Injection molding is a manufacturing process for producing parts out of plastic materials. It uses a heated chamber and a plunger like device to inject heated plastic into a mold which is created as per the final product design. The heated plastic flows and takes the shape of the mold and when cooled, is removed from the mold. Injection molding is a relatively fast and cost-effective method and is widely used in manufacturing a variety of components and products.
Despite being widely used, this method of plastic component making has certain drawbacks. This article will analyse and list the drawbacks of injection molding before explaining possible ways to correct these issues.
The first major drawback of injection molding is heat distortion. Heat distortion is a phenomenon where the plastic components become misshaped due to heat generated during the injection molding process. The heat is generated when the heated plastic flows into the molds and it tends to change the shape of the component due to its own heat. This issue can be countered by reducing the amount of heat generated during the injection molding process and improving the cooling process for reducing the residual heat in the component.
The second issue is that of sink marks. A sink mark is an indentation in the component which occurs due to the cooling of the molten plastic in the mold. In such cases, the thicker parts of the component tend to cool faster than the thinner portions and thus, indentations appear on the surface of the component. This issue can be addressed by controlling the cooling process. It is essential to maintain uniform thickness throughout the component so as to avoid this problem.
Thirdly, injection molding also results in flash formations. Flash means an extra portion of the material that is forced out of multiple parting lines and occurs along the parts of the component that are close to the edges of the mold. This could imply that the design or the construction of the mold may be wrong. The easiest way to reduce this problem would be to ensure that the molds are of proper size and design.
Fourthly, warpage is another issue with injection molding. Warpage occurs when the component comes out of the mold with uneven sides which result in change in shape. This occurs due to the residual stresses which develop within the component. To ensure that this problem is avoided and the components come out with consistent shape and size, the injection velocity should be kept at a consistent level, along with controlled cooling and uniform pressure during and after the injection.
Finally, injection molding also leads to surface imperfections. These imperfections usually occur due to the difference in temperature along the surface of the component which may result in it having a blurred surface. To avoid this issue, the combination of the internal temperature of the component, the speed of injection, and the pressure of the injector should be controlled and maintained to keep the surface smooth and uniform.
In conclusion, injection molding is a popular method of plastic component manufacturing and has been used for more than a century. However, this method has certain drawbacks in terms of heat distortion, sink marks, flash reforms, warpage and surface imperfections. To tackle these issues, it is essential to control the injection pressure, velocity and timing, as well as maintain a consistent cooling process. The molds should also be designed and developed in a way that these problems are minimised. The combination of these measures can help to produce parts with very little imperfections and deformities.
