THE 1216 BALL PLATE IS A SIMPLE, INEXPENSIVE AND VERY VERSATILE DEVICE FOR COORDINATE MEASURING MACHINE CALIBRATION AND EVALUATION. THE BALL PLATE CONSISTS OF A RATHER LARGE RIGID 12 INCHES (305 MILLIMETERS) BY 16 INCHES (406 MILLIMETERS) PLATE THAT IS 1.5 INCH (38 MILLIMETERS) THICK.

STANDARD 1216 BALL PLATE WITH GRADE 5, POLISHED, STAINLESS STEEL BALLS

SATIN FINISHED CERAMIC BALLS ON A FLAT BLACK PLATE FOR OPTICAL EVALUATION THE 1216 BALL PLATE WITH ULTRA PRECISE STEEL BALLS

SATIN FINISHED CERAMIC BALLS ON A FLAT BLACK PLATE FOR OPTICAL EVALUATION

THERE ARE A SERIES OF 20 ULTRA PRECISE 19 MILLIMETER (.748 INCH) DIAMETER, HARDENED STAINLESS STEEL OR ALUMINUM OXIDE CERAMIC BALLS PERMANENTLY MOUNTED ON THE TOP FACE OF THE PLATE. TO REDUCE THE WEIGHT FOR EASE OF HANDLING, THE REAR SURFACE OF THE PLATE IS RELIEVED SO THAT THE COMPLETE PLATE WEIGHS ONLY 19 POUNDS (8.6 KG).

THE VERY NATURE OF A SPHERICAL GEOMETRY IS UNIQUE IN THAT IT IS THE ONLY FORM THAT HAS A SINGLE POINT THAT DESCRIBES ITS EXACT POSITION IN THREE-DIMENSIONAL SPACE. THE PERFECTION OF THIS POINT IS ONLY LIMITED BY THE SPHERICITY AND SURFACE QUALITY OF THE BALL. IN ADDITION TO THEIR HAVING EXCEPTIONAL SPHERICITY, THE ENTIRE 20 BALL SET IS CAREFULLY SELECTED TO BE AS EXACTLY THE SAME DIAMETER AS POSSIBLE.

THESE ULTRA PRECISE BALLS ARE SPHERICAL WITHIN LESS THAN 0.000005 INCHES (127 NANOMETERS) AND ALL 20 OF THE BALLS IN THE SET ARE MATCHED FOR SIZE WITHIN 0.000005 INCHES (127 NANOMETERS). THESE MICRO GRAIN STAINLESS STEEL BALLS ARE HARDENED TO 58 HRC MINIMUM AND THERMO CYCLED TO DEVELOP LONG TERM DIMENSIONAL STABILITY.

THE ALUMINUM PLATE CAN BE BLACK ANODIZED AND EQUIPPED WITH SATIN FINISHED CERAMIC BALLS FOR OPTICAL APPLICATIONS. IT IS ALSO AVAILABLE WITH CERAMIC BALLS.

THE REAL VALUE OF THE BALL PLATE OVER OTHER ARTIFACTS IS ITS ABILITY TO MAKE A FAST ACCURATE EVERY DAY OR INTERIM EVALUATION OF THE MEASURING MACHINE'S PERFORMANCE. THE TERM VALUE IS USED HERE, AS A RATIO OF IS PERFORMANCE TO ITS COST. THIS COST IS BOTH ITS INITIAL COST AND THE COST TO USE IT IN EVERYDAY OPERATION. THE LARGE NUMBER OF ALMOST PERFECT SPHERE CENTER TO SPHERE CENTER ADDRESSES TESTS ALL ASPECTS OF THE C.M.M. SYSTEM'S PERFORMANCE, AND IT DOES IT VERY QUICKLY. EACH OF THE 20 BALLS HAS AN ENGRAVED NUMBER ON THE PLATE TO IDENTIFY IT.

HOW CAN YOU AVOID THE VERY EXPENSIVE LABORATORY CALIBRATION THAT IS TYPICALLY EXPECTED TO BE MADE ON ALL CALIBRATION DEVICES? WHAT AN INTERIM OR EVERYDAY EVALUATION IS TRYING TO ACHIEVE, IS TO MAKE SURE THAT ALL ASPECTS OF THE MACHINE ARE PERFORMING PROPERLY IN BETWEEN YEARLY CALIBRATIONS. IMMEDIATELY AFTER THE TECHNICIAN COMPLETES THE ANNUAL MACHINE CALIBRATION, PLACE THE BALL PLATE ON YOUR MACHINE AND MEASURE IT. TO BE EXTRA CAREFUL, ROTATE THE BALL PLATE 90 DEGREES AND MEASURE IT AGAIN. FOR ALL PRACTICAL PURPOSES THE SPHERICAL ARTIFACTS ON THE BALL PLATE ARE THEMSELVES PERFECT. WHAT YOU ARE DOING BY MEASURING THEIR POSITION ON THE BALL PLATE IS CALIBRATING THE BALL PLATE WITHIN YOUR MACHINE'S RESOLUTION. ON THIS FIRST MEASUREMENT, THE MACHINE IS CALIBRATING THE BALL PLATE, AND AT THE SAME TIME THE BALL PLATE IS CHECKING THE MACHINE.

WHEN YOU ARE AUDITED, YOU CAN POINT TO YOUR BALL PLATE AS THE DEVICE USED TO EVALUATE THE EVERYDAY OR INTERIM PERFORMANCE OF THIS MACHINE. EVEN WHEN THE QUESTION OF TRACEABILITY COMES UP, YOU HAVE AN UNBROKEN DOCUMENTATION CHAIN GOING BACK TO THE LABORATORY ARTIFACTS USED BY THE TECHNICIAN FOR THE MACHINE'S YEARLY CALIBRATION.

THE BALL PLATE IS AN EXCELLENT DEVICE FOR DOING A COMPLETE YEARLY C.M.M. CALIBRATION; BUT WHEN USED IN THIS MODE, THE BALL PLATE ITSELF REQUIRES A PERIODIC LABORATORY CALIBRATION THAT IS VERY EXPENSIVE. AT THE VERY MINIMUM, THE EXACT THREE DIMENSIONAL DISTANCE FROM THE NUMBER ONE (#1.) MASTER BALL TO EACH OF THE OTHER BALLS ON THE PLATE MUST BE MAPPED.

DOING THE COMPLETE CALIBRATION OF A C.M.M. BY MEASURING THE BALL PLATE IN THE NUMBER OF DIFFERENT POSITIONS REQUIRED IS QUITE TIME CONSUMING, BUT EXTREMELY ACCURATE. A RATHER ELABORATE ON BOARD SOFTWARE PACKAGE IS REQUIRED TO ANALYZE THIS MEASUREMENT DATA AND TO PINPOINT THE ERROR SOURCES, SO THAT THEY CAN BE MANUALLY CORRECTED OR SOFTWARE COMPENSATED.