Offset printing is currently the main printing method for printing companies. The failure of lithographic offset printing due to the output system is the main reason for the inaccurate overprinting, uneven ink color, and even the failure to print, which delays the delivery time. This is one of the more difficult problems that printing workers most often encounter.
1. Double or multiple paper feeding failure
1. The paper is uneven and the edges are upturned. When the air flow from the loose paper blowing nozzle touches the edge of the paper, the edge of the paper is raised to an arc angle, and the air flow is divided into two parts. One part of the airflow lifts the paper upward, while the other part of the airflow presses the paper downward, making the paper unable to separate, and the paper blocking brush is also useless, resulting in double or multiple sheets, or even a large stack of cardboard. The general processing method is to remove the paper for knocking paper processing, so that the paper is smooth and easy to separate.
2. The paper loading height exceeds the allowable height of the paper stopper. According to the previous printing experience, the height of the general paper loading should be about 5mm lower than the paper teeth. If the adjustment is inappropriate and exceeds its allowable range, double or multiple sheets will be produced to enter the cardboard. The general processing method is to use a stopper wedge to control and keep the paper on the same plane. If there is a model with an adjuster, you can use the adjuster to reduce the paper height to solve.
3. The blower presser foot and paper blocking brush extend too little into the edge of the paper. According to the previous operation experience, the general paper blocking brush extends into the paper edge about 8mm, and the air blowing pressure foot extends into the paper edge about 10-15mm. Double or multiple sheets will appear if the adjustment is incorrect or the paper is not cut properly. Generally, the paper feeder is adjusted closer, the separation nozzle is about 5mm away from the edge of the paper, and the paper blocking brush and the air pressure foot are adjusted to solve.
4. When the paper is too thin, the air volume is not adjusted properly. When printing 70g / m2 thin paper, if the air volume is not adjusted properly, it is also easy to produce double or multiple sheets. The general processing methods are as follows: (1) Adjust the blowing foot downward, increase the distance between the stack and the separation nozzle; (2) Adjust the air volume appropriately; (3) Reduce the separation nozzle Rubber band or transparent glue to reduce the wind force; (4) Press the paper brush down and increase its pressure to control.
5. The paper is not loose or sticky. Generally, when cutting paper, there is adhesion at the cutting edge, or when printing the full version of the semi-finished product, water stains and ink stains cause adhesion, thereby forming double or multiple sheets. Therefore, before printing, that is, when the paper is loaded into the machine, it must be shaken hard and stacked, and the semi-finished products should be loosened one by one, and the package should be installed a little less to avoid sticking due to heavy pressure. .
6. The blower foot is worn. When the blower presser foot is used for a period of time, it will wear out. When it presses down on the paper, the paper will make an oblique angle, the force will change the direction, the paper will move forward, and the paper blocking brush will be lost Function, when the paper separation nozzle sucks the paper down, it will suck on the edge of the paper and form double or multiple sheets. Generally, it is replaced by a new blower presser foot. If the wear is not too serious, it can be solved by welding copper sheets and then filing with a file.
Second, the product ink color uneven failure
The reasons for the uneven ink color of the product are: (1) The cylindricity wear of the rubber rollers of water transfer, ink transfer, ink distribution and version ink, the wear of the shaft head of the bearing, the aging of the rubber roller skin, the decline of the ink transfer ability, etc. ; (2) Peeling of the water roll roller layer, cylindricity wear and tear, thin ink layer on the surface, and ink accumulation bands on the two ends, causing uneven roller ink squashing; (3) The support depends on the plate water 〠The lock of the ink roller and the swinging bracket are seriously worn, which causes the rubber roller to jump when it is against the plate, resulting in unstable pressure of the plate, resulting in unbalanced ink and ink, uneven ink color, dry plate, ink bar, old version Excessive pressure) and other phenomena; (4) the aging or poor quality of the water roller fleece causes the water transmission capacity to decrease; (5) the pressure of each ink roller and plate cylinder and the plate ink roller is not regularly checked; (6) if the roller The transmission gear wears out of tolerance, and regular "gear ink bars" appear at the same distance as the gears.
3. Overprint failure
1. The effect of printing plate deformation on overprinting. The metal sheet has a certain degree of extensibility, which will produce tensile deformation under the action of tension, and the tensile deformation of the zinc plate is more obvious. Under normal circumstances, we find that overprinting is not accurate when printing, and most of them are adjusted by stretching the printing plate. The greater the tensile force, the greater the tensile deformation of the layout, and the uneven distribution of the tensile deformation. The maximum stress is applied to the grip and edge of the plate, and the tensile deformation is also large, the internal force is small, and the tensile deformation is also small. Therefore, try to reduce the problem of inaccurate overprinting by using as few plates as possible.
2. The effect of the increase or decrease of the roller pad on the overprint. In the printing process, when the overprint is not accurate due to the expansion and contraction of the paper, the method of increasing or decreasing the thickness of the roller pad can be used to solve the problem of inaccurate overprint between the diameters. The increase or decrease of the printing plate liner affects the printing plate deformation. The thicker the plate liner, the larger the graphic size extension. When the printing plate liner is reduced and the rubber cylinder liner is increased, it is revealed that the tensile deformation of the grey cloth increases and the radial deformation of the figure increases. The other is to reduce the thickness of the rubber cylinder and increase the thickness of the plate pad at the same time, then the amount of deformation of the rubber sheet is reduced, and the latter is generally used.
3. The effect of blanket elongation on graphic overprinting. The blanket is stretchable. The tighter the blanket is stretched on the roller, the smaller the elongation, and the smaller the graphic change. (1) Choose a rubber cloth with a small elongation. (2) During the process of overprinting, try to keep the rubber band tightness unchanged.
In addition to the above reasons, we should pay attention to mechanical, adjustment, paper and other issues. In short, overprinting is usually generated at the moment of high-speed printing, which is accumulated by a small amount of change It is difficult to observe directly. Therefore, as long as we pay full attention to printing, analyze the reasons, and take the most appropriate measures, we can avoid or reduce the occurrence of overprinting errors.
Normally, Cookie Cutter thickness is 0.3mm, height for each one is 3cm, unit price not include package cost. With this fantastic set of Cookie Cutters, you will easily be able to make gorgeous Pinterest-inspired cookies for holiday gifts and cookie trays. We use these Cookie Cutters ourselves and want the best for our family and yours. The simple design is easy to clean, the folded edges are kind to hands, and the welded seam won`t come unstuck. Your new set of cookie cutters will be such a pleasure to use, you`ll soon be creating trays of beautiful and delicious cookies. And the cookie cutters also pass FDA test.
Cookie Cutter
Ss Cookie Cutter,Shape Cookie Cutter,Color Coated Cookie Cutter,Pp Cookie Cutters
Homefelt Houseware co.,ltd , https://www.dghomefelt.com