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D. Site Reports – Europe

Site:Carl Zeiss Industrielle Messtechnik, GmbH

73446 Oberkochen, Germany

Data Visited:April 4, 2005

WTEC Attendees:T. Kurfess (Report author), H. Ali, K. Cooper, K. Ehmann, T. Hodgson

Hosts:Mr. Karl Seitz, Director New Technology, Tel: +49-7364-20-4326,
Fax: +49-7364-20-2101, Email:

Mr. Roland Roth, New Technology Systems Integration, Tel: +49-7364-20-3940,
Fax: +49-7364-20-2101, Email:

Mr. Mauricio de Campos Porath, New Technology, Tel: +49-7364-20-8140,
Fax: +49-7364-20-2101, Email:

Background

Carl Zeiss Industrial Measuring Technology (IMT) employs about 1,300 personnel globally. It is part of Carl Zeiss, Inc., which was founded in Jena, Germany in 1846. Currently, Carl Zeiss, Inc. has approximately 13,700 employees. The company generated revenues of approximately €2.1 billion last year.

Research and Development Activities

The primary reason for the visit to Carl Zeiss IMT was to review their new small-scale coordinate measurement machine (CMM). It is currently in the final phases of development. It will be on the market within a few months, and has already been disclosed to the public. Currently, the machine is called the F25. Figure 5.2 shows the F25. This report is broken into three separate sections. First, an overview of the F25 is presented, and then the major system innovations are discussed. Finally, the probing system used in the F25 is presented.

F25 Overview

The F25 is a three-axis prismatic coordinate measurement machine that is specifically designed to measure small-scale parts. The F25 employs two different sensors for metrology operations, a charged-couple device(CCD) optical sensor with a 13X objective for 2D sensing, and a tactile probe that can be used in either a point-to-point measurement mode or a scanning mode. Figure 5.4 shows the measuring head of the F25 with the tactile probe and the CCD sensor. A camera is also mounted on the F25 measurement head to provide visual feedback when using the tactile probe.The F25 is designed to use both the tactile sensor and the optical sensor in conjunction with each other. That is to say, that the geometric relationship between these two sensors is well known. Thus, measurements made with the tactile probe can be geometrically related to those made with the optical sensor. The measurement volume of the F25 is 100 mm× 100 mm× 100 mm when using both sensors in conjunction with each other. If a single sensor is used, the measurement volume is increased to 135 mm× 100 mm× 100 mm. The F25 is designed for a maximum part mass of 5 kg.

The F25 uses Heidenhain glass scales (2 µm physical grating steps with enhanced interpolation) for a resolution of 7.5 nm. The volumetric accuracy of the CCD sensor is approximately 500 nm. Currently, the repeatability of the CCD sensor is less than 200 nm (this depends on sub-pixel interpolation). The volumetric uncertainty of the tactile probe in point-to-point mode is 250 nm, with a repeatability of less than 50 nm and a resolution of 7.5 nm. The system capability in scanning mode has not been determined at the writing of this report. It has a maximum travel velocity of 20 mm/s along a single axis with a maximum 3D velocity of 35 mm/s. The maximum scanning speed with the tactile probe is 0.5 mm/s. The maximum acceleration of the F25 is 500 mm/s2 per axis. Error mapping is used on the F25. All 21 errors (position, straightness, angular and squareness errors) are mapped for this system. Furthermore, dynamic error correction is also employed. Finally, the Zeiss personnel indicated that a new proprietary error correction technique was developed and employed on the F25.

F25 Technical Innovations

The F25 is an extremely well-designed machine. It employs state-of-the-art scales for metrology feedback. It is also enclosed in an environmentally controlled chamber. The temperature within the chamber is controlled to ±1C. A major innovation of the F25 is the complete elimination of the Abbe offset in the X and Y directions (horizontal). The design is based on a PhD dissertation from the University of Eindhoven supported by Zeiss. The basic design, which is patented, allows for the entire metrology systems (glass scales) for the X- and Y-axes to move with the machine. The system is designed to have a Z-axis (vertical) Abbe error zero at the mid-point of the Z-axis stroke.

