Method for operating a coordinate measuring machine

Patent metadata

Field	Value
Publication number	US-9970744-B2
Application number	US-201615192799-A
Country	US
Kind code	B2
Filing date	Jun 24, 2016
Priority date	Jun 24, 2016
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

A method is disclosed for operating a coordinate measuring machine (CMM) including a CMM control system, a surface scanning probe that measures a workpiece surface by outputting probe workpiece measurements, and a probe measurement timing subsystem. The method comprises: operating the CMM control system to output a measurement synchronization trigger signal at predictable times; operating the probe measurement timing subsystem to determine a pre-trigger lead time that is a fraction of a current duration of a probe workpiece measurement sample period, to initiate a current instance of the probe measurement sample period at the pre-trigger lead time before a next predictable time of the measurement synchronization trigger signal; operating the CMM control system to latch a current set of CMM position coordinate values; and operating the surface scanning probe to output the current instance of the probe workpiece measurement in association with the current set of CMM position coordinate values.

First claim

The invention claimed is:

1. A method for operating a coordinate measuring machine (CMM) including a CMM control system, a surface scanning probe that measures a workpiece surface by outputting probe workpiece measurements, and a probe measurement timing subsystem, the method comprising:
operating the CMM control system to output a measurement synchronization trigger signal at predictable times;
operating the probe measurement timing subsystem to determine the predictable times, and to determine a current duration of a probe workpiece measurement sample period during which the surface scanning probe acquires measurement data associated with a single instance of the output probe workpiece measurements;
operating the probe measurement timing subsystem to determine a pre-trigger lead time that is a fraction of the current duration of the probe workpiece measurement sample period;
operating the probe measurement timing subsystem to initiate a current instance of the probe workpiece measurement sample period at the pre-trigger lead time before a next predictable time of the measurement synchronization trigger signal, and determine an associated current instance of the probe workpiece measurements;
operating the CMM control system to output a current measurement synchronization trigger signal at the next predictable time and to latch a current set of CMM position coordinate values associated with the current measurement synchronization trigger signal; and
operating the surface scanning probe to output the current instance of the probe workpiece measurements at a time associated with the current measurement synchronization trigger signal, such that the CMM control system associates the current instance of the probe workpiece measurements with the current set of CMM position coordinate values.

2. The method of claim 1 , wherein operating the probe measurement timing subsystem to determine the pre-trigger lead time comprises determining a pre-trigger lead time that is approximately one half of the current duration of the probe workpiece measurement sample period.

3. The method of claim 1 , wherein the CMM control system outputs repeated measurement synchronization trigger signals at a trigger frequency, and operating the probe measurement timing subsystem to determine the predictable times comprises inputting the repeated measurement synchronization trigger signals to the probe measurement timing subsystem at the trigger frequency, and determining a timing of the repeated measurement synchronization trigger signals.

4. The method of claim 3 , wherein operating the probe measurement timing subsystem to initiate a current instance of the probe measurement sample period at the pre-trigger lead time before the next predictable time of the measurement synchronization trigger signal comprises initiating the current instance of the probe measurement sample period at a time after a previous measurement synchronization trigger signal that corresponds to the pre-trigger lead time before the next predictable time of the measurement synchronization trigger signal.

5. The method of claim 1 , wherein the probe measurement timing subsystem is located in the surface scanning probe.

6. The method of claim 1 , wherein the probe measurement timing subsystem is located in the CMM control system.

7. The method of claim 6 , wherein the probe measurement timing subsystem is located in an interchangeable card in the CMM control system.

8. The method of claim 7 , wherein the interchangeable card is specifically associated with at least one of the surface scanning probe in particular or a surface scanning probe model in particular.

9. The method of claim 1 , wherein the surface scanning probe is a contact type surface scanning probe that senses a variable amount of deflection of a stylus.

10. The method of claim 1 , wherein:
the probe measurement timing subsystem initiates the current instance of the probe workpiece measurement sample period by outputting a pre-trigger signal to the surface scanning probe at a pre-trigger lead time t lead before the next predictable time of the measurement synchronization trigger signal;
during a single probe workpiece measurement sample period the surface scanning probe acquires n samples at a sample timing interval t cyc ;
the CMM control system receives data from the surface scanning probe with a total system latency t lat ; and
the pre-trigger lead time t presynch is determined by the expression:

t
lead

=

(

(

n
2

)

-
1

)

⁢

t
cyc

+

t
lat

+

(

t
cyc

2

)

.

Assignees

• Mitutoyo Corp

Inventors

• Hemmings Scott Ellis
• Patzwald Andrew

Classifications

• G01B21/04 Primary

  by measuring coordinates of points · CPC title

• G01B5/008 Primary

  using coordinate measuring machines · CPC title

• G01B21/045

  Correction of measurements (G01B9/02055 takes precedence) · CPC title