When I used Guanghua PZ650 offset printing machine to print a batch of graduation commemorative albums, I found that the offset printing machine can print paper of general size smoothly, but when printing larger size paper (less than 650mm × 480mm), it will produce a transmission surface The phenomenon that the paper is not in place prevents the paper from passing through the paper feed detector. In severe cases, the paper feed detector will also issue a paper skew alarm, causing the paper feeder to stop working.
Failure analysis
After careful inspection, it was found that the adjustable slider on the side gauge collided with the paper feed row on the delivery roller at the handover position, and the front and rear positions of the front gauge and the height of the front gauge baffle and the cardboard were not consistent. Therefore, the phenomenon that the paper under the transmission surface is not in place is caused. In this regard, the author readjusted the height of the paperboard, the front and back positions of the front gauge and the detection time of the paper detector. After the adjustment is completed, the phenomenon that the paper under the transmission surface is not in place can be solved, but the large-size paper still cannot pass the paper feed detector.
Here, the author first analyzes the positioning sequence of the paper: the front gauge first descends to the positioning position, and then the paper reaches the front gauge for circumferential positioning. After the paper is collided at the front gauge, the side gauge performs lateral orientation The paper is pulled to complete the axial positioning of the paper. After the paper is positioned, it is transported to the printing unit for printing.
The moment when the front gauge drops into place and the side gauge pulls the paper is the stage where the front gauge detection system makes judgments and handles whether the paper reaches the front gauge as required. If the proximity switch indicator lights up, it indicates that the paper has reached the front gauge; if the "early arrival" indicator lights up, it indicates that the paper has reached the front gauge before the front gauge drops into place. Once this situation is encountered, the system The program will order the device to stop urgently, otherwise the paper will not only be unable to be accurately positioned, but will also cause damage to the device; if the “late arrival†indicator lights up, it means that the paper is skewed or the side gauge starts to pull the paper before the paper has reached the front gauge At this time, the system program will order the feeder and printing unit to stop working to prevent late paper from entering the printing unit. In addition, the system will default to normal paper transport.
From this point of view, the author believes that the large size paper cannot pass the paper feed detector is most likely due to a detection error in the detection system at the front gauge, so that the proximity switch indicator has been lit before the front gauge has been lowered into place. . Specifically, when printing large-size paper, the signal path is turned on by the proximity switch before the previous paper leaves the previous specified position, and the indicator lights up, causing the system program to consider the trailing edge of the first paper as the latter The mouth of the sheet of paper is wrongly judged as the "early arrival" phenomenon of the next sheet of paper. The system program orders the device to perform an emergency stop. Therefore, large-size paper cannot always pass through the paper feed detector, while normal-size paper Because the width is narrow, it can pass the paper feed detector smoothly.
The author believes that the key to eliminating such faults is to ensure that the front gauge proximity switch can always operate in accordance with the front gauge and the side gauge. Therefore, it is necessary to accurately adjust the front gauge proximity switch. The key to the adjustment of the front gauge proximity switch is that the rotation angle of the delivery tooth row should be consistent with the opening angle of the induction iron sheet. The specific adjustments are as follows:
â‘ Install the induction iron piece in the center of the proximity switch slot and keep a distance of 2mm from the bottom of the proximity switch slot. It is worth noting that during installation, avoid the sensor iron touching the proximity switch.
② Install the dial to keep the angle between the gripper of the transfer roller and the panel at 90 °, and return the encoder to "0".
③Reverse the delivery tooth row by 15 ° to reach the edge of the induction iron sheet, and the edge of the induction iron sheet should be in the proximity switch slot. At this time, the proximity switch indicator light just lights up or goes out. When the vacant part passes through the proximity switch slot, the proximity switch indicator should always be on.
After the commissioning is completed, the test printing is started and the fault is completely eliminated.
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