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Heat treatment of plastic mould

The main reason for the failure of plastic mold is due to improper heat treatment process, such as heating temperature, holding time, cooling speed and so on. Plastic mold in the process of processing, cracks or deformation, surface oxidation and decarburization phenomenon, is mainly because the mold failure.

First of all, on the impact of oxidation and decarburization, mainly because the mold quenching is stopped at high temperature, but can not be strictly controlled. In addition, after decarburization on the surface of the die, quenching cracks are caused due to the difference of microstructure between the inner and outer layers and the larger structure stress during cooling.

The second is about the rate of heating. Because the die steel contains more carbon and alloy elements and poor thermal conductivity, the heating speed should not be too fast and should be stopped slowly to avoid deformation and cracking of the die. In order to avoid oxidation and decarburization during heating and quenching in air furnace, the heating speed should not be too fast and the diathermy should be slow.

The above will not produce large thermal stress, relatively safe. If the heating speed of the mold is fast and the diathermy is fast, the thermal stress inside and outside the mold will be very large. If the control is not good, such as deformation or crack, it is very easy to occur, in the prevention, it is necessary to use preheating or slow down the heating rate.

Due to the large size of the worktable and die, it must be able to meet the requirements of large-scale worktable and die, In addition, small diameter end mills with large elongation are often used to process the mold cavity, so chatter is easy to occur in the processing process.

In order to ensure the machining accuracy and surface quality of parts, the high-speed universal milling machine manufactured by mould must have high dynamic and static stiffness to improve the positioning accuracy, tracking accuracy and anti vibration ability of the machine tool.

High speed and high-power high-speed machining is the development direction, high-speed milling has shown great advantages in mold processing. In order to adapt to the processing of the mold cavity surface, the radius of the tool should be less than the minimum radius of the cavity surface, so as to avoid “interference” between the tool and the workpiece. Because of the small diameter of the tool, the spindle speed is required to be very high. The main shaft speed of foreign high-speed machine tools has reached 40000-100000 R / min, and the rapid feed speed can reach 30000-60000 min. The rough and finish machining of the cavity and other parts of the mold parts is often completed in one-time clamping of the workpiece, so the spindle power should be high. The spindle power of the medium-sized mold milling machine and machining center is usually 10-40kw, some even higher.

The die cavity is composed of complex six curved surfaces and grooves, and many dies have deep cavity. In order to achieve high precision, high speed and high stability machining of 3D surface, the machine tool needs multi axis linkage, and has good comprehensive cutting ability of deep hole cavity. Five axis linkage machining center can be used, in addition to the linear motion of three coordinates, there are also two rotation coordinates of feed motion. The milling head or worktable can realize continuous rotary feed by multi axis linkage, so it is suitable for machining mold parts with complex cavity surface. It can be said that compound machining is one of the development directions of mold processing.

Processing center is written language, English Name: CNC machining center; computer gong is a common saying, more in Hong Kong, Taiwan and Guangdong. In this area, milling machines are called gongs when they are in the machining center, so milling machines are also called gongs, and computer gongs are also derived from this. Computer gongs, as the name implies, are gongs controlled by computers, so they are also called CNC milling machines. In fact, they are upgraded from CNC milling machines. The original principle is the same. The difference is that the machining centers use good materials with high precision, high speed and load The traditional CNC milling machine is half cover type, and most of the machining center has been changed to full cover type, which is more safe for processing and can effectively prevent the overflow of iron chips and the splashing of chips. Computer gong is an automatic machine tool equipped with program control system. The control system can process and decode the program with control code or other symbol instructions logically, so that the machine tool can move and process parts. Also known as CNC machining mold or CNC machine tools.

The computer gong can be divided into two parts, the body part and the system part.

Fuselage part:

1) Casting, which is the most important part of computer gongs, directly affects the accuracy, stability, wear resistance and the life of machine tools. After the casting is finished, it is not immediately used in production. A good casting is that it is subjected to wind and rain, sunlight exposure, natural weathering, and some of them are soaked in sea water. After the casting does not change, the machine tool is not easy to change and can maintain the stability and accuracy of the machine tool for a long time.

