“For example, the standard inline-drive spindle on our 40-taper VF series machines runs at 8100 rpm, and our torque doesn’t start to taper off until we’re past 3000 rpm,” he continued. “You’re typically not going to run a half-inch end mill at more than 200 or 300 sfm [61 or 91.4 m/min] in titanium, which is below 2500 rpm; that’s still well within our wide torque band. The great tool coatings available allow us to go as high as 350 sfm [107 m/min], but at an rpm that keeps us in the meat of our torque curves.” He noted that the Haas CM-1, a compact 20-taper machine with a 30,000-rpm spindle and available fi ve-axis rotary table, is widely used to machine tita- nium dental implants and small titanium medical parts. When machining titanium, training is crucial to under- standing cutting forces, chip thickness, and radial engage- ment, according to Makino’s List. “We need to identify the red line—a maximum surface speed at which titanium can be machined. As long as the cutting tool stays under this ‘red line’ it will continue to machine properly.” However, that red line is increasing. “High-fl ow, high-pressure coolant systems have moved the red line to higher speeds. This higher speed, combined with the large axial depths of cut possible on a stiff machine construction, are producing productivity rates never before possible,” said List.
New Tool Geometries Changes in cutting tool design are widely credited with
more productive Ti machining. “We’re all running the same sfm and using chip loads between 1 thou’ and 5 thou’ per tooth,” said Terryberry of Haas. “The only thing we can play with is our radial engagement and the number of tool fl utes. There are now end mills with 13 or more fl utes, which allows increased feed rates. And instead of 10% radial engage- ment, some shops are as high as 30% radial engagement.” He noted that multifl ute tools tend to pull out of conventional toolholders, so more secure options are required. Tools specifi cally designed to cut titanium and other challenging materials are an important part of a machinist’s arsenal. “Our TurboForm [TF] Chip Form, with high positive geometry, is effective in shearing titanium and reducing heat in the cut zone,” said Jim Wyant, applications engineer/ project development, for Greenleaf. “It works well in titanium, Inconel and other heat-resistant alloys.” Greenleaf’s Andersson added that milling and turning
titanium requires different strategies. “For milling, you need lower engagement to get chip thinning. You can tolerate high temperatures but they have to be even.” Turning is focused
February 2017 |
AdvancedManufacturing.org 63
U.S. MANUFACTURER OF CUSTOM AND STANDARD CARBIDE CUTTING TOOLS
On-site manufacturing gives MITGI the ability to deliver high quality standards and specials every time.
MITGI standard tools are available in
three days or less: • Micro End Mills • Micro Drills • Coolant Thru Micro Drills • Coolant Thru Thread Mills • • • • • •
Reamers Drafted Mold Tools • Deburring Knives
Clearance Cutter Mold Tools Tapered Rib Cutter Mold Tools Hard Milling End Mills Step Drills
Phone: (320) 455-0535 Web:
www.mitgi.us
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