Notes on the use of the CTP version (on)

Plate printing is very important for prepress and printing processes, directly affecting the quality of printing and the economic benefits of printing companies. Therefore, it is very meaningful to exchange and discuss the operation of printing plates. Here, this article will combine the work experience, the use of the CTP version of the precautions, and exchanges with the industry colleagues.

Plate preparation
The preparation of the printing plate mainly includes two aspects: preparation before the machine and replacement of the printing plate.

1. Preparation before going to the machine
The following steps must be taken according to the specifications before the plate is placed on the machine.
(1) Check the quality of the printing plate to check whether the product name and plate printing specifications of the printed plate are consistent with the production process; check the color of the printed version; check the integrity of the text and graphic lines on the printing plate; , hand touch, check the cleanliness and flatness of the surface of the printing plate; measure the size of the printing plate.
(2) Measure the thickness of the plate Before using the machine version, measure the thickness of the plate with a micrometer. Due to the different quality of the plate base, the thickness of the same plate may be different, so at least the measurement of the mouth, the tip and the like should be carried out. Generally, the measurement point is not less than 4 points, and then the average value is obtained to facilitate the process according to the process requirements. The thickness of the liner paper was calculated.
(3) If the drawing rule line is multi-color overprinting, when the printing plate needs to be replaced in the middle, in order to ensure the basic accuracy after the plate loading, the method of “painting rule line” can be adopted in daily printing. The specific method is: draw the extension line on the corner line or the rule line on the printing plate, so that the extension line on the side of the printing plate can correspond to the positioning line drawn on the drum before the old printing plate is removed. The ruler line includes a circumferential (upper and lower) positioning line and an axial (left and right) positioning line.
(4) There are two types of mounting methods commonly used for mounting plates or nests: “hook type” and “plug type”. For presses that use the hook-and-load version, it is necessary to install a clip on the plate and the tip of the plate before the plate is used. When installing the clip, first loosen all the screws on the spare clip, then insert the plate between the plates and finally tighten the screws. Note the following when loading the plate: 1 plate must be installed in the middle of the plate, not to one side, to adjust easily after the plate is on the machine; 2 when tightening the plate screw, start from the middle to both sides It should not be carried out from the two sides to the middle to prevent the printing plate from wrapping up in the middle, which affects the flatness of the printing plate; 3 The printing plate must be tightly clamped to prevent it from falling off due to unclamping during printing.
For presses with a plug-in version, since the plates are attached to the plate cylinder of the press, the plate is required to be "rounded". The purpose of the rounded corners is to facilitate the insertion of the clips into the clips when the machine is installed. The specific method is: gently bend the printing plate into a suitable angle at the tip of the printing plate from the side of the printing plate 20 to 30 mm (depending on the model). Need to pay attention to the corner: 1 the corner of the corner should be appropriate, not too far from the edge of the plate, not too close, according to the angle of the plate cylinder and the drum surface; 2 angle of the angle can not be too large Generally, it should not exceed 60 degrees, and the bend should be avoided.
(5) Preparation of liner paper Pad paper should be made of special paper of different thickness with high flatness, tight texture, uniform thickness, clean and complete. Other papers cannot be used instead of liner paper, otherwise it will be deformed by liner paper. Or uneven thickness affects the printing pressure, thus affecting the quality of the printed product.
1 Calculate the thickness of the liner paper according to the thickness of the printing plate. The empirical formula is: thickness of the liner paper = standard liner thickness - plate thickness.
2 Select the liner paper according to the calculated thickness of the liner paper, and make the total thickness meet the required requirements, and not exceed or less than the required liner paper thickness.
3 The selected liner papers are overlapped in order from thick to thin (the thin paper is in contact with the roller body). If the length of the liner paper is not uniform (the size of the liner paper is not less than the standard size), it should first be guaranteed. The edges of the mouth are neat, and the liner paper is adhered with lubricating oil or grease at the mouth of the mouth to prevent the liner paper from being displaced from each other after the machine is turned on, causing a change in the local printing pressure.
4 On the paper surface in contact with the plate cylinder body, the oil is applied around the middle and the middle portion of the liner paper to prevent moisture on the printing plate from entering between the printing plate and the roller body during the printing process. The rust plate and the roller body affect the service life of the plate and the drum body.
5 Put the prepared liner paper together with the corresponding color plates, and avoid placing the liner paper randomly, so as not to be confused with other color liner papers, resulting in increased or reduced printing pressure. , affecting the quality of printing.
6 When preparing the liner paper, it should also be noted that sandpaper, iron filings and other debris should not be trapped in the liner paper to prevent damage to the printing plate and affect normal printing.

