The error of the transmission chain will affect the correctness of the tool movement, and in some cases, it is the main factor affecting the machining accuracy. For example, when hobbing gears, the ratio of the rotational speed of the hob to the rotational speed of the workpiece needs to be constant and a strict motion relationship is maintained.

When the transmission elements in the transmission chain (such as hobbing pulleys, indexing worm gear pairs, etc.) have manufacturing errors and assembly errors, as well as wear during use, the correct motion relationship will be destroyed, causing the rolled out gears to produce Errors (such as pitch error, accumulated pitch error and tooth profile error, etc.). Therefore, the transmission accuracy of the machine tool transmission chain first depends on the manufacturing and assembly accuracy of each transmission element, and secondly is related to the position of each transmission element in the transmission chain.