Plate alignment correction operation and experience
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In the more advanced management abroad, one of the most important aspects of the control of production costs is the control of the so-called press Make-ready time. The three main parts of this so-called printing preparation time are the setting of the printing press, the correction of the ink color of the printing, and the timing of the position correction. The speed of the work of the position correction will directly affect the preparation time of the entire printing preparation. The extension of the printing preparation time will mean the idle printing equipment, which means the printing cost is increased. Therefore, it is necessary to discuss how to quickly and accurately adjust the registration of the plate. Below we will discuss some of the plate alignment correction operations (hereinafter referred to as the school edition) in the preparation of the printing and how to effectively improve the efficiency of this work.
There are two factors to consider in the school work. One is the positioning of the core (the graphic part) on the substrate, and the other is the registration between the version and the version (which also includes the registration between the front and back of the print). ).
First, the position of the printing plate in the graphic part.
The positioning of the plate's heart on the substrate is the first step in correct calibration.
The so-called positioning of the core is actually to accurately position the graphic on the printing plate on the substrate, thus meeting the requirements of overprinting and post-press processing. For our more common prints, the printed parts we need to print are completely printed on the surface of the substrate, and there must be margins to meet the requirements of the finished product, while also meeting the special requirements of some post-press processing.
· For different plates and substrates, the positioning of the core should follow the following principles:
1. In order to meet the follow-up work of printing (cutting, binding, etc.) can be carried out accurately and smoothly, unless it is not allowed, generally require the core border (the dotted line of the figure) and the edge of the substrate (Figure 1 a thick black line frame ) Parallel.
2. If the core is small and the substrate is large, the core should be centered on the substrate, up and down, left and right.
3. When the core is large and the substrate area is compact, at least the cutting distance of the edge of the graphic should be guaranteed (the red arrow in Figure 1 refers to the cutting distance).
4. For angular plates, all four corners are generally printed and the size of the mouth is the same. When it is not guaranteed that all the four corner lines are printed, the size of the cornice can be appropriately reduced without affecting the clarity of the image of the cornice, so that all the corners of the drag are printed.
5. According to the characteristics of the printed graphic and the characteristics of the offset printing process, the positioning edge of the printed head or the printed sheet should be kept as large as possible, and the non-positioning side of the foot or the printed sheet should be kept smaller.
6. Under the premise of ensuring the correct position of the core, it is necessary to ensure that the error between color and color does not exceed 0.1 mm for multi-color prints, and the back overprinting should not exceed 0.5 mm.
· In actual production operations, in addition to strict work orders, we have the following considerations:
1. The actual printed paper cannot completely guarantee that the edges of the paper are completely neat due to the cutting reasons (that is, the cutting size is deviated). Therefore, when we are correcting the position, we should make the appropriate movement of the core to the rule according to the error degree of the paper size.
2. When there is a graphic text in the position of the printed version of the heart, especially the "bleeding" printing, try to drag the heart of the plate. There are two advantages to doing this. One is to ensure that the part of the picture can be printed as much as possible; the other is to reduce the damage to the picture part due to the serious version.
3. For some products with special binding requirements, it should be carefully analyzed. For example, as shown in Figure 2, the figure requires the first steps of 2 and 2 rolling to complete the binding, which requires us to set the distance a and the distance b. The alignment is corrected when the plate is corrected, or a is slightly smaller than b (if a is greater than b, the left edge will be folded at B at 2 folds, which may result in difficulty in binding).
Above, we briefly introduced some issues that need to be paid attention to during the calibration of the printing plate. The position of the core on the substrate should be well known.
The overprinting between the color and the color of the printing plate and the front and back is actually the same as the positioning operation of the printing plate on the substrate. It is only necessary to pull the printing plates to the predetermined printing plate positioning position (or use Other ways, the following are introduced), it can be, this article is no longer discussed.
Second, the actual operation of the school version.
