The quality control of hot stamping:
Currently, regardless the appearing of new hot stamping process, the national aluminum is an important process of printing, and it’s not desolate among people. It has specific decorate impacts and good operating process, and now still has good reputation.
The national hot-pressing aluminum foil transfers pattern and words onto the material surface by using the way of heating and pressing. To complete this process, we need a hot stamping machine, which engraves special edition of pattern and word, the temperature of heating, transfer pressing and relevant times. We should pay attention to choose proper aluminum when hot stamping different materials, and also choose proper temperature, press, times to reach the ideal hot stamping effects.
Hot stamping version: high qualified hot stamping version is the main factor in protecting the hot stamping quality. Nowadays, producing hot stamping version uses photograph corrosion technology and electronic engraving technology, the material is mostly copper and zinc. Copper material is fine and smooth. The surface fineness and heat transfer effects is superior to zinc. Using high qualified copper can improve the glossiness of patterns and edge sharpness.
The national photograph corrosion technology has simple process and low costs, but short lives. It is mainly used in words, lines, and normal patterns. To some hot stamping versions with fine and different patterns, we need use electronic engraving technology. Electronic engraving technology can show the rich delicate change of levels, improving the ability of performance. This technology is benefit to environments, but the electronic engraving equipment investment is too much, the engraving deepness is not ideal. It is easy to result in filling in. But it has good printing resistance and is suitable for long versions such as cigarette box. Holographic anti-imitation technology has high requirements and long periods. It only used in packaging products in bulk.
Hot stamping equipment: the choice of hot stamping equipment is the key factor of deciding hot stamping quality. Sheet-fed hot stamping machine has three types: flat flatten, Round flatten and round rounded. The most popular one is flat flatten machine.
These three types of machines have their own advantages and disadvantages. Round flatten and round rounded printing use linear pressure, total pressure is small, it can hot stamp big areas easily with relatively small pressure. Round rounded type has high efficiency, and it is suitable for hot stamping products in bulk. Because the arc surface of copper is difficult to process, the cost is high and heating expansion cylinder is more difficult than heating flat. The operation of flat flatten is flexible and convenient, and it is used for short products.
National hot stamping equipment has obvious advantages in price and performance when comparing with importing hot stamping equipment. The precision, stability and performance of importing hot stamping equipment is superior to national ones. It is suitable for processing top grade products packaging.
Hot stamping applicability: it means choosing proper aluminum foils according to hot stamping speed, temperature, press. When the equipment is stable, mastering hot stamping applicability is the most important ways to improve hot stamping quality. The process of hot stamping is as follows: preparation, lock up, fill up, adjust parameter, experiment, sign, hot stamping.
As the hot stamping process shows that three basic factors of hot stamping are temperature, pressure and times. To make ideal hot stamping effects, we should master proper hot stamping temperature, speed and pressure. In addition, the quality of materials related to hot stamping should be paid much attention. For example: the applicability of products, the performance of aluminum materials and the quality of hot stamping editions. One of the links will affect the hot stamping conditions.
Trouble shooting of hot stamping
Hot stamping troubles are related to the factors such as products surface characteristics, the properties of aluminum, hot stamping temperature and pressure.
① The powder on the products’ surface is too much, printing oil is not dry so much or oil surface have additives such as adhesions and enamel. These will obstruct adsorb of aluminum and papers. So we can solve them by dealing with the powder or printing process.
② The choice of aluminum will also affect the fastness of hot stamping. So we should choose proper aluminum foils according to different areas and properties of hot stamping. There are different aluminum foils in the market, all this different foils are related to different products and proper hot stamping scopes. The differences between them are adhesive force and stripping conditions. Aluminum foils with bad adhesive and fastness will result in bad hot stamping conditions.
Referring to following assortment when choosing aluminum foils: aluminum foils hot stamping on normal products are 88一I, PM of KURZ, such as cigarette box, cosmetics printings. Hot stamping aluminum foils including printing gold and silver have 88-2. Fine stroke stamping such as packaging of cigarette and cosmetics have 88-3 and 88-4. PM288 papers that are suitable for OPP and PET film have UV oil papers. Lighting papers have 88-4、K、LK、and SP.
③ Hot stamping equipment, times and temperature will all affect the hot stamping fastness and pattern edge sharpness.
There are differences in hot stamping equipment, materials, times and temperatures. For example: high speed round rounded machine is connected with lines, so the hot stamping temperature should be higher than round flatted or flat flatted. Under normal conditions, the temperature of round rounded is about 190 to 220℃, round flatted is about 130 to 150 ℃, flat flatted is about 100 to 120 ℃. Certainly, hot stamping times, temperatures, and producing efficiency are related to aluminum transfer performance. We should also pay attention to whether the pressure is balanced. Some difficulties in printing should also be related to checking the hot stamping editions.
Counter pull is to pull off the printing oil or lights from aluminum. The main reason is that oils on the products surface are not dry enough or processing of UV surface is not good. These will result in the fastness between oil UV lights and paper being not perfect.
Hot stamping can be made after drying the products. Or we can choose aluminum foils with low separating force and good transitivity.
The reasons of filling in are that hot stamping editions are not good or installing aluminum foils incorrectly. High temperature of hot stamping will change the color of aluminum foils. Additionally, the wrinkle of aluminum will also change the color. We can solve them by reducing the temperatures. Making an air fine on the round flatted will remain the foils and avoid aluminum contacting to the hot stamping editions.
Destroying the lights of aluminum, the pattern will be bad. Hot stamping which need operate on films will hot stamping first, which will result in destroying the lights of aluminum foils. Water solubility glue will make the aluminum black, resulting in bad patterns. It will hollow under the pressure, and the glue is unable to permeate the surface of the aluminum. These all will affect the quality of products. The correct process is to hot stamping after membrane, and choosing the proper aluminum related to OPP.
In total, there are many factors that will affect the quality of hot stamping. When the equipment is stable, mastering hot stamping applicability is the most important ways to improve hot stamping quality. Producing of cigarette is not the same as other products. It has its own specific requirements, such as quality, decoration, imitation. Companies should check the constructions carefully before producing. Maintaining the machines carefully in daily lives, mastering the properties of aluminum foils, being familiar with the connections between temperature, pressure and speed, the quality of hot stamping will be remained perfectly.
