Error Allocation in the Design of Precision Machines

Machining accuracy is an important index to evaluate the performance of a precision machine. However, the machining accuracy of parts is seriously limited by the designed machine’s errors. Therefore, error allocation in precision machine design is the key element to produce the components with a closed tolerance. In this chapter, the main errors for the designed machine that affect the machining accuracy are introduced, which include machine tool geometric error, machine tool thermal deformation, and load-induced errors. Among them, the geometric error after the assembly of the machine tool has the most direct impact on the machining accuracy, in which the position- and pose-related errors between each component transmit through kinematic chain and lead to the error combination. The essence of error allocation design is to use tolerance to limit the error of every part and finally ensure the overall output trajectory accuracy of the cutting tool. The deformation error caused by uneven temperature distribution is mainly caused by cutting process, friction behavior, and the surrounding environment, and it will further change the relative position of each part of the machine tool. Finally, load error under the action of force is introduced, which produces the elasticity or even structural deformation and further affects the relative position of the machine tool components. It shows that reasonable error allocation under the influence of multiple errors for the precision machine design is critical to ensure the machining precision.