Risk is being driven out of the use of heavy-duty diamond cutting tools,
thanks to a E800,000 EU-backed research programme at Greenwich University
in London, to determine the true operating characteristics of this type
of equipment. Previously, the research team had simply estimated the
torque by calculation (using drive motor current and power consumption) -
an inaccurate method because every motor has its own, unique signature of
characteristics that can have a significant effect on the performance of
the tool.
In order to obtain an accurate performance profile of the tool, the
actual torque of the blade or cutting tip needs to be measured as it
rotates, and for this a non-contact sensor is required. After testing
several options, the researchers plumped for Sensor Technology's
Torqsense system, which operates on the principle of surface acoustic
waves.
In order to measure torque, two sensors are bonded to the shaft of the
tool at 45° to the axis of rotation. When the shaft is subjected to
torque, a signal is produced and transmitted to a stationary pickup via a
capacitive coupling comprising two discs, one of which rotates with the
shaft, the other being static. For this project, the sensor had to be
mounted so that it could move linearly to accommodate the cutting
progress of the tool. The researchers experienced a few initial problems,
but were eventually able to construct an accurate mechanism that allowed
the sensor to shadow the progression of the transducer, and so complete
their research.