The operation of the school version seems to be a very simple question. Many people think that it is only a skilled process. Most operators are often from the perspective of the master. Few people are trained in this aspect. There are many ways to manipulate the position correction. Many people think that no matter what method is used, just correct the position. In fact, the author believes that there is only one correct corrective idea, and the correct idea can be used to make it fast and accurate. The correction of the position, and the wrong or irregular correction method will often be in the middle of the work, affecting work efficiency, and even lead to unnecessary quality problems. Let's talk about how to operate the plate correction.
**The way we often use to adjust the position of the plate (actually the relative position between the plate and the substrate) is:
1. Top page operation. That is, the axial position of the plate is adjusted by the top plate screws at both ends of the plate plate.
2. Pull the plate operation. The circumferential position of the plate is adjusted by the plate screws (also called the plate screws) on the plate plate.
3. Side gauge adjustment. The axial position (relative to the substrate) of all the color plates on the press is simultaneously adjusted by changing the position of the side gauges.
4. Front regulation. The circumferential position (relative to the substrate) of all the color plates on the press is adjusted by changing the front and rear positions of the front flap. The range of this adjustment is generally small, not more than 0.3mm, and the author's experience in the work does not advocate adjusting the relative position of the plate by adjusting the front gauge.
5. Adjustment mechanism adjustment. Generally, the adjustment mechanism is generally available on two-color or more printing machines, and the adjustment is simple, rapid, accurate, and intuitive, but generally the adjustment range is small (the axial direction is generally ±0.4; the circumferential direction is ±0.2), which is printed. When the version error is large, it depends on the top plate and the pull plate for adjustment. The adjustment mechanism has axial and circumferential adjustment mechanisms, and the modern high-speed multi-color machine also has a plate skew adjustment mechanism (although the adjustment range of this adjustment mechanism is generally very small, only 0.1mm). The above operations are mainly performed by a manual wheel or a console.
6. Borrow the drum. The circumferential position of the printing plate is adjusted in parallel by changing the relative positions of the plate cylinder and the drum end drive gear. When the circumferential position of the printing plate needs to be changed greatly, and the pulling mechanism is incapable, or when the adjustment by the drawing mechanism is more time consuming and troublesome, the borrowing roller is usually used.
For general printed matter, it is usually first adjusted (coarse adjustment) in the trial printing by the top plate and the stencil screw on the plate cylinder. When the printing plate is within the range that can be controlled by the adjustment device, the tone is used again. The device is fine-tuned (fine tuning).
** Generally there are several steps for the school work:
1. Firstly, the circumferential position of the printed matter on the substrate is adjusted by the side gauge. Generally, the work is done after the previous batch of printing is printed, and the next batch of printing is adjusted according to the size of the substrate before starting the printing. It does not need to be moved during the calibration process, but if it involves the simultaneous translation of the axial position of all the plates on the printing press, it is very convenient and quick to adjust using the side gauge.
2. Trial printing operation.
3. For printing plates with a large difference in circumferential position, the operation of the borrowing roller (the surface of the plate cylinder is scaled) is performed. According to the results of the trial printing, the first calibration of the printing plate is performed according to the rule line on the printing. This adjustment is generally by means of drawing and topping. Of course, the error is relatively small and can be adjusted directly through the adjustment mechanism.
4. Repeat the test print. If the layout is still very different, repeat the third step.
5. Until the error between the plates is relatively small (to reach the adjustment range of the plate-changing mechanism), the plate is precisely adjusted by the plate-adjusting mechanism.
6. When the positioning of the printing plate on the printed product and the positioning between the plates reach the printing precision required for the printing, the color correction can be performed, or the printing can be started after the color correction.
** In the above-mentioned school calibration operation, it is more time-consuming to make a rough adjustment of the position of the printing plate in steps 3 and 4. In the following, we will explain this process by taking two-color overprinting as an example:
The characteristic of the A picture is that the red plate and the black plate are parallel and misaligned. This situation is the simplest to correct. The difference between the plates seen on the rule line and the length of the actual plate is the same. Simply loosen the stencil screw at the red plate and pull the plate to the corresponding length. Finally, re-tighten all the tensioning screws that are slightly pulled, then tighten the screws in the middle of the mouth. (Another case is that the plates are axially parallel and dislocated. As in the case of A, as long as the top plate screws in the corresponding positions are loosened, the top plate screws can be used to move according to the distance seen on the plate).
