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| 2006 Tutorials |
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| Sunday, October 15, 2006 8:00 a.m. to 12:00 p.m. Thermal Effects Thermal effects represent the largest single source of systematic error and apparent non-repeatability in Precision Engineering. This tutorial will present the reasons for this unhappy situation and describe some past and future solutions. The principal sources of thermal error are room and coolant temperatures different than 20°C, heat from people, mechanical friction, electrical components, the cutting process, and thermal soakout. These heat sources interact with the three element system consisting of the part, the machine frame and the scale in a special way which must be thoroughly understood by the precision engineer before attempting solutions to the problem. This understanding will be developed through use
of the Thermal Error Diagram. This is a valuable tool that illustrates
the various sources of thermal errors and how they interact with the
three element system. Key concepts such as the 20°C Reference Temperature,
Temperature Variation Error (TVE), the Thermal Error Index (TEI), and
Thermal Resonance will be presented. The American Standard ANSI/ASME, B 89.6.2 on "Temperature and Humidity Environment" will be summarized. The recently issued, (March 15), ISO Technical Report ISO/TR 16015 on "Measurement uncertainty due to thermal influences" will be also be summarized and compared to B89.6.2. The new ISO standard 230 on "Thermal testing of machine tools" will be mentioned. Future solutions (as well as past solutions) are based on three general approaches: (1) control of heat flows into the three element system, (2) redesign of the frame and scale to reduce their sensitivity to heat flow, and (3) compensation. Compensation is often regarded as the first choice. Experience has shown, however, that it is not always a simple, or economical solution.
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