In the process of injection molding, plastic resin, (which is the raw material for plastic injection molding) is fed into the loader of the machine as the first step. What comes next is the rotation of the raw materials using the screws while in contact with the heating barrel. Through the heating barrel, the plastic resin is melted and accumulated at the front of the screws. From there, the molten plastic is injected into the mold through a nozzle pushing air out through the vents. Once the mold is completely filled up, the molten plastic is cooled to the desired temperature then expelled. You first have to understand the impact of the parts of the injection molding machine, then check the process.
Parts of the injection molding machine
Barrel- this is the part of the machine where the plastic resin (the generic term for plastic material) is fed into the machine for heating and mixing. The barrel contains the screws that facilitate the heating and mixing process. The screws help to move the resin forward and towards the mold.
Nozzle- this is the part through which the molten plastic gets fed into the mold. The other name for the nozzle is the sprue.
Mold- this is the part of the machine that is specifically designed to the desired shape and design of the product. The mold is an intricate part whose configuration depends on the product and the sup-parts of the mold like the gate, the windows, and the grate. The core is made up of two main parts (the core and the cavity).
Cavity – this is the hollow part of the mold that is often referred to as the A-side. The molten material enters the cavity through the gate.
Core – is the second half of the mold which fills the hollow side that is often referred to as the B-side.
Parting line – is the line formed in the molded part where the core and the cavity meet.
Ejector pins- is the part used to eject the material from the mold once it is adequately cooled.
Cold runner- this is the channel found in the mold through which the material flows to the cavity, and hardens with the part. Once the material has hardened, it is removed through the cold runner following the ejection.
Clamps- this is the part of the injection molding that is used to close the mold as it fills up with the molten plastic. The amount of force that is needed for this task is referred to as the clamping force.
Types of Injection Molding Machines
There are three main types of injection molding machines:
- Hydraulic injection molding machines
- Electric injection molding machines
- Hybrid injection molding machines
Some of the most crucial aspects of the injection molding process include temperatures for melting resin, nozzle temperatures, the rate at which the plastic molten flows, pressure with which the molten flows into the molds, rates of cooling/heating, and lastly the timing of cooling/heating.