Figure 2 The voltage between the MDF workpiece and tool for the
non-cutting, sliding, and cutting conditions at 330 rpm. The depth of cut
for cutting was 0.005 in. The non-cutting condition is almost coincidental
with the zero axis.
These circulatory currents could exist within or between the
tool and workpiece. An accurate description of the electric
current and potential between the tool and workpiece for
wood machining has not been provided in the literature.
These voltages and currents have been previously measured
with relatively slow volt-ohmmeters and ampmeters. This
study characterizes the possible voltage and amperage waveforms to provide additional insight into the electrical effects
on tool wear and give new directions to research in wood
machining, particularly in tool wear.
A series of turning tests on MDF and voltage measurements were undertaken with M- 2 high-speed steel tools at 550
and 330 rpm, 0.005-inch depth of cut, and 10 and 15 degree
clearance and rake angles, respectively. During normal cutting conditions the HSS tool was grounded through the tool
holder, Electrical activity at the tool-workpiece interface was
indicated by electrical currents flowing between the tool and
ground. To monitor these currents during the cutting tests
described in this paper, the tool was electrically insulated
from the tool holder, and grounded through a 1 ohm resistor, using very short connecting wires (see Figure 1). The
transient voltage measured across this 1 ohm is then a direct
measure of the tool current, in amperes.
Additional information about the electrical processes at
the tool-workpiece interface is obtained by monitoring the
transient tool voltage when the tool is insulated from ground
by a very high ( 1 M ohm) resistance. The transient voltage
and current signals were measured and recorded with a
Tektronix TDS-510 dual-channel digital storage oscilloscope.
The high sampling rate of this oscilloscope allows observation of the very short electrical events which are present
during the cutting process. Voltages were recorded for the
non-cutting (no contact between the tool and MDF-work-piece), sliding and cutting situation between the tool and
Electrical characteristic voltage waveforms from the tool
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