IN THE LOOP: HIGH TECH IS NOT AN OPTION
Markets are slowing down. Customer needs are shifting. To survive, Claude Fourtune of Redex SA says there is only one answer.
Posted: February 9, 2009
On a 30,000 sq m campus in the province of Milan, Italian OEM Giuseppe Giana SpA (Magnago, Italy) manufactures grinders, boring machines, milling machines and milling/planing machines – including Europe?s biggest grinder for flat surfaces – for the energy, oil and aerospace industries in the U.S., Denmark, and the Netherlands, and more recently for emerging markets such as China and India.
On the brink of the current global slowdown, the company decided to strategically position itself on the higher level of machine tool technology. Company manager and technical director Giulio Maria Giana explains that, "Our customers once looked first for power and second for high speeds. But now, with materials being tougher and precision requirements becoming higher, we will continue to focus more on international markets with highly specialized multitasking lathes, large scale lathes, perforators and superfinishing machines."
"As the only way to survive," adds Giana, "this strategy included the launch of the GGTronic high-powered turning and milling center for heavy-duty machining in the precision mechanics sector." The idea behind this machine tool was to stay one step ahead of the competition by eliminating most of the needs for regrinding parts after machining. And it appears to be working: recent orders include CELSA, in Poland, for manufacturing wind propellers and Nordmark Maskinfabrik in Denmark.
Because the GGTronic can machine cylinders and complex components up to 4,000 mm dia and 20,000 mm long in an unmanned environment, "one of our key objectives during the design stage was the machine's ergonomic features," says Giana, "along with ease of clamping, tool visibility throughout various machining stages, and different measurements once the part is finished."
The types of parts being machined with this equipment have very tight tolerances, despite huge weight and dimensions. Several stages of machining can last for hours on each part before being finished. To make the machining process as fast as possible, traverse speeds of 20,000 mm/min can be reached, as well as accelerations to 4 m/s2.
Very high rigidity is obviously crucial when milling and turning big mechanical parts. Positioning must be very precise, so this machine reaches values as low as ±0.01 mm, with a repeated accuracy of ±0.005 mm. The machine structure, built entirely of cast iron, is strong enough to hold anti-vibration boring bars suitable for internal boring to a depth of over 5,000 mm.
The main technical issue in terms of rigidity is the Z-axis, which has the longest stroke of 25,000 mm. For high linear drive performance, a TwinDRIVE Rack and Pinions system from Redex Andantex (Ferrières, France) is used. This turnkey drive system consists of two parallel mounted planetary servo reducers that are coupled electrically. The preload system eliminates backlash and contributes to positioning precision and repeatability as low as ± 0.01 and ± 0.005 mm, together with exceptional global stiffness.
Extreme rigidity comes in all directions from an integrated output pinion shaft supported by reinforced output bearings. This unique concept provides torsional stiffness characteristics and exceptional rigidity along the other axes, in turn enabling the use of up to twice the acceleration rates or weight capacities of other drives.
Strongly reinforced output bearings are combined with pinions integrated into the output shaft (chill cast, case hardened and ground, and the same diameter as the shaft). The pitch diameter is optimized from the rack point of view for the best ratio between the torque being transmitted and rigidity.
The bearing arrangement consists of two tapered roller bearings, preloaded and generously oversized, that support the pinion as close as possible to the applied force. Only the thickness of the locknut separates the pinion from the output bearing.
For longitudinal movement, the X- and Y-axes slide on preloaded roller guide shoes. On a B-axis machine, parts can be machined on five sides in a single setup or by using all five axes to machine any complex profile. With a B-axis the piece can be worked on five sides after being positioned only once, and the five axes may be interpolated to make any kind of complex profile.
"This turnkey drive is not the only advantage we get from this supplier," states Giana. "In the past, each time we answered a specific customer request we had to rebuild the complete mechanical drive system and go through a lot of work to make changes. Adjusting power and speed meant changing the reducer and several components. Now we just indicate the power and speed and Redex prepares the right rack and pinions system for us. Modifying everything, including the speed/load ratio, is very simple."
– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
Claude Fourtune is the marketing communications manager for Redex SA, ZI – BP 79 F-45210, Ferrières, France, 06 72 14 58 78 or 02 38 94 42 62, Fax: +33 2 38 94 42 99, www.redex.fr, cfourtune@redex.fr.
Andantex USA Inc., 1705 Valley Road, Wanamassa, NJ 07712, 800-713-6170, Fax: 732-493-2949, www.andantex.com.
Giuseppe Giana SpA, Via Manciatelli, 22, 20020 Magnano (MI) Italia, ++39 033/657380, Fax: ++39 033/306460, www.giana.it.
Subscribe to learn the latest in manufacturing.
