Record Machining Rate for Titanium

The stiffness of a Giddings & Lewis HMC 1600 from Fives Machining Systems, Inc. (Fond Du Lac, WI) combined with the machine’s potent 42.3 kN (9,500 lb) cutting thrust, provided an ideal platform for the high-torque T-Rex spindle to demonstrate the industry’s highest titanium metal removal rate (MRR) for a single spindle at 33.1 cu in/min. The recent test for an aerospace customer on titanium 6Al-4V utilized a Harvi indexable-insert end mill with 76.2 mm (3 in) tool diameter. The tool was driven at 245 rpm with an axial depth of cut at 76.2 mm (3 in) and a radial depth of cut at 25.4 mm (1.0 in), with a feed rate of 1.14 mm/rev (0.044 in/rev).

“This cut produced an excellent surface finish with no sign of chatter and virtually no vibration,” said Pete Beyer, the director of product strategy and development at Fives Giddings & Lewis. “The power of this spindle is so great that it easily handled the full Y-axis thrust of the machine, which can be equipped with higher torque axis motors to produce even higher metal removal rates. This power, coupled with the stiffness and vibration damping of the machine, puts the HMC 1250/1600 in a class by itself for large hard-metal parts.” The T-Rex spindle, available on four-axis HMC 1250/1600 machines, can deliver up to 2,600 Nm (1,918 ft-lb) torque to produce extreme metal removal rates on large workpieces of hard to machine materials, such as titanium, Inconel, and Carpenter 465. Developed for the machining needs of aerospace, energy and heavy equipment manufacturers, the T-Rex spindle is engineered with 130 mm (5.1 in) ID bearings to handle the 42.3 kN (9,500 lb) cutting thrust capability of the HMC 1250/1600 series horizontal machining centers.

The T-Rex spindle is available on four-axis machines and provides 60 kW (80.5 hp) continuous power. The HMC 1250/1600 can also be provided with a five-axis high-torque tilt spindle with continuous torque of 1161 Nm (856 lb ft). Many other spindle options are available for the HMC series as well, including quill spindles and high speed units up to 24,000 rpm. Meeting industry needs for tighter part tolerances and accuracies, the HMC Series comes standard with linear scale feedback in X, Y and Z axes, providing 8 micron (0.0003 in) positioning accuracy and 5 micron (0.0002 in) repeatability per ISO 230-2. Heavy-duty hardened and ground roller guide ways enable a rapid traverse rate of up to 35 m/min (1,378 ipm) with high acc/dec rates, double the load capacity, and nearly ten times the wear life of ball-type ways.

In other equipment applications, Fives offers the new Cranfield Precision TTG machine that introduces a radically new concept. While conventional machine tool platforms use stacked linear axes as the primary motion control system, the Cranfield Precision range coordinates two rotary axes and a short linear axis in a ‘Twin Turret’ design. It uses a unique (and patented) combination of rotary and linear axes to produce relative motion (both position and angle) between tool and workpiece over a swept working area. Compared to conventional machines, this platform offers two main advantages:

• Stiffness: the new machine base is effectively two rotary, highly damped hydrostatic bearings that resist machining forces.
• Thermal stability: the ‘Twin Turret’ design enables a simple non-contacting labyrinth seal, making the machine base almost immune to distortions. These are usually caused by the heat generated from constantly changing coolant return path as the grinding wheel carriage moves along the linear axis.

This design provides a common platform for multiple machine configurations and processes, including O/D grinding, I/D grinding, profile grinding, milling, polishing, hard turning, diamond turning dicing and in-situ metrology. The machine is supplied in two sizes: TTG100 and TTG400 for up to Ø100 mm and Ø400 mm components respectively. The trend towards superabrasives demands a highly stiff and thermally stable machine geometry. The new design of this machine responds to the needs of the most demanding applications looking for extreme accuracy in their grinding processes:

• The optics industry for grinding spherical, aspheric and free-form surfaces on a wide variety of materials.
• Universal CNC grinding of more conventional parts held in a chuck or faceplate using aluminum oxide or superabrasives.
• Multi-function machining center offering grinding, milling, turning, polishing and measurement options on a single machine platform.

The experiences gained by Fives over many years for its Cranfield Precision range of products in the optic industry show that ductile regime grinding of brittle materials can deliver considerable process advantages over conventional grinding processes. This mode of operation is not possible to support unless the machine system is extremely stiff, highly damped and capable of sub-μm position control.

Fives Machining Systems, Inc., 142 Doty Street, Fond du Lac, WI 54935, 920-906-2860, Fax: 920-906-2522, www.fivesgroup.com.