Control and reduce color difference

In the printing and dyeing industry, the concept of poor continuous dyeing has a wide range of defects, such as color difference between samples, color difference between batches, color difference at the bottom, left and right color difference, and color difference within batches. This is a complex and difficult-to-solve quality problem that printing and dyeing workers have long encountered. As China's textile exports have expanded, participation in international competition has become increasingly fierce, and the requirements for quality have become stricter. At present, in the export dyeing products, the left-right color difference and the color difference within the batch are required to be higher than Grade 4.5, which is far higher than the national standard of our country. At the same time, the assessment of color aberrations has also shifted from traditional gaze ratings to computer color measurement and identification. That is to say, the craftsmanship of traditional craftsmen has risen to science and technology, the color transfer has begun to change from physical objects to digits, and the color of the computer is CMC, the value of DE is controlled within 0·6, and the color difference within the batch is within 0.9. In addition, the color light source has also evolved from ordinary office lights D65, CWF, TL84, D75 to U3O, HORIZON, INCA, and other light sources, and has been increased from one lamp pair to two lamps. change. In order to meet the customer's quality requirements, improve the export competitiveness of enterprises, control, reduce or even overcome the color difference has become an important issue for dyeing and printing workers. In this article, the author mainly focuses on how to reduce the left-right color difference (commonly known as edge color) and batch color difference (commonly known as LOT color). Based on years of practical experience, for reference only.

First, do a good job of raw material stability, reliability, is the basis for controlling color;

The raw materials for dyeing products mainly refer to the grey cloths and dyeing materials. Regardless of the batch size, the requirement for uniform quality before and after the raw materials is an important condition to ensure that the LOT color is overcome. Even if the quality of raw materials is objectively different, we must be aware of what is happening and treat it differently so that the LOT color is strictly controlled within the minimum range. Specific practices include the following:

l. Gray fabrics of the same color shall require the purchasing department to purchase as much as possible the same cotton fabric factory and the grey fabric of the same batch production area.

2. If the brokers supply blanks, they must distinguish the products of different cotton mills. If there are two factories, the gray fabrics must be put into production according to the batch number when they are put into production. If necessary, pre-treatment and dyeing process materials should be properly adjusted to overcome the color difference within batches of the batch.

3, For some special products, such as linen, linen cotton and other semi-floating blanks, although the pre-treatment, but the sensitive color is still difficult to control the LOT color changes. The method of control can be first

(Volume) Sampling l meters, make a record of the number of each sample (volume) and sample, try to dye more sensitive colors. Then according to the results of the LOT color of the sample, each batch (volume) is batch-produced. Batch adjustment during dyeing can reduce the LOT color.

4. Where the same color number product meets the change of raw materials (including source origin, dyes, finishing agents), the supply department must notify the technical department, sort and stack, and strictly contrast the test, so that the process and technology can be reasonably adjusted. Change.

5, deuteration material to adhere to the amount required to be sufficient by batch, a color regardless of size, the first requirement is the same origin, the same batch, the same color, concentration of dye. The dyestuff is best to use the full test method. If it is found to be different, it should be used separately and the sample must be re-tested to avoid the LOT color caused by the different shades and strength of the dye.

6, do not ignore the softener and other finishing agents on the shade, depth and edge color. A large batch of colors, in the soft finishing process, it is best to use the same batch of products

Produced on the same machine. At the same time, the color tracking control must also be cut, otherwise the LOT color and edge color in the batch are difficult to control.

7. The correct choice of dye is another key to controlling LOT color and edge color. Many companies receive samples from customers and submit them to the lab for proofing. The compatibility of dyes is determined by the sampler. The problem is that some samplers are precisely lacking experience in production practices. They only aim at sample and customer samples, but it is difficult to grasp the level of dye uptake, the speed of shade change, the stability of compatibility, and the size of different color samples of different colors. The sample was often sent to the customer for confirmation. The problem was discovered when it was produced. At this time, the compatibility of the dye was changed, and the color was changed. This made the display very passive. To this end, we use color matching from the computer. According to the dye combinations selected at ordinary times, we choose the best combination of DE values, and the compatibility of one type of six, and then send the dyeing director according to the product frame, the stability is strong (the dyeing curve is generally the same ), the principle of low cost to select one group of compatibility, and then to test the laboratory proofing, such samples are not only meet the requirements of customers, but also ensure that the production of color difference can be controlled to the most stable.

