Most of the power tools on CNC lathes have only a limited speed of 5000r/min, for large diameter tools this speed limit will not be a problem, however, most of the machining on Swiss machines is small diameter, for small diameter drills and milling tools, high speed is extremely critical to increase the feed rate and to provide productive cutting efficiency accordingly. High-speed electric spindles always significantly reduce the cycle time for drilling, which is usually the slowest process, to 1/5 of the original drilling time.
IBAG, a Swiss manufacturer of precision high-speed electrospindles, has brought micro-precision high-speed milling and drilling electrospindles to the Swiss lathe (automatic CNC centering lathe) market in particular. The new products include a 25mm diameter model with 80,000r/min, a 22mm diameter model with 80,000r/min and 20mm, 19mm and 16mm diameter models with 80,000r/min. The high speed, high power, and high stiffness of the electric spindle allow small diameter end mills to machine stainless steel, brass, and other alloy materials at high speeds. The use of high speed cutting technology also greatly reduces burr generation. All electric spindles are dynamically balanced to ensure smooth and quiet spindle operation at any speed, and virtually zero vibration. Excessive vibration not only reduces bearing life, but also shortens tool life and even causes tool breakage. IBEG electric spindles are compact and powerful with DC brushless motor technology. DC brushless technology allows smaller motors with more drive power and less heat than with standard AC motor technology, and high drive power and high torque are necessary when milling tough materials such as stainless steel, brass and other alloys.
In terms of thermal stability, the motor spindle is air-cooled, eliminating the need for external water and air cooling. The bearings used (both front and rear bearings) are sealed composite ceramic bearings (steel slides and ceramic balls), permanently grease filled. The electric spindle design includes a positive overpressure air seal that injects a small amount of compressed air into the stainless steel shaft of the electric spindle and prevents dust, coolant and other contaminants from entering the spindle. This protects the bearings inside the spindle, extending the spindle’s life and increasing uptime, which is critical for high-speed production requirements.
The maximum allowable taper runout is 2 mm. When the tool runout is in the range of 0.001 in (0.0025 mm), it is not possible to drill with a 0.020 in diameter drill bit because the bit will wander and wear extremely, and in most cases, break immediately upon contact with the workpiece. The tool on the Ibeg electrospindle is fixed with a precision ER-8 cartridge system with a maximum shank diameter of 3/16in (5 mm). The electrospindle can be integrated with the CNC for operational control (on/off and speed) and can monitor any error signals from the CNC. The integration of the CNC can use the idle M-code to activate the corresponding spindle as required.
When milling a modified Torx20 concave drive bracket with 316 SST bone screws (Figure 2), conventional milling takes 3.3 min, using a 4-slot, 0.032in diameter vertical milling cutter at 3000r/min. When using a high-speed motor spindle at an appropriate surface line speed of 300ft/min, the cutter can The machining speed of 36800r/min reduces the cutting time to 45s.