Arrangement of cnc processing sequence

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

Arrangement of cnc processing steps:

(1) Coarse and fine

For example, in the order of rough turning-semi-finishing turning-finishing turning, the machining accuracy is gradually improved. The rough turning will cut off most of the machining allowance (the part shown in the cool dot drawing line in Figure 2-4) on the surface of the workpiece in a short time. On the one hand, the metal removal rate is improved, and on the other hand, the remaining uniformity requirements of the finished car are met. If the uniformity of the remaining margin after rough turning cannot meet the requirements of finishing, a semi-finishing turning should be arranged to prepare for finishing. To ensure the machining accuracy of the finished car, cut out the outline of the part according to the size of the drawing.

(2) Near and far

In general, the modern parts from the tool setting point are processed first, and the parts from the tool setting point are processed later to shorten the tool moving distance and reduce the idle travel time. For turning, the near-to-far sea is beneficial to maintaining the rigidity of the blank or semi-finished product and improving its cutting conditions.

(3) Internal and external intersection principle

For parts with both an inner surface (inner cavity) and an outer surface that need to be processed, when arranging the processing sequence, the inner and outer surfaces should be roughed first, and then the inner and outer surfaces should be finished. Never process a part of the surface (outer or inner surface) of the part before processing other surfaces (inner or outer surface).

(4) the principle of advancement

Surfaces used as fine references should be processed with priority. This is because the more accurate the surface of the positioning datum is, the smaller the clamping error is. For example, in the processing of shaft parts, the center hole is usually processed first, and then the outer surface and the end surface are processed with the center hole as a fine reference.

(5) The principle of "first come first, then second come"

The main working surface and assembly base surface of the part should be processed first, so that early detection of modern defects in the main surface of the blank may be found. The secondary surface can be interspersed, after the main processing surface is processed to a certain extent, and before the final finishing.

(6) The principle of "face first and then hole"

Boxes, brackets and other parts have larger plane outline dimensions. Generally, planes are processed first, and then holes and other dimensions are processed. The processing order is arranged in this way. On the one hand, the processed plane is used for positioning, which is stable and reliable; on the other hand, it is easy to machine holes on the processed plane, and it can improve the machining accuracy of the hole, especially when the axis of the hole is not easy when drilling Partial.