NEW PRODUCT

Centerless for Form Grinding of Micro Tools

Mobile IT devices and others are becoming more compact and functional. Consequently, minuteness and high precision are required in grinding the holes of printed circuit boards and the molds. Koyo has developed innovative production technology for grinding the micro tools indispensable for production of these devices. Through combining the technologies of newly developed push-through-feed grinding method and electrical discharge truing that extracts superior grinding capability of diamond grinding wheels, the newly developed centerless grinding machine has realized full automatic high-mixed low-volume production not available with conventional centerless grinding machines, and micro diameter grinding of 0.015 mm dia.

Outline

As to conventional grinding methods on micro tools, cylindrical grinding method was mainly adopted where the shaft was fixed by a and was rotated. However, there were problems in grinding accuracy, processing time and tool changes. For preventing breakages, centerless grinding method was most effective and improve coaxiality of shank and tip required in micro tools. But, it was not adopted because of too much time needed for set-up change to grinding various types. The newly developed grinding machine has solved these problems and realized centerless grinding. The performance has significantly exceeded cylindrical grinding machines and, as a result, contributed in spreading high precision micro tools.

Features

· Push-through-feed grinding method Superior coaxiality is secured as the outer diameter of workpiece is used as the grinding datum. Weak points of conventional centerless grinding were overcome. Thus, high-precision micro tools free from breakages can be manufactured without difficulty. · Grinding section without support / Able to grind ultra small diameters · Set-up change without grinding and regulating wheel truing / Efficient set-up change · Set-up change without blade change / Efficient set-up change · CNC biaxial control (work feed and feed) / Variety of shapes can be ground

Grinding wheel Regulating wheel

Pressure roller CNC biaxial control

Push feed

Push-through-feed grinding method

KOYO MACHINE INDUSTRIES CO., LTD.

Koyo Engineering Journal English Edition No.167E (2005) 71 · Electrical discharge truing unit mounted on machine The full-automatic electrical discharge truing unit mounted on the machine provides high precision truing of diamond grinding wheels for superior cutting edge, which was difficult due to hardness of diamond grinding wheels. Also the combined truing method has drastically improved the surface roughness and eliminate breakage of the micro tools.

1.2 1.2 1 1 mRz

l 0.8 0.8 0.6

mRz 0.6

l 0.4 0.4 roughness, 0.2 Necessary surface 0.2 Surface roughness, 0 0 Electrical Combined 0.1 0.08 0.06 0.04 0.02 0 discharge truing truing Processing diameter, mm Effect of combined truing method Surface roughness and processing diameter

OD: 0.02 mm OD: 0.05 mm L/D=100

Raw material Taper Back Multiple- Straight Stepped OD: 1.5~6 mm taper Step Ground samples Variety of shapes can be ground.

Coaxiality 0.11lm Three-dimensional display Coaxiality: 0.11lm (center shaft) ° (mm) Z 128° 38 73.22 218° 368°

62.21

43.47 1lm View angle: 263°

Raw data

Example of carbide grinding

KOYO MACHINE INDUSTRIES CO., LTD.

72 Koyo Engineering Journal English Edition No.167E (2005) Main Specifications

Capacity Shank diameter 1~6 mm OD × Width × ID 150 × 8 × 63.5 mm Grinding Revolution 5 700 min−1 wheel Surface Speed 2 700 m/min Regulating OD × Width × ID 115 × 34 × 63.5 mm wheel Revolution 20~240 min−1 Electric Grinding wheel 1.5kW motor Regulating wheel 0.09kW Power Main Power AC200V 50/60Hz source Controlled voltage 100V (DC24V) Machine weight Approx. 1 600 kg

KOYO MACHINE INDUSTRIES CO., LTD.

Koyo Engineering Journal English Edition No.167E (2005) 73