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Three-dimensional hot stamping is a combination of the effect of pressing bump and hot stamping, which has good anti-counterfeiting and artistic effect, so it has been widely used. But the quality control of three-dimensional hot stamping is a relatively complex problem. This paper briefly describes the three-dimensional hot stamping quality control points and defect processing, the content for friends reference:
 
The Quality of Three-dimensional Hot Stamping
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Give full play to the characteristics of anodized and plate material, so that the equipment, materials, environment, temperature, pressure, speed and other factors and printing between the formation of a good combination, the formation of the best process balance, and finally produce a satisfactory three-dimensional hot stamping products.
 
Hot Press Edition
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Compared with the ordinary bronzing plate and embossing plate, the production process of the three-dimensional hot stamping plate using the same place, and there are significant differences. Because three-dimensional hot stamping is a hot stamping or press bump to complete the process, so the hot stamping version than a simple hot stamping and embossing plate quality standards are higher, plate making requirements are more stringent, the process is more complex. , for example, ordinary bronzing version of the bottom die is flat, do not need to be specially made, and the three-dimensional hot stamping due to form the three-dimensional relief pattern, so its very hot pressure version of the bottom die must be with hot version that corresponds to the male mould letterpress, namely hot pressure on the part of the recess on the bottom die should be raised, and the height of the bumps and hot pressure is corresponding to the version of the depth of the recess.
High quality hot stamping plate is an important basis to ensure the quality of three-dimensional hot stamping products. Hot pressing version must be made of high quality metal materials, generally made of bronze plate by laser engraving. Stainless steel is also the production of hot stamping version of the excellent material, because of its very smooth surface, compared with the bronze version, stainless steel hot stamping version of the hot stamping text glossiness and definition is higher, the effect of concave and convex pressure is also better.
Because the hot pressing version is operated under high temperature and high pressure, the small defects that are not obvious under normal conditions may have a great impact on the quality of the product. Therefore, in the hot pressing version of quality control must strive for excellence, in order to eliminate the quality hidden trouble from the source.
In general, hot pressing version should be uniform thickness, pattern, text engraving clear, consistent depth; Bottom die should be flat without scratches, the same size, no cracking, full of toughness; Hot pressing version and the bottom die can not be visible to the naked eye deformation, collapse, bubbles, burrs and other defects.
 
Electrochemical Aluminum
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The quality of anodized directly determines the appearance of three-dimensional hot stamping products. Qualified quality of anodized aluminum should have no obvious bright spots, dark spots or laser plate seam, the surface protective layer is smooth and transparent, no fog and gray phenomenon. When the anodized light inspection, there should be no visible white spots, dirty spots, glue spots, sand holes and other quality defects.
In addition to appearance performance, the suitable hot performance of aluminum oxide is also very important. It is one of the decisive factors affecting the quality of hot stamping, and its adhesion, peeling force and impact resistance are directly determined by its hot stamping performance. In order to ensure the best electrochemical aluminum can show the optimum hot performance, not only should carefully choose paper, ink, light oil, chemical coatings, such as varnish also deal with hot stamping process parameters such as temperature, speed, pressure to set reasonable, should also try to hot before mass production, so as to ensure the yield when the mass production.4
In addition to confirm the suitable ironing properties of anodized aluminum by trial ironing, special instruments or tape should also be used to test the peel strength, impact resistance and other properties of anodized aluminum. If the peel strength of anodized aluminum is too small, in the hot stamping transfer process may appear to drop aluminum or transfer poor problems; On the contrary, anodized is difficult to completely transfer, hot stamping does not appear on the quality fault. If the impact resistance of anodize is poor, the problem of dropping aluminum will occur in the process of pressing concave and convex, and the performance of the finished product is the incomplete and damaged hot stamping part. Therefore, the primary measure to solve the three-dimensional stamping process of aluminum, incomplete, foaming, layer separation and other quality defects is to fully grasp the various properties of anodized aluminum. In the production of three-dimensional hot stamping of cigarette package, holographic laser anodized aluminum with high temperature resistance and anti-counterfeiting is generally selected. This kind of anodized aluminum has good peel strength and impact resistance, is not easy to deformation, and is suitable for hot stamping performance, so it can effectively ensure the quality of finished products.
 
In addition, for three-dimensional positioning hot stamping anodized plate distance must be consistent, can not exceed the set step parameter error (error < 0.1mm). Because in the hot stamping step calculation, the plate distance as the laser eye tracking point, even if there is only a small error, after many hot pressing, the cumulative error will be quite surprising, sometimes even up to tens of centimeters, causing a lot of material waste, so the anodized plate distance should be strictly controlled.
 