2) Spindle, the spindle is used to directly face the workpiece. It is driven by the motor to rotate at a high speed. If the tool holder is installed on the spindle, the workpiece can be cut to meet various production needs. The quality of the spindle will also directly affect the machining accuracy. If the internal bearing is worn, it will easily cause the spindle to swing, and the accuracy of the processed things will naturally have a deviation of several wires 。 At present, the speed of the spindle is generally around 8000 rpm, and the high-speed machine can achieve more than 20000 revolutions. Each machine has only one spindle.

3) Screw rod is also a machine

Accuracy of CNC cutting technology

The introduction of CNC cutting technology precision 1. Multiple cutting technology multi cutting technology is the fundamental means to improve the machining accuracy and surface quality of low-speed WEDM. It is a scientific integration of design and manufacturing technology, numerical control technology, intelligent technology, pulse power technology, precision transmission and control technology. Generally, through one-time cutting forming, secondary cutting to improve the accuracy, more than three times to improve the surface quality. In order to achieve high-quality surface, the number of times of cutting is as high as 7-9 times, but now it only needs 3-4 times. 2. The corner processing technology is constantly optimized and improved. Because of the lag of the electrode wire when cutting the corner, the corner will collapse. In order to improve the accuracy of corner cutting, researchers have adopted more dynamic corner processing strategies. Such as: change the wire path; change the processing speed (sheet); automatic adjustment of water pressure; control of processing energy. By using the integrated corner control strategy, the corner shape error can be reduced by 70% and the matching accuracy of 5 μ M can be achieved at one time. 3. High speed CNC adopts the technology of improving flatness. High precision finishing circuit is the technology of improving flatness, which is considered to be of great significance to thick workpiece processing. 4. The structure of the machine tool is more precise. In order to ensure high-precision machining, many technical measures are adopted to improve the accuracy of the host machine: ① control the temperature. Using water temperature cooling device, the temperature inside the machine tool is the same as the water temperature, and the thermal deformation of the machine tool is reduced. ② Linear motor is adopted. High response, precision positioning can achieve 0.1 μ m equivalent control, feed no vibration, no noise, improve discharge frequency, maintain stable discharge, twice cut ry5 μ M. ③ The thermal inertia of ceramic and polymer artificial granite is 25 times larger than that of cast iron, which reduces the influence of temperature change on cutting accuracy. ④ Fixed worktable and column moving structure are adopted to improve the bearing capacity of worktable, which is not affected by immersion processing and workpiece weight change. ⑤ Immersion machining is used to reduce the thermal deformation of the workpiece. ⑥ Motor servo, closed loop wire tension control. ⑦ High precision tool setting: using voltage modulation tool setting power supply. The tool setting accuracy can reach ± 0.005mm without damaging the workpiece, whether dry or wet. 5. In order to carry out the micro precision machining of small fillet, narrow slot, narrow slot and micro parts, high-speed CNC wire cutting technology is researched by many manufacturers. At present, the main manufacturing enterprises of EDM in the world can use 0.02-0.03mm electrode wire for cutting. Precision surface grinder is a common machine tool for machining. There are high requirements for the motion stability, commutation accuracy and commutation frequency. At present, the surface grinding machine is developing towards large-scale and high-speed, and the reciprocating speed of some surface grinding machines has reached 40% n []. Large high-speed surface grinder has a large inertia. When it changes direction, it will lead to a sharp rise in back pressure, resulting in reversing impact, which will have a disastrous impact on the machine tool. Therefore, the stability of reversing has become an important factor restricting the improvement of the working speed and machining accuracy of the grinder. The reversing mode and reversing control parameters in the system play a decisive role in reversing impact. The surface grinder adopts hydraulic transmission. It is urgent to design a new hydraulic reversing system. In this paper, the reversing impact of grinder is discussed from the perspective of commutation method and control strategy. 1. The mechanism of reversing impact is that in its hydraulic system, when the hydraulic transmission surface grinder changes direction. The valve port of the directional valve is closed instantaneously, and the oil circuit is suddenly disconnected, which makes the oil in the oil return chamber unable to drain. The larger m and V, we can see. The greater the kinetic energy, the greater the reversing impact. For the surface grinder with large inertia and high speed, its reversing impact is huge, which not only affects the machining accuracy of the machine tool, but also hinders the normal operation and service life. 1. Product analysis through product analysis should obtain certain composition information and some specific processing requirements. 2. Graphic design graphic design the graphic design should be based on the detailed analysis of the product, determine the type of graphics by analyzing the processing requirements, and draw through the graphics software. 3. Process planning is based on the analysis of the appearance and processing requirements of the workpiece products in the early stage, so as to reasonably establish each processing step from the overall processing situation. 4. In fact, the process of path generation is to realize the process planning through software, and optimize the tool path by setting parameters. 5. After the path simulation path is generated, we generally have no intuitive sense of its final performance on the machine tool. Here we can check the possible problems through path simulation, thus reducing the actual processing scrap rate. The general inspection focuses on the effect of workpiece appearance, whether it is overcut or undercut, and whether the process planning of the path is reasonable. 6. Path output path output is a necessary step for software design and programming to realize on the machine tool. Through the path output, the relationship between the two can be established by the intermediate reference. If you have a professional background in CNC, it can also be understood as the post-processing of tool path.

