Tool tip conductivity contact sensor and method

A method for detecting a contact of a tool to a workpiece, comprising the steps of:

• electrically coupling a first lead to one of the workpiece and a holder and a table, the holder removable supporting the workpiece, the table supporting the holder;
• electrically coupling a second lead to a machine at a point electrically insulated from the first lead, the machine operating the tool;
• generating an input signal whenever a circuit between the first lead and the second lead is closed;
• comparing a DC offset to the input signal;
• generating a trigger signal from the trigger circuit whenever the input signal is greater than the DC offset;
• and
• generating an indicator signal in response to the trigger signal, the indicator signal indicating the contact of the tool to the workpiece.

A method for detecting a contact of a tool to a workpiece, comprising the steps of:

• electrically coupling a first lead to one of the workpiece and a holder and a table, the holder removably supporting the workpiece, the table supporting the holder;
• electrically coupling a second lead to a machine at a point electrically insulated from the first lead, the machine operating the tool;
• generating an input signal whenever a circuit between the first lead and the second lead is closed wherein the input signal is a pulsed trigger signal;
• and
• generating an indicator signal responsive to the input signal indicating the contact of the tool to the workpiece, the generating step including the steps of:
• supplying the pulsed trigger signal to a comparator;
• connecting a resistor to an input of the comparator;
• and
• connecting a capacitor in parallel with the resistor, the capacitor receiving a charge from the pulsed trigger signal and dissipating the charge across the resistor when the pulsed trigger signal ends, and wherein the output of the comparator is the indicator signal.

A method for detecting a contact of a tool to a workpiece, comprising the steps of:

• electrically coupling a fast lead to one of the workpiece and a holder and a table, the holder removable supporting the workpiece, the table supporting the holder;
• electrically coupling a second lead to a machine at a point electrically insulated from the first lead, the machine operating the tool;
• generating a signal indicating the contact of the tool to the workpiece whenever a circuit between the first lead and the second lead is closed;
• supplying the signal to a first oscillator adapted to received the signal;
• supplying an activation signal from the first oscillator to a piezoelectric acoustic transducer;
• supplying the signal to a second oscillator, the second oscillator supplying an output to the first oscillator;
• and
• periodically preventing resonance of the piezoelectric acoustic transducer using the output of the second oscillator.

An apparatus for detecting a contact of a tool to a workpiece, comprising:

• means for electrically coupling a first lead to one of the workpiece and a holder and a table;
• the holder removably supporting the workpiece, the table supporting the holder;
• means for electrically coupling a second lead to a machine at a point electrically insulated from first lead, the machine operating the tool;
• means for generating an input signal whenever a circuit between the first lead and the second lead is closed;
• and
• means for generating an indicator signal responsive to the input signal indicating the contact of the tool to the workpiece, the means operable to produce a constant indicator signal when the input signal is a pulsed trigger signal resulting from periodic contact of an edge of the tool with the workpiece.

An apparatus for detecting a contact of a tool to a workpiece, comprising:

• means for electrically coupling a first lead to one of the workpiece and a holder and a table, the holder supporting the workpiece, the table supporting the workpiece and the holder;
• means for electrically coupling a second lead to a machine at a point electrically insulated from the first lead, the machine operating the tool;
• means for generating an input signal whenever a circuit between the first lead and the second lead is closed, the generating means including a trigger circuit comparing a DC offset to the input signal and generating a trigger signal whenever the input signal is greater than the DC offset;
• and
• means for generating an indicator signal responsive to the input signal indicating the contact of tool to the workpiece.