The process of 3D modeling, prototyping, and design refinement are extensive for any engineer. The last common step is preparing the designs for injection molding, but that can be confusing to figure out where to start. Additionally, how much time will it take before going from the initial part designs to finally having molded parts? It’s a lengthy and difficult journey that often intimidates engineers.
In this article, we’ll help you understand what is injection molding and share the main reasons why businesses swear by this process when it comes to increasing production and dominating the market.
Photo by Alexander Grey on Unsplash
Plastic Injection Molding Basics
Plastic injection molding is a process of manufacturing components by injecting heated plastic into a mold. This method of production provides many benefits, such as being cost-effective and allowing for detailed designs to be created. Injection molding machines can quickly create large quantities of parts in a single production run, making them an ideal choice for mass production.
Plastic injection molding demand has increased in many industries, such as:
- Automotive. Producing components such as interior trim pieces, exterior body panels, lighting fixtures, and engine components.
- Aerospace. Components such as housings and other aircraft parts may also be produced through this process.
- Medicine. Many disposable products like syringes and IV catheters are created with plastic injection molding.
- Consumer goods companies. They rely on this manufacturing technique to produce items like toys, kitchenware, and more.
Plastic injection molding is a versatile process that can be used to create products for nearly any application.
Needed Equipment for Injection Molding
For this process, there are two main parts necessary: an injection molding machine and a mold of the upcoming product.
An injection molding machine generally works in a horizontal manner. It is made up of several parts, which include:
- A material hopper;
- Clamping unit;
- A barrel;
- An injection ram/rotating screw;
- A heating device;
- A moveable pattern;
- Ejectors.
Usually, companies buy existing molding machines, and this is the biggest expense they’ll experience in a while. On average, large industrial injection molding machines cost between $50,000-$200,000. Molds on the other hand cost $3,000-$6,000 each.
Photo by Bekky Bekks on Unsplash
The Plastic Injection Molding Process
The process itself consists of four phases including clamping, injection, cooling, and ejection of the final product. Even though there are several phases, the process takes from several seconds for small products up to several minutes for larger products, with the cooling phase being the longest one of them all.
Clamping
The mold usually comes in two parts, and it needs to be sealed tight before molten plastic is injected. To do this, the clamping unit secures the two halves of the mold together. The force of the unit is very strong and keeps the mold shut while hot liquid plastic is being injected. Smaller molds with tinier openings require less time to be clamped together.
Injection
The injection molding machine forces molten plastic into a mold to create the desired shape. The raw material, usually in pellet form, is fed into the machine and directed toward the mold under high pressure. The screw device inside the barrel of heated zones melts the pellets until they reach a liquid state before injecting them into the mold. The amount of material that is injected during this process is called the shot. After it has been fully clamped, the machine will inject the material into the mold.
Cooling
The plastic cools and becomes solid as soon as it touches the mold, creating the shape of the new product. It’s essential to realize that the part may become smaller during this process. Note that you cannot open the mold until the plastic inside is completely cooled, and the time needed can vary depending on the product properties such as size, shape, and wall thickness.
Ejection
The part cools inside the mold until it’s ready to be ejected by the machine. The machine uses a mechanical ejection system to push the cooled part out of the mold. By the time the part is fully ejected, the mold has prepared another shot of plastic so that it’s ready for cooling and ejecting again.
Bottom Line
Injection-molded products are surrounding us, and because of the benefits the process offers, more and more industries started implementing it for mass production and increasing efficiency and success. Refer to this post if you want to know the basics of the injection molding process, as well as some details that can help you to better understand it.
