When to use color code?
In order to obtain the most ideal process and further control the production process, each sample of each job, whether it is a pre-proofing sample or a digital sample, and each color plate printed should include a color mark. In the actual printing production process, it is often an undesirable situation because the cutting size and group size of the printing machine occupy the entire imaging area, and there is not enough space to place the color mark. If such a phenomenon occurs frequently, the operator can operate according to the following methods:
· Intentional printing of color marks, for example, once or twice a week, as a test plate or directly as a production plate containing this information, so that operators, managers and related technical personnel can understand the plate and printing Changes in machine performance, paper, ink, and other input parameters.
· With the permission of the printing customer, at a certain place in the printing plate, select some target elements, such as dot expansion, density and gray balance, etc. This information will not cause opposition from the printing customer. In fact, some customers have included these elements In the layout, and remind the reader that these color blocks are used for quality control.
· Consult with the printing client to include test objects in the editorial design. USA Today is such an example, their logo is the solid ink density and overprint control object.
· At least somewhere in the printing plate, add 75% tonal values ​​and solid patches of each color to measure the print contrast, which helps to estimate the overall print quality and the relationship between density and dot expansion.
It should be noted that color coding is not a prerequisite for printing high-quality images; many printers and color separation personnel can produce high-quality products without using color coding. Moreover, many printing industry personnel and color separation personnel are more profitable without using color marks. However, few printing and color separation personnel who do not use color marks can achieve higher profits and quality levels than those who contain and use color marks. Color coding is a key factor for proofing and printing in high-productivity and high-profit production methods. Through color coding, process changes can be determined more quickly and purposefully to avoid errors and distortions in image appearance. Because the color scale can be objectively measured, it can provide the necessary parameters and information knowledge for process improvement, which helps to continuously improve quality and reduce costs.
When is the color scale measured?
In actual production, the color scale should be measured frequently. The following provides some suggestions based on the information published by Gretag, which is helpful for training production operators:
At the beginning of the printing preparation and color confirmation (ok) process, the operator often uses a correct proof or pre-proof proof as the color reference and relies on visual adjustment. Even at this stage of printing preparation, color scales are useful because operators can use color scales:
· Check the density, dot expansion, contrast and other data that need to be confirmed to determine whether the printing process can obtain the desired effect.
· Insight into the problems that may occur in the printing preparation process, and ensure that the obtained printed sheet matches the sample sheet. At the end of the printing preparation process, the role of color coding was further expanded. At this stage, it is recommended to measure the following elements of the main page and advertisements under standard conditions:
· Solid patches of each color;
· 25% and 50% color patches for each color, and printing contrast;
· Two-color overprint color blocks (red, green and blue blocks) of solid ink. Under normal conditions during the printing operation, measure the following elements of the main page or advertisement:
· Solid patches of each color;
· 25% and 50% color patches for each color, and printing contrast;
· Two-color overprint color blocks (red, green and blue blocks) of solid ink. After making ink supply adjustments or printing shutdowns, measure:
· 25% and 50% objects of each color and print contrast of the main page or advertisement.
If these rapid initial measurements show unusual values, or show that the entire operation process is unstable, the operator should measure other color-coded elements on the printing material and increase the frequency of measurement to ensure tracking of changes in the printing press Process, make appropriate adjustments. In these examples, a device running chart or X control bar / R chart is very valuable, because it will provide us with some information. Through the measurement results, we can determine whether the operation process has undergone major changes or normal fluctuations. These recommendations are just the starting point for developing internal operating procedures and guidelines; in particular, companies that use statistical process control (SPC) often have their own experiments and measurement methods.
What measuring elements are included on the color scale?
The color scale usually contains two types of elements:
Objective elements such as density elements, 25%, 50%, and 75% texture, overprint colors, and other elements that can be evaluated with a densitometer or other color measurement equipment.
Subjective elements: ghosting elements, plate exposure indicators, gray-balanced tones, and graphic elements that are evaluated visually.
The measurement of these two types of elements is very important and very useful, because visual objects can provide immediate information about unacceptable changes to the operator and the measurement process. These changes can be verified, quantified, controlled, and finally measured by objectively measuring other objects write it down.
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