Lithography troubleshooting (1)
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Chapter 1 Paper feeding and delivery
This chapter lists common problems with paper feeding and delivery, possible causes and treatments, and overcomes or avoids it. Under certain conditions, some treatment methods are unusable. For example, the printing machine may not be equipped with equipment that can handle specific problems. The manager should consider adding the necessary equipment to enhance the production efficiency of the printing press. If the processing method is recommended to be refurbished, the management should arrange the time. Come repair.
Replace paper or ink or plates and contact the manufacturer or supplier if problems occur after the problem has been diagnosed. (Another method can be called to the PIA / GATF Paper and Ink Lab (8 0 0 – 9 1 0 4 2 8 3 ext. 5 8 5). The PIA / GATF Laboratory Services team can print both before and after printing. Evaluating materials and addressing the difficulties of printing as planned, all PIA / GATF ink and paper tests are performed according to industry standard methods).
1. The paper is not in place or given to double sheets
Reason 1 : Whether the stack height is appropriate, if it is too high, it will probably exceed one sheet of paper; if it is too low, it will be a paper feed error.
Remedy: Adjust the stack to the top of the front bezel 3 / 16 in. (5 m m ); then set the height of the paper to adjust the nozzle.
Cause 2: There is too much blowing in the separation and the mouth setting is too low.
Remedy: Readjust the blow port to match the stack height and reduce the blow pressure.
Cause 3: The nozzle function is not appropriate.
Handling: ① If the nozzle is dirty, clean it and keep it clean.
②If the nozzle is worn, replace it.
③ On older presses, the rotary valve in the paper feed head must be cleaned.
④ If you want to adjust the nozzle, adjust the separation nozzle to only touch the topmost paper at the appropriate height of the stack. This occurs when the blown air is still in progress. The stroke of the nozzle surface must be parallel to the paper surface. .
⑤ When the nozzle that is being sent is at the rear, the front nozzle should be matched with the time when the separation nozzle has just sucked the paper. Refer to the printer's operating manual to use the various nozzles, whenever the vacuum is at maximum. If the paper is deformed or damaged, use a dedicated nozzle.
Cause 4: The paper sticks together when cutting.
Handling: Intake air into the paper and loosen the paper so that it no longer sticks.
Cause 5: The paper is static.
Handling: ① Install air ion enthalpy in the air tube, which should be replaced every year.
② Keep the humidity in the equipment room above 3 5 % (the printing room is usually at 50% ± 5% relative humidity, but 3 5 % can greatly reduce static electricity).
2. Paper feeding is not smooth
Cause 1: The paper separated above gives too much or too little air, and too much blowing causes the front end of the paper to wave, causing the paper to be uneven. Handling: Use only enough air to separate the top sheets of paper. If the paper is stuck, it is best to re-stack and roll off the paper, which is better than using a stronger blow.
Reason 2: The flywheel head rotation valve is not clean, the groove of the runner is blocked by dusting, oil stains and debris. This valve controls the vacuum and blowing of the nozzle. If one of the front feed nozzles is faster than the other, the paper may be twisted and the paper feed may be uneven when it is fed to the paper feed table.
Treatment: Clean the rotary valve.
Cause 3: The mouthpiece is not aligned correctly.
Remedy: Smooth the mouthpiece.
3. There are smudges on the printing paper
Cause: The compressor is overheated or improperly refueled. Overheating can be caused by negligence, using improperly lubricated oil or operating air pressure is too high. The lubricating oil evaporates due to overheating and cools down as it passes through the gas pipe, which is usually caused by excessive lubrication of the compressor.
Disposal: According to the supplementary lubrication and maintenance in the operation manual, adjust the air-discharging valve so that the compression air pressure is at a moderate level, flush the compressor twice a year, according to the correct detergent and washing method in the supplementary instructions.
4. Skewed or blocked on the paper feed table
Cause 1: The paper feed roller is concave, uneven, or too smooth.
Remedy: Replace the new rubber on the wheel. Adjust the front feed roller on the feed roller when adjusting the paper feed table according to the operation manual.
Cause 2: The conveyor has a flare or small crack, or the belt joint is loose. Such problems can damage the end of the paper or cause distortion and blockage in the front gear. Remedy: Replace the strap.
Cause 3: The board is rusted or damp.
Handling: Keep the cardboard clean.
Cause 4: The front end of the paper is curled or the corners cannot enter the edge gauge and cause skew and blockage.
Remedy: Re-stack, eliminate the problem of the front and corners of the paper (hand flattening, flattening).
Cause 5 : Static electricity is accumulated on the paper or the conveyor belt.
Handling: ① Install a commercial static eliminator.
② If the relative humidity is too low, the printing room should be humidified.
5. The abnormality of the front gauge (not allowed)
Cause 1: The gap between the platen and the paper is not enough.
Handling: When printing thin paper, use a thickness gauge to adjust the space through which the paper can pass. For papers with a thickness of more than 0.25 m m, adjust the space 1.5 times thicker than the paper.
Cause 2: The gap between the platen and the paper is too large, which will make the paper curl up or bounce back from the front.
Remedy: Adjust the space as the Cause 1 method.
Cause 3: The wheel at the end of the plate is too late or too far forward.
Remedy: Re-adjust the position of the pressure roller to the front gear position according to the end of the paper. Use a steel or soft brush wheel (no rubber wheel is available).
Cause 4: There is no perfect straight line at the front or rear end of the paper, or the length from front to back changes. The result is similar to the position of the rear wheel.
Cause 5: The pressure roller has insufficient gripper tension, and the ink viscosity is too high, causing the printing paper to slide in the biting claw and causing the front gauge to be inaccurate.
Handling: ① Clean the jaws and adjust them on time. The printing press should clean and adjust the claws every three months.
② The bite pad should be replaced if it is damaged.
③ Check the average of the jaws and increase the pressure if necessary.
Reason 6: The front end of the paper is curved (inside or out). This problem does not occur in a three-point positioning press, but there are many front-end designs that make the front end of the bite warp, or print paper. The bite has different angles resulting in poor positioning, which causes the front end to lose its head and wrinkles and other problems. Handling: Check the straightness of the front end of the paper. If it is not straight, it is necessary to re-cut or change the paper. For example, just adjust the front block to cut the wrong paper, so it may be printed, but the printed paper is printed. There is a problem with the paper folding machine or the binding machine.
Reason 7: The gripper on the swing arm or the rotary type is not synchronized with the gripper of the platen roller. This situation is caused by the wear of the machine, so the axis of the feed gripper cannot match the press roller at the moment of transfer. Claw the claws.
Remedy: Replace the parts.
Cause 8: The timing of the feed roller is incorrect.
Remedy: ① Adjust the timing of the feed roller so that the paper reaches the jaws and the pressure roller is slightly arched.
② Adjust the front gear, and some presses can fine tune the front gear to accommodate uneven paper.