Comparative Analysis of Thermal Deformations in Structural Elements of Measurement Stands and Supports

Abstract

Thermal deformations in structural elements of a stand and measurement support are estimated and values for the thermal deformation coeffi cient are determined. Recommendations are made regarding the use of stands and supports for nanometer-range measurements. Keywords: temperature coeffi cient of linear expansion, nanometer range, linear dimension.Results of investigations are presented in [1], suggesting that a signifi cant contribution is made to overall measurement error by a component attributable to thermal deformations of the measurement stands on which measurement devices are mounted. Since measurement supports are often used in place of measurement stands, a comparative analysis is presented here of thermal deformations in the structural elements of these devices (measurement stage, pillar, sensor attachment points, etc.), based on the results of investigations carried out at the metrology laboratory of the STANKIN Center for Common Use.Per standard [2], the design of stands and supports must ensure secure mounting of the measuring head, movable parts, and assemblies in a specifi ed position, and provide a capability to position it in any position in space, as determined by the height of the pillar and maximum rod extension. Tolerances for the perpendicularity of the axis of the hole for the measuring head and the fl atness of the reference and basic surfaces of stand elements are strictly specifi ed. Tests for exposure to ambient climatic factors should be carried out only when stands and supports are transported. Procedural guidelines [3] propose the selection of measurement devices with inductive transducers (linear displacement transducers) attached to them; however, standards documents provide no recommendations for selecting and using such attachments to carry out precision measurements in the nanometer range.The authors had previously proposed and approved a method for determining thermal deformations in measurement stands from the change in position of the point of contact between the test lead of an inductive transducer and the measured object [1,4]. The procedure called for the adoption of measures in which the temperature coeffi cient of linear expansion was an order of magnitude smaller than that of the measurement system. This article considers investigations performed to compare thermal deformations in two devices: a measurement stand that uses a vertical contact interferometer (IKPV) and a HEIDENHAIN CS 200 gage stand measurement support (DR. JOHANNES HEIDENHAIN GmbH), which differ fundamentally in their structural designs. These devices were selected because they are widely used to carry out precision measurements, calibration testing, and calibration of measurement devices. The IKPV stand is C-shaped and consists of a substantial metal base, a measurement stage, and a fi xed vertical pillar,