Interpretation of ultra-precision cutting technology

?Ultra-precision machining refers to the machining technology in which the dimensional accuracy of the machined parts is 0.1~0.01μm, and the machined surface roughness is of the order of Ra0.03~0.0051μm. With the development of processing technology, the technical indicators of ultra-precision machining are constantly changing. Ultra-precision cutting processing is mainly carried out with high-precision machine tools and single crystal diamond tools for processing. Therefore, it is generally known as diamond tool cutting (Simple Point Diamond Turming, SPDT).

The History of Ultra-Precision Cutting

　　In the early 60's, due to the gyroscope for astronautics, magnetic drums and disks for computers, multi-faceted prisms for optical scanning, large-diameter non-circular curved mirrors for high-power laser fusion devices, as well as stereoscopic mirrors for infrared light of various complex shapes, etc. Various mirrors and multi-faceted prisms with extremely high precision requirements, the use of grinding, lapping, polishing, etc., not only the processing cost is very high, but also very difficult to satisfy the requirements of precision and surface roughness. Surface roughness requirements. For this reason, the research and development of the use of high-precision, high-stiffness machine tools and diamond tools for cutting processing method processing.

　　Ultra-precision cutting started with SPDT technology, which is supported by air bearing spindle, pneumatic slide, high rigidity, high precision tools, feedback control and ambient temperature control, and can obtain nano-scale surface roughness. Mostly using diamond tools, it is widely used in the processing of flat and aspheric optical elements of copper, organic glass, plastic products (such as plastic lenses for cameras, contact lens lenses, etc.), ceramics and composite materials.

　　Ultra-precision cutting technology is adapted to the needs of modern high-tech and the development of advanced manufacturing technology, high-tech cutting-edge product development is indispensable to the development of key technologies, is an important symbol of the level of a country's manufacturing industry, but also the modernization of equipment is indispensable to the development of one of the key technologies, in the military and civil industry has a very broad application prospects.

Schematic diagram of finished optical components processed by SPDT

The various shapes of parts shown in the figure are deoxidized copper or aluminum alloy materials.

Application of ultra-precision cutting processing

1、Flat mirror cutting

Flatness<0.06 μm; surface roughness Rmax<0.02 μm

2、Cutting of glass mirror

Measurement results

3、Multi-surface mirror cutting

Laser printing machine, copying machine. Face indexing accuracy 7.5", face tilting accuracy 3.6", flatness<0.07 μm, surface roughness<Rmax0.02 μm

4、Spherical mirror cutting

5、Cutting of other parts

Spherical surface (ball bearing) turning, photocopier toner cartridge (cylindrical surface) turning, disk substrate turning

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Selection of cutting speed for ultra-precision cutting

Ultra-precision cutting speed selection: usually based on the dynamic characteristics of the machine tool and the dynamic characteristics of the entire cutting system selection.

　　Generally, the cutting speed at which the machine vibrates the least is selected to ensure the machined surface quality.

Improve the benefits of machining precision

1、Improve the performance and quality, stability and reliability of products;

2, promote product miniaturization;

3, enhance interchangeability, promote automated assembly applications.

Factors affecting the roughness of the cutting surface

(1) The effect of the roughness of the cutting edge

(2) The effect of the cutting edge of the reflection of the cutting edge

(3) The influence of scale spurs and machining deterioration layer

Tool wear and life during ultra-precision cutting

　　Ultra-precision cutting of non-ferrous metals with natural monocrystalline diamond tools, such as normal cutting conditions, no accidental damage to the tool, tool wear is very slow and tool durability is extremely high.

　　Natural monocrystalline diamond tools for ultra-precision cutting, breakage or wear and can not continue to use the sign for the processing surface roughness exceeds the specified value.

　　The life of the diamond tool is usually measured by the length of its cutting path. If the cutting conditions are normal, the life of the diamond tool can reach hundreds of kilometers.

　　The actual use of diamond tools often do not reach the above durability, often due to the cutting edge to produce a small chipping and can not continue to use, which is mainly due to the vibration of the cutting or blade collision caused by.

1、Ultra-precision diamond tool cutting mechanism of the tool cutting model

　　In the ultra-precision cutting process, the depth of cut is only a few microns below, in the cutting process, the microscopic shape of the tool is extremely important, so the tip of the tool should be regarded as a rounded corner with arc radius R. The tip of the tool should be regarded as a rounded corner with arc radius R

?Two-dimensional cutting model near the tool tip: When the given depth of cut is t, the actual depth of cut is t1 due to the local deformation of the tool tip δ1, and when the tool passes over, there will be δ2 elastic deformation of the workpiece surface to recover the amount of elastic deformation. Therefore, the actual removal layer will be smaller than the actual depth of cut. δ1 and δ2 can be calculated by approximation.

2、Minimum cutting thickness of ultra-precision diamond tool cutting mechanism

　　The actual minimum cutting thickness is related to the sharpness of the diamond tool, the performance status of the ultra-precision machine tool and the environmental conditions.

　　In 1986, Osaka University in Japan and LLL Laboratory in the United States to carry out cooperative research. Continuous and stable chips can still be obtained when the cutting thickness is extremely small (1nm).

　　The relationship between the minimum cutting thickness and the radius of the tool edge: critical point A, the material above point A will accumulate to form chips, and the material below point A will be formed by elastic-plastic deformation to form the machined surface.

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