Process variability in injection molding and the manufacturing of plastic parts leads to a variety of set-backs, such as product waste, low productivity, and poor quality parts. In other words, when the process of injection molding varies or becomes less efficient, these unwanted effects can result. To prevent inefficiency or poor quality parts from happening, process control (PC) is used to monitor and control process variability.
Plastic parts manufactured at The ERC have measurable attributes such as mass, dimensions, mechanical properties, and visual appearances. These attributes are affected by natural and assignable causes. Natural causes are inherent to the process and may include variables such as ambient temperature, machine variation, and relative humidity. Although it is difficult to control these variables, by monitoring the process and detecting these natural causes, it is easier to detect assignable causes.
Assignable causes are controllable and include items such as bad or worn-out machine components that should be replaced. Correcting or preventing assignable causes prevents the manufacturing of defective plastic parts. So, the advantage of Process Control is just that: to prevent the manufacturing of defective products and increase efficiency and productivity.
Check out Dr. Rex C Kanu's Study of Process Variablility to learn more about plastics materials and processing.