Exchange of Experience: Squeegee Troubleshooting Guide (Part 2)

● Adjust the corrective of the printer: "non-uniformity" issues.

You must be able to avoid and control the difference between these stripes and colors, because when they occur with the scraper blade problems, you will spend a few days and hours to solve them. This is why rotating the squeegee is a simple and important step.

To further distinguish the real blade problem (Figure 1) and other reasons, keep in mind the following rules:

(1) The characteristics of the streaks due to the jagged or notched edges of the scraper blade;

• In contrast to the predominantly dark stripe caused by the cracking of the inked panel, alternating light and dark ink streaks are exhibited.

Continuation of the stripe along the entire length of the squeegee

• Straight and parallel to each other (and if printing is done automatically by the machine, parallel to the screen frame in the squeegee direction).

(2) Caused by the scraper blade (because the scraper blade is worn or the height of the squeegee is uneven) The color unevenness has the following characteristics:

● The dark, slender part that continues throughout the entire length of the squeegee.

● If the squeegee blade is not straight, multiple parallel sections appear.

In general, the solution to these problems is to sharpen the squeegee so that the worn, saw-toothed or nicked blade is worn off and the squeegee blade is straightened to remove the uneven parts. Unfortunately, grinding scrapers is not as straightforward as it sounds.

As in every other screen printing operation, there are a large number of parameters that may enhance or hinder the sharpening process. The most important of these parameters are:

● The squeegee's physical properties.

● The compatibility of squeegee and printing ink.

● The state of the squeegee before sharpening.

● Have a squeegee ready for printing.

Scraper physical properties

Hardness, wear resistance and chemical resistance determine the main physical properties of the squeegee. In theory, none of these features affect the method of squeegeeing or squeegeeing. In reality, however, all three features affect both the squeegee blade and the sharpening method.

The hardness indicates the hardness and elasticity of the squeegee, which affects the number of blades to be ground to obtain a straight and uniform blade. In general, when grinding the cutting edge instead of cutting off a part of the cutting edge, grinding out a little bit of the cutting edge will make the cutting edge straight. If you cut a part of the edge, the part that must be cut off will become large, and the hardness will decrease.

Abrasion resistance is a feature that prolongs the use time of the squeegee. This benefit, if taken together, becomes like this: The wear-resistant scraper is difficult to grind, so it is also ground again with a grinding device. The sharpening of the highly wear-resistant squeegee is mainly limited to the knife cutting equipment.

The chemical resistance itself does not affect the grinding, but it affects the polished blade. The higher the chemical resistance of the squeegee blade, the sharper the squeegee blade may be without worrying about the previous blade breakage.

Each of these physical properties means that you must carefully evaluate the squeegee in order to ensure that it suits your needs. It must be compatible with grinding (the number of times a uniform printed image is ground), grinding equipment (grinding or cutting), and the type of ink required for the printed product.