Note: 1. When pulling the screw at the loose tip, it is longer than the actual length of the plate, and try to loosen it as much as possible to avoid the friction between the plate and the plate cylinder obstructing the plate, thus causing the plate. Stretching deformation; 2. When the distance between the two colors is relatively large, after loosening the screw, the left and right ends of the printing plate (for the misalignment of the axial direction are the mouth and the drag) are separated by one millimeter. Alternately pull the plate (that is, you can not pull the end and then pull the other end) to avoid large sliding of the plate on the plate cylinder. 3. When the axial parallel adjustment and the circumferential parallel adjustment of the printing plate need to be carried out at the same time, the top plate and the back plate should be pulled first. This is a principle that the author insists on in the work, which can effectively avoid the parallel printing plates. There is a skew. 4. The tension of each plate should be consistent. 5. In the above-mentioned and following drawing operations, the stencil screw is the plate tensioning screw on both sides of the plate holder, instead of the intermediate tensioning screw.
The characteristic of the B picture is that the angular line at the left side of the mouth is basically registered, and the remaining rule lines have large or small deviations. We can imagine a shaft or a center of the circle. When correcting the position, let the plate rotate along this axis. Assume that the screw at the lower left corner of the mouth is this axis, and release all the pull plates of the red version. Screw (the right end can not be loose), first drag the left end of the top plate screw to the right to the right distance, and then pull the corresponding distance of the edge of the screw, and finally pull the slightly screw and the mouth in the same way as A Screws.
Note: 1. Be sure to first position the axial position of the corresponding position, and then adjust the circumferential direction, because the printing plate is slightly sandwiched between the mouth and the mouth, and generally will not be deformed. When the printing plate is topped and then the drawing operation is performed, the circumferential direction of the printing plate is not easily deformed. 2. The distance of the top plate cannot be determined by the difference in the angle. Because, as we just mentioned, the process of correction is as if the plate is rotating around a center, and the distance between the screw and the corner of the top plate is different from the center of the circle. Therefore, the difference in the distance on the corner cannot be directly passed. The top plate screws are corrected at the same distance. Coincidentally, the circumferential error of the plate at the corresponding position is exactly the same as the length of the top, and generally we need to pull more in the work. 3. The greater the skew of the plate, the greater the length of the plate (top) should be greater than the error displayed on the middle (corner) line (generally this increased range should be continuously gained by accumulating experience) ). 4. When the circumferential error of the printing plate is less than 0.5mm, the top plate can be used, and the pull-down plate can be directly pulled in the relative position. Since the degree of skew of the printing plate is not very large, pull directly. It is possible to straighten the skewed plate, in which case the plate deformation described above does not occur.
The C picture is a bit more complicated, and all the rules are misplaced, but we can also think of the red version as a misalignment that occurs in a counterclockwise direction. After the analysis, we found that in the process of correction, the left end of the red needs to be pulled slightly, and the right end of the red needs to be pulled toward the mouth. According to our analysis in B, when the plate is severely skewed, the top plate should be pulled first. The specific steps are to loosen all the plate tensioning screws except the screws that need to be pulled (to the leftmost end and the rightmost end of the jaw). After the mouth and the slightest position of the top plate, pull the plate. When the drawing is finished, you should promptly tighten all the screws on the plate.
This is a cumbersome situation in the registration of the printing plate, especially when the degree of skew of the printing plate is relatively large, the main reason is that the amount of the top plate is not well determined. How much is the top of the mouth? How much is it to be dragged? Let's remember the following formula: drag the top amount of the plate + the top plate version = the amount of the mouth pull plate + drag the amount of the plate
Generally speaking, the amount of the plate is well determined, as long as the degree of skew of the plate is integrated from the printed rule line (there is a certain experience here). What about the top plate? Although we can't directly determine the amount of topping, we can initially estimate the proportion of left and right skew. By relying on this ratio, we can easily calculate the amount of the top plate. This process seems complicated. In fact, after mastering the proficiency, you can calculate the errors of the four plates in one or two minutes.