New energy development

In China, the amount of conventional energy resources is only 60% of the world average level. In order to meet the growing energy demand, it is necessary to accelerate the development and utilization of new energy. At present, the 9% share of new energy in the energy structure is relatively low compared with the developed countries in the world, and there is still a lot of room for development.

Although the latest statistics of 2008 have not been released yet, the proportion of China’s new energy production in the overall energy structure will exceed 9% based on the data from various aspects, especially the growth rate of China’s new energy production and consumption in the past 10 years.

2008 is an extraordinary year for China’s energy work. Affected by the changes of the world macro-economic situation and natural disasters, the supply and demand of energy has experienced a roller coaster like operation from “tight supply” at the beginning of the year to “demand slowing down” at the end of the year. Authoritative experts pointed out that the easing of the tense situation of energy supply and demand does not mean that China’s energy demand has dropped significantly, nor does it mean that China’s energy supply can achieve absolute self-sufficiency. Therefore, the task of developing new energy is still urgent. Compared with the level of developed countries, 9% of new energy in China is still at a relatively low level.

In 2007, China produced 2.35 billion tons of standard coal, of which coal accounted for 76.6%, oil accounted for 11.3%, natural gas accounted for 3.9%, and other unconventional energy accounted for 8.2%; while the total energy consumption in this year was 2.66 billion tons of standard coal, including 69.5% of coal, 19.7% of oil, 3.5% of natural gas and 7.3% of unconventional energy. In terms of total amount, there is still a gap in energy consumption in China. From the structural analysis, in China’s energy structure, the dominant position of coal has not changed. Although the development speed of new energy is fast, its proportion is still too small.

China has a long way to go in developing new energy, whether in terms of structure or total demand. First of all, the development of new energy is an effective guarantee to maintain rapid economic growth. From 2003 to 2008, the average annual growth rate of China’s GDP is close to 10%. In order to maintain the stable and sustainable development of economy, we must have strong energy guarantee. Throughout China’s resource reserves, the total amount is large and the per capita share is small, so it is difficult to form a sustainable support only relying on traditional energy.

Secondly, the development of new energy is an effective way to alleviate environmental pressure. Compared with traditional energy, new energy has the characteristics of less pollution and high efficiency. Vigorously developing new energy will help to reduce economic losses caused by environmental damage and achieve the goals set in the eleventh five year plan.

Third, the development of new energy is an effective means to ensure the safe supply of energy. Energy security is an important part of a country’s economic security and an important barrier to ensure the independent and healthy development of a country’s economy. At present, China has to import a part of its oil every year, and its dependence on foreign countries is relatively high. To ensure the safe supply of energy, we must adhere to the diversified strategy, and vigorously developing new energy is the concrete embodiment of this strategy.

Fourth, the development of new energy is a powerful weapon to solve the dilemma of unbalanced regional development in China. There is a big gap among regions in China, which is unfavorable to the sustainable development of economy and society. The development of new energy in the vast western regions and remote rural areas not only improves people’s livelihood, but also promotes economic development.

