A process of manufacturing and production of parts by using the technique of injecting molten materials into the mold of the machines is called plastic injection molding. Several materials can be used for injection moldings such as glasses, primarily metals, confections, thermoplastics, elastomers, and thermosetting polymers. A heated barrel is used to mix the parts of the production materials and then to inject them into the mold cavity which will harden them after they are cooled down for the configuration of the cavity.
A special-purpose machine is used for injection molding that has mainly 3 parts: the injection unit, the clamp, and the mold. To facilitate the molding process, the design of the injection molding is to be done carefully and with utmost care such as the material used for the desired shape and characteristics of the part, the material of the mold, and the properties must be considered of the molding machine. The breadth of designs mainly facilitates the versatility of the molding machine.
Applications of injection molding:
Many useful things that are used in daily life are manufactured through injection molding, for example, packaging, swirl pools, bottle caps, and components, toys, pocket combs, some musical instruments, one-piece chairs, storage containers, small tables mechanical parts which may also include gears, and plastic products that are used and available in the present. Injection molding is used commonly in the modern world where manufacturing custom plastic parts is routine work because of its ideal approach of producing high quantities of commodities.
Parts of the machine:
A material hopper, an injection ram/rotating type plunger, barrel, heating device (heater), ejector movable pattern, and a mold inside the mold cavity are considered to be the main parts of the machine.
Usually, injection molding machines work in a horizontal manner. The injection molding machine consists of a cylindrical pipe named barrel. the barrel is a long tube-like thing that has a hopper attached to it at the end. A hydraulic ram or rotating is driven by an electric motor providing the force which is located inside the barrel. To melt the material, a heating part known as a heater is attached to the barrel so that it can melt the material down the hopper.
A mold cavity is attached to the other side of the barrel. The mold is located inside the mold cavity and a running pattern is used throughout construction. The mold is usually made of copper, aluminum, and tool steel. The life cycle of different physical molds is different. It can be selected as per the requirement.
Working of the machine:
The function of injection molding is like that of Plastic extrusion, and it works like injection as the name suggests. The molding material/raw material is put into the hopper by the feeding device. After that, the molding material moves down into the cylinder (barrel) under the action of gravity. A peripheral heater located on the barrel is used to melt the material. When the barrel is dawned with the powder form of the molding material the powder from the hopper starts the melting process and a hydraulic ram or maybe rotating pushes the material into the mold by applying some extent of pressure. A closed mold attached to the other side of the barrel and is used in the split mold is injected with molten plastic material. The molding material moves forward by rotating continuously. Pressure is applied by the hydraulic system. The injection pressure is usually 100-150 MPa. after injection, pressurized for some time or locked in the same position with some force. The heavy machineries that need temperature control like excavates, wheel loaders etc make use of bobcat temp gauge to maintain the required temperature.
Every machine works at its own pace and on its own specifications. Such is the case with the machine of injection molding. It works at optimum factors for better product quality. It is necessary to follow the precautions and instructions if we want our finished products according to our demands. We have gathered a list for you to get familiar with these parameters for future references:
- The process parameter varies according to the situation and requirements.
- The weight of the parts produced by this process generally ranges from 100 to 500 grams.
- The cycle time for producing a part is typically 5 to 60 seconds depending on the parts being manufactured.
- The heating temperature of the molding material is 150-350 degrees centigrade.
- The injection capacity of the molding machine is 12,000 to 2.2×〖10〗^6 mm〗^3.
- The injection pressure is 100-150 MPa.
- The locking force is 0.1 to 8.0 MN.
The injection molding principles may sound simple and easy to try or do but it is a very complex process that requires the right kind of equipment and the right expertise. If all of this procedure is done perfectly and without any fault it will deliver excellent results throughout with consistency even if the projects seem challenging. Make sure to design the plastic product correctly and create the plastics prototype before you begin the mass-manufacturing process.