The above-mentioned situations are just a few typical examples of the position correction in our daily work. In fact, what we can encounter in daily work is often the case where these situations are mixed together. We are at work. As long as you carefully analyze the amount of parallel misalignment in the printing plate (the amount is directly visible from the printed product), the amount of skew is large (the judgment is often important) Then you can combine the amount of the top plate and the amount of the plate to be combined, but pay attention to the principle of first pulling back.
A, B, C adjustment should pay attention to a problem, that is, when tightening the screw, do not use brute force, and the strength of the tension plate is the same (each plate of a plate should be the same, each color plate The tension of the screws should be the same as each other).
When the initial adjustment mentioned above is finished, that is to say, after the trial printing, the graphic overprinting error on the printed product is less than the range that can be adjusted by the adjustment mechanism, we can use the plate mechanism to precisely adjust. . (In fact, in many domestically produced old-fashioned printing presses, there is no adjustment mechanism or it is damaged, so it is further adjusted by manual drawing and top printing). This kind of adjustment is generally simple and intuitive, so it is not introduced too much.
Third, the tips for speeding up the school work:
1. If the printing work of the printing factory has not changed all the year round (for example, many manufacturers who mainly print books and periodicals, and the types of printed products are very monotonous throughout the year), you can draw lines on the roller of the plate cylinder as the standard, each time printing. Draw an extension line on the corner of the plate at the front of the plate to follow the drawn online version on the roll. In this way, the error in the circumferential direction is generally not higher than 0.5mm. If the plate is positive, it can be directly corrected by the automatic or manual adjustment mechanism to complete the overprinting work.
2. When printing the upper plate, pay attention to loosening the tensioning screw at the mouth to two to three wrenches (according to the experience of the tight plate), fix the plate to the plate, and tighten the plate with a slight screw. Then, tighten the screw at the plate mouth (just to get back the amount of loosening at the beginning). This can effectively avoid moving the plate to the mouth of the mouth about 0.5~1mm after each plate-up, and when the plate is pressed, the plate will be pulled back in the direction of the drag.
3. Before the operation of the upper plate, pay attention to centering the plate at the mouth of the plate, and use the plug to adjust the top plate screw on the side of the mouth to 0.3 mm from the inner wall of the side of the drum. The way of the cycle is realized); the plate is centered on the plate at the mouth of the plate when the plate is on the plate (the model with the positioning pin can be positioned directly, and the model without the pin can draw the rule line at the center of the mouth) Reverse the extension so that the extension line is aligned with the gap on the clip or the center line that was previously found and marked). The above operation can effectively control the error of the initial position of the printing plate when it is on the machine, and can basically ensure that the top plate operation is not performed at the position of the mouth. When the plate is skewed, it is sufficient to just push the top plate.
4. When the plates of all color groups on the machine need to be adjusted synchronously, sometimes it can be realized by adjusting the front and rear positions of the front gauge. However, we do not advocate this in the old-fashioned printing machines, because the adjustment of the front gauge on the old-fashioned domestic printing press is often very troublesome, and it seems to save trouble, in fact, it is a waste of time. If in some cases the front gauge must be used for adjustment, make a record and adjust it back to the original position after the end of this printing to avoid confusion at the working position.
5. When the mouth of the plate changes, the pre-adjusting screw must be pre-adjusted before the plate. (If the plate is required to be larger than the previous one, it will be on the plate before the plate. The screw is adjusted accordingly (that is, the corresponding pre-adjustment of the jaw tensioning screw).
6. When the encounter is slightly registered and the mouth has not been put on (or the mouth is covered and the tip is not set), it can be set as far as possible by appropriately tightening the tensioning screw at the corresponding position. quasi.