Geometrical instruments – Gauge – With calibration device or gauge for nuclear reactor element
Patent
1992-03-31
1993-12-14
Will, Thomas B.
Geometrical instruments
Gauge
With calibration device or gauge for nuclear reactor element
73 1J, G01B 300
Patent
active
052690679
DESCRIPTION:
BRIEF SUMMARY
In industrial quality assurance, increasing use is being made of coordinate measuring instruments close to the point of production and even integrated in production. As in metrology rooms, it is necessary for the operators of the measuring instruments to ensure the maintenance of the permissible measurement uncertainty within the scope of equipment monitoring. This can be ensured only by regular monitoring measurements. The use of specimens for the measurements required for this purpose has become established in recent years. The simplicity and speed with which monitoring can be carried out using specimens may be adduced, in particular, as reasons for this: these are factors which are very important in the field of production.
In principle, in this monitoring process the dimensions determined by means of the coordinate measuring instrument to be checked are compared with the corresponding calibrated measured values. In the course of this, it is checked whether measurement errors are within the specified limits of accuracy. The description of a monitoring process is given, for example, in the draft of the VDI/BDE Guideline 2617 "Monitoring coordinate measuring instruments by means of specimens".
Specimens constructed in one, two or three dimensions already exist. The present prior art is represented in an overview in the contribution, entitled "Specimens for coordinate measuring instruments, machine tools and measurement robots", by H. -H. Schubler in Technisches Messen, Vol. 51, 1984, No. 3. Difficulties occurring in manipulation given the simultaneous occurrence of large dimensions and in the calibration of the specimens owing to excessively large masses limit their use to coordinate measuring instruments having measurement volumes that are smaller as a rule than 1 m.sup.3. With existing specimens, the limits of the dimensions are 2500 mm for one-dimensional design, and approximately 800 mm for the largest side length for two- or three-dimensional design.
It is the object of the present invention to propose specimens which are also suitable for monitoring coordinate measuring instruments having large measurement volumes, and in the process simultaneously ensure ease of manipulation and simple and reliable calibration.
This object is achieved according to the invention by the characterizing features of claim 1. The subclaims relate to advantageous further developments.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a one-dimensional specimen;
FIG. 1A is an enlarged detail of the area X in FIG. 1;
FIG. 2 shows a two-dimensional specimen;
FIG. 2A is an enlarged detail of the area Y in FIG. 2;
FIG. 3 shows a three-dimensional specimen; and
FIG. 3A shows an enlarged detail of the area Z in FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In this case, advantages attach to those specimens which the user can disassemble and rejoin, while maintaining accuracy. The specimens consist of reference elements which are held at a defined distance by means of rod connections. It is possible in this way to build up on-, two- and three-dimensional structures (specimens). The reference elements are constructed in such a way that their position can be uniquely detected by the coordinate measuring instrument to be checked.
Balls, for example precision balls made of industrial ceramic, are preferably suitable as reference elements. Rods can be produced from, for example, invar, Zerodur or carbon fiber composite.
According to the invention, a connection of rods and balls that can be reproduced with a high degree of accuracy is achieved by precise machining of the rod ends with the ball radii (for example CNC machining and subsequent lapping with balls of the same radius). Balls and rods are pressed together by means of spring force; this results in a dimensional stability of the total structure which is comparable with that of specimens produced from one piece. The advantage of spherical, and thus large, contact surfaces resides in the relative insensitivity of the transition dimension with respect to varying pre
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H.-H. Schuussler, Technisches Messen T.M., vol. 51, No. 3, Mar. 1984, pp. 83-95.
Trapet Eugen
Waeldele Franz
Leitz Messtechnik GmbH
Will Thomas B.
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