Testing and calibration of large machine tools

Measurement and compensation of all geometric deviations

Large machine tools with axes travels from 3 m to 30 m are used in many high-tech areas. Examples are the manufacturing of structures in the aerospace industry, mold making in the automotive industry, production of turbines or large gears for energy applications or the production of construction machinery.

The total investment for these machines is often in the range of several million Euros; A significant part of the costs is due to the high accuracy requirements for the machine axes, the machine structure and the foundation.

Positioning and straightness errors, but especially angular deviations like pitch, yaw and roll of all axes have a high impact on the total machine accuracy. In addition, rotary heads with substantial tool lengths amplify the effect of the geometry deviations on the manufacturing results.

During the life cycle of the machine the geometry can be significantly affected by foundation changes, aging of machine parts or altered thermal conditions.

Therefore, on large machines, the volumetric compensation, i.e. the complete measurement and compensation of all geometry deviations in the entire working volume, has a particularly high potential.

Solely based on interferometric length measurements, Etalon’s technology offers unsurpassed accuracy in the volumetric measurement of geometry deviations. Due to the unique multilateration principle all geometric deviations of linear and rotary axes can be detected with highest accuracy, nearly unaffected by environmental influences.

The technology used to acquire geometric deviations of large machine tools has to meet the following requirements:

• High accuracy: Only measuring techniques that make a single micrometer visible even at great distances are useful for being used in today’s manufacturing.
• Complete information: In addition to the positioning error of each axis, as provided by a conventional laser interferometer, the other geometric parameters such as straightness, pitch, yaw, roll and position of the individual axes must be detectable.
• Measurement time: Machine time on large machines is extremely precious, therefore the measurement method should take minimal time and be automated as far as possible.
• Easy implementation: The measurement has to be carried out in production environment by experienced technicians.
• The data obtained must be transferred with simple interfaces to the machine controllers for compensation.

The Etalon technology with its innovative measuring principle, its high-precision measurement technology and sophisticated and comfortable software can meet these requirements. It enables the accurate detection of all geometric deviations in the shortest time and offers certified interfaces to the far-reaching compensation possibilities of advanced NC controls like Siemens, Heidenhain, Fanuc, Fidia, Mazatronik and others.