Plastic injection molding can seem complex to those not involved with the industry, but this industrial manufacturing process is used to make everyday products like Lego bricks and plastic tableware. It has many benefits over other manufacturing processes and can provide high volume production with low per-piece costs.
The plastic injection molding process starts with a product design, which is then sent to a tool-maker who creates a mold to fit that product. The plastic resin pellets are then melted and injected into the mold under pressure to form the finished part. The tooling costs for plastic injection molding are quite high, but once the mold is made it can be used for multiple runs with only minor cosmetic wear, which significantly reduces the cost per product.
This type of production can use a wide variety of polymers, which are also called resins, or a combination of plastics. The most common polymers for injection molding are thermoplastics, which are polymers that can be heated to melt them and then cooled to solidify them. These types of polymers can be mixed with additives such as colorants, recycled material, glitter, and specialty ingredients to enhance the performance of a final molded product.
After the melted plastic is injected into the mold, it is allowed to cool and harden before the machine unclamps the mold and ejects the molded part. The ejection process can be assisted with mechanical provisions that work with the mechanical features designed into the custom plastic injection mold to ensure a smooth, quality surface finish and proper dimensional accuracy for the molded part.
Cycle times are an important factor in the plastic injection molding process, as they determine how long it takes to manufacture a plastic product. The injection time, cooling time, and resetting or changeover time are all factors that can be reduced to lower production costs. The quick mold change systems from EAS help to reduce these times, reducing production costs and improving lead-times to market.
The injection process is based on heating and cooling, which can be affected by several variables such as the temperature of the plastic, the size of the screw, and the injection speed. Incorrectly set temperatures can result in brittle or weak parts, while short cooling times can cause warping. Moisture in the plastic caused by hygroscopic resins can be trapped in the molded parts, leading to corrosion and poor quality finishes.
A successful injection molding process depends on the design of the plastic injection mold, ensuring that it will be able to handle the tremendous amounts of pressure during the process. This pressure is needed to inject the molten plastic into the mold cavity, and it can also be applied as packing pressure to complete the mold filling and compensate for thermal shrinkage. A faulty plastic injection mold could crack under the intense pressure, which is why it is so important to make sure that all of the critical details are considered during the design stage. plastic injection molding