Fifth, it is feasible to develop new energy. With the improvement of technical level, the cost of new energy development has dropped sharply, and the cost of some new energy has been close to or even lower than that of conventional energy.

The reporter interviewed the national energy administration and relevant people in the industry. The unanimous judgment is that the development trend of China’s new energy will, on the whole, maintain a sustained and rapid development momentum and have a bright future.

From the perspective of policy environment, the recently concluded energy work conference has determined the work direction with the theme of structural transformation, which indicates the arrival of a new era of new energy industry. Both the promulgation of new energy and renewable energy planning and the implementation of the new energy law in the future have brought unprecedented opportunities for the development of new energy.

From the perspective of investment, international capital is optimistic. Even in the context of the international financial crisis, investment in the field of new energy will still become the hot spot of capital pursuit. Under the influence of policy guidance, domestic capital will follow suit one after another. The continuous rise of new energy sector in A-share market is sufficient evidence.

From the perspective of the internal structure of new energy, the priority development direction in the future is still wind energy, solar energy and nuclear energy with high technology maturity and economic feasibility. Economic feasibility is an important bottleneck restricting the development of new energy, which will be solved gradually with the improvement of China’s technical level.

High speed computer gong processing feeder

The basic knowledge of high speed computer gong processing feeding mechanism

Auxiliary device computer gong processing index control feed machine some necessary supporting parts, to ensure the operation of CNC feeder, such as cooling, chip removal, lubrication, lighting, monitoring, etc. It includes hydraulic and pneumatic devices, chip removal device, exchange table, CNC turntable and CNC dividing head, as well as cutting tools and monitoring and detecting devices.
Driving device high speed Gong machining is the driving part of the executive mechanism of NC feeding machine, including spindle drive unit, feed unit, spindle motor and feed motor. Under the control of the electric servo system or hydraulic control of the spindle. When several feed linkage, positioning, straight line, plane curve and space curve processing can be completed.
The main machine is the main body of CNC feeding machine, including body, column, spindle, feed mechanism and other mechanical parts. It is a mechanical part used to complete various cutting processes. Programming and other auxiliary equipment: it can be used to program and store parts outside the machine.
High speed Gong machining of CNC device is the core of NC feeding machine, including hardware (printed circuit board, CRT display, key box, paper tape reader, etc.) and corresponding software, which are used to input digital part program, complete input information storage, data transformation, interpolation calculation and realize various control functions. Basic requirements of large CNC machining system
In the process of large CNC machining, the worktable may require forward or reverse operation at any time according to the shape of machining track. CNC lathe machining center prompts you to consider the conversion of electrical energy and mechanical energy between starting and braking during forward and reverse operation, so as to realize rapid braking.
In order to adapt to different processing conditions, servo has a wide range of speed regulation and excellent speed control characteristics.
High rigidity and high speed stability servo for large CNC machining should keep the feed rate constant under different load conditions or when the cutting conditions change, which requires the servo to have excellent static and dynamic load characteristics.

In order to ensure the contour cutting shape accuracy and low surface roughness of the machined surface, the servo should have good fast response characteristics and no overshoot.

High precision in order to meet the machining accuracy, it is necessary to ensure the positioning accuracy and feed accuracy of the machine tool, that is to say, the servo should have high static resolution, and the dynamic characteristics should be at least a first-order error free system.
Large CNC machining low speed and high torque, the characteristics of machine tool processing is cutting at low speed, the feed drive should ensure rated torque output at low speed, that is to say, servo should have constant torque output.

