CNC Technology – Page 21 – CNC Machining & Turning, Milling, Metal parts

CNC machining of stainless steel

In order to increase the cross-sectional area of the hole cutter as much as possible, it is generally enough to leave 1-2mm cutting allowance in the radial direction. The cutter bar should be circular, the main cutting edge of the cutter is in the longitudinal section through the cutter bar axis, and the shorter the cutter bar length is, the better,

When grinding the arc flank of the inner hole cutter, great attention is paid to it. It is a place with high technical content in inner hole machining, and it is also the main aspect to solve the chatter pattern,

In fact, the above is basically about the upper level, and the most important thing is the tool grinding. If the tool grinding is not good, it is difficult to process qualified parts,

a. First of all, the materials of cutting tools are different for different parts. For stainless steel, red copper and brittle materials, tungsten cobalt type cutting tools should be used. For plastic materials such as carbon steel, tungsten cobalt titanium type cutting tools should be used. For materials with high hardness, YW series cutting tools should be used, that is, tungsten cobalt titanium tantalum niobium type cutting tools,

b. The most important point is that the grindability of grinding wheel and grinding wheel is better, and the rigidity of grinding wheel machine is better. It is better to have two grinding wheels, one with brown corundum wheel (grinding cemented carbide) and the other with white corundum wheel (grinding high speed steel). If the above two kinds of grinding wheels are installed on one grinding machine at the same time, it is difficult to grind the standard cutting tools.

Generally, the machining of stainless steel parts is to first process the outer circle and then the inner hole, because the deformation of the outer circle is smaller than that of the inner hole,
Stainless steel parts processing is a very practical work, it needs a long time of actual operation to verify your idea

The density of aluminum profile is only 2.7g/cm3, which is about 1 / 3 of that of steel, copper or brass (7.83g/cm3 and 8.93g/cm3 respectively). Aluminum exhibits excellent corrosion resistance in most environmental conditions, including in air, water (or brine), petrochemical and many chemical systems.

conductivity

Aluminum profile is often used because of its excellent conductivity. On the basis of equal weight, the conductivity of aluminum is nearly twice that of copper.

Thermal conductivity

The thermal conductivity of aluminum alloy is about 50-60% of that of copper, which is beneficial to the manufacture of heat exchangers, evaporators, heating appliances, cooking utensils, as well as the cylinder head and radiator of automobiles.

Non ferromagnetism

Aluminum profile is non ferromagnetic, which is an important characteristic for electrical industry and electronic industry. Aluminum profiles are not self ignitable, which is important for applications involving handling or contacting flammable and explosive materials.

Machinability

The machinability of aluminum profile is excellent. In all kinds of wrought and cast aluminum alloys, as well as in all kinds of states of these alloys, the machining characteristics change greatly, which requires special machine tools or technology.

Formability

Specific tensile strength, yield strength, ductility and corresponding work hardening rate control the variation of allowable deformation.

Oil leakage in CNC machining

The oil change does not meet the requirements.

It often causes oil leakage in CNC machining center. There are three main problems in oil change. First, for the parts with high viscosity lubricating oil, it will affect the sealing performance of the corresponding box, shaft hole and other parts, and sometimes greatly reduce the sealing performance of these parts. Second, if the oil tank is not cleaned when changing oil, the dirt in the oil tank may enter into the lubrication system, block the oil circuit and wear the seals, causing oil leakage. Third, when changing the oil, the amount of oil is too much, especially in the parts with rotating parts, because of the stirring effect of rotating parts, it is more prone to oil spill.

Improper selection and adjustment of lubrication system parts cause oil leakage.

For example, when CNC machining and maintenance personnel select the oil pump with too high pressure or too large oil output, or when adjusting the system pressure, the pressure of relief valve, safety valve and pressure reducing valve is too high, and the flow of CNC machine tool lubrication system is too large, which does not match with the oil return system and sealing system, it will cause oil leakage.