Operating Points
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In the three-dimensional hot stamping production process, from the “hot” and “pressure” two aspects of quality control, to avoid poor adhesion, ink back pull, hot stamping is not high-quality defects; To straighten out the aluminum oxide adhesive hot melt and ink, varnish, varnish between the affinity relationship; Also need to set up quality control points in the printing machine, pay close attention to the amount of ink, ink drying effect, the amount of powder spraying on the hot pressing process, and strict control, timely solve the quality problems.
 
Temperature Control
To the temperature regulation as a key point of three-dimensional hot stamping quality control, strict control of preheating time, and ensure that the temperature rise, fall range and hot stamping speed to keep in sync. The amount of anodized hot melt adhesive coating is very small, so if it receives a slight deviation in hot stamping heat, it will directly affect the transfer quality of anodized aluminum. In addition, anodized surface coating of metal aluminum layer is also very thin (thickness is only 1 ~ 2μm), and is very sensitive to temperature changes, so we must carefully control the hot stamping temperature.
But the temperature regulation is not easy to control, so in the actual production process, often due to hot stamping temperature fluctuations and some quality problems. For example, hot stamping temperature is too low, anodized hot melt glue melting is not sufficient, it is prone to hot stamping incomplete, paste version, hot stamping, hair and other quality defects; When the hot stamping temperature is too high, the surface of anodized aluminum layer will melt, there will be splashing phenomenon, but also produce discoloration, surface fog, no laser gloss and other quality defects. In addition, foaming, aluminum, peeling and other faults and hot stamping temperature control have a great relationship, the producer should be based on the specific performance of the quality of the fault to adjust the hot stamping temperature.
 
Pressure control
In order to make three-dimensional hot stamping products and simple pressure concave and convex products of the concave and convex effect comparable, it is necessary to ensure the hot stamping effect at the same time, the quality of the concave and convex pressure control. Because three-dimensional hot stamping is completed at the same time and press concave and convex process, the pressure size not only affects the adhesion of anodide, but also related to the effect of press concave and convex, sometimes there may be irreconcilable contradictions between the two. For example, the pressure set a little larger, you can increase the adhesion of anodization on the paper, good for hot stamping, but in the process of press concave and convex paper damage may occur.
Therefore, in order to achieve the best hot stamping effect on the basis of not crushing paper, it is necessary to carefully set the pressure, and reasonably adjust the height of the hot pressing layout, accurate calibration of the concave and convex bottom die, to ensure that all the hot pressing version and the bottom die height, flatness are consistent. In addition, but also to check the quality of the bottom die tracking, especially in the bottom die has been subjected to tens of thousands of times of impact resistance, special attention should be paid to check the deformation degree and toughness of the bottom die, and timely replacement of the worn bottom die.
 
Fault Handling
In the production process of three-dimensional hot stamping, quality faults may occur at any time, and need to be dealt with in time. Among them, and anodized ink fitness is closely related to the main defects including anodized adhesion, ink back pull, hot stamping, incomplete aluminum and so on.
 
Attached to the Bad
In the three-dimensional hot stamping production process, the failure of anodized adhesion is often shown in the following two aspects, the reasons are also different.
One is that the anodized aluminum can not be firmly pasted on the printing surface, and may even be completely hot stamping, and the phenomenon of aluminum or large incompleteness will appear when the tape is pulled. In the final analysis, this is due to the poor adhesion of anodized aluminum, at this time the need to improve the suitable hot performance of anodized aluminum, or replace the new anodized aluminum.
The other is hot stamping after anodized aluminum can be firmly pasted on the printing surface, but there will be ink back pull phenomenon. This phenomenon is caused by the poor adhesion of ink, and ink and paper printing adaptability and ink drying is not completely related to other factors, at this time, we need to improve the printing ink and paper adaptability, or adjust the drying rate of ink.
 
Hot Stamping Lose

The main reasons for hot stamping lose are as follows: one is too much powder on the surface of printing, which is the most common reason; Two is the ink is not completely dry on the hot stamping; Third, the surface of the ink layer is coated with a layer of protective varnish, varnish and other resin coating, so as not to have “affinity”. Encounter hot stamping not on the quality problems, we must proceed from reality, specific problems specific analysis, do not rush hot stamping, to prevent the production of large quantities of waste quality accidents.


Post time: Jul-21-2021