xiehe model

Machining process analysis of high precision machining shaft is the preparation process of CNC turning. Whether the process is reasonable has an important impact on the program compilation, the machining efficiency of machine tools and the machining accuracy of parts. In order to develop a reasonable and practical processing program, programmers should not only understand the working principle, performance characteristics and structure of CNC lathes, master programming language and programming format, but also master the workpiece processing technology, determine a reasonable cutting program. Correct selection of tool and workpiece clamping method.

The main content of CNC turning process analysis includes: according to the drawing analysis of parts processing requirements and rationality; Determine the clamping mode of the workpiece on the CNC lathe; The processing sequence of each surface, the feed route of the tool, the number of the tool, the fixture, the cutting choice and so on.

1. Drawing analysis of turning parts

Part drawing analysis is the most important task in making NC turning technology. It mainly carries on the dimensional method analysis, the contour geometric element analysis, the precision analysis and the technical requirement analysis. In addition, the rationality of parts structure and processing requirements should be analyzed to select process benchmarks.

2. Selection of fixtures and tools

(1) Clamping and positioning of turning workpiece

In CNC turning, as far as possible in a clamping after processing all or most of the machining surface, and as far as possible to reduce the clamping times, in order to improve the processing efficiency, ensure machining accuracy. For shaft parts, usually the cylindrical surface of the parts as a positioning reference; For sleeve parts, the inner hole is the positioning reference. CNC lathe fixture in addition to the universal three claw automatic centering chuck, four claw chuck, hydraulic, electric and pneumatic fixture, there are a variety of good versatility of special fixture, in the actual operation should be reasonable choice.

(2) Tool selection

In addition to tool life, tool life is also closely related to tool diameter. The larger the tool diameter, the greater the cutting capacity. Therefore, as long as the shape of the part allows, the use of the largest tool diameter is an effective measure to extend tool life and increase productivity. CNC turning tools commonly used in general divided into three categories, namely sharp turning tools, arc turning tools and shape turning tools.

3. Selection of cutting quantity for turning processing

The cutting quantity of, including the backward feed AP, spindle speed S (or cutting speed υ) and feed speed F (or feed rate F).

The selection principle of cutting quantity and the reasonable selection of cutting quantity are very important to improve the machining quality of CNC lathe. In determining the cutting quantity of CNC lathe, must be selected according to the requirements specified in the machine tool manual and the durability of the tool, can also be determined by analogy according to actual experience.

4, turning process division, planning processing sequence

(1) Turning process division principle

When machining parts on CNC lathes, the common process division has two principles.

① Maintain the principle of accuracy. The process usually requires as much concentration as possible, and roughing and finishing are usually done in one group. In order to reduce the influence of thermal deformation and cutting force deformation on the shape, position accuracy, dimensional accuracy and surface roughness of the workpiece, roughing and finishing should be carried out separately.

② The principle of improving production efficiency. In order to reduce the number of tool change, save tool change time, improve production efficiency, need to use the same tool processing parts processing completed, should change another tool processing other parts, empty stroke should be minimized.

(2) determine the sequence of turning processing

The formulation of processing sequence generally follows the following principles:

① After the first rough is fine. According to the order of rough car, half fine car, gradually improve the processing accuracy.

② Far before far. The parts near the tool point are processed first, and the parts far from the tool point are processed after, so as to shorten the moving distance of the tool and reduce the empty walking time. In addition, near and far turning also helps to maintain the stiffness of the blank or semi-finished product and improve its cutting conditions.

③ Cross inside and outside. For parts with inner and outer surfaces, the inner and outer surfaces should be roughed first, and then the inner and outer surfaces should be finished.

(4) The base surface goes first. Surfaces used as precision reference should be treated preferentially. The more accurate the positioning datum, the smaller the clamping error.