Common Problems in the Hot Foil Stamping Process and How to Solve Them

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Hot stamping is a key process in the post-press processing of paper printed products, which can greatly increase the added value of printed products. However, in the actual production process, due to problems such as workshop environment and improper operation, hot stamping failures can easily occur. Then I have sorted out the 9 most prone to hot stamping problems for you, and given solutions for your reference.

1.     Hot stamping is not strong

Main reason 1: The hot stamping temperature is low or the pressure is light. 

Solution 1: The hot stamping temperature and pressure can be readjusted; 

Main reason 2: During the printing process, due to the excessive amount of drying oil added to the ink, the surface of the ink layer dries too fast to cause crystallization, so that the hot stamping foil cannot be hot stamped.

Solution 2: First, try to prevent the occurrence of crystallization during printing; secondly, if crystallization occurs, the hot stamping foil can be removed, and the printed product can be air-pressed under heating to destroy the crystallization layer, and then hot stamping print. 

Main reason 3: Adding wax-containing lightening agents, anti-sticking agents or non-drying oily substances to the ink will also cause poor hot stamping.

Solution 3: First stick a layer of absorbent paper on the printing plate and air-press it once, and then carry out the hot stamping operation after the wax and insoluble oil on the bottom ink layer are absorbed.

2.     Hot-stamped pictures and texts are blurry and dizzy

Main reason 1: The hot stamping temperature is too high. If the hot stamping temperature of the printing plate is too high, the hot stamping foil exceeds the acceptable limit. At this time, the hot stamping foil will expand around, resulting in dizziness and voids.

Solution 1: The temperature must be adjusted to an appropriate range according to the characteristics of the hot stamping foil. 

Main reason 2: hot stamping foil coking. For the coking of hot stamping foil, it is mainly due to the prolonged shutdown of the hot stamping process, which makes a certain part of the hot stamping foil contact with the electrothermal high-temperature printing plate for a long time, and the phenomenon of thermal coking occurs.

Solution 2: In case of shutdown during the production process, the temperature should be lowered, or the hot stamping foil should be removed, or a thick piece of paper can be placed in front of the printing plate with a higher temperature to isolate the hot stamping foil from the printing plate.

3.     Fuzzy handwriting, pasted version

The main reasons: the hot stamping temperature is too high, the hot stamping foil coating is too thick, the hot stamping pressure is too large, the hot stamping foil installation is loose, etc. The main reason is that the hot stamping temperature is too high. During the hot stamping process, if the temperature of the printing plate is too high, it will cause the base layer and other film layers to transfer and stick, resulting in unclear handwriting and paste. 

Solution: During hot stamping, the hot stamping temperature should be appropriately adjusted according to the temperature range of the hot stamping foil. In addition, a hot stamping foil with a thinner coating should be selected, the appropriate pressure should be adjusted, and the pressure of the pressing roller and the tension of the winding roller should be properly adjusted.

4.     Image and text edges are uneven and unclear

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Main manifestations: During hot stamping, burrs occur on the edges of graphics and text, which affects the printing quality.

Main reason 1: The pressure of the printing plate is uneven, mainly because the layout is not flat when the plate is installed, which causes the pressure to be uneven everywhere on the layout. Part of the adhesion to the substrate is not the same, resulting in uneven printing.

Solution 1: The hot stamping plate must be flat and firm to ensure that the hot stamping pressure is even and the pictures and texts are clear. 

Main reason 2: If the pressure of the printing plate is too large during hot stamping, it can also cause the image and text to be unevenly printed.

Solution 2: Adjust the hot stamping pressure to an appropriate level. It is necessary to ensure that the pads of the embossing machine should be accurately fitted according to the area of the pattern, without shifting or moving. In this way, it can be ensured that the image and text are consistent with the pad layer during hot stamping, and the hair around the image and text can be avoided. 

Main reason 3: The pressure is uneven after hot stamping on the same plate.

Solution 3: This is because the size of the image and text area is very different. The pressure of the large area of the image and text should be increased. The padding method can be used to correct and adjust the pressure of the large and small areas to make them equal. 

Main reason 4: When the temperature is too high during hot stamping, it will also cause the image and text to be unevenly printed.

Solution 4: According to the characteristics of the hot stamping foil, reasonably control the hot stamping temperature of the printing plate to ensure that the four sides of the picture and text are smooth, smooth and hair-free.

5.     The image and text imprints are incomplete and missing strokes

Main reason 1: The printing plate is damaged or deformed, which is one of the important reasons for the incomplete image and text imprint.

Solution 1: If the printing plate is found to be damaged, repair or replace the printing plate immediately. The deformation of the printing plate makes the printing plate unable to withstand the applied hot stamping pressure, and the printing plate should be replaced and the pressure should be adjusted. 

Main reason 2: If the hot stamping foil cutting and conveying deviation, the margin is too small when the hot stamping foil is horizontally cut, or the cutting is skewed when unwinding is transported, the hot stamping foil will not match the printing plate graphics and texts. Some of the pictures and texts are left out, resulting in incompleteness. 

Solution 2: In order to prevent such a problem, when cutting the hot stamping foil, it should be neat and flat, and the margin size should be appropriately increased.

Main reason 3: Improper conveying speed and tightness of hot stamping foil can also cause this kind of failure. For example, the hot stamping foil splicing device is loose and displaced, or the winding core and the unwinding shaft are loose, the unwinding speed changes, the tightness of the hot stamping paper changes, and the position of the graphics and text deviates, resulting in incomplete graphics and text. 

Solution 3: At this time, it is necessary to adjust the rewinding and unwinding positions. If the hot stamping foil is too tight, the pressure of the pressing roller and the tension of the rewinding roller should be adjusted appropriately to ensure a suitable speed and tightness. 

Main reason 4: The printing plate part moves or falls at the position of the bottom plate, the pad of the imprinting mechanism is displaced, etc., so that the normal hot stamping pressure changes and is uneven, which will cause the image and text to be incomplete. 

Solution 4: During the hot stamping process, the hot stamping quality should be checked frequently, and the quality problems should be analyzed immediately, and the printing plates and pads should be checked. If it is found that the printing plate moves or the backing material is displaced, adjust it in time, and put the printing plate and backing material back in place and fix it.

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