In China printing factory, the hot stamping operation is using the hot pressing, to melting off the hot melt organic silicon resin disjointed stratum and adhesive, the adhesive force of silicone resin which with hot melt is reduced after melting, the aluminum foil layer in anodized aluminum had been stripped from the polyester membrane, under the effect of hot pressure, and a short period of pressure maintaining, on the back surface of this silicone resin, adhesive state of hot melt can be joint transferred effectively to the hot stamping bearing surface, will firmly attached to the hot stamping bearing surface after cooling. From the principle of hot stamping operations, we can easily see that the performance of anodized materials, and the temperature, pressure and speed when hot stamping, also the adaptation of hot stamping bearing surface material, are the reasons for the quality of hot stamping. The following I will talk about my understanding of the common problems of hot stamping production, hopes to initiate learning and improving together with you.
1. Cannot hot stamping
(1) The crystallization of the ink on the hot stamping bearing surface.
Solution: it is recommended to use good quality and strong adhesion of 15# anodized aluminum material, or go through with adding thin and soft cushion on the corresponding position of impression roller to extend the pressing time to solve the problem. However, to fundamentally solve the problem of hot stamping must be strictly controlled red dry oil adding volume on ink layer of hot stamping bearing surface in the printing process, this adding volume should not exceed 0.5%.
(2) The model selection of anodized aluminum is not proper.
Solution: when hot stamping for larger area of the pattern, it is recommended to use anodized aluminum which is low fastness, small compactness, and easy to transfer.
2. Hot stamping unstable
(1) The hot stamping temperature and pressure are not enough.
Solution: according to the characteristic of hot stamping bearing material and the type of anodized aluminum, to determine the appropriate hot stamping temperature and pressure. We recommended hot stamping temperature control at 75~120 degrees, hot stamping pressure control at 25 ~ 35kg/cm².
(2) The improper additive is added to the base ink layer.
Solution: after confirming adding additives containing wax in base ink layer, through the way that cover printing again by 991# light reduce agent with 2% white light dryness oil agent on the base ink layer surface, to change the ink layer surface printability, improve the affinity between ink layer surface and anodized aluminum foil.
3. Imprint are not finished
(1) The edges of imprinted appearing rough edges.
Solution: to improve the hot stamping temperature, increase hot stamping pressure (also to increase hot stamping pressure by thickening the cushion).
(2) Imprint lacks with painting.
Solution: appropriately adjust the unwinding and winding tension of anodized aluminum.
4. Imprint become grew dim or spot removal
(1) The ink layer is not dry on the hot stamping bearing surface.
Solution: for the surface of the ink layer of wet substrate, should be carried out in a timely manner airing, to ensure that the ink layer drying then operate the hot stamping
(2) Excessive amounts of white ink are added to the ink.
Solution: usually we use hand wipe the surface of ink substrate layer, if some residual ink on hand, that indicating the light color ink had been added white ink in dilute color excessive, here to organize workers to evenly wipe with the hot stamping parts by soft cotton cloth, to improve printability of hot stamping substrate surface.
(3) Excessive printing spray volume.
Solution: wipe the surface of ink substrate layer by hand, if there is a sense of stagnation and accompanied by powdery pigment residue on the hand, namely that the printing spray volume is too large, here to organize workers to evenly wipe with the hot stamping parts by soft cotton cloth, in order to reduce the printing spray volume and floating ink layer, increase the area of anodized aluminum and printing ink layer, which can fully transfer and attach from anodized aluminum to the substrate layer.
Paste version refers to the printed text blurred, and even cannot identify.
(1) The corrosion depth of the hot stamping is not enough or the wear and tear and aging. Solution: when making the hot stamping, make sure that the stamping parts need to be enough corrosion depth; when hot stamping is wear and tear and aging, the printing plate should be replaced in time.
(2) Excessive stamping pressure.
Solution: usually stamping pressure should be controlled at 25 ~ 35kg/cm².
(3) improper choice of anodized aluminum.
Solution: When start book printing, dense lines patterns and small text of hot stamping, should as far as possible to choose fastness and compactness of better anodized aluminum.
6. Weak lustrousness of image-text
Cause analysis: Weak lustrousness of image-text after hot stamping, mainly due to heating plate temperature is too high while hot stamping, that resulting in oxidation between anodized aluminum foil and dye layer, and even change color, lead to reduced brightness of image-text and lose luster.
Solution: appropriately reducing the temperature of the electric board, so that it always stay in the appropriate range; according to the selected model of anodized aluminum, choose its corresponding hot stamping temperature.
7. Imprint, beading, or appearance of auroras
Reason analysis: after hot stamping, imprint, beading, or appearance of auroras, mostly due to excessive hot stamping temperature.
Solution: appropriately reducing the hot stamping temperature, so that it always stay within the appropriate range.
Article from: http://www.chinaprintingmasters.com/News107.html