In fact, it is not just the above points that cause the oil leakage of CNC machining center. If we encounter similar problems in operation, we must do a good job in checking and find out the reasons in time to avoid unnecessary losses. After the purchase of the machining center, do a comprehensive inspection to see if there are casting defects or parts damage, if any, contact the manufacturer in time. When operators use CNC machining center to process workpieces, they should also pay attention to the following points:

(1) For the first trial cutting process of CNC machining, the single-stage operation mode should be adopted.

(2) When the CNC milling machine starts to run automatically, the fast rate and feed rate s are in the lowest gear, and then the efficiency is improved after cutting into the workpiece.

(3) In the operation of NC milling machine, we need to pay attention to the coordinate display of CNC system.

(4) It is forbidden to touch tools and chips of CNC milling machine by hand. The chip must be cleaned with a brush.

Precision CNC machining

When the precision of precision machining is nanometer or even atomic unit (the atomic lattice distance is 0.1-0.2 nanometer), the cutting method can not adapt to it. It needs the help of special machining method, that is, the application of chemical energy, electrochemical energy, thermal energy or electric energy, to make these energies exceed the bonding energy between atoms, so as to remove the adhesion, bonding or bonding between some atoms on the workpiece surface In order to achieve the goal of ultra precision machining. This kind of processing includes mechanical chemical polishing, ion sputtering and ion implantation, electron beam exposure, laser beam processing, metal evaporation and molecular beam epitaxy. The characteristic of these methods is that the amount of material removed or added to the surface layer can be controlled very finely. However, to obtain ultra precision machining accuracy, it still depends on precision machining equipment and precise control system, and uses ultra precision mask as intermediary. For example, in VLSI plate making, electron beam is used to expose the photoresist (see lithography) on the mask to make the atoms of the photoresist polymerize (or decompose) directly under electron impact, and then the polymerized or unpolymerized parts are dissolved by the developer to make the mask. Electron beam exposure plate making requires ultra precision processing equipment with positioning accuracy of ± 0.01 micron.

What are the characteristics and functions of the system? It is an automatic machine tool controlled by program. The control system can logically process the program with control code or other symbol instructions, decode it by computer, so that the machine tool can execute the specified action, and the blank can be processed into semi-finished parts by cutting tools.

The traditional mechanical lathe processing is manual operation, ordinary machine operation, lathe processing with hand shaking mechanical tool cutting metal, rely on the eyes with calipers and other tools to measure the accuracy of the product. Modern industry has long used computer-controlled machine tools for operation, which can automatically process any product and parts according to the program compiled by technicians in advance.

The information is stored in the information carrier (such as disk, perforated tape, magnetic tape, etc.) and then read in by the CNC system on the machine tool (or directly input through the keyboard of the CNC system, or input through the communication mode). By decoding the information, the lathe can process the action and parts, and the modern CNC machine tool can be widely used It is a typical product of mechatronics and the technical foundation of new generation production technology and computer integrated manufacturing system.

The development trend of modern CNC lathe precision machining is high speed, high precision, high reliability, multi-function, compound, intelligent and open structure. The main development trend is to develop intelligent full-function universal numerical control device with open structure in both software and hardware. Numerical control technology is the basis of machining automation and the core technology of numerical control machine tools. Its level is related to the national strategic position and the level of reflecting the national comprehensive strength. It develops with the development of information technology, microelectronics technology, automation technology and detection technology. CNC machining is a kind of numerical control machine tool with tool magazine, which can automatically change the tool and process the workpiece in a certain range.

Independent performance of CNC machining

There is a certain difference between the two ways to make precision hardware processing parts. What’s more, they use different steel to make different workpieces. CNC lathe is composed of bed, headstock, turret feed system, cooling and lubrication system and CNC system. Different from ordinary lathe, CNC lathe feed system is qualitatively different from ordinary lathe

It does not have the traditional tool box, slide box and change gear frame, but directly uses servo motor or stepper motor to drive slide and tool through ball screw to realize feed movement. The CNC system consists of CNC unit, input and output module and operation panel.

