Kornel Ehmann
James N. and Nancy J. Farley Professor in Manufacturing and Entrepreneurship

Dept. of Mechanical Engineering
Northwestern University
2145 Sheridan Road, Room A215
Evanston, IL60208, USA

TEL: (847) 491-3263
FAX: (847) 491-3915

email: k-ehmann@northwestern.edu

BS Mechanical Engineering, University of Belgrade (Yugoslavia), 1970
MS Mechanical Engineering, University of Belgrade, (Yugoslavia), 1974
PhD Mechanical Engineering, University of Wisconsin-Madison, 1979

Research link: Machine Tool Dynamics and Control and Metal Cutting Processes

Editor: Journal of Manufacturing Science and Engineering

Honors and Awards

Research: Micro/meso-scale manufacturing; Precision engineering; Machine tool dynamics and control; Material removal processes; Automation and robotics

The pervasive theme throughout Professor Ehmann's research activities is the accuracy, precision and dynamic stability of shape generation and replication processes. To this end, three interrelated problem areas are considered.
  1. Process modeling: This involves the study of the physical mechanisms that govern material removal processes, the understanding of the mechanisms that lead to dynamic instabilities (self-excited chatter vibrations), and the prediction of surface characteristics of manufactured components as a function of process variables.
  2. Process control and monitoring: The availability of process models constitutes the foundation for the development of pragmatic engineering solutions for new process implementations and enhanced control of process outcomes. Specific emphasis is placed on active machine error and chatter compensation in multi-axis manufacturing machines and processes to enhance their efficiency.
  3. New manufacturing machines, processes and tooling: The development of new processes and miniaturized processing equipment for small precision mechanical components coupled with the design of new products is the focus of this activity. Specific current examples include the development of micro-cutting processes and of miniaturized micro/meso-scale machine tools (mMTs) for the manufacture of components in the 100 - 10,000 μm range.

In the Classroom

Professor Ehmann teaches courses in the areas of design and manufacturing. In particular, Introduction to Design and Manufacturing and one or more of the courses in the Computer Integrated Manufacturing sequence, i.e., Manufacturing Processes, CAD/CAM, and Manufacturing Automation. All these courses heavily rely on regular hands-on laboratory exercises with state-of-the-art software and industrial quality equipment that go well beyond typical laboratory experiences. In the design area, Professors Stoll and Ehmann co-teach Mechanical Systems Design that is aimed at senior students. The course focuses on design methodology, principles of precision machine design and design of mechanisms. It assumes an open-ended view in its homework and group project assignments.

Professor Ehmann also teaches courses at the graduate level. These include Computer Control in Manufacturing that emphasizes the use of digital and adaptive control methods for process and motion control in a variety of machine tools and robots, Metal Cutting in which the mechanics of material removal processes, their stability and pragmatic implementation are studied, and Micromanufactuting that focuses on the emerging field of miniaturization technologies through the consideration of the associated design, processing and metrology issues.

Selected Publications

"Development of Curved Helical Micro-Drill Point Technology for Micro-Hole Drilling," Mechatronics, 8(4), 337-358 (H.C. Chyan, K.F. Ehmann) (1998) (Invited)

"Measurement Methods for the Position Errors of a Multi-Axis Machine - Part I: Principle and Sensitivity Analysis," Int. J. of Machine Tools and Manufacture, 39(6), 951-964 (S.M. Wang, K.F. Ehmann) (1999)

"Development of Meso-Scale Machine Tool (mMT) Systems," Transactions of NAMRI/SME, 30, 653-661 (M.P. Vogler, X. Liu, S.G. Kapoor, R.E. DeVor, K.F. Ehmann) (2002)

"Micro/Meso-scale Mechanical Manufacturing - Opportunities and Challenges", Proceedings, JSME/ASME International Conference on Materials and Processing, (Keynote presentation) October 15-18, Honolulu, HI, 1, 6-13 (2002)

"Simulation of Machined Surface Topography in End Milling Processes Using a Shear - Plane Based Cutting Force Model," Proc. Instn Mech. Engrs Part B: Journal of Engineering Manufacture, 218(12), 1767-1793 (C.H. Chiou, M.S. Hong, K.F. Ehmann) (2004)

"Dynamics of Initial Penetration in Drilling: Part 1 – Mechanistic Model for Dynamic Forces," ASME Journal of Manufacturing Science and Engineering, 127, 280-288 (Y. Gong, C. Lin, K.F. Ehmann) (2005)

"Material Characterization of NiTi Based Shape Memory Alloys Fabricated by the Laser Direct Metal Deposition Process", ASME Journal of Manufacturing Science and Engineering, 128(3), 691-696 (K. Malukhin, K.F. Ehmann) (2006)

"Third-Octave-Mode Chatter in Rolling. Part 1: Chatter Model," Proc. Inst. Mech. Eng. Part B: Journal of Engineering Manufacture, 220,1267-1277, (P.H. Hu, H. Zhao, K.F. Ehmann) (2006)

WTEC (World Technology Evaluation Center) Panel Report on: International Assessment of Research and Development in Micromanufacturing, K.F. Ehmann - Panel Chair, (with D. Bourell, M. Culpepper, T. Hodgson, T. Kurfess, M. Madou, K. Rajurkar, R. DeVor), (2007) (Currently in print by Springer)