Development of a High Precision Telescopic Instrument Based on Simultaneous Laser Multilateration for Machine Tool Volumetric Verification

Abstract

<jats:p>This paper presents the design of a high precision telescopic system consisting in three lines, with measuring principle based on simultaneous laser multilateration. The system offers the high precision of the interferometer systems and allows the autonomous tracking of a sphere joined to the spindle nose of the machine tool by simultaneous contact of all the lines. The main advantage of the system is that it allows data capture to be carried out in a single cycle thanks to simultaneous operation with at least three telescopic arms using a novel multipoint kinematic coupling. This results in a significant reduction of the time taken for data capture and improves measurement accuracy due to avoiding the effect of temperature variations between cycles and machine tool repeatability. The work explains the working principle of the system, its main components, and the design parameters considered for the development of the system. The system is simple to operate, compact, agile, and suitable for the verification of small- or medium-sized machine tools with linear and/or rotary axes.</jats:p>

Design of a Multi-Point Kinematic Coupling for a High Precision Telescopic Simultaneous Measurement System

“…The multi-point kinematic coupling was specially developed for a multi-telescopic arm measurement system based on multilateration to be used in the volumetric verification of small and medium-sized machine tools with linear and/or rotary axes [ 25 ]. The telescopic arms have a conventional kinematic support at one end, and a multi-point kinematic coupling at the other end, which connects to a common ferromagnetic sphere attached to the MT spindle nose (see Figure 1 ).…”

“…In addition, the fingers must insert into each other, preventing crashes by interlacing themselves. The geometry selected enables a minimum percentage of non-collision among the three tridents, which was consider as an input in the design process [ 25 ].…”

“…The magnets generate attraction forces that maintain the tridents attached to the sphere and repulsion ones that prevent collisions during the MT verification travels. According to the simulation performed in [ 25 ], a fixed sphere of 1.5 inches in diameter and a trident’s finger diameter of 6.5 mm were selected, which led to a cylindrical neodymium magnet of 6.5 mm in diameter and 3 mm in height with 2.2 kg of force.…”

Thermal Error Compensation Strategy in Simultaneous Laser Multilateration for Volumetric Verification

“…Another measurement system based on interferometry for the verification of small or medium Machine Tools (MT) is identified in [6,7], where a single-arm telescopic system is used to perform the tracking mechanically. In [8] the 3D coordinates of the MT header are obtained measuring three distances simultaneously with a three arms High Precision Telescopic Instrument (HPTI) based in interferometry from three fixed points in the MT worktable to a sphere joined to the MT header. The laser interferometer used provides results with accuracy levels suitable for robot and machine tool verification applications.…”

Machine tool calibration: Measurement, modeling, and compensation of machine tool errors

“…In addition to the uncertainty associated with the laser tracker, the effect of the environment temperature gradients and air turbulence results in uncertainties as high as 60 µm within typical machine workspaces[346]. To reduce environmental effects, Aguilar et al developed a telescopic instrument to carry out multilateration measurements[9]. A commercial instrument similar to this is also available[111].…”