Using Squeegee to Solve Ink Roll Scratch and UV Ink Splash

In the field of flexo printing, we often encounter some issues related to the squeegee. Two of the issues that people often talk about are ink roller scratches and splashes of UV inks. Actually, before starting formal production, people can take many measures to avoid the occurrence of scratch lines or ink splashes. In addition, the type of squeegee also affects the final printing effect.

Ink roller scratches usually refer to the appearance of an annular fine line in the embossing process of the anilox roller. These lines are usually perpendicular to the length of the ink roller. From shallow to deep, they may eventually become clearly visible dark marks.

Once scratches or streaks appear on the roller, one should remove it from the press, and the cost of replacing a new roller is quite high. For example: the cost of printer downtime, ink waste, substrate waste, and human resources should all be calculated into the cost of replacing the ink roller.

The cause of the scratch

During the embossing process, there are three elements of the printing press that can contact the anilox roll: plate, ink and squeegee. Since the squeegee is the only fixed object that can contact the moving anilox roller, the problem of scratches is still to concentrate on the squeegee. The arrangement of the doctor blade box or holder, the loading pressure of the doctor blade box, and the surface conditions of the anilox roller can all affect the scratches of the ink roller.

The arrangement of the squeegee box or stand is critical to the normal operation of the printing press and high quality printing. With the ageing of the squeegee case, wear and breakage caused by bending or twisting may cause deformation of the stent itself. Due to this change, the stents may not remain parallel. The press operator should apply more pressure to them to ensure that the entire squeegee is put in.

In general, before the ink-jet knife contacts the anilox roller, it must first be deflected by a certain angle so that the entire blade can be brought into full contact with the anilox roller. The most important thing is to let the squeegee stand vertically against the top of the stand; and all the squeegees must touch the ink roller at the same time, both from the top and bottom ends, and from the conveyor to the operator. Other factors, such as improperly cleaned brackets, can also interfere with the squeegee alignment. Note that setting details is very important to eliminate the problem of scratches on the ink roller.

Excessive stent loading pressure can cause the squeegee blade to bend or curl, causing the blade to deflect, which can cause wear on the backside of the squeegee blade. This is one of the reasons for scratches. The squeegee should be in contact with the anilox roller at the same time. If the applied pressure is too great, squeegees will appear on the squeegee. If these burrs continue to develop, they will form scratches. In general, the less pressure the squeegee needs, the better, as long as it satisfies the need.

Another reason for scratching the squeegee is that the anilox roller is carved too deeply. During the process of engraving the anilox roller, the laser beam penetrates the ceramic. As the ceramic melts, the ink roller surface forms an ink hole. In general, these ink holes have a hexagonal structure. However, in the hundreds of millions of ink holes, it is not possible to arrange each one on the anilox roller so evenly because they are limited by the casting method. Our goal is to make the wall of the ink hole as thin as possible to facilitate the transfer of thinner ink film. The thinner the ink film, the easier it is for people to control the substrate, resulting in clearer, cleaner images.

If the performance of the anilox roller has a large number of raised points, people must process and polish the engraving. However, by polishing, the ink hole support line will distort, eventually damaging the carved ink hole and reducing the ink film consistency. The higher the number of ink roller lines, the greater the chance of ink roller scratches.

Squeegee and ink roller scratches

When the problem of ink roller scratches occurs on older printers, or due to vibrating, unstable pumping systems or unknown variables, the best solution is to use a coating squeegee.

One case in which the use of a coating squeegee is required is when a mechanical failure of the printing press exerts excessive pressure on the squeegee. Although the coating of the doctor blade may also produce burrs, problems do not occur at least in the coating of the doctor blade.

Inconsistent ink line or recast pressure may cause unevenness in the ink roller and print. To solve this problem, one can use a nickel-plated squeegee. It is said that this type of squeegee is particularly suitable for eliminating scratches. . But on some printing machines, no matter how small you have to recast, the uneven support line of the ink roller may cause scratches. The nickel-plated squeegee is a self-healing squeegee that ignores and compensates for the rough surface of the ink roller for normal production.

The benefits of using a cloth squeegee to solve the scratch problem are:

* Due to the use of durable materials, the life of the doctor blade is longer.

* The anilox and squeegee wear is less because the squeegee has a lower coefficient of friction.

* Protective coating prevents the squeegee from being corroded.

UV ink splash

Today, the demand for high quality images in the UV flexographic printing market is very high. Although UV flexographic technology has made great progress in the entire printing industry, the phenomenon of UV ink splashing is still widespread.

There are many reasons why this problem continues to occur

We often hear that inks, anilox rollers, squeegees, angles, plates, and other factors can cause ink flying. Although all of these variables can affect the operation of the press, there is only one reason for the UV ink splash: UV ink itself.

In fact, the transfer of UV inks on printing presses is very different from aqueous and solvent based inks. The viscosity of aqueous and solvent inks on the Viscometer No. 2 is 25 to 27 seconds. In contrast, UV inks are five to seven times more viscous in the press transfer area than the first two inks.

Because the UV ink is thicker and the transfer is different from other inks, it will cause some physical change in the transfer point between the ink roller, the doctor blade, and the plate cylinder. This depends mainly on the thixotropy of UV inks. When the doctor blade scrapes the ink from the anilox roller and transfers it to the plate, the ink generally splashes. This is also the reason for the UV flying ink phenomenon.

What happened in the process? Imagine your rain wiper scraping the rain off the window while the car is driving at high speed. Your front is bright. Now imagine that if the cold rain forms a thin layer of ice on your windshield and because the ice is thicker than water, the wiper can't completely scrape it off, then a window will form on your window. Incomplete film. Once your windows are not clean enough, your sight will be affected.

If you reduce the size of the brush to a quarter of its original size, it will clearly increase its ability to recuperate ice, because it will not be deformed to a large extent. This theory can also be applied to squeegees and UV inks. If you increase the printing speed while the anilox roller is rotating, the UV ink will show resistance to transfer. If you increase the thickness of the squeegee, there will be no serious quality problems as it scrapes the ink.

Although many companies and industry experts have found ways to alleviate this problem, the squeegee experts revisited and investigated the phenomenon of flying ink around the characteristics of the squeegee. Tests in the pressroom have proven that using a thicker squeegee can effectively mitigate UV ink splashing. Thicker squeegees with coatings and adhesives are more commonly used because of the high viscosity of the ink. This "thick squeegee effect" has already been recognized because it can resist the pressure of this UV ink by the corresponding treatment of the squeegee and ensure the smooth progress of production.

However, if the ink film is not thin enough, the printed substrate will be damaged. This will also affect the printing effect, the back of the print, and the bar code.

Problem-oriented

Research, development, and testing can help people create a highly advanced squeegee system that contains alloys. It should be able to effectively reduce the occurrence of UV ink splashes without affecting the printing results.

This special squeegee has a thicker bottom (the squeegee is mounted on the paper plus portion) and is very close to the contact measurement point. Its top design ensures print quality and standard squeegee characteristics.

The special design of this squeegee allows the thicker ink to self-measure, just like a normal squeegee, but because the bottom of the squeegee is relatively stable, it reduces the degree of bending of the blade. In this way, people can perform stable ink film measurements while avoiding ink slides. This can also effectively eliminate or reduce the UV ink splash phenomenon.

Now, UV ink printing plants have made great progress in the high-quality image printing market. The correct choice of squeegee is exactly the decisive factor in achieving high quality and high quality printing.