Multi-color printing process and quality control of offset paper
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Product quality is the life of an enterprise and is directly related to the market competitiveness of the enterprise. This article will share some experiences and communicate with you on the process control and print quality inspection involved in the multi-color printing process of offset paper.
Printing process control
1 plate quality control
When printing on the plate, the color code is added to the PS plate by the body, the outer part and the trailing part. Thus, when checking the printed product, it is easy to find the overprinting, the reverse of the paper, the full-page offset caused by the double sheets and different printing plates. Mixed use of the problem.
Before printing on the plate and on the machine, you must carefully check the quality of the PS plate and film to avoid affecting the production due to the quality of the plate. At the same time, the school edition should be proficient and accurate, and try to reduce the number of proofs; the force should be even when pulling the plate to avoid the printing plate being inaccurate due to artificial deformation.
2 printing consumables selection
(1) Paper
Use paper with good sizing degree and strong adaptability to avoid the phenomenon of paper pulling and falling powder. Before printing, prevent the paper from being affected by moisture deformation and affecting the printing paper.
(2) Ink
The bright and fast drying ink is suitable for the printing of offset paper, which can avoid the phenomenon of powdering, matt, sticky, and pulling of the resin type ink, and the drying speed is fast. However, during use, it is necessary to prevent the ink from drying and crusting.
(3) Blanket
During the normal printing process, wipe the blanket. The new blanket is stretchable and the tension on the machine should be gradually carried out. During daily operation, each time it is tightened, wait for the offset press to stop and then tighten it again, so that it is tightened several times to achieve the requirement of tightening the blanket.
3 printing pressure control
The surface of the offset paper is rough and the ink absorption performance is good. In order to make the printing ink thick and the dots are clear, the printing pressure should be appropriately increased during printing.
In addition, the pressure of the water roller and the ink roller should be appropriate to maintain good water transfer and ink transfer performance.
4 control of printing conditions
(1) Control of pH value of dampening solution
The pH of the dampening solution should be controlled at 4.5 to 5.5. If the pH of the dampening solution is not properly controlled, it will affect the drying speed and printing quality of the blotting.
(2) Control of ink balance
In the printing process, it is necessary to maintain the balance of ink and water to achieve the best printing state of "small ink dry water". When the water is moistened, the amount of water is increased first, and when the pressure is pressed at a constant speed, the amount of water is returned to the original state to avoid ink emulsification caused by "large water and large ink".
(3) Control of temperature and humidity in the workshop
In order to achieve the best printing, the workshop should be equipped with air conditioners and humidifiers to ensure that the workshop temperature is 20 ~ 25 ° C, humidity is 55% ~ 65%.
Print quality inspection
Pay attention to the following points when conducting print quality inspection.
1 first piece inspection
The core work of the first piece of inspection is to proofread the graphic content and determine the ink color. If the first piece is not signed by the relevant personnel, the offset printing machine shall not be mass-produced. The first piece of inspection should do the following work.
(1) Pre-preparation work
1 Check the production order. Production orders have detailed descriptions of production process requirements, product quality standards and customer specific requirements.
2 plate inspection and review. The content of the plate must be consistent with the customer's sample content, and there must be no errors.
3 paper, ink inspection. Different prints require different papers and should be checked for consistency with customer requirements. The accuracy of spot color inks is the key to restoring the color of the sample, which should be enhanced during ink inspection.
(2) Commissioning work
1 equipment debugging. Do not make the first sample in the state where the device is turned on and off.
2 ink color debugging. To avoid inaccurate ink weighing or to add ink to the sample close to the ink color. Each time the ink color is adjusted, it must be re-weighed, and the equipment should be adjusted to the pre-production state to ensure that it can be put into normal production at any time.
(3) First sample
After the first signing and printing is finished, the first piece will be checked and verified. After the signature, the signature team leader and the quality inspector will sign and confirm it, and hang it on the sample stand as the inspection basis for normal production. Only the first sample can be mass-produced.
2 print sampling
In the mass production process of printed matter, the operator (receiver) needs to take out the printed matter from time to time, and use the proof sheet as the inspection basis to check the color, graphic content and overprinting precision of the printed matter one by one, find out the problem and stop the problem in time, and use the small paper strip. Remarks for the purpose of unloading the paper.
3 finished product inspection
After the printed matter is placed for a period of time (about half an hour), the operator needs to transfer the material to the paper stack and check the quality of the printed matter. In particular, the part that finds the problem during the sampling inspection should be checked to avoid missing the problem into the post-press processing. The finished product inspection shall be based on the quality standards established in the factory, and the details shall be checked against the proof sheet. In the inspection process, it is strictly forbidden to mix waste products and semi-finished products into the finished product. If non-conforming products are found, they should be strictly implemented in accordance with the “Control Procedure for Non-conforming Products”, and do relevant work such as recording, marking and distinguishing.
4 quality deviation processing system
The smooth implementation of print quality inspection is inseparable from an effective quality management system. To this end, the company can implement a quality deviation treatment system, relevant personnel should analyze the reasons according to the problems, propose solutions and corrective measures, to achieve "who is responsible for who is responsible, who is responsible for who is responsible", all quality during the annual quality month Deviation summary, assessment of the implementation of rectification measures, and focus on recurring quality issues.
In today's increasingly fierce competition in the printing market, it is the premise and key for printing companies to obtain good print quality by doing a good job in printing process control and attaching importance to print quality inspection.