Apparatus and method for assessing the beam profile of a non-contact tool setting apparatus
A method assesses the beam profile of a light beam of a non-contact tool setting apparatus, the apparatus including a transmitter for emitting the light beam and a receiver for receiving the light beam. The receiver generates a beam intensity signal describing the intensity of received light. The apparatus is mounted to a machine tool having a spindle that is moveable relative to the non-contact tool setting apparatus. The method includes loading an object having an edge into the spindle of the machine tool and using the machine tool to move the spindle relative to the apparatus so that the edge of the object passes through the light beam. The beam profile of the light beam is then determined using the beam intensity signal generated at a plurality of positions during the step (ii) of moving the edge of the object through the light beam.
1. A method for assessing a beam profile of a light beam of a non-contact tool setting apparatus, the non-contact tool setting apparatus comprising a transmitter for emitting the light beam and a receiver for receiving the light beam, the receiver generating a beam intensity signal describing the intensity of received light, the non-contact tool setting apparatus being mounted to a machine tool having a spindle that is moveable relative to the non-contact tool setting apparatus, the method comprising the steps of:
(i) loading an object having an edge into the spindle of the machine tool, and
(ii) using the machine tool to move the spindle relative to the non-contact tool setting apparatus so that the edge of the object passes through the light beam;
(iii) determining the beam profile of the light beam using the beam intensity signal generated at a plurality of positions of the light beam relative to the edge during the step (ii) of moving the edge of the object through the light beam; and
(iv) performing a tool measurement operation to measure a position of a part of a tool carried in the spindle of the machine tool,
wherein the beam profile determined in step (iii) comprises a value indicative of the beam width.
2. A method according to claim 1 , wherein step (iii) comprises recording a plurality of beam intensity values that describe the beam intensity signal at a plurality of positions of the spindle relative to the non-contact tool setting apparatus during step (ii).
3. A method according to claim 2 , comprising the step of determining the beam profile by fitting a mathematical function to the plurality of beam intensity values.
4. A method according to claim 3 , wherein the mathematical function is a linear function and the linear function is fitted to beam intensity values within a certain beam intensity range.
5. A method according to claim 4 , wherein the line obtained by fitting the linear function to the beam intensity values is extrapolated or interpolated to determine first and second positions of the object that correspond to different percentages of the beam clear intensity, the spatial separation of the first and second positions providing the beam profile.
6. A method according to claim 3 , wherein the mathematical function is a polynomial function of second or higher order.
7. A method according to claim 1 , wherein step (iii) comprises determining a plurality of positions of the spindle relative to the object when the beam intensity signal crosses a plurality of different intensity thresholds, the beam profile being determined from the plurality of positions.
8. A method according to claim 1 , wherein step (ii) comprises moving the spindle relative to the non-contact tool setting apparatus at a substantially constant speed.
9. A method according to claim 1 , wherein step (ii) comprises moving the spindle relative to the non-contact tool setting apparatus at a known speed.
10. A method according to claim 1 , wherein the light beam has a substantially circular cross-section.
11. A method according to claim 1 , wherein steps (ii) and (iii) are repeated with the object being moved through the beam in different directions to allow the beam profile to be sampled along a plurality of directions.
12. A method according to claim 1 , wherein steps (ii) and (iii) are repeated so as to measure the profile of the light beam at multiple points along the length of the light beam.
13. A method according to claim 1 , wherein the beam profile determined in step (iii) is compared with a previously determined beam profile.
14. A method according to claim 1 , wherein the tool carried in the spindle of the machine tool is the object.
15. A method according to claim 1 , wherein step (iv) includes replacing the object loading into the spindle in step (i) with the tool, and then measuring the position of the part of the tool.
16. A method according to claim 15 , wherein the object loaded into the spindle in step (i) is a calibration pin.