1. Appearance:

The bar code symbol has a clean surface without obvious dirt, wrinkles, damage or perforation.

The numbers, letters and special symbols in bar code symbols are printed completely, clearly and without ambiguity.

the bar code symbol has no obvious deinking, stain and disconnection; The edge of the strip is neat, and there is no obvious bending deformation.

the ink color of bar code symbols is uniform, and there is no obvious difference.

2. Technical requirements:

It conforms to the national standaRds for bar codes adopted by samples. For these technical requirements, the national standards for bar codes have detailed quantitative indicators, including:

bar (empty) reflectivity, printing contrast (PCS value/print contrast signal):

PCs = (Rl-rd)/rl. In fact, most barcode readers (such as QUICKCHECK 4, XAMINER 65, etc.) can automatically calculate PCS values. If you want to calculate by yourself, you need to measure the reflectivity of empty bars and strips with a bar code reading pen (demonstration instrument and operation method), and then substitute the above formula to get the PCS value, which needs to meet the technical indicators specified in the national standard GB1294-1998. In principle, the colors of bars and spaces should be selected properly, and the reflection density values of bars and spaces should be separated as far as possible, so that the PCS value will not be a problem. Therefore, this item mainly requires choosing the right color in the design and controlling the color in the printing process.

for the dimensional error of strips (empty), a length measuring instrument with an accuracy of more than .1mm can be used. However, this is also a test item in the main design process. In the actual process, if the bar or space size is wrong, the bar code will not be readable. The national standard has strict regulations on the deviation of the original film and printed matter, and relevant standards can be found if necessary. At present, there are special softwares that automatically generate bar codes, like MBC software of Macs, so it is rare that the size of bars and spaces is not right now.

it is quite common that the size of the Quiet Zone at both ends is not right, because sometimes it is easy for designers to ignore this requirement when space is limited. The measurement method is simple, and it can be done with a length gauge with an accuracy of .5 mm.

bar height refers to the bar height of a bar code, which should not be less than the integer value of the bar height size in the standard. This item is flexible, so it is relatively simple to measure, but it cannot be directly measured by a bar code reader, so care should be taken in design.

the numbers and letters should be in OCR B character set (GB/T1258). these characters or letters for human identification should be printed on the bottom of the bar code and correspond to the corresponding bar code characters. their sizes should meet the national standards and be enlarged or reduced at the same magnification as the bar code. This item can't be measured directly by bar code reader, so it should be carefully designed.

the check code can be checked according to the calculation method stipulated by the state.

the correctness of decoding, that is, the readability of bar code, is very important and must be judged by bar code reader.

magnification factor refers to the ratio of the length dimension of bar code symbol to the standard dimension. Generally, the magnification factor is .8-2., as long as a pair of standard bar code films is used.

the printing thickness refers to the difference between the bar code symbol and the blank, which must be below .1mm .. That is to say, the printing must be as uniform and flat as possible, and it can be measured with a thickness gauge with an accuracy of .1 mm.

the printing position should be visually inspected according to GB/T14257. The above technical requirements are the factors and inspection items that must be considered when designing bar codes.

2. Common quality problems in bar code printing

The following items are the most common quality problems in the printing process, and judging these problems mainly depends on the bar code reader. At present, there are many kinds of such instruments abroad, and they have quite many functions, such as QUICK-CHECK 4, XAMINER 65 and so on. Taking XAMINER 65 as an example, this paper explains how to check and control the quality problems in bar code printing.

1. according to the function of bar code, its main quality characteristic is its Readability, and readability is the ability to decode with a special bar code reader. In the usual printing process, the common problem is that the bar code is unreadable, which comes from many reasons. Usually, bar codes cannot be decoded because some characteristics of bar codes fail to meet the specified requirements. Generally speaking, the bar code reader has two analysis modes. One is ANSI (American National Standards Institute) mode: this mode divides the PCS value, ECMIN value (minimum edge contrast), DECODABLE value, SC value (blank contrast), DECODABILITY (decoding ability), DEFECT (defect) and so on of the bar code into A, B, C, D and so on. If we set the passing level as C (which is used by most customers), the bar code reader will automatically calculate the average value of each measurement result or several measurement results (according to the instrument setting) and get the bar code level. If the level above C is like A and B, it means that it is readable. On the contrary, if one of the values is lower than Grade C, the overall measurement result will not pass. If the PCS value or ECMIN value or SC value is lower than C, it indicates that: ① the colors of bars and/or blanks are not matched correctly; (2) the color of the strip is printed too lightly, such as water, small amount of ink and low pressure; ③ The background color is printed too deeply, such as dry water, large amount of ink and heavy pressure; ④ Some strips are printed too lightly, like water, with sundries, etc. This kind of printing quality problem is easy to appear, especially because it is difficult to predict such problems in design. Most barcodes are placed on the back or bottom, and in order to pursue the overall decoration effect, barcodes are always printed on the background color or in a blank area. However, in order to save the cost, the existing color in the picture will always be selected, so it is very easy to appear that the PCS value of the barcode will be affected by following other colors. This requires experienced technicians to reduce such problems by properly adjusting the film or typesetting method.