8, although there are thousands of changes in the three primary colors, but the three primary colors are not omnipotent. Practice has proved that: not all in accordance with the three primary colors match, in the face of any one color, the best way is to choose an approximate color dye-based color, according to the color light and then fine-tune with other dyes. At the same time, the compatibility of dyes should adhere to the principle of less, less, and better.

Second, reforms to strengthen internal management of enterprises are the guarantee of reducing the color difference.

The reason why printing and dyeing products are difficult to do, the reason why printing and dyeing plants operating difficult, is the production characteristics of printing and dyeing products. Printing and dyeing products often go through more than 10 processes from grey fabrics to finished products. The production process combines chemical, physical, mechanical, environmental, and human factors changes. More than 10 production processes and problems in any one of the links will affect the quality of the final product. Therefore, continuous reforms and enhancement of production and management of printing and dyeing products are needed to control the reduction of color difference and ensure product quality.

1. Adhere to the technology-oriented production operation management is a feasible way to control the color difference:

In the traditional enterprise management of printing and dyeing plants, there are drawbacks of planning and technology, workshops and technology, and technology and equipment. It is disadvantageous to highlight the location of process technology and product quality. A few years ago, we merged technology and plans into the Ministry of Public Works, and the whole plant production was led by only one department of the Ministry of Works. At the same time, the management of production operations has been reformed into a technology-oriented and quality-focused management model. Under the premise of ensuring a small color difference, the pre-treatment process is specially designed for difficult colors, varieties, and colors. Changed the previous practice of multiple bleaching and bleaching. Emphasize the technical protagonists in the production and operation management, planning, workshop, equipment as a supporting role. The procurement of dyestuffs and materials is under the control of the Ministry of Works. In the production process, whether it is the adjustment of the plan or the handling of the problem, whether it is day shift or midnight shift, the decision-making power and commanding power are in the hands of the technical supervisor. In this way, the contradiction of mutual wrangling and heavy production and light weight are avoided, and the "process-centered" role is ensured to ensure quality.

2. Intensifying on-site technical management in production and operation is the key to reducing the color difference:

Due to the characteristics of the production of printing and dyeing products, the vast majority of color differences or other quality problems arise during production operations. For a long time, printing and dyeing factories often mentioned "prevention first". But how is it reflected in the actual operation? We believe that the on-site monitoring, quality tracking, and prevention and control of printing and dyeing plants are the most practical "prevention-based". Over the years, we have attached great importance to the management of production sites. All production plans, technicians, and office locations are located in production workshops. Regardless of the manager of the Public Works Department, the workshop director, or the technical supervisor and technician of the bleaching, dyeing, padding, and finishing, the focus of the daily work is on the workshop floor, and the workshop (workshop) is the office. In this way, the technicians are fully aware of the operation of the product, the operation of the machine, the operation of the employees, and the changes in quality. At the same time, they are required to make "three arrivals" (when starting up, transferring varieties, and stopping at the scene for any reason), checking "four firsts" (the first piece of cloth, the first piece of cloth, and the cleaning machine After the first piece of cloth, the first piece of cloth after equipment maintenance), and earnestly "doing a good job of three" (unified technical operation, systematic inspection on the process, quality standardization of the next machine), and picking up the car on the process of product operation The "third degree" (temperature, speed, and concentration) can be maintained correctly and consistently, so that the quality of each semi-manufactured product can also be stable and consistent, which is the key to control the reduction of chromatic aberration.

3. The performance of quality veto rights at all levels is the guarantee to control the reduction of color difference:

The most deadly drawbacks of printing and dyeing production are loose management and sloppy checks. A large number of quality problems often appear before the root cause. In addition to strict management, effective methods of managing color differences require careful and careful checks of quality at all levels. We perform the quality veto rights at all levels, and practice has proved to be another guarantee for reducing the chromatic aberration.

1 The use department finds the difference in the quality of raw materials, and has the authority to instruct its return and replacement authority.

