Sharp SV-4328, Maintenance Manual

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14
PRECISION MACHINE TOOLS
Ver 2 Maintenance Manual
2-1 Cautions for High Speed Processing
During high-speed processing (S = 8000 rpm or above; F = 300 mm/min or above), the shank and
the style of the cutter has a critical impact on spindle lifespan and processing precision. Matters that
need more attention are:
1). Grasp the cutter before running the spindle to avoid damaging the spindle.
2). During high-speeding chipping (8000rpm or above), use only G2.5 level cutters and shanks that
have been calibrated for dynamic balance. The reason is that vibration generated from centrifugal
force may damage the spindle bearing and rapidly wear out the cutter.
3) Balance tolerance for the shank and the cutter combination is affected by the following three
factors: rotation speed of the cutter, balance tolerance of the spindle, and weight of the shank.
Therefore, using a shorter cutter with a smaller diameter for high-speed chipping is advantageous in
terms of spindle vibration, temperature increase, thermal deformation, and processing precision.
4) The geometric shape of the cutter blade has an effect on cutter abrasion. Increase the angular
backlash of the blade can reduce abrasion due to scratches. Suitable cutter materials can also
minimize abrasion during high-speed processing; for example, cermet, tin or tic coated carbide
cutters have longer lifespan than conventional cutters. Ceramic (Si
3
N
4
) cutters are better than cermet
cutters.
5) Perform another dynamic balance calibration after combining the cutter and the shank together.
The dynamic balance standard should be G2.5 or above.
50 – 6000 rpm Level G6.3 Balance level
6000 – 18000 rpm Level G2.5
Spindle Rotation Speed (rpm)
Cutter Diameter (mm) Cutter Length (mm)
6000 – 8000 125 250
8000 – 10000 100 250
10000 – 12000 80 250
12000 – 15000 65 200
15000 – 18000 50 200