different aspects of the final product.
Reference
Custom-Pak Inc. (2020). Injection Molding vs. Blow Molding: What is right for you? – Custom-Pak, Inc. Retrieved 30 July 2020, from https://www.custom-pak.com/injection-molding-vs-blow-molding-what-is-right-for-you/