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1. (WO2019048833) NON-CONTACT OPTICAL TOOL LENGTH MEASURING APPARATUS AND METHOD
注意: このテキストは、OCR 処理によってテキスト化されたものです。法的な用途には PDF 版をご利用ください。

Claims

1. A method for tool length measurement using a non-contact tool setting apparatus mounted to a machine tool, the non-contact tool setting apparatus comprising a transmitter for emitting a light beam having a beam width and a receiver for receiving the light beam, the receiver generating a beam intensity signal describing the intensity of received light, the method being for measuring the length of a tool having a nominal tool diameter less than the beam width such that fully inserting the tool into the light beam only partially occludes the light beam, the method comprising the steps of;

(i) moving the tool through the light beam thereby causing a change in the beam intensity signal,

(ii) generating a trigger signal that indicates the beam intensity signal has crossed a trigger threshold, and

(iii) determining the length of the tool using the trigger signal generated in step (ii),

characterised in that the method comprises a step of applying a tool length correction that accounts for the nominal tool diameter being less than the beam width.

2. A method according to claim 1, wherein the step of applying a tool length correction comprises adjusting the trigger threshold that is applied in step (ii), the trigger threshold being adjusted so that the amount of obscuration of the light beam required for a trigger signal to be generated is reduced for smaller diameter tools.

3. A method according to claim 1, wherein step (ii) comprises providing a trigger delay between the trigger threshold being crossed and the issuance of the trigger signal to the machine tool, wherein the step of applying a tool length correction comprises reducing the trigger delay for smaller diameter tools.

4. A method according to claim 2 or claim 3, wherein the step of applying a tool length correction causes the trigger signal of step (ii) to be generated when the tips of tools having different tool diameters are located at substantially the same position within the light beam.

5. A method according to claim 1, wherein step (iii) comprises calculating an uncorrected tool length and the step of applying a tool length correction comprises applying a tool length correction value to the calculated uncorrected tool length.

6. A method according to any preceding claim, wherein the step of applying a tool length correction comprises calculating the tool length correction by referring to a calibration equation or look-up table that describes a relationship between the required tool length correction and the effective tool diameter.

7. A method according to claim 6, wherein the step of applying a tool length correction comprises a step of assessing the effective tool diameter from changes in the beam intensity signal that occur as the tool is moved through the light beam.

8. A method according to claim 7, wherein the step of assessing the effective tool diameter comprises measuring the beam intensity signal when the tool is fully inserted into the light beam thereby partially occluding the light beam.

9. A method according to any one of claims 6 to 8, comprising the step of deriving the calibration equation or look-up table describing the relationship between the required tool length correction and the effective tool diameter.

10. A method according to claim 9, wherein the step of deriving the calibration equation or look-up table comprises measuring the change in the beam intensity signal that occurs as a plurality of tools of different width are moved through the light beam.

11. A method according to claim 10, wherein the step of deriving the calibration equation or look-up table comprises identifying a feature related to the effective tool diameter from the change in the beam intensity signal that occurs when each of the plurality of tools are moved through the light beam

12. A method according to any preceding claim, wherein the step of applying the tool length correction is performed entirely by the non-contact tool setting apparatus.

13. A method according to any preceding claim, comprising the step of applying an adjustment to account for any variation in the intensity of light received at the receiver when no tool is located in the light beam relative to a reference light level.

14. An apparatus for performing non-contact tool measurement on a machine tool, comprising;

a transmitter for emitting a light beam having a beam width, a receiver for receiving the light beam and generating a beam intensity signal describing the intensity of light received at the receiver, and

a trigger unit for analysing the variation in the beam intensity signal that occurs when a tool having a nominal tool diameter is moved through the light beam, the trigger unit generating a trigger signal when the beam intensity signal crosses a trigger threshold, the trigger signal being usable by the machine tool to determine a length of the tool,

characterised in that the apparatus comprises a tool length correction unit that applies a tool length correction when the nominal tool diameter is less than the beam width.

15. An apparatus according to claim 14, wherein the tool length correction unit applies the tool length correction by adjusting the trigger threshold of the trigger unit or delaying issuance of the trigger signal to the machine tool.