Abstract : When turning a profiled part, the working angle of the Tool is not only related to the feed motion and installation position, but also related to the cross-sectional shape of the workpiece. The front and rear angles of the tool will vary with the shape of the workpiece. The machining camshaft is taken as an example to analyze the change of the working angle of the tool.
With the development of technology and production, more and more special-shaped cross-section parts have been used in mechanical design and manufacturing, such as multi-edge shafts, camshafts, polygonal shafts, crankshafts, etc., in order to meet the performance requirements of these parts, Processing accuracy and surface quality requirements are also increasing. This paper starts with the analysis of the processing method and characteristics of the special-shaped cross-section parts, focusing on the precision turning and abrasive belt grinding technology of the special-shaped cross-section parts.
1 Processing method for profiled parts
There are usually three ways to process the profiled parts: 1 direct forming method, such as casting, forging, stamping, etc.; 2 cutting motion synthesis method, such as car, milling, planing, grinding, etc.; 3 special processing methods, such as wire cutting, electric spark , laser processing, etc. Among them, the direct forming method is the main forming method of the special-shaped cross-section parts, but due to its low manufacturing precision and large surface roughness value, it cannot meet the finishing requirements of the special-shaped cross-section parts. Special machining methods have limited application due to their low efficiency, high cost and the inability to machine non-circular cross-section parts with complex axial cross-section shapes. Therefore, the motion synthesis method is the main way to obtain high-precision profiled parts.
Car, milling, planing, grinding, etc. are the most common methods of motion synthesis cutting, which can process different complex shape parts. Among these methods, milling and planing are currently difficult to achieve high machining accuracy. Grinding is a commonly used precision machining method, and has high production efficiency, but the ordinary grinding process has a large negative rake angle of the grinding wheel, small cutting thickness, easy passivation of the abrasive grains, easy to block the grinding wheel by the chip, and grinding temperature. High application, high grinding force, difficulty in grinding workpieces with large curvature changes, etc., its application is limited. Precision turning is a fast-growing precision machining technology in recent years. Especially with the wide application of CNC machine tools and diamond tools, the machining precision and machining efficiency of precision turning are greatly improved.
2 Turning of profiled parts
The turning machining methods of the special-shaped cross-section parts mainly include: 1 mechanical motion synthesis method, that is, the turning motion trajectory of the profiled section is generated by the multi-directional motion synthesis of the mechanism; 2 by the analog shape processing method, that is, the master mold is used to control the turning tool and the workpiece. Relative motion trajectory, forming the required workpiece shape; 3 CNC turning method, that is, using the program command to control the machine tool on the CNC lathe, so that the machine tool can automatically complete the specified machining process. Among them, CNC turning method has high production efficiency and processing precision, stable quality and wide processing range, and can be used for automatic turning of various profiled parts. When the processing object changes, only the NC program needs to be adjusted to complete the machining operation, which is especially suitable for automated production of multiple varieties and small batches.
3 Tool angle analysis of turning machining of profiled section parts
Since the working angle of the tool changes when cutting a profiled part, a large negative or negative relief angle may occur during turning. When a negative back angle occurs, the turning surface of the turning tool and the workpiece are severely squeezed and rubbed, which deteriorates the surface quality of the workpiece, and it is even difficult to cut off the workpiece material. Therefore, the negative relief angle must be prevented when machining the profiled part to ensure that the turning tool has a normal working angle.
When turning a profiled part, the working angle of the tool is not only related to the feed motion and mounting position, but also to the cross-sectional shape of the workpiece. The front and rear angles of the tool will vary with the shape of the workpiece. The machining camshaft is taken as an example to analyze the change of the working angle of the tool.
Figure 1 Change of tool angle when turning camshaft
Glass bits have a spade-shaped carbide point, used to drill holes in materials of glass, ceramics,etc. They generate high temperatures and have a very short life. Holes are generally drilled at low speed with a succession of increasing bit sizes. Diamond drill bits can also be used to cut holes in glass, and last much longer.
It is an alloy triangular bit mounted on the ordinary Electric Hand Drill, which has high hardness, sharp blade and good precision, and is specially used for opening holes in ceramic tiles. But the drill wears too much into concrete to be used on concrete.
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