Calibration method and method of obtaining workpiece information

1. A method comprising:

a) causing a tool mounted on a machine tool to work on a workpiece, wherein at least one sensor, which is configured to measure one or more aspects of the tool and/or the machine tool, collects sensor data during the working;

b) a measurement device inspecting a part of the workpiece that was worked on at step a) to obtain measurement data; and

c) calculating sensor-to-workpiece data calibration information from the sensor data and the measurement data.

2. The method as claimed in claim 1 , further comprising using the sensor-to-workpiece data calibration information and the sensor data collected during the working of the workpiece to infer information about the workpiece.

3. The method as claimed in claim 2 , wherein the information inferred about the workpiece from the sensor data comprises measurement data.

4. The method as claimed in claim 2 , further comprising using the inferred information about the workpiece to adjust subsequent working of the, or a subsequent nominally identical, workpiece.

5. The method as claimed in claim 2 , wherein the measurement data and/or the inferred information comprises at least one of: position, dimension, surface roughness, surface waviness of the workpiece.

6. The method as claimed in claim 1 ,

wherein the workpiece of step a) is one of a series of nominally identical workpieces to be worked, and

wherein for at least one further workpiece in the series, information about the at least one further workpiece is inferred from the sensor-to-workpiece data calibration information and sensor data obtained during its working of the at least one further workpiece.

7. The method as claimed in claim 1 , wherein the method comprises:

d) working the same or a nominally identical workpiece, using the same or a nominally identical tool and the same or a nominally identical machine tool as those used in step a), and e) using the sensor-to-workpiece data calibration information to infer information about the workpiece from sensor data, which was collected during step d) by the same or a nominally identical sensor as that used in step a).

8. The method as claimed in claim 1 , wherein the sensor data comprises at least one of: vibration, deflection and/or load.

9. The method as claimed in claim 1 , wherein working on the workpiece comprises at least one of: cutting, drilling, grinding, polishing, turning, reaming and milling.

10. The method as claimed in claim 1 , wherein the tool comprises the at least one sensor.

11. The method as claimed in claim 10 ,

wherein the tool comprises a tool insert and a tool body via which the tool insert is mounted to the machine tool apparatus, and

wherein the tool body comprises the at least one sensor.

12. The method as claimed in 11 , wherein the at least one sensor is located toward an end of the tool holder that is proximal the tool insert.

13. The method as claimed in claim 1 , wherein step b) is performed by a measurement device mounted on the machine tool.

14. The method as claimed in claim 1 , wherein the measurement device comprises a measurement probe for measuring dimensional properties of the workpiece.

15. The method as claimed in claim 1 , wherein step c) comprises adjusting prior determined sensor-to-workpiece data calibration information based on the sensor data and the measurement data.

16. A method of inferring measurement data about a workpiece worked on by a tool mounted on a machine tool, the method comprising, in any suitable order:

a) taking sensor data obtained by at least one sensor, the sensor data relating to one or more properties of the tool and/or the machine tool whilst the workpiece was being worked on by the tool; and

b) using sensor-to-workpiece data calibration information, which is for a particular combination of the tool, the workpiece, and the machine tool, to infer information about the workpiece from the sensor data.