How thick should the knife plate spring pad be used for the knife mold?

Selection and Application of Die-cutting plate Spring Pads: A Practical Guide to Enhancing the Stability of Die-cutting Processes

In the die-cutting process, the knife plate spring pad, as an auxiliary accessory, plays a practical role in ensuring smooth production and stable quality. It is usually installed on both sides of the die-cutting knife line. Its main function is to help the paper separate smoothly from the die-cutting knife and reduce the phenomenon of adhesion.

Under high-speed die-cutting conditions, paper is susceptible to static electricity or fiber pulling. The elastic pad of the die-cutting plate, through its own elasticity, promptly eliminates the adhesion between the paper and the cutting edge, thereby reducing the probability of paper jams, sheet breaks or inaccurate die-cutting positions.

The knife plate spring pad also helps maintain the die-cutting quality. It provides uniform rebound force when under pressure, making the contact pressure between the knife line and the paper more consistent, thereby supporting die-cutting accuracy and the neatness of the cut edge. In creasing processing, appropriate spring pads can reduce the occurrence of burrs or uneven depth on the creasing line.

According to the weight of the paper and the complexity of die-cutting, reasonably controlling the hardness and thickness of the spring pad of the knife plate can improve problems such as incomplete die-cutting or paper delamination caused by uneven pressure.

I. Basic Principles for Thickness Selection

The thickness selection of the knife plate spring pad should refer to the clear technical specifications. It is generally recommended that the thickness of the elastic pad be 1 to 2mm higher than that of the knife mold. If the hardness of the die-cutting material is relatively high or it is prone to tool jamming, the thickness can be appropriately increased.

This suggestion is applicable to multi-number die-cutting scenarios. For instance, the common specification of 45-degree sponge block die-cutting auxiliary materials is 300×300×9mm, which can meet the requirements of general flatbed die-cutting machines.

For thin die spring pads (such as about 1mm), there may be a slight difference in thickness on both sides, which is related to the process characteristics of the entry and exit edges of the tool. For the knife plate spring pad with a thickness of about 10mm, the error on both sides is usually small and does not affect normal use.

If the thickness is not properly selected, it will directly affect the die-cutting effect: if it is too thin, it may lead to insufficient rebound and the product will be difficult to demold. If it is too thick, it may cause the edge indentation of the product to be too deep, and even damage the bottom rubber pad.

Ii. Selection of Hardness and Material Combinations

Apart from thickness, hardness is another important parameter of the knife plate spring pad. According to the actual application requirements, the knife plate spring pads can be classified into multiple grades based on hardness to adapt to different die-cutting materials and conditions.

For instance, the commonly used knife plate spring pads in cigarette package printing enterprises generally include several types such as 25-degree slightly soft models, 35-degree gray breathable sponge strips, 60-degree micro-porous sealing white rubber strips (often referred to as solid rubber strips), and 75-degree white arched rubber strips (also known as explosion-proof rubber strips).

Different die-cutting materials require elastic pads of different hardness. Take the 55-degree hard knife plate spring pad as an example. It can play a supporting role in gray plate die-cutting. Its structural density is relatively high, which can provide sufficient rebound force when the cutting edge cuts in, helping to cut the fibers at one time and reduce the fuzzing of the cutting edge.

For corrugated paper die-cutting, it is usually necessary to select a 30-degree hardness knife plate spring pad to prevent the corrugated structure from collapsing under pressure.

Currently, the hardness range available on the market is quite wide, covering various specifications such as 15 degrees, 25 degrees, 35 degrees, 45 degrees, 55 degrees, 65 degrees, and 75 degrees, which can meet the die-cutting needs of all kinds from precision electronic materials to thick corrugated paper.

Iii. Practical Reference for Selection

When choosing the appropriate die-cutting plate spring pad for different die-cutting materials and equipment types, the thickness, hardness and material properties should be comprehensively considered.

Circular die-cutting has high requirements for the cutting resistance of the bottom rubber pad, and it is necessary to maintain a tight surface structure after multiple cuts. If the durability of the base rubber pad is insufficient, the surface will gradually loosen, which will lead to incomplete die-cutting, decreased linear speed and reduced precision.

Some general-purpose knife plate spring pads have a wide range of applications and can be adapted to medium and high-speed die-cutting machines, including equipment from brands such as Boster, Heidelberg, Evergreen, Beiren, Xuheng, Shengli, and Guowang, as well as various rotary and flatbed die-cutting machines.

When installing the spring pad of the knife plate, accurate positioning is extremely crucial. For example, the width of the knife line for cutting sealing rubber strips is recommended to be controlled between 1 and 3mm. If the width is too large, the sealing rubber strip may cause lateral repulsion when subjected to force, damaging the connection points or paper lines. If the width is insufficient, it will be difficult to prevent the cardboard from sticking to the knife.

Iv. Explanation of Application Examples

A certain printing enterprise has long been troubled by white edges and dust problems when die-cutting grey board materials. Despite replacing various cutting tools, the issue remains unsolved. After trying out the 55-degree hard knife plate spring pad, the situation improved.

The thickness of the grey board is usually no less than 1.5mm. If the rebound of the elastic pad is insufficient, the blade will repeatedly pull the fibers, forming white edges and debris. If the rebound is too strong, it is easy to shake off surface dust and powder, polluting the environment. The 55-degree hard knife plate spring pad evenly distributes stress, keeping the cut vertical while reducing dust generation.

After using this elastic pad, the automatic die-cutting machine can still maintain neat cuts after continuous operation for eight hours, the frequency of waste removal has been reduced, and the operational continuity of the gift box production line has been improved.

Another case involves bulging at the edge of the vertical crease of corrugated cardboard. The solution is to use a 1.42mm steel wire die, with a rubber strip attached beside the press line, making it 1mm higher than the line surface but not exceeding the height of the die. If the quality of the core paper is poor, it is prone to pitting. Generally, when attaching the protective strip beside the line, high-elasticity glue is selected. The protective strip should be 1 millimeter higher than the die-cut line, which helps to reduce the occurrence of messy paper, loose paper and burrs.

Contact information for Shenhua Printing Materials: Mr. Ji, 19924506937