Dimensional measurement of hot parts, such as forgings, is desirable to permit real-time process measure and control,
but typically it is not convenient as a result of the difficulty in working with very hot workpieces. On the contrary, the
disadvantage of high temperature of the hot parts can properly be used to measure the dimensions based on CCD
(Charged Coupled Device) sensors. It is well known that the hot parts can transmit lights, so the general CCD can be
applied to measure the dimensions of the hot part (e.g. length and diameter etc.) rapidly and non-contact without any
illuminator. Since the illumination system can be omitted, the measurement system can be more flexible and convenient.
In this paper the principle of the measurement based on CCD is briefly described at first. Then the structure of
measurement system is presented in detail. At last, some experiments are performed to measure the diameter of hot parts.
The experimental results indicate that the measured diameter is correlated with the luminance of hot parts and the
luminance has something to do with the temperature of the hot parts, and the methods to avoid this question are
discussed. In addition, the error sources in the measurement system are also discussed. From these experiments, the
method to measure the dimension of hot parts based on inexpensive CCD sensor is feasible.