The Importance of Properly Fitting the Squeegee
Proper installation of the squeegee is critical to optimize printing performance and control costs. Due to the complex design of the carton printing machine in the past, it was difficult to install the drawdown blade, and changing the blade often caused the printing machine to stop for several hours. Mounting the squeegee blade requires careful fitting in place to ensure successful ink transfer to ensure effective printing.
If the drawdown blade is properly installed, both the drawdown blade and the screen roller will benefit from extended life, while maintaining a consistent printing effect. If the drawdown blade is installed improperly, it will accelerate the simultaneous wear of both the drawdown blade and the screen roller, ink leakage in the drawdown blade chamber, increase the downtime of the printing machine and waste production time. Factors that affect the correct installation of the scraper, such as: the installation position and direction of the scraper, blade contact angle, level adjustment and pressure, will be introduced one by one below:
The installation position and direction of the scraper
When installing the squeegee, first of all, the squeegee and sealing knife must be positioned accurately to obtain a suitable printing effect. Depending on the direction of rotation of the anilox roll, the drawdown blade can be mounted on the top or bottom of the doctor chamber. Remember that the drawdown blade is the last contact blade for ink transfer to the screen roll, and the sealing blade is always installed opposite it.
If the squeegee and sealing blade are installed in the wrong position, then the squeegee will not have the correct contact point and will not be able to scrape the correct amount of ink before ink transfer. The tip of the drawdown blade bevel should face toward the doctor chamber to prevent streaks. The anilox roller and drawdown blade are designed to work together, so correct blade installation and orientation are important for the mutual coordination between the two.
Blade Contact Angle
The blade contact angle is the angle at which the blade contacts the anilox roll. The ideal contact angle between the blade and the circumference of the anilox roller should be 30°. If the angle is less than 30°, most of the edge of the blade will be in contact with the anilox roller, and if the contact surface is too large, it will be difficult to scrape properly; the same In some cases, if the contact surface is greater than 30 degrees, the blade will not be able to squeegee ink better.
Level adjustment and pressure
When the drawdown blade is installed properly, it can maintain a balanced and consistent contact with the anilox roll. When the blade is adjusted properly, only light pressure on the anilox roll can produce a consistent ink removal effect. The recommended pressure is 25-30 lbs. or 1.7-2 bar. When the blade is installed, it must be tightened from the middle to both ends, and the clamp should not be too tight when clamping, otherwise it will cause the blade to bend. If the blade is installed with too much pressure, it will be forced to bend and lose the good contact point with the anilox roller. In this case, the anilox roll is filled with ink. Remember that proper clamping pressure of the scraper can not only ensure the quality of scraping ink, but also prolong the pressure of the scraper and the screen roller.
If the screen roll is not in parallel contact with the doctor chamber, it will be uneven. There are several reasons for this: the worm chamber is not kept level, the blade is not well positioned in the fixture, the pressure on both sides of the doctor chamber is uneven, or the doctor is locked. The bolt pressure adjustment of the sheet is caused by unevenness. When this happens, the operator often increases the pressure until the blade and the anilox roll are all in contact with the anilox roll. However, the additional pressure and friction will accelerate the wear of the drawdown blade chamber and the anilox roll.
Press operators also often try to solve the problem of ink leakage by placing the doctor chamber close to the anilox roller, which often exacerbates the problem of ink leakage from both ends of the doctor chamber. In fact, choosing a suitable ink seal pad and replacing it regularly can prevent ink leakage. Avoid relying on increasing blade pressure to solve the problem that the doctor chamber is not level or ink is leaking from the doctor chamber.
To ensure proper operation of the scraper chamber system, the following steps may be followed:
Before installing the ink sealing pad, install the scraper and sealing knife first.
Slowly bring the drawdown blade close to the anilox roll.
Make sure that the drawdown blade and sealing blade contact the anilox roller at the same time, if not, adjust the system until the two blades contact the anilox roller at the same time.
This is repeated on the drive and operator sides of the press.
Set the scraper chamber so that the scraper blade moves back and forth in contact with the anilox roller not more than 1/8''.
