Abstract
We have developed a computer assisted instruction system for machine drawing. The system has a function to show the 3-dimensional (3-D) geometry made from the projection view of the object. In the case of including mistakes in the drawing, the incomplete geometry is presented on the display so that one can find mistakes without help from teachers. However, since the system employs wireframe models for 3-D description, it is often difficult to understand precise features. Therefore, the system was refined by employing surface models in this study. It was demonstrated that the visibility of the model is improved and the difference between the correct and the illegal model can be seen clearly by using the refind system. The results of the trial use shows that the system is effective for self-exercise.
