Method for detecting overprint errors of photogravure press on the basis of field programmable gate array (FPGA)

Abstract

The invention discloses a method for detecting overprint errors of a photogravure press on the basis of a field programmable gate array (FPGA). The method comprises the following steps of: (1) taking a pulse signal after detecting a color code by two photoelectric eyes as a detecting pulse; (2) taking pulses A and B of an encoder as reference pulses and clock signals of an encoder pulse counter, taking a high-frequency clock in the FPGA as a clock signal of a system clock counter, and determining actual position values of the two photoelectric eyes according to an encoder pulse counter value corresponding to the detecting pulse, a system clock counter value, and system clock count value respectively corresponding to two pulses adjacent to the reference pulses respectively corresponding to two detecting pulses; and (3) determining the pulse count of the two photoelectric eyes within a time interval, wherein the arithmetic product of the pulse count and a pulse equivalent weight is an overprint deviation value. In the method, the high-frequency clock of the FPGA is used for subdividing the encoder to improve the resolution of the encoder so that the detection accuracy of the overprint errors is greatly improved and can meet photogravure registering requirements.

Description

technical field [0001] The invention relates to the field of overprint error detection of a gravure printing machine, in particular to an FPGA-based method for detecting an overprint error of an electronic axis gravure printing machine. Background technique [0002] When the unit-type gravure printing machine performs color printing, in the process of multi-color overprinting, due to various reasons, such as poor parallelism between the guide roller and the pressure roller, inflexible rotation and poor dynamic balance, fluctuations in tension, and uneven thickness of the printing material Uniformity and thermal deformation will inevitably produce color deviation. The occurrence of this color registration deviation is random, and the difference is also uncertain. Therefore, it is necessary to track, detect and adjust the registration of each color group in real time to ensure the printing quality. [0003] At present, photoelectric detection methods are mostly used to detect...

AI Technical Summary

Problems solved by technology

The encoder pulse counting method indirectly measures the position difference between the two color marks by detecting the encoder position signal. The detection circuit is simple, but the detection accuracy is limited by the resolution of the encoder, which is difficult to meet the high-speed and high-precision requirements; the speed-time method uses a high-frequency counter The time interval between the detection of two color marks is multiplied by the speed of the printing plate cylinder detected by the encoder, so as to obtain the position difference between the two color marks. Due to the fluctuation of the rotation speed of the printing plate cylinder during the printing process, there is a deviation in speed measurement, and the detection of color registration deviation fluctuates greatly.

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