Experiences With Closed-Loop Density Control

A concluding report in a series on the topics of the closed-loop control of inking in a heatset press gives the results of the practical experience with the system in a production environment. Results have been obtained of the behavior of the inking controller in production conditions and in response to many kinds of disturbances of the offset process and the printing press functions. The results show that the system can respond effectively to disturbances and maintain a constant density level for each of the four colors on both sides of the printed web. The user interface of the system seems to satisfy the needs of the printer when making special manual correction of individual pictures printed in special situations. The heatset printing press used as a pilot machine was about seven years old. The system gave satisfactory results. It has also been shown that the control is not an easy, straightforward operation, but a large, integrated control system.