DBB Guidebook - History

Quality systems and ISO 9000 standard preconceive that production machinery is inspected regularly. The knowledge of machine tools' capability to meet the designed tolerances is important especially when the machines are the key factors of the production system. Nowadays, as automation and labour saving are introduced in machining, it is desirable to reduce the time and manpower for assembly and inspection. Conventional measurement equipment as laser interferometer, square gauge, straight edge etc. require skilful technicians and are time consuming, therefore the development of the other methods was necessarily.

Double Ball Bar (DBB) method is one of so called rapid tests for measure the motion error of a milling machine, a machining centre or another machine tools which are driven by NC and have circular interpolation motion. The measuring equipment records the points on a circular curve, enlarges the extension or contraction of the bar and then shows them in polar co-ordinates, it is called the motion error trace. Then the trace is analysed and the volumetric accuracy is evaluated. Very valuable work concerning the phenomena in DBB measurements was studied in the laboratory of Kakino at late 80's. The most of later studies and work are based on this research.

Unfortunately, the analysis of the motion error trace has been much more difficult as first was thought and this has been a limitation of the common usage of the method. Within the Eureka Maine FMS Maint project machine tools were tested on regular basis with the aid of a DBB device and all analysing procedures was made by PolarCheck Analysis program. The program was made at Institute of Production Engineering at Tampere University of Technology .

References:

(# published in Finnish)

Bryan J. B. A simple method for testing measuring machines and machine tools. Part 1: Principles and applications. In: Precision engineering, 1982. Vol 4, no. 2, p. 61-69.

Bryan J. B. A simple method for testing measuring machines and machine tools. Part 2: Construction details. In: Precision engineering, 1982. Vol 4, no. 3, p. 125-138.

# Hölsä, J. Analysis and Simulation of Double Ball Bar Method. Tampere: Tampere University of Technology, 1995. M.Sc. Thesis. 101 s.

ISO/DIS 230-4. Test code for machine tools - part 4: Circular tests for numerically controlled machine tools. Geneve, Switzerland: International Organisation for Standardisation, 1996. 12 p.

Kakino, Y., Ihara, Y., Shinohara, A. Accuracy Inspection of NC Machine Tools by Double Ball Bar Method. München, Germany: Carl Hanser Verlag, 1993. 190 p. ISBN 3-446-17430-3.

# Oksanen, P. A Machine Tool Inspection and Maintenance Control by Double Ball Bar Method. Tampere: Tampere University of Technology, 1995. Lic.Techn. Thesis. 101 s.