Advertising in MoldMaking Technology offers
Issue link: https://mmt.epubxp.com/i/214665
Hot Runners By Sal Benenati Gain Process Control with a Specialized Hot Runner Temperature Controller Photos courtesy of Orycon Hot Runner Systems. Hot runner systems present unique thermal situations that require specialized temperature control for manifolds and nozzles. T ypically, a hot runner system refers to the heated manifold and nozzles that go into a mold; in reality, the controller, once it is coupled with the mold, also becomes an integral part of the system. When it comes to successful mold operation, the controller's performance is just as critical a factor as the mold components' performance. Accurate and responsive temperature control is essential, as the best manifold system in the world is not going to do the job all by itself, and obviously a great controller without a good manifold system is not going to be of much use. For the continued Consider specialized temperature controllers for manifolds accuracy of any and nozzles because of the very controller, it is very unique thermal siutation a hot runner system presents. For important to keep example, the manifold needs to the circuitry clean be kept at fairly elevated temand properly cooled. peratures, while the mold with which it is in contact needs to be cooled. General-purpose controllers, which may be adequate to control the temperature of a press barrel, are not going to work well in the dynamic environment of a hot runner system. In order to control both sides (heating and cooling) and optimize the entire system's performance, there is great value in finding suppliers who manufacture both controllers and manifold systems. Heat generated by internal circuits is transferred to the controller housing. The Controller Breakdown Hot runner controllers that are model-predictive and not proportional-integral-derivative (PID) allow users to zero in on the requirements of the hot runner system more readily, and without the trial and error of the conventional PID routine. The difference is that PID responds to parameters that are preset by the manufacturer and, in certain situations, by the user, based on expected zone conditions. However, conditions within the same hot runner system may differ substantially from one point to another. For instance, a manifold zone and a nozzle zone will behave completely different from one another, and if the same control parameters are used for both, the result is going to be less than desirable in one or the other. If one tries to make a universal PID setting, the result may be a compromise in performance for both zones. By contrast, model-predictive controllers sample the zone for current load (watts), response time and the rate of temperature rise, in addition to other conditions, and then use an algorithm to predict how and when to apply power in order to get the required results. Also, adjustment to the control parameters is constantly occurring during operation to compensate for factors moldmakingtechnology.com 27