Machining center integrates cutting and marking
Massimo Costetti
An Italian-designed and built workstation delivers world-class results in manufactured metal products. Mauro Tanini, the owner of Tanini Photoengraving in Rosano, Italy, explains how this system produces printing plates in brass, steel, and aluminum formats. He asserts that the ability to perform both heavy-duty metal removal and laser finishing has optimized performance and lead times in his processes while delivering consistency across heavy work cycles.
Italy is world-famous for its wines: Prosecco, Brunello di Montalcino, Chianti, and Franciacorta. There are many businesses that contribute to the success of this Made in Italy excellence by supporting the export of these wines throughout the world. Among these is the company Fotoincisione Tanini (Rignano sull'Arno, Tuscany, Italy), which for years has specialized in making the cylinders used to produce labels for wines.
The company, which was established in 1975, manufactures punches and dies for printing works, lithographers, and label printers. They started by making offset printing plates made with procedures of photocomposition, and then they moved on to the first computers and photo plotters. In 1992, they introduced the process of chemical engraving of magnesium for hot stamping and embossing (Figure 1). The development of this industry brought the company to computer-to-plate (CTP) systems able to photograph the drawing directly on metal plates. In 1998, the search for new possibilities to produce dies for embossing with three-dimensional characteristics of higher quality than chemical engraving led Tanini to develop a manufacturing process that included Cielle CNC machines, among which is the Gamma Dualtech machining center introduced in 2006. "The primary need," says Tanini, "was to have a solid, rugged, and precise machine that could be used in the production of plates for hot stamping and embossing. And with Cielle Gamma Dualtech, we have found exactly what we needed."
Optimizing production
The Cielle Gamma Dualtech 60/50 is a four-axis machining center with a mobile working table for producing plates and punches (Figure 2). The machine's cast-iron structure allows for the machining of materials using two technologies: a ytterbium laser head with average power of 20W to finish the most difficult details, and a liquid-cooled, 36,000 rpm, 8kW HSK-E40 electrospindle ideal for heavy material removals. This double solution allows cutting and marking engraving objects with extreme precision and time-effectiveness.
The machine is equipped with three axes of motion, with the addition of a fourth rotary axis for cylindrical machining. All of them have motors controlled by CNC-DSP control, re-circulating ball screws, blocks and motion rails, and an automated magnetic system for hooking and keeping the laser head. It has a protection cabin with camera to safely monitor the laser head machining and a cooling unit and filters for the exhaust of metallic vapors.
Choosing the Gamma Dualtech stemmed from the need to have a high-performance machine for engraving brass cylinders that are used for hot stamping on self-adhesive material used for wine and liqueur labeling. Tanini says, "In most cases, the removal of material by laser takes longer than mechanical machining, but in the case of micro-engraving, the mechanical process may be repeated several times due to tool wear. The laser guarantees the finished result after the first pass."
The machining process
An example is the process of engraving a brass die with very small details, such as the inner part of the letter A. After importing the vectorial file provided by the customer, Cielle's Incicam software installed on the Gamma Dualtech, identifies and fixes any possible problems, such as intersections in the layout. Then, a first machining process is employed, for instance, with a cylindrical tool with a 3mm cutting width, which will machine the parts of the raw plate. A second pass might be made with a conical tool with a 0.4mm cutting width, which will work on the remainders left by the previous tool around the sketch. To further refine the removal, the machine performs the same operation with a 0.1mm cutting width tool, which will work on the remainder of the removal made by the 0.4mm tool. At this time, the laser head is used; if the sketch has fine details and close lines, the laser will work on the residuals of the 0.1mm tool until achieving a detail of 0.04mm. Once the procedure has been established, it takes 10–15 min to set up the job, which is then converted into the tools' path. When the machine is started, it selects the required tools and executes the different phases of the job, including the laser processing, until its completion.
"When we used to make detailed processing by using only mechanical tools, we often had to check the engraved part and we ascertained that it needed to be reworked by replacing the finest tool, which wears out very easily," asserts Tanini. "Reworking the same piece involved extra time and risks for the quality of the result. By adding the laser processing, we don't need to rework the edges of the engraved paths anymore; therefore, we don't have to worry anymore about the final result. Furthermore, if the machining is complex, it is always recommendable to use the laser in order to have a uniform outcome, which would be harder to get if we were to change a 0.1mm tool because it's broken or worn."
Precision and resistance in one machine
Use of Cielle double technology allowed Tanini to optimize working times and productivity. "In the beginning, we were almost exclusively engraving chemically on magnesium because of the high speed of this process—in less than an hour, you can get plates of any dimension," he says.
However, this process is not able to support long production cycles and, most of all, it is not suitable for both hot stamping and embossing. "With Gamma Dualtech," Tanini explains, "you can go from 1.5 hr cycles for engraving a small cylinder to up to 32 hours of continuous working on a large-size cylinder engraved on its whole surface. And I can say that other types of engraving—such as micro-engraving on copper—would be unthinkable without the double technology. We work only with unique pieces and therefore we cannot allow ourselves any error margins. With brass, which presents problems in the heaviest production, the double technology offered by Cielle allows each piece to be subjected to double machining by using the same machine without risks. This optimizes the machining times and assures more efficiency in the processing of orders. Having the certainty of a satisfactory final result is what led us to choose Cielle's machine."
MASSIMO COSTETTI([email protected])is business development manager at M31 LLC. San Jose CA.