Processing method of precision hardware parts:

Solid solution strengthening: because the solute atoms enter into the gap or node of the solvent lattice, the lattice will be distorted and the hardness and strength of the solid solution will be increased. This phenomenon is called solid solution strengthening.
Compound: a new crystal solid structure with metallic properties is formed by the combination of alloy components. Mechanical mixture: an alloy consisting of two crystal structures. Although it has two kinds of crystals, it is a component with independent mechanical properties.
Ferrite: interstitial solid solution of carbon in a-Fe (body centered cubic iron).
Austenite: interstitial solid solution of carbon in g-fe
Cementite: stable compound (Fe3C) formed by carbon and iron.
Pearlite: a mechanical mixture of ferrite and cementite (F + Fe3C contains 0.8% carbon)
Ledeburite: a mechanical mixture of cementite and austenite (containing 4.3% carbon) Metal heat treatment is one of the important processes in mechanical manufacturing. Compared with other processes, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but endows or improves the performance of the workpiece by changing the microstructure inside the workpiece or the chemical composition on the surface of the workpiece.

Computer gong processing method

Using precision level instrument and other testing tools, the main bed level of the computer gong processing machine tool is precisely adjusted by adjusting the pad iron, so that the geometric accuracy of the machine tool can reach the allowable tolerance range;
For the automatic tool changing device, adjust the position of tool magazine, manipulator, stroke parameters, etc., and then check the action with instructions to ensure accuracy;
For the machine tool with APC automatic exchange table, after adjusting the relative position, carry out automatic exchange;
After adjusting the machine tool,

Carefully check whether the parameter setting values in the numerical control system and the programmable controller conform to the data specified in the random index, and then test the main operation functions, safety measures, and the execution of common instructions.

Check the normal operation of the machine tool and accessories. CNC computer gong NC machining is the basis of modern manufacturing technology, the invention of electricity for the manufacturing industry, has epoch-making significance and far-reaching influence. When clamping the workpiece, according to the way of clamping and placing in the programming operation instruction, it should be considered to avoid the processing parts and the situation that the cutter head may encounter the fixture in the processing.

After the workpiece is placed on the pad iron, it is necessary to pull the table for the workpiece datum according to the drawing requirements. For the workpiece that has been ground on six sides, it is necessary to check whether its verticality is qualified.

The nut must be tightened after the work-piece is pulled to prevent the work-piece from shifting during the processing due to the loose clamping; pull the work-piece again to ensure that the error does not exceed the tolerance after the clamping.

3、 Number of workpieces touched

For the clamped workpiece, the contact head can be used to set the processing reference zero position. The contact head can be used in photoelectric type and mechanical type. There are two kinds of methods: middle collision number and unilateral collision number

Photoelectric static, mechanical speed 450 ~ 600rpm. Manually move the x-axis of the worktable according to the collision number to make the collision number head touch one side of the workpiece. When the collision number head just touches the workpiece and the red light is on, set the relative coordinate value of this point to zero. Then manually move the x-axis of the worktable to make the collision number head touch the other side of the workpiece. When the collision number head just touches the workpiece, record the relative coordinate at this time.

According to the relative value minus the diameter of the collision head (i.e. the length of the workpiece), check whether the length of the workpiece meets the requirements of the drawing.

Introduction of CNC machining center

Machining center is often divided into vertical machining center and horizontal machining center according to the state of the spindle in the space. The vertical machining center whose spindle is vertical in the space is called vertical machining center, and the horizontal machining center whose spindle is horizontal in the space is called horizontal machining center. Spindle can be vertical and horizontal conversion, known as vertical and horizontal machining center or five machining center, also known as composite machining center. According to the number of machining center columns, there are single column type and double column type (gantry type).

According to the coordinate number of machining center movement and the coordinate number of simultaneous control, there are three axis two linkage, three axis three linkage, four axis three linkage, five axis four linkage, six axis five linkage, etc. Three axis and four axis refers to the number of motion coordinates of the machining center. Linkage refers to the number of coordinates that the control system can control at the same time, so as to realize the position and speed control of the tool relative to the workpiece.

The technology of high-speed CNC machining is the premise to ensure the production of high-quality parts.

On lathe, the shape and size of the blank can be changed by the rotary motion of the workpiece and the linear or curvilinear motion of the cutter, and it can be processed to meet the requirements of the drawing.

