When someone mentions the country of Switzerland, what is the first thing that comes to mind?
Swiss watches? Chocolate? Banks? Perhaps, the Swiss Alps? All responses are acceptable from the average person, but not a printer. This small country has made huge contributions to printing over the last 60 years, more than most people realize.
The invention of the lamella tip doctor blade changed the world of printing forever. To this day, it is still the largest selling style of doctor blade worldwide.
The basic task of the doctor blade is to wipe off excess inks, varnishes or coating media from the surfaces of gravure cylinders or anilox rollers, so that only the ink required for printing, the varnish to be transferred or the coating medium to be applied, remains in the cells of the impression cylinder or anilox roller. After removing the excess, the surface of the cell walls should be free and the cells optimally filled. This function is also the origin of the name “doctor blade”, which goes back to the French verb “racler”–to wipe off, to brush off.
The Start
To understand the invention of the Lamella tip, we need to look at the history of rotogravure printing and where the need first emerged. In the 1920s, rotogravure was being used for more than black and white newspapers. At that time, everyone read the newspaper, so all the stores and companies wanted to advertise in the local paper.
The market continued its growth to include magazines, where more colors were being introduced. As early as 1922, the Ringier print shop in Zofingen, Switzerland, began printing “Ringiers Unterhaltungs-Blätter” (Ringiers Entertainment Magazine), also known as, The Yellow Magazine because of its outside yellow cover, the publication quickly became Ringier’s flagship product due to its hot topics, illustrated short stories and novels.
As the magazine grew, Ringier became the largest gravure printer in Switzerland by the 1960s. With this growth came challenges in print quality. The lettering “Ringiers Unterhaltungs-Blätter,” to be printed on the yellow title page, was a specified brown color. This color was extremely difficult to print and the undesirable, but then unavoidable streaking and toning occurred.
In addition, the permanent wear of the beveled or “wedge” doctor blade (Figure 1), used at the time, rapidly increased the contact area between the doctor blade and the cylinder surface and severely impaired the quality of the doctoring. The inability to print the magazine title was a real challenge and satisfactory quality was not easy to achieve. Ringier, the largest gravure printing company in Switzerland at the time, urgently needed a solution, therefore began to work closely with Daetwyler.
All photos courtesy of Daetwyler
Why & How
In the 1960s, the method of making a doctor blade was to take a piece of straight steel (Figure 2) and use a polishing stone to create a very rudimentary bevel, at this time probably somewhere between a 50–70 degree bevel.
This process was done by hand with very inconsistent results across the industry. As time progressed, larger stones were added and a machining process incorporated. Both eliminated the hand honing, but not the wiping issues. This method created a contact area of the tip that was reasonably sharp and good for a short period of time, but would wear very quick, grow the contact area, and therefore, the printed ink tone was constantly changing and led to tonal value fluctuations, due to the inconsistency of the tip.
This weak point of the printing process was pointed out by former Ringier employee Hans Burgener, with the idea of a lamella doctor blade, thus opening a new chapter in the history of this tool. Together with Hans Burgener, Daetwyler recognized the fundamental problem of conventional doctor blades and participated in transforming his idea of a lamella blade into a technically practicable solution. In this context, the term lamella means the beveled scraper edge, i.e. the actual functional area-the machined tip.
The newly developed idea for this doctor blade was first done with an etching solution and achieved the first improvements in gravure printing. Testing proved to be very successful as the contact zone surface remained virtually unchanged throughout the entire printrun. (Figure 3). Nevertheless, the team was not yet fully satisfied with this new development.
Max Daetwyler immediately recognized the hidden potential of this invention and within a very short time a wide variety of test stations were set up. Hans Burgener opened a new chapter in the history of the “scraper” with the idea of a lamella doctor blade and it was up to Daetwyler to perfect the process.
It became increasingly obvious that the etching technique would not be a viable option in manufacturing the lamella doctor blade. Max Daetwyler and his team developed a precision blade grinding process with self-developed automatic grinding machines and achieved more consistent doctor blades that achieved better printing results.
In 1972, Daetwyler achieved the great breakthrough with the lamella doctor blade. (Figure 4). The know-how gained through in-house development could now be used to manufacture innovative and practical doctor blade products. Parallel to the development of this very special grinding technology, the doctor blade steel was also subjected to various strict tests and its composition was constantly improved. Early on, it became evident that, to machine a better doctor blade, the steel had to be the best. That finding holds to this day. In fact, a metallurgical team in Switzerland continues research into potential improvement.
The lamella tip doctor blade made its first appearance in the United States in 1975 when Peter Daetwyler, son of Max, opened up Daetwyler USA in Hauppauge, NY. In principle, the lamella doctor blade is a thin, resilient strip of alloyed steel, but with this ingenious invention, Ringier and Daetwyler revolutionized gravure printing 52 years ago. Without the development of this high-end tool, high-quality flexo printing would not be where it is today.
Today’s Market
Since 1972, the lamella tip has been modified and redone in a multitude of ways, but the focus remains the same—helping printers overcome print issues and ensuring the highest quality printed product possible. Today, just as one example, the Daetwyler line of lamella tip variations includes more than 20 distinct options.
During the late 1990s, anilox rolls were not kind to the thin machined 75-micron lamella tip blades. The blade wore faster because of the rough aggressive engravings on the ceramic rolls. Introduction of the round edge, or radius tip doctor blade, was needed at this time. This style blade usage grew fast and was well received, but as with all things at that time in the flexo industry, technology was changing fast.
Higher line screen anilox rolls being produced with a high-quality ceramic, resulted in smoother surfaces with smaller less aggressive cell walls. High plate screens with alternative dot technologies required less ink. The large contact area of the radius tip blade had run its course and now the earlier issues we discussed about gravure printing are front and center in flexo.
The bevel blade contact area grew too large too fast and let more ink pass the blade than needed. This resulted in streaks, tonal shifts, color changes and dot gain. Same result with the radius tip in flexo. The doctor blade controls ink film thickness that is transferred to the plate. That is its only job!
The only blade tip that can do that is a lamella tip in the newly modified configurations specifically made for flexo printing. The more popular sizes are the 125-micron tip thick blades, Multiflex (Figure 5), specifically designed for UV ink spitting issues. Similarly, the Multiblade (Figure 6) a hybrid lamella tip/ bevel designed for high-speed wide web presses. All evolved from the original lamella tip design and continue to help fuel the growth of flexo.
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