Product quality is the life of printing industry,and it is directly related to the market competitiveness of an enterprise.In the printing process,industry must take the work seriously which ensure the quality of presswork and put an end to quality problems caused by technical errors and improper human handling.
 
Printing process control

Printing quality control
When you printing down,add color in the PS version,the outer body,and drag & shoot.So, in the inspection of printed product, easy to find that register difference, double sheet caused by the full page leaked and mixed use of different plate printing problems.
Besides, printer must carefully check the quality of film and PS version, and the plates should be checked before they start work, to avoid the problems which influence the quality of printing production.At the same time,the edition should be proficient and accurate,as far as possible to reduce the version number; Pulled the plate uniformly, to avoid printing plate register difference due to stretching deformation.
 
Selection of printing consumables
(1)Paper
In the multi-color printing process,better size fastness and strong adaptability of the paper should be choosed, to prevent the sheet from the phenomenon of ink picks, and off powder.Before printing,the paper should be packed separately to prevent it from being affected by damp deformation.

(2)Ink
Light and quick-drying ink is penetration drying ink,suitable for offset printing,possible to avoid powder matte and set-off, ink picks phenomenon,whose drying speed is fast.But in the usage, frequently stir ink, to prevent ink from being drying and crusting.
(3)Blanket
In the normal printing,frequently wipe the blanket to cut down the accumulation paper powder and ink,to avoid influencing reducibility of blanket.Due to the good elasticity and extensibility of the new blanket,machine taut shall be carried out gradually.In the daily operation, every tight, after waiting for offset press or pressure to stop tightening again, repeatedly so take up a few times, so as to make the blanket tight requirements.
 
The control of printing pressure
Because of the rough on the surface of offset paper,the better ink absorption performance,in order to make the printing ink thick, clear dots, when printing should be appropriate to increase the printing pressure. In addition, form dampening roller and form inking roller pressure should be appropriate. Make an adjustment in the requirements of the specification ,and maintain good water transmission and ink transmission properties

The control of printing conditions
(1)The control of PH value of dampening solution
The dampening solution pH value should be controlled at 4.5 ~ 5.5.If the pH value is not properly controlled, the drying speed and printing quality will be affected.If the fountain solution of acid too strong, it will increase the layout of the blank part of the sand and the graphic part of the lipophilic corrosion will cause "flower version" phenomenon, so that the printing plate decreases.At the same time, it also causes the ink emulsification, form inking roller rubbing off phenomenon, so that the final printed is gloomy and without light.If the fountain solution of acid is too weak, it will make the printing plate empty part of the hydrophilic oil repellent performance weakened, and the layout easy to be dirty, and also easy to filling in phenomenon caused by the printing dot gain.

(2) The control for ink balance
In the process of printing,it needs to keep the balance of ink to reach the optimum printing state of “dry ink and small water”.When make the water plate,it need to add water quantity first.In the constant pressure and constant speed printing,the water falls back to the original state, so it can avoid the ink emulsification caused by “large water and ink”.

(3)The control of temperature and humidity in the workshop
In the process of offset printing paper, when the workshop humidity is large, easy to produce crepe paper, galling , off powder and so on;The workshop humidity is small, and easy to produce electrostatic printing. In order to achieve the best results, the workshop should configure air conditioning and humidifier, in order to ensure the workshop temperature is 20 to 25 degrees Celsius, humidity is 55% ~ 65%.
 
The quality inspection of printing
In the printing,looking the sample is the most common method to check the printing quality.The operator must compare presswork with sample pages over and over again and find out the difference between the presswork and sample pages so as to make a timely correction.In the quality inspection of printing, should pay attention to the following points.
 
Initial workpiece inspection 
First piece inspection work is the core of the proofreading graphic content and determining the color of the ink.If the initial workpiece do not get signed review of relevant personnel, offset machine shall not make batch production. This work is crucial in the control of quality.If the first error is not found, it will cause more typographical errors. First piece inspection needs to do the following work.
 
(1)Preparatory work
①Check the production order sheet.Production order sheet has a expatiation to the requirements of the production process,the standard of production quality and the special requirement of clients.
②The inspection and review of printing plate.The quality of the printing is directly related to presswork whether the printed material meets the customer's quality requirements, so the content of the printing plate must be consistent with the customer's sample content, and there shall be no mistakes.
③The inspection of the paper and ink.Different presswork has a different requirement to paper,there needs to check it whether it is consistent with clients’ requirements. In addition,the deployment accuracy of spot color ink is the key to restore color sample,this work should be strengthened in the ink inspection work.

(2)Debugging work
①Testing of equipment.Normal operation of paper feeding, paper taking, paper collection and stability ink balance are the prerequisite for producing printed materials that meet the standard.Must not be on the state of the edge of the device and the edge of adjustment starting up to initial sample signature.
②Testing of inky.The presswork which is in accord with sample pages inky must go through several debug printings. But avoid ink weighing is accurate or close to sample and add ink phenomenon. Every time the deployment of ink must be weighed again,at the same time,equipment is adjusted to pre-production state to ensure it put into normal production.

(3)Initial sample signature
The collar machine in the first piece samples after printing, should check the proofreading,check without error and hand over to group leader and inspector who sign and confirm it.At the meantime,hung on the sample bench as the normal production of the test basis. Only after the initial sample gets the signature, will it make mass production.
The first sample signature ensures the correctness and reliability of mass production. It provides the guarantee for meeting customer's requirements and preventing serious quality accidents, thus avoiding serious economic losses.
 
Printed inspection
In the printing production process, the operator (delivery personnel) need not extracting the printed proofs to sign for the inspection basis, the printing color, graphic content and accuracy check one by one, found problems in a timely manner to stop, and made a note saying to be convenient to remove paper and check it. The maximum effect of unloading rake printing product sampling can be timely detection of quality problems and make solutions, to minimize the loss.
 
Finished product inspection
The finished rake role is to remedy quality problems have caused the harm and influence for quality defects. Print for a period of time (about half an hour after operation), staff need to stack the material and transfer, and check the quality of printing products, especially for the sampling found part of the problem should focus on the rake, avoid the problem being omitted to the finishing process.The finished rake should regards the quality standards as reference, the details should be controlled to sign test specimen. In the inspection process, prohibited waste and semi-finished products into the finished product.If found substandard products, should be strictly in accordance with the "nonconforming product control procedures", and do a good job of relevant records, identification and differentiation.
 
Quality deviation handling system
The smooth implementation of printing quality inspection cannot do without an effective quality management system. Therefore, our company implements the quality system of the deviation, related personnel should be based on the analysis of the problems, propose solutions and corrective measures to achieve "who handles,who is responsible, who checks, who is responsible for" ,quality month each year, all quality the deviation need to be made a summary,the implementation of corrective measures are assessed,and the quality problems recurring will be placed emphasis on.
 
It is the prerequisite and key for printing enterprises to get good quality of printed matter by making good control of printing process and paying attention to the quality inspection of printed matter.