Appearance quality inspection equipment and inspection standards

First, inspection equipment

The pre-printing factory finished product inspection shop usually uses cloth inspection machines as inspection equipment. The cloth inspection machine is equipped with a tilt angle of approximately 45. The sloping plate, above the swash plate, is equipped with a light source that satisfies the illuminance of the test. The illuminance of the plate surface is generally not less than 750LX. The inclined plate is equipped with a white frosted glass plate and is equipped with a lower light. If necessary, a light test can be turned on. The speed of the finished cloth during the test can be adjusted within the range of 0-40m/min. The eyes of the inspector face the fabric, and the distance between the eyes and the fabric is 50-60cm. The length of the test cloth is measured by a randomly equipped stopwatch. The automatic edge-to-edge rolling machine is turned into a roll.

Second, the color light source

In the finished product before the machine inspection by the quality inspection personnel sampling color sampling is a very important part. Pairing should be done in a dedicated color-coded lightbox, and matched against the light source specified by the customer. At present, the light sources specified by the customers are generally several types such as D65/D75/CWF/TL84/Horizon/Inca A/U30/UV (there are many kinds of color light sources commonly used in the world). Some customers may specify the second light source and the third light source in addition to the main light source. Because in the production practice will also encounter a "jumping lamp" phenomenon, that is, there are different colors of the same spectrum phenomenon, and some customers will reject the "jumping lights" of the finished product, which should also pay special attention.

The so-called metamerism, explained from the perspective of the color theory, means that two color samples have different spectral reflectance curves, and that there are the same tristimulus values ​​under a given light source, that is, the two color samples. Conditional color. Once the light source changes (the energy distribution of each light source is different), the tristimulus values ​​generated are no longer equal, which results in a “jumping lamp” phenomenon.

The key to solving the problem of “jumping lights” is to strengthen checks during proofing. When dyeing samples in labs, use experience or use a computer colorimeter to select dyes. If the sample and sample are made of the same fiber material, the choice of dye is easier; if the fiber material is different and the type of dye used is not the same, it is very likely that there will be a “jumping lamp” phenomenon. This must be clearly explained to the customer, or only to the main lamp, or to the L/D swatches confirmed by the customer only when coloring (not to the original plate). Just do the dyeing and dyeing used to make large samples. (L/D-like) The same dyes are used to ensure that they do not “jump.” It is very passive to avoid finding this problem during the inspection of finished products.

Third, the inspection standard

China has issued GB/T 411-2008 national standard for cotton printing and dyeing cloth, issued GB/T 5326-2009 national standard for combed polyester-cotton blended printing and dyeing cloth, and released 08/14,011-2008 for cotton printing and dyeing corduroy. standard. In these several standards, explicit regulations were made on appearance quality inspection scores and internal quality classification rules. In addition, the scores of local defects in these national standards also adopt the internationally popular four-point system standard, which can be used as the inspection standard for commercial trade transactions. However, the relevant provisions of these standards are more complex. To master these standards, there is still a certain degree of difficulty for ordinary inspectors at a printing and dyeing plant. More importantly, most customers, especially foreign customers, are still accustomed to directly using the relatively simple four-point inspection system (ASTM D5430 Four Point System) in the printing and dyeing factory's business transactions.

The test scores for fabric defects for printed and dyed fabrics are exactly the same as those for fabric inspection . In the actual operation process, the biggest difference between the appearance quality inspection of finished products and the inspection of grey fabrics is that there is a big difference in the performance patterns of defects. The most important thing in the inspection of dyeing and finishing products is the inspection and control of color difference, but there is no such item during inspection of grey fabrics . The common defects of finished fabrics are the printing and dyeing defects in addition to the blanks. In addition, the physical quality and feel of finished products are also clearly defined in the finished product inspection project. Compared with the inspection of grey fabrics, the technical content of the appearance quality inspection of printed and dyed products is also higher.

The allowable scoring standards for localized defects of dyeing and printing products shall be negotiated by both parties according to the requirements of the customer contract. There is no uniform international standard. The requirements for different fabric types and different customers will also vary greatly. For example, the allowable score for linen is much greater than the allowable score for cotton-blend fabrics. According to the author's many years of experience, for the average pure cotton printing and dyeing cloth, the ratings that most customers can accept are within the following range.

The acceptable score for each (reel) fabric is <20-28 points, 83.61 per square meter (100 square yards); the average acceptable score for each batch is <15-20 points, 83.61 per square meter (100 Square yards>.

In line with the above standard Huai can be used as A-class products or as first-class products, and those that fail to meet the above-mentioned standards are called B-class or second-class products. It should be noted that Grade B products are not products that cannot be used at all, but only finished fabrics whose ratings exceed the allowable standard will have greater loss of processing than normal wear at the time of garment manufacture. Ordinary customers will accept part of the B-level product through negotiation, but the purchase price will be slightly lower.

Fourth, the inspection process

Inspection of printed and dyed finished fabrics is generally performed according to the following procedure.

Finished cloths that have passed the intrinsic quality test—Column-sampling and color-matching—Experienced-machine-on-machine inspections are scored and cut on the color bars—by batch color difference batching (LOT color)—Grade A batch product is “I tagged. And packaged in the human database - quality control department (QC) sampling test - the customer quality control personnel sampling inspection of qualified products - defective goods arranged for repair or as a B-class personnel library.

Quality inspectors use the naked eye to inspect each roll of cloth passing through the inspection machine, and a detailed record shall be made of the inspection, including the order number, fabric name specification, color number, length, fabric name and rating. The head and tail of each piece of cloth must be preserved according to regulations and used as a basis for color matching and batching. These strings are stored by the printing and dyeing factory and will also be given to the customer. Plants equipped with EPR systems can also enter information about each piece of cloth into the computer by order number and color number.