Key points of CNC lathe processing
The development of modern manufacturing technology and the wide use of NC machining equipment have greatly promoted the progress of cutting technology. With the need of numerical control and automation in the production process, higher requirements for metal cutting tools are put forward, such as high reliability, high precision, long life, rapid displacement replacement and good chip breaking. It is very important to set reasonable working procedure according to different machining characteristics for realizing highly automatic cutting or unmanned machining. The following is a brief introduction of the process of metal cutting for lathes.

I. reasons for processing stages

(1) To ensure the machining quality, in the roughing stage, because the cutting force and heat produced by the thick metal layer are relatively large, and the clamping force required is also large, the workpiece will produce greater elastic deformation and internal stress, resulting in greater machining errors and greater surface roughness, through semi-finishing. Work and finishing gradually reduce cutting parameters, cutting force and cutting heat, gradually modify the deformation of the workpiece to improve machining accuracy.

(2) High-efficiency equipment with high power and low precision is generally used when rough machining is needed for rational use of machine tools and equipment, and high-precision machine tools are used in finish machining. This not only improves the production efficiency of rough machining, but also prolongs the service life of high precision machine tools and reduces the processing cost.

(3) Easy arrangement of heat treatment process The insertion of heat treatment process naturally divides the machining process into several stages. For example, in precision spindle processing, after rough processing, stress relief aging treatment, after semi-finishing quenching treatment, after finishing cold and low temperature tempering treatment, and finally finishing processing.

(4) The defects of rough workpiece can be found as early as possible after the defects of rough workpiece are discovered in time, and the defects can be repaired or scrapped in time, so as to avoid further processing and increase the loss. Moreover, the finishing stage is arranged at the end, so that the surface after finishing can be protected as far as possible from damage.

Two. Divide the lathe into cutting stage.

That is, the whole process is divided into several stages, so that rough and fine processing can be carried out separately. The machining process of molds can be generally divided into the following stages:
(1) The main task of roughing stage is to remove most of the surface allowance, so that the shape and size of the blank as close as possible to the finished product.

(2) The main task of the semi-finishing stage is to eliminate the errors left by rough machining on the main surface, to prepare necessary precision and allowance for finish CNC machining, and to finish Finishing on the secondary surface, such as drilling, tapping threads, milling keyways, etc.

(3) The main task of the finishing stage is to ensure that the main surfaces meet the technical requirements specified in the drawings.

(4) Finishing process is arranged for surface which requires high dimensional accuracy and surface roughness. The main task of this stage is to improve the dimensional accuracy of the machined surface and reduce the surface roughness, but generally can not correct the shape error and position error.

Three, reasonably divide lathe cutting process.

Two points show that dividing the process into several stages is for the whole process, and can not be judged simply from the processing of a surface or the nature of a process.

(1) Processing of positioning datum of workpiece is always given priority, and it is common, sometimes even necessary, to arrange some rough machining processes such as drilling in finishing stage.

(2) it is not absolute to divide the processing stage. It is not necessary to divide the processing stage for workpiece with good cutting quality, low machining accuracy or small allowance. Some heavy parts with high precision require time-consuming and labor-consuming transportation and installation, and generally do not divide the processing stages, but complete all rough and finish machining tasks under a single clamping.

(3) In order to reduce the influence of clamping deformation on machining accuracy, the clamping mechanism can be loosened after rough machining, and then the workpiece can be re-clamped with a smaller clamping force, which is beneficial to improve the machining accuracy.


Four. Selection of cutting tools

Tool selection is an important part of CNC machining process. Cutting tools not only affect the machining efficiency of machine tools, but also directly affect the machining quality of parts. Because the spindle speed and range of NC machine tool is far higher than that of ordinary machine tool, and the output power of spindle is larger, so compared with traditional machining methods, higher requirements are put forward for CNC cutting tools, which require high precision, high strength, good rigidity and high durability, and require stable size, installation and adjustment. It's convenient.

Five. The use of special cutting oil.

Generally, in order to clean the finished product easily, the better viscosity should be determined according to the difficulty of processing and degreasing conditions. Some workpiece raw materials will react with chlorine additives, so we should pay attention to the problem of white rust when choosing cutting oil. The cutting oil containing sulfur and chlorine compound additives can ensure the extreme pressure processing performance, and avoid burrs and cracks on workpiece.