|
An injection polymer molding process involves filling a relatively cold, negative mold with a predetermined quantity of heated and plasticized material by injecting it under pressure. Upon solidifying, the injected material is cooled further and the mould is opened to remove the product. A horizontal plunger type injection moulding machine illustrates the main steps of the process. Following are the steps that lead from the granule to the finished product, as illustrated in the diagrams:
Above the injection unit, the granulate is placed in the hopper of the measuring or dosing unit. Predetermined quantities of material are thrown into the plunger from the hopper. The plunger pushes this charge forward so that it is deposited on top of the injection plunger, and then after it has been withdrawn, directly in front of it. The injection plunger forces the material into the heating cylinder as it advances through the plunger guide.
The material is forced through successive strokes of the plunger until, at the front of the cylinder, it becomes a homogeneous melt, ready for injection. The injection nozzle forces the melt into the mould. Molds are essentially two parts that are clamped or bolted together in the injection machine. One side is mounted on the stationary platen, while the other side is mounted on the moving platen. The two halves are known as A, B plates, while the speed at which they are injected is regulated to fit the material and components.
Sprue bush is where material passes through after being injected into the nozzle or fixed side of the mould. The melt is distributed into the cavities through interconnected channels or runners. When the cooling period ends, the mould is opened and the components (T) are ejected through ejector pins, which are engaged by the ejector tail hitting the stroke limiting screw as the mould reaches its fully opened position. Accordingly, the injection moulding process can be divided into five stages:
Steven Cheng is a China injection molding expert with Topworks Plastic Mold, a company that offers comprehensive services from design to production. For customers, Topworks offers a one-stop for injection molding of polycarbonate and ABS plastic part. As a result of the company’s extensive experience in the plastics industry, it provides customers with prompt responses and high-quality service. |
| https://www.plasticmoulds.net/injection-molding-process.html |
Frequently asked questions
What are the main steps of the injection molding process?▼
The injection molding process consists of five key stages: measuring granulate, melting material in a heating cylinder, injecting the melt into a closed mold, cooling until solidification, and opening the mold to eject the finished product using ejector pins.
How does the heating cylinder work in injection molding?▼
An electric resistance heater band heats the outside of the cylinder to melt thermoplastic material. A spreader (torpedo) inside the cylinder distributes heat evenly by pushing material against the hot inner walls, creating a homogeneous melt ready for injection.
What is the purpose of the sprue bush in injection molding?▼
The sprue bush is the entry point where melted material passes through after injection into the mold. It distributes the melt into the cavities through interconnected channels or runners, ensuring proper filling of all cavity areas.
How are products removed from the mold?▼
After the cooling period ends and the mold opens, ejector pins remove the solidified components. These pins engage when the ejector tail hits the stroke limiting screw at the mold's fully opened position, pushing out the finished product.
What materials can be used in injection molding?▼
Injection molding primarily uses thermoplastic materials, including polycarbonate and ABS plastic. These materials can be heated to a plasticized state, injected under pressure, and cooled to form the desired product shape.