Function debugging of high speed computer gong machine tool accuracy

High speed computer gongs use precision level instrument and other detection tools, mainly by adjusting the pad iron way to fine adjust the level of the main bed of the machine tool, so that the geometric accuracy of the machine tool can reach the allowable tolerance range;
For the automatic tool change device, adjust the position of the tool magazine, manipulator, travel parameters, etc., and then check the action with the command, which is required to be accurate;
For the machine tool with APC automatic exchange table, after adjusting the relative position, carry out automatic load exchange;
After the adjustment of 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, execution of common instructions, etc.
Mold processing to check the machine tool auxiliary function and accessories normal work. It is usually composed of CNC system, main drive system, feed servo system, cooling smooth system and so on. 1. The spindle box contains the spindle box and spindle drive system, which is used to clamp and rotate the cutter. The spindle speed scale and output torque have a direct impact on the machining. 2. The feed servo system is composed of feed motor and feed actuator. According to the feed rate set by the program, the relative motion between the tool and the workpiece is completed, including linear feed motion and rotary motion. 3. Control system CNC milling machine motion control in the middle of the implementation of NC machining program control machine tools for processing. 4. Auxiliary equipment such as hydraulic, pneumatic, smooth, cooling system and chip removal, protection and other equipment. 5. The base parts of high-speed computer gong machine tools usually refer to the base, column, beam, etc., which are the foundation and structure of the whole machine tool. Die making technology of extrusion die for high speed CNC machining of aluminum profile 1. Due to the bad working conditions of aluminum alloy extrusion tools and dies, high temperature, high pressure and high friction are required in high-speed CNC machining. Therefore, high-strength heat-resistant alloy steel is required. The melting, casting, forging, heat treatment, electrical machining, mechanical processing and surface treatment of these steels are very complex, which brings about the development of die and mold A series of difficulties. 2. In order to improve the service life of tools and moulds and ensure the surface quality of products, it is required that the roughness of the working belt of the die cavity should reach 0.8-0.4 μ m, and the roughness of the die plane should be less than 1.6 μ M. therefore, special polishing process and polishing equipment should be adopted when making the mold. 3. Due to the development of extrusion products in the direction of high precision and sharp, the wall thickness requirement of some profiles and pipes is reduced to about 0.5mm, and the tolerance of extruded products is required to reach ± 0.05mm. In order to extrude such ultra-high precision products, the manufacturing accuracy of dies is required to reach 0.01mm

Wheeled Construction Machinery

The fuel consumption of Wheeled Construction machinery is one of the major construction costs. Therefore, the fuel oil with freezing point 3-5 ℃ lower than the minimum temperature should be selected according to the temperature of the construction area. The fuel saving measures for construction transport vehicles and engines are as follows:

(1) Try to reduce the weight of the vehicle. Increasing vehicle weight will increase fuel consumption correspondingly. Therefore, unnecessary additional equipment should be removed from the vehicle during construction without affecting the project quality

(2) The resistance to acceleration and fuel consumption should be reduced as much as possible.

In construction, if the speed is below 400km / h, the air resistance can be ignored. It should be noted that the rolling resistance. When the vehicle is driving on an uneven road surface, the deformation of suspension device and tire increases due to its frequent jumping, resulting in a large increase in rolling resistance. Compared with the situation of driving on good road surface, the fuel consumption increases by 30% – 50%. Therefore, it is necessary to repair and maintain the construction access road. At the same time, the tire pressure has a great influence on the rolling resistance. If the tire pressure is reduced on the hard road surface, the tire deformation will be large and the rolling resistance will be increased; if the tire pressure is reduced on the soft road surface, the contact area between the tire and the ground will increase, and the pressure per unit area will decrease, which will reduce the rolling resistance. Therefore, it is necessary to pay attention to the changes of road conditions in construction and select appropriate tire pressure to reduce fuel consumption.

The transmission ratio of each gear of vehicle transmission has a great influence on fuel consumption. The high-speed gear with small transmission ratio should be selected as far as possible in construction, so as to save fuel.

(3) Increase the engine compression ratio to the standard value. The compression ratio of diesel engine is generally between 16 and 22. With the increase of compression ratio, the temperature and pressure at the end of compression are increased, which is beneficial to the combustion and expansion of the mixture, the thermal efficiency of the engine is improved, the effective power is increased and the fuel consumption is reduced. The specific measures are as follows:

Reduce the resistance of the intake system. The filter should be cleaned and maintained in time to ensure that there is enough air to enter the cylinder in time.

