After selecting the cnc machining method and dividing the process, the main content of the process route is to rationally arrange the order of these machining methods and processes. The cnc machining process of parts usually includes cutting process, heat treatment process and auxiliary process (including surface treatment, cleaning and inspection, etc.). The sequence of these processes directly affects the machining quality, production efficiency and machining cost of the parts. Therefore, when designing the advance cnc machining process route, the order of cutting, heat treatment and auxiliary processes should be reasonably arranged, and the connection problem between the processes should be solved.

Arrangement of CNC machining process:

• (1) First rough and then refined
• For example, follow the order of rough turning-semi-finishing turning-finish turning to gradually improve the machining accuracy. Rough turning will cut off most of the machining allowance on the surface of the workpiece in a short time. This on the one hand improves the metal removal rate, on the other hand, it satisfies the requirement for the uniformity of the precision turning. If the uniformity of the margin left after rough turning cannot meet the requirements of finishing, semi-finishing turning should be arranged to prepare for finishing. Fine turning must ensure the machining accuracy, and cut out the contour of the part according to the size of the drawing.
• (2) Near before far
• In general, the modern parts away from the tool setting point are processed first, and the parts away from the tool setting point are processed later in order to shorten the tool moving distance and reduce the idle travel time. For turning, it is beneficial to maintain the rigidity of the blank or semi-finished product and improve its cutting conditions.
• (3) Principle of crossover between inside and outside
• For parts that have both inner surface (inner cavity) and outer surface to be processed, when arranging the advance cnc machining sequence, the inner and outer surface should be roughed first, and then the inner and outer surface should be finished. Do not process other surfaces (inner or outer surfaces) after machining part of the surface (outer or inner surface) of the part.
• (4) The principle of base first
• Priority should be given to the surface used as a fine reference. This is because the more accurate the surface of the positioning reference, the smaller the clamping error. For example, when machining shaft parts, the center hole is usually processed first, and then the outer surface and end face are processed on the center hole as a fine reference.
• (5) The principle of first and second
• The main working surface and assembly base surface of the part should be processed first, so that modern defects may be found on the main surface of the blank as early as possible. The secondary surface can be interspersed, placed on the main machining surface to a certain degree, before the final finishing.
• (6) The principle of face before hole

The plane outline size of the box body and bracket parts is relatively large. Generally, the plane is processed first, and then the holes and other sizes are processed. Arranging the advance cnc machining sequence in this way, on the one hand, the machined plane is used for positioning, which is stable and reliable; on the other hand, it is easy to machine holes on the machined plane and can improve the machining accuracy of the holes, especially when the axis of the hole is not easy when drilling. Partial.