Precision Engineering 35 (2011) 116–125 Contents lists available at ScienceDirect Precision Engineering journal homepage: www.elsevier.com/locate/precision Volumetric distortion assessment of a five-axis machine by probing a 3D reconfigurable uncalibrated master ball artefact Tibet Erkan a , J.R. René Mayer a,∗ , Yannick Dupont b a Department of Mechanical Engineering, École Polytechnique (Montréal), P.O. Box 6079, Station Downtown, H3C 3A7 Montréal, QC, Canada b Pratt and Whitney Canada Corp., Longueuil, QC, Canada article info Article history: Received 11 November 2009 Received in revised form 7 July 2010 Accepted 18 August 2010 Available online 24 August 2010 Keywords: Five-axis machine tool Volumetric errors On-machine probing Ball artefact Reconfigurable artefact Uncalibrated artefact abstract In this paper, a method is proposed that uses an artefact assembled in situ and exploiting the on-machine probing capability to perform a rapid volumetric distortion assessment of a five-axis machine. The 3D reconfigurable uncalibrated master ball artefact (RUMBA) is an assembly of the machine pallet and an adjustable number of master balls located within the machine working and probing envelop. The artefact design philosophy allows flexibility in the number and positions of the balls thus conferring the recon- figurability attribute. Reconfigurability allows adaptation of the artefact to the machine topology and geometry and its construction around a fixture and workpiece to reduce disruption to machine produc- tion. On the down side, the artefact is uncalibrated as its construction concept hinders precise knowledge of its geometry. During a test, combinations of all the machine axes are used to move and probe the mas- ter balls. A mathematical model is developed in order to identify the setup errors of each master ball and the probe. Simultaneous identification of the rotary axes’ linear offset with the setup errors is proposed to improve the parameter estimation and volumetric distortion prediction. The machine contribution to the volumetric distortion is then computed from the ball centre data excluding the setup errors. Tests are conducted in a laboratory on a horizontal machining centre. The results show that the proposed mathe- matical procedure is capable of removing the influence of the uncalibrated artefact geometry, excluding scale, and that the proposed design is suited to the machine environment. © 2010 Elsevier Inc. All rights reserved. 1. Introduction Five-axis machine tools are key players in the manufacture of complex parts such as those found in the aerospace field. Their ability to orient the rotating cutting tool relative to the workpiece offers a significant reduction in the number of setups required thus allowing high productivity for the machining of complex mono- lithic parts. This is even more so when combined with high speed machining methods which through careful selection of process parameters boost the material removal rate while maintaining good surface finish and spindle integrity. In parallel with this trend, manufacturers are now realising that the inspection processes are becoming relatively costly and time-consuming and are looking at ways of reducing their dependence on the part metrology functions while ensuring part geometric and dimensional conformity. One approach to achieve this objective is to control and measure impor- tant characteristics of the manufacturing process, those that have an impact on the part’s form and size errors. Numerous standards and instruments are available to conduct thorough metrological ∗ Corresponding author. Tel.: +1 514 3404711x4407; fax: +1 514 3405867. E-mail address: rene.mayer@polymtl.ca (J.R.R. Mayer). evaluations of machine tools and provide a wealth of information useful for machine performance evaluation for example at the time of purchase and commissioning. This is often limited to the mea- surement of individual axes although some combined axis motion may also be conducted by bringing special instruments within the machine. However, those approaches are generally beyond the reach of most machine shops and demand human intervention thus requiring specialised personnel and reducing the machine produc- tion time. In order to be effective, checks should be frequent and automated. These objectives lead to the development of volumetric methods which are based on artefact use. Mechanical artefacts such as ball arrays or ball plates are used for conducting routine checks of multi-axis machines. There is also much research on artefact probing on CMMs [1–5], and on NC machine tools since most machines now have on-machine prob- ing capability, usually used for part setup compensation. A modular space frame, tetrahedron shaped artefact with a ball plate and mag- netic links that connect the balls, was developed by De Aquino Silva and Burdekin [4] for volumetric accuracy analysis of CMMs. The cal- ibration of the artefact was performed by calibrating the ball plate and magnetic ball links separately. A mathematical model using response surface methodology (RSM) was implemented to deter- mine the machine error components from the volumetric error 0141-6359/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.precisioneng.2010.08.003