Injection moulding machines are widely used in many industries in order to create a variety of different moulded products. The use of such machines requires the correct operation of a number of components and systems in order to ensure that parts are produced with the required level of accuracy and the correct repeatability. One of the components in a moulding machine that requires constant monitoring and knowledgeable operation is the hot runner system.
The hot runner system is responsible for controlling lines of molten plastic that run between a heated manifold and the injection moulding tool. These lines are generally comprised of small diameter pipes, known as ‘runners’, with a series of hot runner nozzles located at the far end. It is these nozzles that control the molten plastic as it is injected into the moulding tool. As the molten plastic is delivered to the moulding tool it takes the shape of the desired product and as the plastic cools it is ejected from the tool.
While this hot runner system is a key component in the moulding process, it is also prone to a number of faults which can lead to significant issues in the production process. The most common of these faults are a result of incorrect set up of the hot runner system, such as the wrong temperature settings, poor calibration, or the incorrect sizing or placement of the runners.
When these faults occur, it can result in problems with the quality and consistency of the parts, as well as the overall efficiency of the moulding process. These faults can be difficult to diagnose and rectify as they require a detailed knowledge of the injection moulding process and the characteristics of the moulded part.
In order to overcome these issues and ensure that the hot runner system is running smoothly, it is important to apply a methodology known as root cause analysis (RCA). RCA is a systematic approach to the analysis of a problem which enables the identification of the root cause of the problem, and thus, its resolution.
The RCA process involves identifying the key variables affecting the production process, including inputs and outputs of molten plastic. The possible causes of the fault can then be explored in detail, with a particular focus on failures related to the temperature and calibration settings of the hot runner system, as well as the materials of construction for the nozzles and runners. Once a likely cause has been identified it is important to perform tests in order to validate the conclusions and then to rectify any underlying issues.
In addition to the methodology of RCA, there are also a number of other measures which can be implemented in order to reduce the risk of hot runner system faults and improve the overall efficiency of the moulding process. One of the most important of these is the regular maintenance of the hot runner system. This includes cleaning, inspection and calibration of the temperature and runner settings, as well as the replacement of worn components. Other measures include implementing a monitoring system to ensure that components are not operating outside of the specified parameters, and the use of modern materials and processes which can help to reduce hot runner system vulnerabilities.
Overall, the hot runners system is a key component of the injection moulding process and understanding the common faults and their causes is important in order to ensure that the process runs smoothly and efficiently. The use of RCA and other measures to improve the reliability of the hot runner system can help to drastically reduce the amount of time and energy required for maintenance and rework, enabling more efficient production and reducing costs.
