06REF176-063 - Accuracy Verification

CUSTOMER SERVICE DEPARTMENT FAST FAX

To: FaroArm User From: Customer Service DepartmentFORM: 176-063

6 Pages total including this page. Contact us immediately if pages are missing or not legible.

TOPIC: Full Acceptance and Accuracy Certification for Serial Arms

Results of Accuracy Tests

Please initial each test to make sure they have all been performed. All the data must be recorded and a print out attached to the e-mail or fax to avoid delays.

Preliminary Arm Evaluation Initials

1. Diagnostic Test:a. Was the temperature stable? Yes or No ________b. Printout attached ________

2. Probe Calibration:

Probe Calibration #1

Probe Calibration #2

XYZTip Error

a. Printout attached probe calibration #1. ________b. Printout attached probe calibration #2. ________

3. Single Point Certification- Repeatabilitya. Printout attached single point certification. ________

Once all the tests have been performed, please fax or e-mail this page and your test results to the Customer Service Department at (407) 333-8056 or [email protected] Arm Evaluation Tests

Revised: December 6, 2011 LM-06REF176-063.doc© 2011 FARO of 5

mailto:[email protected]

1. Diagnostics Select – Devices\CMM\Temperature from the CAM2 Measure Toolbar (Devices\Temperature

in versions previous to 3.9.) Run for 6 minutes. Was the temperature stable? Record Yes or No on the Results of Accuracy Tests page (first

page).

2. Calibrate the Factory ¼” or 6mm Ball Probe Attached is a zipped video clip. This video shows the proper technique for probe

calibrations (Gold\Silver\Bronze\Sterling series only.)

Install and secure the Factory ¼ “ or 6mm ball probe. Do not use a point probe. Perform two probe calibration tests on the 1” sphere; refer to the video file showing the

proper technique for probe calibrations. See the certification section of the manual for specific procedures on how to calibrate a

probe. NOTE: When calibrating the probe on a 2-2-2 or 2-2-3 configuration arm, please make sure the elbow of the arm is lying horizontal instead of vertical.

Record the data on the Results of Accuracy Tests page (first page). Please send in a picture of the surrounding area of the arm and a picture showing how you

performed the probe calibration.

Accuracy Evaluation The Single Hole Certification test will provide the repeatability evaluation. Please do NOT use the FARO ball bar for accuracy verifications. It has been discontinued, FARO has determined that the data from the test is inconclusive and does not provide sufficient diagnostic information.

3. Single Point Certification - Repeatability test:(This is not a single hole probe calibration nor is it a ball bar test.)

Under the Measure – Certification single point. Use our 1/4" or 6mm calibrated probe, the ball should not be deformed. Find a machined hole less than the ball diameter (e.g. .200”) so the probe sits in it

repeatably. Make sure that the holes platform is clamped down, that it is stable, and that there are no vibrations in the area.

It is recommended that you remove the probe from the hole, move all encoders, and place it back in the hole between data points. At least 100 points are recommended, take 50 with the arm in a "right elbow" configuration, then flip it to a "left elbow" configuration and take the other 50. The arm must be in either of these two configurations. All counter spring compensations have been accounted for in these configurations. Do NOT use the arm with the "elbow" pointing up (vertical) this will add improper balance errors to the results.

The results of this test are used to analyze single point repeatability. All the X values, Y values, Z values, and the bar values are to be analyzed. Each of these values should be within the specified bandwidth for the model of FaroArm used.

Attached is an example of the Ball Bar Printout, please take at least 50 points as described above. Please forward a copy of your data and pictures to [email protected]



If the test results do not meet the required specifications, please try the test again. If after the second try the test results still do not pass please submit the data and the Results of Accuracy Test page (first page).

Please verify your setup by sending in a picture of the holes platform you are using, a picture of how it is clamped down, a picture of the surrounding area of the arm, a picture showing how you perform the probe cal, and a picture of how you perform the repeatability test.

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Accuracy Test Standards and Definitions

FaroArm Specifications

In accordance with industry standards, FARO expresses its accuracy in terms of standard deviations or sigma. Note: Three Sigma = (min.-max.)/2.

Data Analysis

In all cases, a significant number of measurements should be taken in order to ensure that enough data is available for proper statistical analysis. FARO recommends at least 100 measurements per test. The results of the temperature, probe calibration and ball bar tests can significantly affect the accuracy. All of the tests must be done in Caliper 3D or CAM2. All the test results need to be recorded on this document and all printouts and pictures must be attached.

All data should be compared to the specifications of your FaroArm.

2 Sigma Test Methods for Serial Arms:Single Point Sphere Test: The probe of the articulating arm scans hundreds of data points averaging them to resolve the center of the sphere. The sphere is measured from multiple approach directions; data is analyzed as a range of deviations of the resultant sphere single point locations. This test method is typically used for machine-to-machine comparison and is not recommended for determining machine repeatability. Data averaging and collection techniques may not reflect true repeatability of a single point measurement values. (See single point cone testing below).

Single Point Cone Test: The probe of the FaroArm is placed within a conical socket, and individual points are measured from multiple approach directions. Each individual point measurements is analyzed as a range of deviations about the average value for the point location. This test is the most recognized method for determining articulating measurement machine repeatability.

Length Accuracy: Is determined by using certified ball bar artifacts, which are measured at various locations and orientations throughout the working volume of the FaroArm. This test most accurately represents reasonable expectations for machine performance in practical applications.


Repeatability Sphere Accuracy

Repeatability Cone Accuracy

Length Accuracy

Gold Series 4’±0.0005in ±0.127mm ±0.0010in ±0.025mm ±0.0014i

n±0.036mm


n±0.058mm


n±0.071mm


n±0.119mm


n±0.168mm

Single Point Accuracy Linear Displacement Accuracy

Sterling Series 4’±0.0020in ±0.051mm ±0.0028in ±0.072mm




Single Point Accuracy Linear Displacement Accuracy


Silver Series 6 or 8±0.0030 in ±0.076mm ±0.0042 in ±0.108mm

Silver Series 10±0.0050 in ±0.127mm ±0.070 in ±0.178mm

Silver Series 12±0.0070 in ±0.178mm ±0.0099in ±0.251mm

Bronze Series 6 or 8±0.012 in ±0.304mm ±0.017in ±0.431mm

Bronze Series 10±0.016 in ±0.406mm ±0.023in ±0.584mm

If more than 5% of the values of any measurement of 50 or more data points shows more than +/-2 sigma, then repeat the test a couple of more times. Variances in the measurement technique can significantly affect the apparent accuracy of the device.

If the data is still not within the +/-2 sigma the FaroArm must be sent in to FARO for further diagnosis.

FARO recommends using the "non-biased" or "n-1" method for calculating standard deviation as described in the following equation:

nx2 -(x)2

= __________________

n(n-1)

Accuracy Types

Single Point Repeatability - The ability of a device to obtain the same value of a single location during successive measurements.

Acceptable Test Pieces Unacceptable Test PiecesArtifact, Machined Hole (not just an indentation)

Production Parts, Plastics, Sheet Metal, Composites, Rubber, Tubing, Clay Models, Castings, Fixtures, Jigs

If you are still experiencing difficulties, please contact the customer service department by telephone at 1-800-736-2771 or by e-mail at [email protected] sure to visit our website at www.faro.com.

FAX questions to: (407) 333-8056


http://www.faro.com/


06REF176-063 - Accuracy Verification

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