Quality control of the hottest printing process

Quality control of printing process

(I) variables affecting printing quality

I. printing color sequence and overprint rate finished paper

1. printing color sequence c-m-y

2. Determination of overprint gravimetric density method

3. Influencing factors: ink layer thickness,

viscosity and viscosity of ink,

drying of ink, etc.

2 Point enlargement

1. Definition of point enlargement:

2. Point enlargement researchers show the calculation method of laboratory wide research results

(1) Phi formula of Murray Davis formula:

fd= [(-dt)/(-ds)] *100%

dot gain= FD FRP

where FRP is the percentage of points on the original version

(2) printing contrast (k value): k=[(ds- DS)t)/ds]*100%

k value is between 0-1. Under the conditions of stable printing pressure and close cooperation between good printing material suppliers and equipment manufacturers, when the K value is the maximum, the dot expansion value is the minimum, and the ink layer thickness on the print sheet reaches the optimal value

3. Control of point enlargement

(1) two basic methods:

a. mathematical calculation method: use the reflection density meter to record the value, determine the point enlargement value through calculation, and also draw the corresponding chart for analysis. Features: this method can give an accurate large value of general technical conditions for bolts, screws, studs and nuts of fasteners (gb/t 16938 ⑴ 997)

b. visual contrast method: use various signal strips and test strips to judge the degree and direction of point expansion through vision. Features: this method can only observe the approximate extent and scope of point expansion, and cannot give an accurate maximum value

(2) test area of point expansion:

Law of point expansion: the expansion of point area is proportional to the length of point edge. The length of the point edge of the middle tone is relatively long, and the point expansion value is the largest. Theoretically, it can be proved that the point increase is the largest when the point increases by 50%; And 75% of the points are the most sensitive to the increased changes, and the visual response is also the most sensitive

4. Influencing factors:

(1) paper

(2) number of lines

(3) field density

(4) ink

(5) fountain solution

(6) pad

(7) printing speed

(8) printing pressure

(9) blanket

(10) printing plate

(11) ink.Roll

among them, the influence of field density on point expansion is greater than that of any other parameters

third, the field density

the field density and the percentage of points together constitute the main factors affecting the quality of image reproduction. In the printing process, the amount of ink is controlled according to the field density. Using field density to calculate printing contrast and overprint rate is an important factor of data management

1. Relationship between field density and ink volume

dv=dvmax (1? E-k?)

the field density does not increase infinitely with the increase of ink layer thickness. When the ink layer thickness increases to a certain value, the ink layer thickness continues to increase, and the field density has reached the maximum, and the ratio is increasing

2. control method of ink amount

print a field color block as a measurement mark at the movable trailing tip of the mouth of the paper, and cycle every 10cm or so

due to different paper, ink and related printing conditions, the field density value is different. For example, the general parameters are: y: 0.90-1.10 M: 1.30-1.60 C: 1.50-2.00

the field density value of proofing is generally slightly higher than that of printing. The expansion of proofing points is small

(II) printing quality control standards

see gb/t 17934.2-1999 printing technology - process control of eye tone color separations, samples and printed products - Part I: offset printing

reproduced from: Chinese printing community