Keep the vehicle in good condition. For the engine cylinder pressure, the general diesel engine should not be less than 20% of the original engine standard pressure, gasoline engine is not less than 30%. For the pressure difference between each cylinder, the diesel engine is generally required to be no more than 8%, and the gasoline engine is not more than 10%. If the cylinder pressure does not reach the specified standard, grind the valve and replace the piston ring as required. It should also be noted that the carbon deposit in the combustion chamber will make the compression ratio increase automatically. If the compression ratio is too high and the carbon deposit is too high, it is easy to cause the cylinder deflagration and increase the fuel consumption. Therefore, it is very necessary to remove the carbon deposit. In addition, the clearance between the inlet and exhaust valves must be adjusted to the specified value, because the fuel consumption will be increased if the clearance is too large or too small.

(4) Good engine fuel supply angle in advance. If the fuel supply advance angle is too large or too small, the fuel consumption of the engine will increase. Therefore, in order to make the engine have good performance, the fuel supply advance angle must be calibrated.

(5) Reduce fuel consumption per unit load. If the vehicle condition permits, the productivity can be increased and the fuel consumption per unit weight can be significantly reduced by increasing the vehicle load to the rated load.

(6) Master the economic speed. In construction, the roads are generally informal roads, that is, access roads. In this case, the correct relationship between safety, fuel consumption and vehicle speed should be grasped. Taking the half load of Tatra T815 as an example, the relationship between fuel consumption and vehicle speed is: when the vehicle speed is 25-30km / h, the fuel consumption is the least, that is, in the construction, this speed can not only ensure the production efficiency, but also be economical and reasonable.

(7) Choose lubricating oil correctly. The selection of lubricating oil is the key factor to reduce power consumption and fuel consumption. Different specifications and brands of lubricating oil should be selected in winter and summer.

First of all, strictly abide by the tire inflation standards, check whether the ministries and commissions have air leakage after inflation, and regularly check the tire pressure to ensure compliance with the standards. Develop the habit of using a barometer to measure air pressure. Do not judge with naked eyes. Ensure that the tire has a certain elasticity, when bearing the specified load, make its deformation not exceed the specified range, and ensure the vehicle has good stability and comfort in driving. The pressure of the spare tire should be higher to avoid running away for a long time.

Secondly, it is necessary to select and install the tire correctly, and use the corresponding inner tube according to the tire specification. Tires assembled on the same machine shall be of the same brand, structure and performance. If this is not possible, tyres of the same brand, specification, pattern and type should be assembled on the same axle; when replacing new tires, the whole vehicle or coaxial should be changed at the same time; tires with directional patterns should be installed in accordance with the specified rolling direction; when replacing new tires, the new tires should be installed on the front wheels, and the repaired tires should be installed on the rear wheels. In order to ensure driving safety, the retreaded tires are not allowed to be used as steering wheels (front wheels).

Third, regular tire rotation. After the vehicle has been running for a period of time, the front and rear tires are different in terms of fatigue and wear. Therefore, it is necessary to change the position in time according to the regulations. There are two ways to change tires: cross method and cycle method. The cross transposition method is suitable for the vehicles which often drive on the road with greater camber, while the cyclic transposition method is suitable for the vehicles that often drive on the flat road.

Fourth, it is also necessary to control the temperature of the tire. In the process of driving, the tire will generate heat due to friction and deformation, which will increase the temperature and pressure inside the tire. When the temperature of the tire is very high, we can’t use the method of deflating and depressurizing, and we can’t pour water on the tire to reduce the temperature, so as to avoid accelerating the damage of the tire. Should be in

Machining – turning

Turning is to change the shape and size of the blank by using the rotary motion of the workpiece and the linear or curvilinear motion of the cutter on the lathe, so as to meet the requirements of the drawing.

Turning is a method of cutting workpiece on a lathe by rotating the workpiece relative to the cutter. The cutting energy of turning is mainly provided by the workpiece rather than the cutter. Turning is the most basic and common cutting method, which plays an important role in production. Turning is suitable for machining rotary surface. Most of the workpieces with rotary surface can be machined by turning method, such as inner and outer cylindrical surface, inner and outer cone surface, end face, groove, thread and rotary forming surface, etc. the tool used is mainly turning tool.

In all kinds of metal cutting machine tools, lathe is the most widely used one, accounting for about 50% of the total number of machine tools. The lathe can be used not only for turning the workpiece, but also for drilling, reaming, tapping and knurling with drills, reamers, taps and knurling cutters. According to the different process characteristics, layout forms and structural characteristics, lathes can be divided into horizontal lathe, floor lathe, vertical lathe, turret lathe and profiling lathe, and most of them are horizontal lathes.

