Quality measurement and control technology of the

Printing quality measurement and control technology

(I) basic principle of quality control

for a real objective evaluation, objective measurement variables and appropriate measurement methods are absolutely necessary

the key to an objective and orderly quality control method is to determine the variables of objective measurement and adopt appropriate measurement methods

keeping the printing color correct throughout the printing process mainly depends on three parameters: ink layer thickness, dot percentage and overprint rate. These three parameters have their corresponding physical quantities that can be objectively measured

eigenvalue optical effect evaluation parameter

ink layer thickness brightness field density

point percentage additive and subtractive f-point density

overprint and color sequence subtraction overprint rate

Description:

(1) ink layer thickness: the printing workshop should use a densimeter to control the ink layer thickness by measuring the field density. Note that infinite density values make nonexistent

(2) point percentage: it is a decisive parameter for printing

the change of dot percentage may occur in the process of plate making or printing, and its change will cause errors in tone reproduction. Point expansion, point reduction, point deformation, ghosting, and slide deformation all belong to point percentage changes

(3) ink overprint rate and color sequence: the quality of ink overprint can be visually inspected and evaluated by observing large two-color and three-color overprint blocks or overprint blocks on the printing control strip. Objective evaluation of ink overprint by using densitometer, the overprint rate can be measured and calculated relatively, which is a relative value

print quality control system

* print quality control strip

* automatic printer control system

remote control

console

the significance of using the control strip and the basic principle of producing the control strip

(II) print control strip

I. Basic Composition:

control strip (color code) is printed on the cutting part of the print to check print variables such as ink density, dot expansion A tool for overprint and printing contrast. It is usually composed of two-color and three primary color overprinted field and dot color blocks (representing about 20% of high key, 40-50% of middle key and 70-80% of dark key respectively), including green, magenta, yellow and black field and dot color blocks. In addition, it can also include monochrome blocks with deformation/ghosting of monitoring points and point expansion

(1) solid dot patches of yellow, magenta, cyan and black (and other spot colors) monochrome field color blocks are used to observe and test the printing density of each monochrome ink, so the thickness of the printing ink layer and the saturation of the ink can be controlled. By testing the density of each monochrome dot color block or directly measuring the actual dot area, you can test and observe the midpoint expansion and printing contrast of each color plate, and provide data information for drawing the printing characteristic curve

(2) overprint color codes (red, green, blue) trapping overprints

three primary color inks overprint (red, green, blue) color codes in pairs on the spot to check the overprint of two-color inks. The overprint rate can be calculated by testing the density of the overprint block

(3) gray balance element

three primary color ink overprint color blocks, including gray balance color blocks overprinted by three primary colors with different dot areas, and three primary color ink field overprint color blocks, which are used to check the gray balance of three color ink overprint. The gray balance can be observed by comparing each different gray balance color block with the relevant monochromatic gray block

the blackness of printing can be checked by comparing the four-color (trichrome ink and black ink) field overprint color block with the monochrome black field color block

(4) point deformation monitoring block dot slur

usually uses equal width horizontal and vertical thin lines to observe the deformation of points. If horizontal (plate axial) slip occurs, the color of the longitudinal line pattern becomes darker; If longitudinal (plate radial) slip occurs, the color of the horizontal line pattern becomes darker

iso 13656 graphic technology application of reflection density and colorimetry to process control or evaluation of prints and proofs and din16527 drucktechnik kontrolfelder an protect the hammer body Wendong im druck puts forward corresponding requirements for the structure of measurement and control strips. It is pointed out that the minimum structure requirements of the measurement and control strip are:

"the measurement and control strip should include ghosting/deformation and printing basic color monochrome ink field color blocks and their overprint color blocks, namely K, C, m, y, (c+m), (c+y), (m+y) and (c+m+y) These color patches. In addition, the measurement and control strip should also include at least Ni, which mainly provides three defined visual tone control color blocks for capacity function, and indicate the standard tone values of each printing basic color K, C, m, y. Among the three defined tone control color blocks, the tone value of one color block should be 20% - 30%, the tone value of the other color block should be 40% - 50%, and the third color block should be 70% - 80%; There should also be a visual adjustment control block for measuring the intermediate adjustment balance and a blank block. This complete measurement and control strip should be placed as repeatedly as possible on the whole width of the printed sheet. "

key

cooperate with the corresponding legend description

visual observation instrument test

visual observation instrument test

mainly for visual observation comparison

mainly for visual observation

mainly for visual observation

II. Common measurement and control strips

1. GATF character signal strip

can inspect the changes of code point area and density by vision

see the color map

2.gatf color control strip

the specification is 1/4 inch X5 inch

including field, overprint field, 40% yellow, magenta, green monochrome block, 40% red, green, blue dot overprint block, star Mark and gray balance block

the supply length of the test strip is 20 inches

3.fogra PMS printing control strip color control strip

consists of field, dot block, overprint block and micro wire block for controlling the exposure of printing plate and film

the specification of the control strip is 8mmx530mm

the PMS control strip is supplied in rolls with a length of 2 ~ 5mm, and supports cutting according to different lengths as needed

4.brunner printing control strip color control strip

is composed of printing fine dot control section, gray balance observation section, overprint and color code detection section, and five thick and thin dot test sections

among them, ultra-fine measuring elements (fine point micrometer segment) are the core of Brunner system

it adapts to the requirements of CPC system and is used in the control of Heidelberg printing press

5. Heidelberg CPC system color control bar

6. digital printing measurement and control bar

is composed of three modules: module 1 and module 2 are used to monitor the printing replication process, module 3 is used to monitor the exposure adjustment

module 1: it includes the following eight field color blocks: C, m, y, K, C +m, c+y, m+y, c+m+y

module 2: (1) color balance color block

(2) Shandong STARCO interviewed many industry insiders. The spring testing machine produced by desico mainly includes: spring fatigue testing machine, spring change testing machine, gas spring testing machine, spring tension and compression testing machine and other categories: BK, C, m, y

(3) direction control block

(4) point control block

module 3:15 gray blocks of different degrees, all printed with black ink

7.rit color test strip

8. Other control strips

(III) automatic printing quality detection and control system

1. Heidelberg CPC system

Heidelberg CPC system is mainly composed of cpc1, cpc2 and cpc3

*cpc1 is a central console, which mainly controls the ink output of each ink area of each color on the multi-color offset press and remotely adjusts the position of the plate cylinder to ensure the overprint accuracy. This part is the essence of CPC system

*cpc2 is a printing quality console. Input the tested and calculated data of the controlled printing sheet into the cpc1 of the relevant machine to correct and adjust the ink supply system of the printer

*cpc3 is a special plate image recognizer, which recognizes general images and determines the ink supply of each section of the plate

*cp2000

2.man Roland CCI system

reprinted from: Chinese printing community