if the DECODABLE value is lower than c, it indicates that there is something wrong with the coding, such as an error in the check code. And if the DECODABILITY value is lower than c, it means that it cannot be decoded. This is a comprehensive assessment, such as: the left and right blank areas are not enough, which is very common. Because some packaging formats are limited, this point is often overlooked, and some barcode readers can decode it, but the risk is too great, and some instruments will not be able to decode it. It is very simple to check this method. Just cover both sides of the bar code with white paper and scan it with a bar code reader to find out whether the blank area is enough. There are other patterns or characters near the bar code, because the bar code reader may treat these as bars or blanks, which makes it impossible to decode them. Attention should be paid to this problem when designing; PCS or ECMIN value or SC value is lower than c; Or the defect level is lower than c; Wrong coding; Bar code size error and so on. If the defect is lower than grade C, it indicates that there are sundries such as ink excrement and ghost on the bar code.

2. Size error of strips or blanks, that is, overweight or underweight. XAMINER also has a traditional pattern analysis (TRANDITIONA): check the dimensional deviation between the strip and the blank. In the printing process, the most common reason is that the strip is overweight due to the large amount of ink or pressure, or the width of the strip changes when the film is copied or printed. Many cases are the same as the previous factors that lead to the unqualified PCS value. For example, the ink amount of bar code is difficult to control due to the influence of other colors in the layout, so designers should consider this factor in color selection and production personnel in typesetting. Generally divided into five levels: too narrow, narrow, normal, fat, too fat, too narrow and too fat will lead to unreadable bar codes. The author once printed a kind of packaging box, whose bar code was printed with black bar code hollowed out on the background of dark violet, which was no problem from the point of color selection. However, because dark violet was printed with four-color screen, black naturally affected dark violet, and the black bar code was easy to print fat. After several failures, we reduced the bar code a little and finally solved the thorny problem.

3. Wrong coding. It means that the numbers or letters or symbols decoded by the bar code reader are different from those encoded. When measuring the bar code, carefully check whether the numbers read by the instrument are the same as those on the bar code itself.

4. Deinking. Refers to the printing defects of bars in bar code symbols, and its reflectivity is close to that of empty bars. In fact, the PCS value is too low, so try to make bar codes with large color contrast.

5. stain. Refers to the printing defects in the hollow or blank areas of bar code symbols, and its reflectivity is similar to that of bars. As for the common problems in appearance, the problems and reasons presented by different bar code printers are also different, and enterprise technicians should find different solutions according to different actual conditions.

The above inspection and control methods are all based on the fact that enterprises have bar code readers or related instruments, but some enterprises may not have relevant equipment to check, so some simple identification methods can be adopted: ① Copy the bar code film from the design company to ensure good decoding, and use it as the standard for checking the bar/space size in production, because the film is transparent and easy to compare. If it is found that it does not match, it needs to be checked with a measuring tool of .1 mm. ② For appearance defects, put the bar code under a standard light source and check it at a position 4mm away from the sample. If it is obvious, there is a problem. ③ Ensure that the left and right blank areas are sufficient. ④ Ensure that the printing color is uniform and there are no printing problems such as dirty paste. ⑤ Be especially careful when the bar code is printed on the reflective laser film, aluminum-plated film, etc., or the background color is similar to red

III. Brand recommendation of data collector:

Dolphin? 61 mobile data acquisition terminal

DENSO BHT-7 series wireless handheld data terminal

MC31 series durable mobile data terminal

MC 1 handheld mobile data terminal.