Rapid motion tapping method

A method for machine tool motion planning of a tapping operation including an air cut step followed by a tapping step, said method comprising:

• providing input data for the tapping operation, including starting states of a tapping tool, a location of a hole to be tapped in a workpiece, a tapping feed speed and a tapping rotational velocity, a spindle predefined acceleration and machine tool mechanical limits;
• computing a transit motion time, an axial servo motion time and a spindle acceleration time for the air cut step from the input data;
• determining which of the transit motion time, the axial servo motion time and the spindle acceleration time for the air cut step is greatest;
• when the transit motion time is greatest, setting an air cut step time to the transit motion time, calculating a transit motion profile to be as rapid as possible based on the mechanical limits, and calculating a spindle start time delay as a difference between the transit motion time and the spindle acceleration time;
• when the spindle acceleration time is greatest, setting the air cut step time to the spindle acceleration time, calculating the transit motion profile to complete at or before an end of the air cut step time, and setting the spindle start time delay to zero;
• calculating an axial motion profile to complete at the end of the air cut step time;
• and
• generating a motion plan for the air cut step and the tapping step, the motion plan for the air cut step using the air cut step time, the transit motion profile, the axial motion profile and the spindle start time delay.

A time-optimal machine tool tapping system, said system comprising:

• a controller including a processor and memory;
• and
• a machine tool in communication with the controller, said machine tool having a spindle holding a tapping tool,
• where the controller computes and sends to the machine tool a motion plan including an time-optimal air cut step immediately followed by a tapping step, where the air cut step ends with a tapping tool axial speed equal to a tapping feed speed and a spindle velocity equal to a tapping rotational velocity,
• including computing a transit motion time, an axial servo motion time and a spindle acceleration time for the air cut step from input data including starting states of the tapping tool, a location of a hole to be tapped, a spindle predefined acceleration and machine tool mechanical limits,
• where an air cut step time is determined from the transit motion time, the axial servo motion time and the spindle acceleration time.