A novel 3D standard for coordinate measuring machines

Ball plates and ball bars are well-established standards for interim checks and corrections of coordinate measuring machines (CMM). To adjust a CMM to a specific task, these standards need to be placed and measured in different locations and orientations within the measurement volume of the CMM. The ZIM project ModulaNo aims at the development of a novel standard, which allows the monitoring of a specific sub-volume of the CMM’s measuring volume used for the measurement task, while reducing the required effort and, if possible the task-specific measurement uncertainty. PTB’s project partner, QS-Grimm GmbH, developed a standard made of industrial-grade ceramics with the dimensions of 0.8 m x 0.8 m x 0.3 m. It embodies a variety of 2D and 3D ball distances. The coefficient of thermal expansion of the ceramics material produced by Kyocera is approximately 2 ∙ 10^-6 K^-1. In future applications, the time and effort to check and adjust a CMM should be reduced by using only sub-sets of the standard’s calibrated distances, depending on the application. With an automatic system to insert the standard into the CMM, it is possible to carry out checks and corrections between two consecutive applications or overnight. It is planned to reduce the measurement uncertainty with these frequent checks of the CMM.

First tests using the standard indicate that the suspension needs further modifications, since the relatively high mass and large dimensions cause unexpectedly large deformations. Consequently, further tests and FEM-simulations are used to optimize the suspension.


Figure 1: Photo of the novel standard. Shown are structures of different heights with alumina balls.