Ordinary machine tools are more and more difficult to meet the needs of processing precision parts. At the same time, due to the improvement of production level, the price of CNC machine tools is falling from time to time. CNC precision parts processing mainly includes ultra precision turning, mirror grinding and grinding.

The primary premise of CNC precision parts processing is the accuracy of process datum. Datum on mechanical drawings are represented by capital letters a, B, C, D, etc. with a specific reference symbol with circle. When the reference symbol is aligned with the surface and its extension line or the dimension limit of the surface, the surface is taken as the datum. When the datum mark is aligned with the dimension line, it means that the solid center line of the dimension is taken as the datum. It is a more general statement that the process is accurate.

Assembly benchmark refers to the precision used to determine the position of parts in components or products during assembly. Measurement datum refers to the specification for the size and position of the machined surface to be measured during the inspection of parts. Positioning datum refers to the datum used for positioning the workpiece in the machine tool or fixture during machining.

CNC machining center

The biggest difference between CNC milling machine and machining center is that the machining center has the ability to exchange machining tools automatically. By installing different tools on the tool magazine, the machining tools on the spindle can be changed through the automatic tool changing device in one clamping, and a variety of machining functions can be realized.

CNC machining center is composed of mechanical equipment and CNC system, which is suitable for processing complex parts. CNC machining center is one of the most widely used CNC machine tools with the highest output in the world. Its comprehensive processing ability is strong, the workpiece can complete more processing content after clamping at one time, and the processing accuracy is high. For the batch workpiece with medium processing difficulty, its efficiency is 5-10 times higher than that of ordinary equipment, especially it can complete the processing that many ordinary equipment can’t complete, and it is more suitable for single piece processing with complex shape and high precision requirements or small and medium batch multi variety production. It concentrates the functions of milling, boring, drilling, tapping and cutting threads on one equipment, so that it has a variety of technological means. Machining centers are classified into horizontal and vertical machining centers according to the spatial position of the spindle. According to the classification of process uses: boring and milling machining center, composite machining center. According to the special functions, there are single table, double table and multi table machining centers. Machining center of single axle, double axle, three axle and changeable headstock.

Computer gong processing high precision parts

The concept, significance and characteristics of high precision parts manufacturing high precision parts manufacturing takes high precision mechanical parts as processing objects. Based on the systematic and integrated theory and technology, according to the structure and requirements of the workpiece, the organic combination and optimization of feeding, processing, detection and handling are realized, and the production of parts is completed under the precise processing conditions.
Application field of high precision parts and components high precision parts and components are used in all walks of life testing equipment – scientific instruments. In China, they are mainly used in the instrument and instrument industry of scientific instruments.
High precision machining has the advantages of high precision, low energy consumption, flexible production and high efficiency. Reducing the size of the whole manufacturing system and precision parts can not only save energy, but also save manufacturing space and resources, which is in line with the production mode of energy saving and environmental protection. It is one of the development directions of green manufacturing.
Compared with ordinary machinery manufacturing, precision machinery manufacturing has high technology content (design and production), excellent processing equipment, high added value, and small batch sales.
Analysis of foreign development situation high precision machinery manufacturing technology is known as one of the key technologies in the 20th century. It is the key development direction in the 21st century and has been highly valued by all countries in the world. Japan, the European Union, South Korea, the United States and other developed countries have invested a lot of human, material and financial resources to develop their own high-precision mechanical parts research and development and technology.
China’s high-precision machinery manufacturing technology was gradually developed in the late 1980s and early 1990s. It is a rapidly developing industry in China today. High precision machinery manufacturing products are widely used in national defense, medical, aerospace, electronics and other military and civil fields.

The beginning and end of CNC machining aluminum

China’s CNC industry is developing rapidly. The average annual growth rates of domestic CNC machine tool production and consumption from 1998 to 2004 are 39.3% and 34.9% respectively. Nevertheless, the development momentum of imported machine tools is still strong. Since 2002, China has become the largest consumer of machine tools and the largest importer of machine tools in the world for three consecutive years. In 2004, the consumption of machine tools in China reached as high as US $9.46 billion. The gap between domestic CNC machine tool manufacturers and foreign countries in the research and development of high-end and large CNC machine tools is more obvious, with more than 70% of this Class a equipment and the vast majority of functional components are dependent on imports.

