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32 MMS June 2014 mmsonline.com rapid traverse Machining Technology in Brief Eliminating Tool Pullout in Titanium Milling By Pe te r Z e li n s k i t oolholders for machining centers tend to work by compressing a cylinder around the shank of the tool. That is the case with either a collet holder or shrink fit. In either case, the weakness of this mechanism for toolholding is in the tool's axial direction. Along this direction—that is, along the Z axis on a three-axis machine—the only thing restraining the tool is friction with the collet or the bore of the holder. If the Z-directed cutting force reaches a high-enough level, the tool can slide within the holder's grip. Technicut, the U.K.-based cutting tool supplier, routinely achieved that high cutting force in its development of an end mill engineered for aggres- sive cutting in titanium. Cutting forces pulling along the Z axis could cause its new tool to minutely slide within the holder, changing the gage length of the tool mid-cut. Toolholder supplier Nikken was brought in to help solve this problem, and the two companies worked together within the Advanced Manufacturing Research Centre of Shef field, England. Stephen Eckersall, group engineering manager for Nikken, says the result of this work—the X-Treme Multi-Lock Milling Chuck—is the company's first new product to have been researched, developed and tested in Europe prior to final design and production in Japan. An existing holder was the starting point of the deve lopme nt wor k. Nik ke n's Multi-Lock uses a clamping ring with precision rollers to compress the toolholder's bore. The result is a strong, concentric grip with favorable damping characteristics, albeit still subject to the same Mastercam/CNC Software Inc., call 800-228-2877 or visit mastercam.com. dynamic tool paths retract only a slight distance— just enough to prevent scrubbing the part floor with the bot tom of the cut ter, which cause s unwanted heat. In effect, dynamic tool paths know how to do little pirouettes—micro-lifts of 0.005 to 0.010 inch to keep the tool safely away from the floor of the pocket. Developers report significant economic ben- efits from using these tool paths. Two and even three times faster machining rates are achievable, especially for high material removal operations such as roughing. Tool breakage and wear are greatly reduced compared to conventional high- engagement, high-torque hogging. Full-flute, higher-speed, minimal-engagement machining requires less torque and therefore consumes less energy. Smaller, less costly carbide tools can be used because lateral forces that damage them are controlled, and using a smaller tool may enable it to perform roughing, rest roughing and finishing as combined operations. Sometimes when sev- eral operations can be performed using a single, smaller tool, surface finishes are better, possibly reducing or eliminating a secondary operation such as grinding. However, CNC Sof tware recognized that a conventional tool path might be preferred over Dynamic Motion in cer tain situations, so both remain as options. The option of using dynamic tool paths is encouraged because the program- ming interface is simple and involves setting a few parameters from a menu. Frequently, the result is significantly higher productivit y and reduced tool wear, regardless of available spindle speed at the machine tool. Even where the pay- back appears to be marginal, there is no reason not to use dynamic tool paths. The company says they are the most reliable, robust and capable way of machining more types of materials and g e o m etr i e s th a n a ny m a c h i n i n g s tr ate g y i n Mastercam's history. 0614_MMS_rapid.indd 32 5/14/2014 10:00:58 AM