Telescoping ballbar systems

Today, one instrument is almost universally accepted as the most practical, convenient and comprehensive test for assessing the contouring accuracy of CNC machine tools; the telescoping ballbar.  

This telescoping ballbar, not to be confused with the fixed length ballbars used for CMM (coordinate measuring machine) calibration, provides a simple, rapid check of a CNC machine tool's positioning performance to recognised international standards (e.g. ISO, ASME etc) allowing users to benchmark and track the performance of their machines and to quickly diagnose problems that require maintenance.  

Regular ballbar testing of machine tools helps to 

• ensure accurate parts, first time, from CNC machines
• reduce machine down-time, scrap and inspection costs
• demonstrate compliance with machine performance and quality management standards
• implement fact based predictive maintenance

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QC20-W system		System software		QC20-W accessories		Why use a ballbar?		QC20-W testing
Everything you need in a handy case. Just add a PC and go!		Powerful analysis  pinpoints errors automatically		Extend your QC20-W system capabilities		What can a QC20-W ballbar do for you?		Simple and quick to set up and run

What is a Renishaw ballbar?

The Renishaw QC20-W ballbar system consists of the ballbar itself (essentially a very high accuracy, telescoping linear sensor with precision balls at each end) and precision magnetic mounts, one (adjustable) attached to the machine table and the other to the machine spindle or spindle housing. In use the balls of the sensor are kinematically located in the magnetic cups. This arrangement enables the ballbar to measure minute variations in radius as the machine follows a programmed circular path around the mount on the machine table.

The data collected is sent to a PC, where Renishaw's software calculates overall measures of positioning accuracy (circularity, circular deviation) in accordance with international standards such as ISO 230-4 and ASME B5.54 or in Renishaw’s own analysis reports. This report uses a unique mathematical analysis to diagnose many additional individual machine errors from the set of linear readings. Data is displayed graphically as well as in numeric format to aid and support diagnosis.

Ballbar history

The ballbar came to prominence following the work of James B. Bryan at Lawrence Livermore National Laboratory in the USA, who received a US patent for a 'Telescoping Magnetic Ball Bar Test Gage' in 1984. Renishaw plc launched their first ballbar, the QC10 Mk1 in 1991, to be followed the next year by the QC10 Mk2; using a serial interface rather than the internal PC board of the Mk1. 

The QC10 continued in manufacture until October 2009 when it was superseded by the QC20-W system. The new QC20-W system is based around a completely new Renishaw designed sensor, Bluetooth® wireless technology and substantially updated testing and analysis capability. Renishaw ballbars have been adopted by many thousands of ballbar machine tool users worldwide and are considered vital equipment by most leading machine tool OEMs, their distributors and independent calibration service providers.