It can be seen that the domestic CNC machine tools, especially the high-end CNC machine tools, are still lack of market competitiveness. The main reasons are that the research and development depth of domestic CNC machine tools is not enough, the manufacturing level is still backward, the service consciousness and ability are lack, the CNC system production and application are not promoted effectively, and the CNC talents are lack. We should see clearly the situation, fully understand the shortcomings of domestic CNC machine tools, strive to develop advanced technology, increase technical innovation and training services, so as to shorten the gap with developed countries.

Recently, with China’s economic development, it has also attracted the attention of some major machine tool manufacturers in the world. In 2000, Mazak, the largest machine tool manufacturer, set up a joint venture factory for CNC machine tools in Yinchuan, China. It is said that the manufacturing level is quite high. It is known as an intelligent and network chemical factory, which is synchronized with the world.

At present, the state has formulated some policies to encourage people to use domestic CNC machine tools, and manufacturers are also trying to catch up. CNC aluminum processing is the most popular machine tool in China. In a purchase plan, 80% of the machine tools are imported, so domestic machine tools can not meet the needs. This trend will not change in the next five years. However, as far as the current domestic needs are concerned, China’s CNC machine tools can meet the orders of medium and low-grade products. We should see clearly the situation, fully understand the shortcomings of domestic CNC machine tools, strive to develop advanced technology, increase technical innovation and training services, so as to shorten the gap with developed countries.

According to the relevant report of the United Nations, a new round of economic recession in Europe and North America has dragged down the recovery of the global manufacturing industry. In the third quarter of 2012, the global manufacturing industry grew by 2.2% year on year, and its growth rate was the lowest since 2009. In particular, CNC aluminum processing and the economic growth of developing countries are slowing down. Developed countries as a whole have experienced the first decline in industrial output since 2009. Among them, Germany’s industrial output dropped by 1.7%, Italy’s by 6.2%, France’s by 1.9%, Britain’s by 0.9% and Japan’s by 4.6%.

While the growth of manufacturing industry in the world’s major economic systems has slowed down or declined one after another, the development of related industries has maintained a high growth rate. According to relevant data, the scale of the international machine tool market has more than doubled in the past 20 years, reaching about US $86 billion in 2011. Since the turn of the century, the consumption of machine tools has increased by nearly 10% annually (in US dollars).

High precision machining of CNC parts

For high-precision parts, the processing is very strict. The processing procedures include feed and output. There are specific requirements for the size and accuracy, such as 1 mm plus or minus micrometers. If the size is too wrong, it will become a scrap. At this time, it is equivalent to reprocessing, which is time-consuming and laborious. Sometimes, the whole processing material will be scrapped, resulting in an increase in cost. At the same time, the parts are definitely unusable.
For the processing of high-precision parts, the main requirements are the size, such as the diameter of the cylinder, there are strict requirements, positive and negative errors within the specified range are qualified parts, otherwise they are unqualified parts; There are also specific and strict requirements for length, width and height, as well as positive and negative errors. For example, if the diameter of an embedded cylinder (take the simplest basic parts as an example) is too large and exceeds the allowable error range, it will cause the situation that it cannot be inserted. If the actual diameter is too small and exceeds the lower limit of the allowable negative error, it will cause the problem that it is too loose and not firm. These are all unqualified products, or the length of the cylinder is too long or too short, which is beyond the allowable range of error. They are all unqualified products, and they have to be scrapped or reprocessed, which will inevitably lead to the increase of cost.
The requirement of high-precision parts processing is actually the most important dimension problem. It must be processed in strict accordance with the additional drawing. The actual size will not be exactly the same as the theoretical size of the drawing, but as long as the processing size is within the allowable error range, it is all qualified parts. Therefore, the requirement of precision parts processing is to process in strict accordance with the theoretical size Work.
The second is the advanced precision parts processing equipment and testing equipment. The advanced processing equipment makes the processing of precision parts simpler, higher precision and better effect. The detection device can detect the parts that do not meet the requirements, so that all the products sent to customers can really meet the requirements.