2 Process technicians must have a rigorous inspection system for the condition of the equipment. When discovering equipment problems and affecting product quality, they have the right to suspend production. Notification Equipment Department

The door will be repaired until it is in good condition.

3 Dyeing technology supervisors have quality veto power for pre-processing quality. When it is found that the semi-finished products of bleaching and bleaching affect the dyeing quality, they have the right to instruct them to rework to the standard.

4 Quality inspectors who check the color and LOT color of the dyeing product fail to meet the standard, and have the right to return the dyeing supervisor to the target of repair.

5 The technical supervisors at all levels have the right to reward, punish, adjust, and retire to their employees' level of operation and performance. Employees who do not meet the technical operation requirements of the post

It must be handled and properly placed.

6 The customer is the "emperor". Any customer who requests the product for repair due to quality problems must accept it unconditionally and must not delay. $Page break $

Third, seriously grasp all aspects of technical organization measures in order to achieve the purpose of reducing chromatic aberration:

Stained edges and LOT colors are not produced by the staining process. The control of edge color and LOT color, in addition to the company's management and raw materials, also includes processes, technologies, equipment, operations, and control methods. The entire process is complicated, and mistakes in any one link will “touch the whole body” and cause color differences.

1, pre-processing is the basis for controlling color difference:

Staining occurs with chromatic and LOT colors, and most people focus their attention on the dyeing process to check the cause. Ignore the basis of the pre-processing chromatic aberration. This one-sided tendency is obviously wrong. It can be said that the consistency of the pre-treatment hairiness and whiteness plays a decisive role in the production of color differences. Therefore, to achieve the purpose of controlling the reduction of chromatic aberration, it is necessary to make every effort to handle the basic work beforehand.

1 Desizing and smelting thoroughly:

Many companies often combine desizing and cooking because of the limitations of equipment or planning and cost factors. However, this boiled process has a high slurry rate.

Products (such as corduroy, grey cloths from Pakistan and India) have very unstable hair after rinsing and bleaching. After exploration, we believe that: The pretreatment of cotton fabrics cannot ignore the importance of desizing. Only after desizing the net can it be cooked thoroughly, and only the desizing can be given a stable precondition beforehand. In practice, we believe that: sewing head → desizing → singeing → boiled and bleached is the most ideal process design. The gross effect of dyeing products generally requires more than 8cm, and the fluctuation of the left, right, and front and back hairs should be controlled within 2cm.

2 roller rolling liquid rate is consistent:

It is a problem easily overlooked by printing and dyeing plants whether the pre-treatment of the rolling rate of the rolling mill is consistent with whether the front, back, and left, middle, and right rolling is maintained. In particular, scouring, bleaching and mercerizing, such as rolling

The liquid rate is not stable, and it will inevitably cause color difference. Therefore, the maintenance of the pre-processing key rolling mill should be upgraded to the level of the dyeing roller to handle it. Weekly rest days,

The equipment department should focus on overhauling. In the first shift of the week, technicians must determine the left, middle, and right roller ratios of the rolling mill and meet the requirements before they can be put into production.

3 In the production of printing and dyeing, it is difficult to avoid sudden electromechanical faults. This has a great influence on the continuous retreat bleaching machine with a large capacity (600-800M). When such problems occur, when the boiled and bleached storage time exceeds the prescribed time, each factory shall formulate rigorous rework measures according to the actual conditions, and notify the dyeing supervisors of the number of reworks and the exact number of the reworked tanks, so that the samples can be put into production separately when dyeing, and the color difference can be avoided. produce.

4 Insist on pre-processing quality inspection and clear handover criteria.

The appearance quality inspection of the pre-processed semi-finished products is relatively simple. Intrinsic quality inspections such as gross efficiency, pH, and slurry-containing inspections are also not difficult. This article has mentioned earlier

The standardization of machine quality must be carried out conscientiously and seriously. However, the above inspection still cannot meet the actual requirements for dyeing color difference. Our approach is: In the previous process of dyeing, we sample 1 meter per box of cloth, and connect the joint head and send it to the dyeing supervisor for inspection. And apply the same or similar color