The F25 is also significantly more rigid than other metrology platforms, due mainly to a new generation of aerostatic linear air-bearing designs. While the stiffness of the machine is proprietary in nature, a significant amount of the stiffness increase was attributed to the improved stiffness of the components comprising the air bearing. The F25 employs a non-iron based linear drive enabling significantly increased acceleration.

Special fixturing was also developed for the F25 to hold two types of microcomponents, prismatic parts (see figure D.63) and rotationally symmetric parts (see Figure D.64).

Figure D.63: Fixture for prismatic parts. / Figure D.64. Fixture for rotationally symmetric parts.

The F25 is controlled by the Zeiss C99 controller, which is a controller used on a number of other Zeiss coordinate measurement machines. They have leveraged this controller as well as their CALYPSO software for geometric analysis (see Figure D.65). This is the standard metrology package that comes with Zeiss CMMs.

Probing System

Tactile probe is for full 3D measurement, and is used in the same fashion as a standard CMM probe. Tactile probe is based on a small probe being mounted on a monolithic flexure, as shown in Figure 5.7. Figure 5.5 provides a perspective as to the size of the probe. The flexure is an etched silicone wafer that has a piezo-resistive membrane on it. When the probe contacts a part surface, it deflects, changing the resistivity of the piezo-resistive material. In a point-to-point mode, a specific change in resistivity generates a trigger indicating that the part has been contacted. In scanning mode, the servo drives of the machine keep a constant force on the probe, generating a constant deflection. Two sizes of probe are currently used. The larger probe employs a 0.300 mm diameter ruby sphere for its tip with a 0.200 mm shaft diameter. The smaller probe uses a 0.120 mm diameter spherical tip with a shaft diameter of 0.050 mm. The scanning force for the large probe is 0.5 mN and the scanning force for the smaller probe is 0.250 mN. These forces generated a tip deflection of 1 µm for their respective tips. The entire probe tip length is 7 mm, enabling the F25 to measure a hole with a depth of 4 mm.

Figure D.65. Calypso software.

The optical CCD sensor is used for 2D measurement. It is a calibrated optical measurement system that relies on knowing the scaling of the image, is calibrated to size. It is employed in much the same manner as using an optical microscope for 2D metrology. The optical probe has several illumination options including a ring illumination that can be fully or partially activated (see Figure D.66), as well as back lighting capabilities.

Figure D.66. Optical sensor with illumination source.

Other Pertinent Issues

This is an entirely new machine. Zeiss believe that there is a good market for such a machine. This particular machine required approximately $6 million to develop and prototype. It was the result of a joint project with the federal German government and Zeiss. The initial project was on the order of $4 million, with the government supplying approximately 30% of the initial project funds. Zeiss provided the extra $2 million required to complete the project. The bulk of the development work was done by the New Technology Group which consists primarily of four Zeiss personnel. Zeiss is relying on integrating their

Future Issues

The F25 is currently in production and available. Presently, lead times for ordering an F25 are 6-8 months. These should be reduced as more F25s are produced, and production levels are increased. The estimated cost of a well-equipped system is approximately $440,000 per unit. This includes an active vibration damping system, software for interpreting CAD models and simulating the inspection process, training, fixturing, installation and 12 styli.

Summary and Conclusions

From a metrology perspective, this system appears to be the first metrology system that is truly 3D in capability. In the very near future, it will be commercially available. It is probably the best 3D metrology system available for microcomponents. However, it does have a high price and the time required to inspect the part can be fairly lengthy. It will serve the R&D community well, but may not be able to meet the needs for process control in the production environment.

References

Carl Zeiss IMT Corporation, (Accessed October 20, 2005).