Hard Milling VMC With Increased Stiffness And Rigidity

Makino’s V33i is a hard milling VMC updated with advancements and refinements to provide tighter accuracy, sustained performance, quality surface finishes and hours of continuous, unattended operation, the company says. The updated VMC is designed for high speed hard milling in materials at 50+ HRc. Refinements to the spindle have further increased stiffness and rigidity, which reduces the potential for tool chatter. According to the company, the machine’s design has reduced potential machine movement and associated thermal growth that could cause inaccuracies during the cutting of long die and mold programs. These features retain accuracy during long periods of unattended operation, the company says. The machine’s worktable is 750 mm × 450 mm with associated travels of 650 mm × 450 mm × 350 mm. The machine workzone will accommodate a maximum workpiece size of 750 mm × 595 mm × 250 mm. The VMC is equipped with the company's Super Geometric Intelligence (SGI.4) control software to improve feed rates, accuracy and reduce part cycle times. The machine features a short spindle that is stiff and rigid. By decreasing the length of the spindle, the VMC is able to operate vibration-free over a range of spindle rpms, thereby reducing chatter and improving both surface finish and tool life. In addition, refinements have been made to the lubrication system design to control (or eliminate) spindle thermal growth during long and continuous, high speed hard milling. The VMC comes standard with a 20-hp, 20,000-rpm spindle. For high speed machining, the company offers optional 30,000 and 40,000-rpm spindles. Spindle nose configurations are available in Cat #40, HSK 63A and 63F, HSK-E50 and HSK-E32 to support a variety of tooling and applications. According to the company, integral, hardened and ground, hand-scraped guideways provide geometric tolerances and precise positioning and repeatability. The no-overhang, fully-supported construction ensures peak motion performance with no lost motion or unsupported components during motion, which guarantees tight dynamic tolerances for hard milling of complex, three-dimensional, sculptured surfaces. The company’s updated high speed spindle features a custom spindle core cooling system, which circulates chilled coolant through the spindle and bearing packages, reducing spindle growth. Increased lubricant flow in the machine further minimizes thermal growth, thus providing greater accuracy and an increased bearing life, the company says. Temperature-controlled lubricant is used throughout the machine to minimize thermal growth during cutting. Cooled elements such as core-cooled ballscrews, lubricated ball nuts, a servomotor cooling jacket system and temperature controlled passageways provide structural temperature control. According to the company, controlling the impact of machine movement on thermal characteristics reduces temperature impact on the machining process and provides sustainable accuracy.

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