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Working principle of slow wire processing

 Slow wire walking, also called low-speed wire walking, is a kind of CNC machining machine tool that uses continuously moving fine metal wire as an electrode to pulse spark discharge on the workpiece to generate a high temperature of over 6000 degrees, ablate metal and cut into a workpiece. The principle of wire processing is the phenomenon that there is a gap between the wire electrode and the workpiece, and the metal is removed by continuous discharge. Since the slow-moving wire cutting machine adopts the method of wire electrode continuous feeding, that is, the wire electrode is processed during the movement, so even if the wire electrode is worn out, it can be continuously supplemented, so it can improve the machining accuracy of the parts and slow the wire. The surface roughness of the workpiece processed by the cutting machine can usually reach Ra=0.8μm and above, and the roundness error, linear error and dimensional error of the slow-moving wire cutting machine are much better t

Hydrostatic guideway of CNC machining lathe

The static pressure slide rail (TTW guide) of the CNC machining lathe transfers the oil with a certain pressure through the throttle to the oil cavity between the sliding surfaces of the slide rail (TTW guide) to form a pressure oil film to float the moving parts , Make the sliding rail (TTW guide) surface in a pure liquid friction state.   CNC machining General CNC machining usually refers to computer digital control precision machining, CNC machining lathe, CNC machining milling machine, CNC machining c17200   beryllium   copper   and milling machine, etc. The feed route of finishing is basically carried out along the part contour sequence. Therefore, the focus of determining the feed route is to determine the feed route of rough machining and idle stroke. In the numerical control processing, the control system issues instructions to make the tool perform various motions that meet the requirements, and the shape and size of the workpiece are expressed in the form of numbers and lette

Classification of CNC Machining Occupation Levels

1. Blue-collar layer:   That is, CNC machining operation technicians, proficient in machining and CNC machining process knowledge, proficient in the operation and manual programming of CNC machine tools (attributes: automated machine tools), understand automatic programming and simple maintenance of CNC machine tools (attributes: automated machine tools), such There is a large market demand for personnel, and they are suitable for operating workers of CNC machine tools (attributes: automated machine tools) in the workshop, but due to their single knowledge, their wages will not be much higher.   2. Gray collar layer:   One, CNC machining programmer:   Master the knowledge of 5 Axis CNC machining Aluminum   technology and the operation of CNC machine tools (attributes: automated machine tools), be familiar with the design and manufacturing expertise of complex molds (title: mother of industry), and be proficient in 3D CAD/CAM software, such as UG, GOOGLE PRO/E, etc. ; Familiar with CNC

The Relationship Between Surface Roughness and Tolerance Level in CNC Machining Industry

Surface roughness is an important technical indicator, it reflects the micro-geometric error of the surface of the part, and it is the main basis for inspecting the surface quality of the parts; whether it is reasonable or not, it is directly related to the quality, service life and production cost of the products.

There are three ways for selecting the surface roughness of mechanical parts, including calculation method, test method and analogy method. In the design of mechanical parts, the most common application is the analogy method, which is simple, rapid and effective. The application of analogy requires enough reference materials. The existing kinds of mechanical design manuals provide more comprehensive information and literature. The most commonly used is the surface roughness that is compatible with the tolerance level. Under normal circumstances, the smaller the dimensional tolerance requirements for mechanical parts, the smaller the surface roughness value of the mechanical parts, but there is no fixed functional relationship between them. For example, some machines, instrument handles, hand wheels, and sanitary equipment, food machinery, and some mechanical parts of the modified surface, their surface requirements are processed very smooth, that is, the surface roughness requirements are high, but their dimensional tolerance requirements are very low. Under normal circumstances, there is a certain correspondence between the tolerance level and the surface roughness value of parts with dimensional tolerance requirements.

In some mechanical parts design manuals and mechanical manufacturing monographs, there are many introductions to the experience and calculation formulas of the relationship between the surface roughness of mechanical parts and the dimensional tolerances of mechanical parts, and the list is for readers to choose, but as long as you read it carefully, you will found that although the same empirical calculation formula is adopted, the values in the list are different, and some are still very different. This has caused confusion for people who are not familiar with the situation in this area. At the same time, it also increases the difficulty of selecting surface roughness in the work of mechanical parts.

In actual work, for different machines, the requirements for surface roughness of their parts are different under the same dimensional tolerances. This is the stability problem of cooperation. In the design and manufacture of mechanical parts, for different types of machines, the requirements for the stability and interchangeability of the parts are different. In the existing mechanical parts design manual, the following three types are reflected:

The first type, it is mainly used in precision machinery, which has high requirements for the stability of the fit. It is required that the wear limit of the parts does not exceed 10% of the dimensional tolerance of the parts during use or after repeated assembly. This is mainly used On the surfaces of precision instruments, meters, precision measuring tools, and the friction surfaces of extremely important parts, such as the inner surface of the cylinder, the spindle neck of precision machine tools, the spindle neck of coordinate boring machines, etc.

The second type, it is mainly used for ordinary precision machinery, which requires high stability of the fit, requires that the wear limit of the part does not exceed 25% of the dimensional tolerance of the part, and requires a very tight contact surface. It is mainly used in machines, tools, surfaces that cooperate with rolling bearings, taper pin holes, and contact surfaces with relatively high speeds of movement such as sliding bearing mating surfaces, gear tooth working surfaces, etc.

The third type, it is mainly used for general machinery, which requires the wear limit of mechanical parts to not exceed 50% of the dimensional tolerance value, and there is no relative moving parts contact surfaces, such as box covers and sleeves, which require tight surfaces, keys and keyways' working surface; contact surface with low relative movement speed, such as bracket hole, bushing, working surface with wheel shaft hole, reducer, etc.

we make statistical analysis on various table values in the mechanical design manual, convert the old national standard of surface roughness (GB 1031-68) into the new national standard (GB 1031-83) issued by ISO in 1983, and adopt the preferred evaluation parameter, namely the arithmetic mean deviation value of contour RA = (1) / (L) ∫ l0 ︱ y DX. Using the first series of numerical values preferred by RA, the relationship between surface roughness Ra and dimensional tolerance it is derived as follows

In the design of the machine, the surface roughness should be selected according to the surface roughness of the machine.

It should be noted in the table, Ra uses the first series of values, and the limit value of the old national standard Ra is the second series of values. When converting, you will encounter the problem of upper and lower values. We use the upper value in the table, because it is conducive to improving product quality, and the individual value is lower. The content and form of the table corresponding to the tolerance level and surface roughness of the old national standard are more complicated. For the same tolerance level and the same size, the same basic size is segmented. The surface roughness values of the hole and the shaft are different, and the values of different types of cooperation are also different. This is due to the fact that the old tolerance and tolerance standards (GB159-59) are related to the above factors. The current new national standard tolerance and coordination (GB1800-79) has the same standard tolerance value for each basic dimension in the same tolerance level and the same size segment, which greatly simplifies the correspondence table between the tolerance level and the surface roughness. More scientific and reasonable.

In the design work, all things must ultimately be based on reality when you are making choice of surface roughness and comprehensively measure the surface function and process economics of the parts in order to make a reasonable choice. The tolerance levels and surface roughness values given in the table can be used for reference for design.

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