In additive manufacturing, separation is an important issue in constrained-surface digital light processing. A force higher than the force peak and a sharp increase in force increase the printing failure rate. This study comprehensively evaluated the performance of a low-cost spring-assisted separation mechanism. The Taguchi method was used to confirm the correlation between the inputs of the spring-assisted mechanism (number, coefficient, working height, free height of spring, and length of working arm) and obtain the parameters that minimize the separation force and time. Compared to the pulling-up and tilting mechanisms, the spring-assisted mechanism reduces the difference between the maximum and minimum separation forces for different geometric shapes and areas by 2.4 and 3 times, respectively. In addition, the spring-assisted mechanism solves the problems of the pulling-up mechanism, which has two separation force peaks, and the tilting mechanism, which has a sharp increase in force before the final separation. Finally, the separation force of specific geometric shapes and areas was predicted by the linear regression equation, and the error rate was maintained within 5%, which helped to significantly reduce the calculation costs and time.