The following is a set of overall inspection solutions for label printing quality:

Testing before printing:

Quality inspection of paper or film: check the physical properties of label materials, such as whether the thickness is uniform, whether the stiffness meets the requirements, whether the surface is smooth, etc. For paper, it is also necessary to check whether its water content is within the appropriate range, so as to avoid affecting the printing quality due to too high or too low water content. For example, the water content of paper is too high, and it is easy to ink out when printing; If the water content is too low, the paper is easy to brittle.

Compatibility test of ink: check the compatibility between ink and label material to ensure that the ink can adhere to the surface of the material well and will not fall off or fade. It can be tested by adhesion test, such as using 3M adhesive tape to stick on the printed label surface, and then tearing it off quickly to observe the adhesion of ink.

Graphic content check: carefully check whether the information such as words, patterns, barcodes and QR codes on the label design draft is accurate, including spelling of words, fluency of sentences, completeness and accuracy of patterns, etc. For example, the key information such as drug name, usage and dosage, and production date on the drug label must be accurate; Information such as ingredient list and nutrient composition list on food labels should also be strictly reviewed.

Confirmation of color mode and resolution: Check whether the color mode of the design meets the printing requirements. Generally, CMYK four-color mode is adopted for label printing. At the same time, confirm whether the image resolution is high enough to ensure the clarity after printing. For example, the image resolution of ordinary labels should be no less than 300dpi.

Design draft review:

Material testing:

Detection in the printing process:

Online inspection system: install online quality inspection equipment, such as high-speed cameras or sensors, to monitor the quality problems in the printing process in real time. These devices can detect defects such as missing printing, printing paste, overprinter deviation, color difference, cutter wire, dirty spots, foreign bodies, etc., and give an alarm in time, so that operators can adjust printing machine parameters or stop processing in time. For example, when it is detected that the overprint deviation exceeds the allowable range, the system will automatically give an alarm to remind the operator to adjust the overprint device of the printing machine.

Color management: use color management system to monitor and adjust the color in the printing process in real time. By accurately controlling the ink quantity, ink balance, printing pressure and other parameters of the printing machine, the color of the printed label is ensured to be consistent with the design draft. For example, the color of printed matter is measured regularly by using color measuring instruments, and the ink quantity and color profile of the printing machine are adjusted according to the measurement results.

Registration accuracy detection: use registration mark or detection system to detect the accuracy of multi-color overprint on the label. Ensure that patterns, characters and other elements of different colors can be accurately overprinted together to avoid problems such as ghosting and dislocation. For example, when printing color labels, by detecting the position deviation of registration marks, the overprint device of the printing machine can be adjusted in time to ensure the registration accuracy within the allowable range.

Post-printing inspection：

Adhesion test: the adhesion of the ink or coating on the surface of the label material is detected by tape sticking method or friction method. Ensure that the ink or coating will not fall off easily during the use of the label. For example, stick 3M adhesive tape on the printed label surface, then quickly tear it off at a certain angle and speed, and observe the shedding of ink or coating.

Water resistance test: after soaking the label in water for a certain period of time, take it out and check whether its appearance and performance have changed. Test whether the label can maintain good printing quality and adhesion in wet environment or in contact with water. For example, after soaking the label in water for 24 hours, observe whether it appears fading, ink migration, ink shedding and other phenomena.

Friction resistance test: the surface of the label is tested by friction tester or manual friction. Check whether the words and patterns are easy to wear and fade, and whether the surface is easy to scratch after the label is rubbed. For example, use a friction tester to rub the label surface for a certain number of times, and then observe its wear.

Bar code and QR code detection: use professional bar code and QR code reading equipment to scan and read the bar code and QR code on the label. Check whether the printing quality of barcode and QR code meets the standard, whether the information is accurate and whether it can be read quickly and accurately.

Visual inspection: under the standard light source, visually inspect the appearance of the label at a specified observation distance and angle. Check the surface of the label for scratches, scratches, bubbles, wrinkles, dirt and other defects; Whether the words and patterns are clear and complete, and there are phenomena such as missing words, broken pens and fuzziness; Whether the color is uniform, bright, colorless and poor. For example, look up at the label at a distance of 30cm and check its surface quality and graphic clarity.

Size measurement: Use measuring tools with satisfactory accuracy, such as calipers and micrometers, to measure the size of labels. Check whether the length, width, height, diameter and other dimensions of the label meet the design requirements and customer's order requirements, and whether the dimensional deviation is within the allowable range. For example, for a rectangular label, measure whether the dimensional deviation of its length and width is within 0.5 mm..

Appearance inspection:

Performance testing:

Data analysis and quality traceability:

Data recording and analysis: record and analyze the quality inspection data in the printing process, including defect type, defect quantity, inspection time, printing batch and other information. Through data analysis, the laws and causes of quality problems are found out so as to take corresponding improvement measures. For example, by analyzing the test data in a period of time, it is found that a printing machine is prone to overprint deviation in a specific period of time, so the equipment can be maintained and adjusted according to this problem.

Quality traceability system: establish a quality traceability system to trace the production process of each label. Record the label's raw material information, printing process parameters, quality inspection data, etc., so that when there is a quality problem, it can be quickly traced back to the source of the problem and effective recall and treatment measures can be taken. For example, when customers feedback that a batch of labels has quality problems, the quality traceability system can quickly query the production information of the batch of labels, find out the problems and solve them in time.