In gravure printing, the transfer of ink is achieved by the pressure of the impression cylinder to the printing plate. The impression cylinder is required to have strong pressure resistance, stable operation, and certain processing accuracy.
1. Conventional technical requirements of impression cylinder
Hardness and deviation of rubber layer, size deviation, circle runout of embossing cylinder, cylindricity, medium-high tolerance, surface quality, bonding quality of coated rubber layer and metal core, dynamic and static balance quality of embossing cylinder, metal core of embossing cylinder Technical requirements, etc.
Second, the quality acceptance method of the impression cylinder
1. Test conditions
Temperature and humidity: the temperature is 23 ℃ ± 2 ℃, the humidity can be determined as required;
Impression cylinder detection and parking time shall not exceed 3 months. Under the specified temperature and humidity conditions, the measured impression cylinder shall be parked not less than 16h after completion of production for testing.
2. Test items
Hardness determination: Use the Shore A hardness tester. When the hardness exceeds 90, the Shore D hardness tester should be used.
Determination of dimensional deviation: diameter is measured with calipers whose accuracy meets the requirements; length is measured with steel rulers or vernier calipers; cylindricity and mid-height are measured with dial gauges; radial circle runout measuring instruments are a pair of coaxial centers with dial gauge Measuring stand.
Surface quality: surface mechanical damage and defects such as impurities, bubbles, trachoma, etc. are inspected visually.
Checking the degree of adhesion between the adhesive layer and the metal core: use a mallet to check.
Dynamic and static balance, use dynamic balance, static balance device for measurement.
3. Judgment of results
The testing items include hardness, diameter, length of wrapped rubber, round runout, mid-height, surface characteristics, adhesion of the adhesive layer to the metal core, etc. If any item fails, the impression cylinder is a non-conforming product.
3. Concession acceptance conditions of impression cylinder
The quality of the impression cylinder is directly related to the printing quality and production cost, and in principle will not yield. If production is urgently needed and the order quantity is small, in order to ensure on-time delivery, concessions can be considered for the following situations, but the follow-up inspection of product quality must be strengthened. When the appearance of the impression cylinder has defects such as extremely fine bubbles, it can be detected by the machine, and it can be determined whether it can be accepted according to the printing situation, and pay attention to the use occasion.
The impression cylinder that gives in to the cylinder should monitor the use process:
1. Restrict the scope of use, faithfully or yellow printing;
2. Appropriately increase the pressure of the impression cylinder for on-machine testing;
3. Check the quality of the printing surface, if it can meet the quality requirements of the product, the impression cylinder can be accepted as a concession;
4. Tracking concessions and accepting the use of impression cylinders, appropriately increasing the frequency of their printed matter detection.
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