Monitoring device of a machine tool
A monitoring device of a machine tool, in particular a circular saw bench, includes a safety unit having at least one first sensor. The monitoring device further includes at least one reference sensor, which is provided to convert a characterizing physical measured variable of the workpiece into an electric characteristic variable during machining of a work piece using the machine tool. The characteristic variable is provided to establish a reference value for a signal of the first sensor.
1. A monitoring apparatus for a machine having a tool that operates on a workpiece, comprising:
a first sensor configured to generate a first signal that corresponds to a physical property of a region surrounding the tool;
a first reference sensor configured to generate a first reference signal that corresponds to a physical property of the workpiece;
an evaluation unit operably connected to the first reference sensor and configured to receive the first reference signal from the first reference sensor and determine a value for the physical property of the workpiece; and
a safety unit operably connected to the first reference sensor and the first sensor, the safety unit being configured to generate a signal that at least partially turns off a motor unit that drives the tool in response to the first signal exceeding a first threshold, the first threshold being dependent on the value for the physical property of the workpiece.
2. The monitoring apparatus as claimed in claim 1 , wherein the first reference signal generated by the first reference sensor corresponds to a moisture content of the workpiece.
3. The monitoring apparatus as claimed in claim 1 , further comprising:
a bearing unit configured support the first reference sensor in a region in front of the tool in relation to a prescribed direction of advance in which the workpiece is moved against the tool.
4. The monitoring apparatus as claimed in claim 1 , the first reference sensor comprising:
an ultra wide band (UWB) sensor unit.
5. The monitoring apparatus as claimed in claim 4 , wherein the UWB sensor unit is configured to operate at a center frequency that varies discretely in a prescribed frequency range.
6. The monitoring apparatus as claimed in claim 4 , wherein the UWB sensor unit is configured to operate at a center frequency that varies periodically in a prescribed frequency range.
7. The monitoring apparatus as claimed in claim 4 , further comprising:
a second reference sensor configured to generate a reference signal that corresponds to the physical property of the workpiece, the second reference sensor comprising a UWB sensor unit configured to operate at a center frequency that is at an interval of at least 500 MHz from a center frequency for the first reference sensor.
8. The monitoring apparatus as claimed in claim 1 , wherein the first reference sensor includes an antenna having a plurality of antenna elements arranged in a coplanar orientation with a dielectric support in the first reference sensor.
9. The monitoring apparatus as claimed in claim 1 , further comprising:
a working surface configured to support the workpiece as the workpiece moves toward the tool; and
a bearing unit configured within the working surface to support the first reference sensor beneath the working surface and opposite the workpiece.
10. The monitoring apparatus as claimed in claim 9 , wherein the first reference sensor is spaced apart from the working surface by an air interval by means of the bearing unit.
11. The monitoring apparatus as claimed in claim 1 , wherein:
the first sensor comprises a capacitive sensor; and
the first reference signal generated by the first reference sensor corresponds to a physical property of the workpiece that affects a capacitive measurement of the first sensor.
12. The monitoring apparatus as claimed in claim 1 , wherein the evaluation unit is configured to generate a signal in response to the value of the physical property of the workpiece exceeding a second threshold.
13. The monitoring apparatus as claimed in claim 1 , further comprising:
a display unit configured to display the value for the physical property of the workpiece determined by the evaluation unit.
14. The monitoring apparatus as claimed in claim 1 , wherein the safety unit is configured to:
discontinue operation of the machine in response to the value of the physical property of the workpiece exceeding a second threshold;
request an acknowledgment from an operator of the machine, after discontinuing operation of the machine; and continue operation of the machine upon receipt of the acknowledgement from the operator.