Who said that lathes can only turn "round" machines?

CNC lathe processing mainly uses turning tools to turn rotating workpieces. Lathes are mainly used to process shafts, discs, sleeves and other workpieces with rotating surfaces. They are the most widely used type of machine tool processing in machinery manufacturing and factories. Normally, we process the surface of the rotary body on a lathe, basically as shown in the figure below:

After people carry out technical transformation of lathes, lathes can also be used for other (non-turning) processing, such as polygon processing, grinding processing, rolling processing and thread milling processing. Many vivid cases have proven that taking technical measures adapted to local conditions not only requires low investment and good results, but can also make up for the problem of insufficient or unmatched equipment. It is an important way to expand the scope of lathe use. It is very realistic for small and medium-sized factories and enterprises. meaning.

Working Principle of Polygonal Processing To process polygonal workpieces on a lathe, a set of special devices as shown in the figure need to be installed.

During turning, it is installed on the middle slide plate, so that the workpiece and the tool rotate in the same direction, and the speed ratio relationship between the tool and the workpiece with a certain number of tool heads is used to realize the relative movement of the tool and the workpiece, so that the shape can be realized according to the law of development. Surface forming, complete the processing of square, hexagon, equilateral triangle, trapezoid, drum, waist, flat, rhombus, irregular polygon and tapered polygon workpieces.

For example, when machining an equilateral triangle, the transmission ratio between the tool and the workpiece is i=3. Therefore, during the cutting process, the trajectory of the tool tip relative to the axis of the workpiece is a periodically repeated closed curve, and the middle part surrounded by the curve forms an approximate triangle.

If the workpiece axis is located outside the tool tip movement circle, we call it the "external cutting method". The triangle presented is as shown in Figure a; if the workpiece axis is located within the tool tip movement circle, it is called the "inner cutting method" and appears. The triangle is shown in Figure b.

It can be seen from the triangular figure presented that whether the external cutting method or the internal cutting method is used, the surfaces of the triangular workpiece processed are not flat surfaces, but approximately flat arc surfaces. Therefore, the method of turning polygons mentioned above can only be used. Used in processing that does not require high surface flatness. The above introduction of widely used tools is based on traditional theory, but in practical applications, there are different forms of tools. The principles are the same, but when the principle is introduced, the tool makes the main movement on the spindle, and the workpiece does Auxiliary movement, while in practical applications, the workpiece makes main movement on the spindle.

In polygon turning, a flying cutterhead is used to cut polygons (three to eight sides) on the sides of an axially symmetric workpiece. The workpiece (main spindle) and the rotating tool (flying cutterhead) work together in a synchronous coupling manner to machine the contact surface.

The amount of surface cut depends on the gear ratio and the number of edges on the cutting tool. The workpiece and tool rotate in opposite directions.

Knives with two blades are used to cut quadrilateral-like shapes, and tools with three blades are used to cut hexagon-like shapes, etc. If a different transmission ratio is used or the number of cutting edges of the tool is changed, larger depressions or prominent deflection arcs may appear on the workpiece surface.

Because of the above principle, the contour trajectory generated by the tool tip point is exactly an ellipse, but the curve implemented on the wrench's force surface is a section with a larger curvature radius in the ellipse, so it does not affect tightening and loosening. Assembly operations.