2. Replace the plate
Since the plate cylinders of various models have different mounting methods, the method of disassembling the plates is also different. As a printing operator, you must be familiar with the loading mechanism and plate loading method of the model you are using, so that you can quickly and accurately replace the plate during work.
(1) When changing the plate of the “hook-type” plate-loading mechanism, first clean the surface of the roller. At the rule line in the middle of the plate, draw a ruled line at the edge of the roller with a long ruler and a thin pencil. Extend the line and measure the distance between the positioning line and the edge of the roller, record it for later use, and then unload the plate. When unloading, loosen the screws on both sides, starting from the edge of the mouth, and remove the plate from the hook together with the plate. Turn the machine (forward) to the plate tip and remove the plate holder from the plate with the plate.
Adjust the adjusting screw at the hook so that the hook is in the middle of the screw so that the new version has sufficient adjustment during adjustment. When installing the new version, first check whether the top plate screws at both ends of the plate holder are in the middle of the screw, and then insert the plate at the tip of the plate into the slider hook of the roller to add the pre-prepared liner paper. Turn the machine a little and observe whether the positioning line drawn in the middle of the plate (including the upper and lower, left and right positions) is aligned with the edge drawn on the roller. If the left and right are not aligned, the plate can be moved. Then, turn the machine to the hook of the mouth, tighten the screws, check the line for errors, and further correct it. Finally, tighten the adjusting screw on the plate to tighten the plate.
(2) Plate replacement of the “plug-in” plate-loading mechanism When performing the demolition of the “plug-in” plate-making mechanism, as in the “hook-type” plate-loading mechanism, first draw the circumferential direction on the roller mouth (up and down) The extension line for positioning can also be based on the corner line of the mouth, and the axial positioning line (left and right lines) can be drawn on the clip of the mouth.
When disassembling, first loosen the fixing screws on the side of the mouth and the tip of the tip, and then start from the tip of the tractor (the different models are handled differently, and some machines can also start from the edge of the mouth) to remove the plate from Pull out the plate, pull the plate and liner paper with your hand, press the slow reverse button, turn the machine upside down, and slowly pull the plate out. When turning to the cornice, stop turning the machine and pull the plate's cornice out of the plate.
Adjust the plate holders on the sides of the jaws and the tips of the tips so that the top, bottom, left and right positions of the plates are at the “0” position of the scale (some imported machines have a micro adjuster, and the indicator should also be attributed to the “0” position). , to prepare for the adjustment of the subsequent plate position.
When installing the new version, insert the mouth into the holder of the plate on the edge of the plate cylinder, and align the plate according to the left and right lines drawn (if the left and right lines are not drawn, the plate needs to be placed in the middle of the plate). The margin on both sides of the plate should be approximately equal.) Tighten the fastening screws on the plate to check whether the upper and lower lines of the plate are aligned with the line drawn on the drum. If the plate clamp adjustment screw is not allowed Alignment. Then add the liner paper and rotate the machine to the tip of the roller. Then, the platen roller is dropped to press it against the printing plate to prevent the printing plate from being displaced. Insert the printing plate tip into the plate of the roller and tighten the fixing screw. Finally, tighten the adjusting screw on the plate to tighten the plate, check if all the screws are tightened, and then wait for the machine to start.
(3) Precautions for loading and unloading the printing plate 1 The loading and unloading work of the printing plate can only be carried out after the machine is stopped, and after the machine is stopped, the parking safety button or the machine electric switch should be locked.
2 When loading and unloading the plate, take the part of the plate. Do not directly grasp the sharp part of the plate by hand, and ask the two to perform the work together.
3 When hanging the plate, first pick up the safety hook of the plate cylinder, hang the plate on the tension hook, and fasten the safety hook.
4 When installing the plate clamp, first check whether the plate clamp screw is damaged. Then, for the center line of the positive plate, the liner paper is clamped together with the plate according to the standard requirements, and the screws are tightened to prevent the printing from falling off and in the drum. Apply oil to the side of the contact liner.
5 When adjusting the position of the plate, it must also be done after the machine stops rotating, and lock the stop fuse or pull down the machine switch.
6 When the clip is installed on one side, you must hold the hand by hand, and the hand should be more than 7cm away from the ink roller.
7When the two sides of the plate are clamped, the wrench should be suitable when tightening the screw. The screw must be tightened to prevent slipping and injury.
(To be continued)

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