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Improving CNC Machining Accuracy Through Thermal Model-Based Control



John L. Michaloski, Frederick M. Proctor, Johannes A. Soons, R King, W Bakula, H Dominguez, N Frampton


The United States Army has a requirement to machine munitions to strict tolerances so that the munitions will launch properly and the explosives will detonate correctly. High precision parts require machine tools to operate with a high degree of accuracy in order to produce parts within tolerance. Unfortuantely, thermal expansion, tool wear and other impediments make high accuracy machining, especially over the long term, a difficult proposition. The idea of smart machine tools that incorporate model based control to compensate for errors during the lifetime of machine operation is an emerging trend. Model based control as applied to machine tools describes a computerized control scheme in which the mathematical model of the process is used to compensate for the inaccuracies that exist in the real world, at any given time. With the advent of commercial open architecture controllers, it is now easier to adapt model-based control into machine controllers to minimize process variablility in order to more accurately machine parts on a daily basis. This paper looks at the incorporation of Nominal Differential-Expansion as a model based control strategy to improve the accuracy of a turning machine and part tolerance. Nominal Differential Expansion (NDE) is the difference between the predicted thermal expansion of the workpiece and that of the master or scale. The theory of NDE will be discussed as well as how it was incorporated into a commercial, open architecture, CNC turning machine. The potential applications of model based control to other areas of distributed manufacturing will be considered.
To Be Determined


CNC, control, model based control, open architecture, thermal compensation


Michaloski, J. , Proctor, F. , Soons, J. , King, R. , Bakula, W. , Dominguez, H. and Frampton, N. (2004), Improving CNC Machining Accuracy Through Thermal Model-Based Control, To Be Determined, [online], (Accessed April 21, 2024)
Created July 20, 2004, Updated October 12, 2021