A comparison of the differences between forward and reverse turning in CNC turning

Cutting direction and tool movement trajectory

The movement direction of the cutting tool is the same as the rotation direction of the workpiece. Take turning an outer circle as an example. The workpiece rotates counterclockwise, and the cutting tool moves from the right end to the left end of the workpiece for cutting. The relative motion direction of the contact part between the cutting tool and the workpiece advances along the rotation direction of the workpiece. This cutting method is similar to going with the flow, with the tool advancing in the direction of the "water flow" of the workpiece's rotation.

Reverse turning: The movement direction of the tool is opposite to the rotation direction of the workpiece. When turning the outer circle as well, the workpiece rotates counterclockwise, and the cutting tool moves from the left end to the right end of the workpiece. The relative motion direction of the contact part between the cutting tool and the workpiece is opposite to the rotation direction of the workpiece. This is just like rowing against the current. The cutting tool has to overcome the "water flow" resistance brought by the rotation of the workpiece to perform the cutting.

Cutting force and the force acting on the tool

As the tool's movement direction is consistent with the workpiece's rotation direction, the component force of the cutting force in the cutting direction is relatively small. The direction of the cutting force mainly acting on the tool is relatively stable, and the impact of the cutting force on the tool is relatively small. This enables the cutting tool to be subjected to force more evenly during the cutting process, which is conducive to maintaining the cutting performance of the tool and extending its service life.

Reverse turning: The movement direction of the tool is opposite to the rotation direction of the workpiece. The component of the cutting force in the cutting direction is relatively large, and the tool needs to withstand greater cutting resistance. This relatively large cutting force will subject the tool to greater impact and wear, which can easily lead to chipping or rapid wear of the tool's cutting edge, thereby affecting the tool's service life and processing quality.

Chip formation and removal

During the formation of chips, as the tool and the workpiece rotate in the same direction, the chips can be easily discharged along the rake face of the tool, and the curling and discharge direction of the chips is relatively smooth. Under normal circumstances, the chips produced during the process are relatively regular in shape, easy to control and handle, and will not cause excessive scratches on the machined surface.

Reverse turning: When chips are formed, as the tool's movement direction is opposite to the workpiece's rotation direction, the chips will be hindered by the workpiece's rotation, which can easily lead to curling, entanglement and other phenomena. Poor chip discharge may lead to chip accumulation in the cutting area, affecting the smooth progress of the cutting process and even scratching the machined surface, reducing the processing quality.

Surface quality

The cutting force is relatively small and stable. The contact between the tool and the workpiece and the cutting process are relatively smooth, which can reduce the vibration caused by the fluctuation of the cutting force. Therefore, the surface roughness of the workpieces processed by turning is generally small, and the surface quality is good, which can meet the processing requirements of higher precision and surface quality.

Reverse turning: Larger cutting forces and possible vibrations can cause the tool to leave more obvious cutting marks on the workpiece surface, resulting in an increase in surface roughness. Moreover, poor chip discharge may also cause scratches on the machined surface, further affecting the surface quality. Therefore, the surface quality of workpieces processed by reverse turning is usually not as good as that processed by forward turning.

Processing efficiency

The cutting process is smooth and the tool is subjected to uniform force. This allows for the use of larger cutting parameters, such as greater cutting depth and feed rate, thereby enhancing processing efficiency. Meanwhile, due to the relatively long tool life, the frequency of tool changes is reduced, which also helps to improve the overall processing efficiency.

Reverse turning: Due to the large cutting force and rapid tool wear, to ensure processing quality and tool life, it is usually necessary to adopt smaller cutting parameters, which will lead to a decrease in processing efficiency. Moreover, frequent tool wear and tool changes will also increase auxiliary time, further affecting processing efficiency.

Applicable scenarios

Shuncha: It is suitable for occasions with high requirements for surface quality, strict processing accuracy, and efficient processing, such as processing the outer circle and inner hole of precision parts.

Reverse turning: In some special circumstances, such as when it is necessary to process workpieces with special shapes, or in the specific layout of certain machine tools where forward turning is inconvenient, reverse turning may be adopted. However, in general, reverse turning will be avoided as much as possible, unless there are special process requirements.