Method for improving torque accuracy of a discrete energy tool

A method of controlling an air driven tool to provide a desired torque to a fastener, the method comprising:

• establishing an air pressure profile for a plurality of torque values;
• determining a calibration factor for the tool including
• measuring a temperature of the tool;
• establishing an expected torque value (TEXP) based on the tool temperature;
• measuring a measured torque value (TMEA) for the tool by applying the tool to a calibration joint at a nominal air pressure (PNOM);
• and
• calculating a tool age calibration factor (CA) by dividing the expected torque value (TEXP) by the measured torque value (TMEA);
• multiplying the desired torque by the calibration factor to determine a calibrated torque value;
• and
• supplying the tool with air at the air pressure profile corresponding to the calibrated torque value.

A method of controlling an air driven tool to provide a desired torque to a fastener, the method comprising:

• establishing an air pressure profile for a plurality of torque values;
• determining a calibration factor for the tool including
• measuring a temperature of the tool;
• establishing an expected torque value (TEXP) based on the tool temperature;
• accessing a nominal torque value (TNOM) for the tool which was established by applying a lab standard tool to a calibration joint at a nominal air pressure (PNOM);
• measuring a measured torque value (TMEA) for the tool by applying the tool to the calibration joint at the nominal air pressure (PNOM);
• calculating a temperature calibration factor (CT) by dividing the nominal torque value (TNOM) by the expected torque value (TEXP);
• calculating a tool age calibration factor (CA) by dividing the expected torque value (TEXP) by the measured torque value (TMEA);
• and
• calculating a total calibration factor by multiplying the temperature calibration factor (CT) by the tool age calibration factor (CA);
• multiplying the desired torque by the calibration factor to determine a calibrated torque value;
• and
• supplying the tool with air at the air pressure profile corresponding to the calibrated torque value.

A method of controlling an air driven tool to provide a desired torque to a fastener, the method comprising:

• establishing an air pressure profile for a plurality of torque values;
• determining a calibration factor for the tool including
• measuring a temperature of the tool;
• and
• establishing an expected torque value (TEXP) based on the tool temperature, said torque value (TEXP) being calculated using the formula:
• TEXPA0+A1* temperature+A3* temperature3
• wherein temperature is equal to a current or averaged temperature value and the A's are coefficients established using laboratory data relating to measured values under standard conditions;
• multiplying the desired torque by the calibration factor to determine a calibrated torque value;
• and
• supplying the tool with air at the air pressure profile corresponding to the calibrated torque value.

A method of controlling an air driven tool to provide a desired torque to a fastener, the method comprising:

• establishing a maximum air pressure value;
• supplying the tool with air at a starting air pressure value greater than an intermediate air pressure value and less than or equal to the maximum air pressure value for a limited time prior to supplying of air beginning at the intermediate air pressure value;
• measuring a torque value at the limited time;
• comparing the measured torque value at the limited time with a limit torque having a predetermined value;
• designating a pre-tightened condition if the measured torque value at the limited time is greater than or equal to the limit torque value;
• and
• if the measured torque value at the limited time is less than the limit torque value, supplying the tool with a continuous supply of air beginning at the intermediate air pressure value that is less than the maximum air pressure value and continuously increasing the air pressure at a desired rate until the torque applied to the fastener is within a predetermined range of the desired torque.