The ideal processing program should not only ensure the qualified workpiece in accordance with the drawing, but also make the function of CNC machine tool be reasonably applied and fully developed. CNC machine tool is a kind of high efficiency automation equipment, its efficiency is 2 ~ 3 times higher than ordinary machine tool. In order to give full play to this characteristic of CNC machine tool, we must analyze the process of workpiece before programming, and select economic and reasonable process scheme according to specific conditions. The improper consideration of turning process is an important factor affecting the machining quality, production efficiency and processing cost of CNC machine tools. It is a process of changing the overall dimension or performance of workpieces with processing machinery. According to the temperature state of the workpiece to be processed, it can be divided into cold working and hot working. Generally, it is processed at normal temperature and does not cause chemical or physical changes of the workpiece, which is called cold working. Generally, the processing above or below the normal temperature will cause the chemical or physical phase changes of the workpiece, which is called thermal processing. Cold working can be divided into cutting and pressure machining according to the difference of processing methods. Heat treatment, forging, casting and welding are common in hot working. There are two steps in the formulation of machining process specification. First of all, it is to draw up the process route of parts processing, and then determine the process size of each process, the equipment and process equipment used, as well as the cutting specifications, man hour quota, etc. These two steps are interrelated and should be analyzed comprehensively.

The main task is to select the processing method of each surface, determine the processing sequence of each surface, and the number of processes in the whole process.

General principles for drawing up process routes

Machining datum plane first

In the process of machining parts, the surface as positioning reference should be machined first, so as to provide precise reference for subsequent processing as soon as possible. It is called “benchmark first”.

Dividing processing stages

The surface with high machining quality is divided into three stages: rough machining, semi finishing and finishing. It is mainly to ensure the processing quality, to use the equipment reasonably, to arrange the heat treatment process, and to find the blank defects easily.

Face before hole

For parts such as box, bracket and connecting rod, the plane should be machined first and then the hole should be processed. In this way, the hole can be processed by plane positioning, which can ensure the position accuracy of plane and hole, and the machining of hole on the plane is convenient.

Finishing

The finishing of the main surface (such as grinding, honing, finishing grinding / rolling, etc.) shall be carried out at the last stage of the process route. The surface finish after processing shall be ra0.8um. Slight collision will damage the surface. In Japan, Germany and other countries, after finishing, flannel shall be used for protection. It is absolutely forbidden to directly contact the workpiece with hands or other objects to avoid polishing The finished surface is damaged due to transportation and installation between processes.

Machining surface quality refers to the micro unevenness of the machined surface of parts after machining, also known as roughness. It is indicated by three codes of RA / RZ / ry and numbers. There will be corresponding surface quality requirements in mechanical drawings. Generally, the surface with surface roughness Ra < 0.8um is called mirror surface. The surface quality after machining directly affects the physical, chemical and mechanical properties of the workpiece. The working performance, reliability and service life of products depend on the surface quality of main parts to a great extent. Generally speaking, the surface quality requirements of important or key parts are higher than that of ordinary parts. Machining this is because the table and good quality parts will greatly improve its wear resistance, corrosion resistance and fatigue damage resistance

Deburring in NC machining

This is to use electrical and chemical energy to dissolve anode and remove burr. The anode is on the side of the positive pole of the part and the DC power supply. The cathode is connected with the forming tool and the negative pole of the DC power supply. There is a certain gap between the two poles to make the electrolyte circulate. When the anode and cathode are immersed in the solution and connected with direct current, electrochemical reaction occurs on the anode surface. The dissolved metal on the surface of the part forms viscous liquid with high resistance and small corrosion. The burr protrudes from the surface of the part, and the liquid film is difficult to form under the influence of temperature difference. After power on, the power line is highly concentrated on the burr The burr nearest to the cathode will be dissolved at the fastest speed until the burr is completely dissolved and the edge gradually forms a fillet, that is to say, the purpose of deburring is achieved.

Electrolytic deburring machine can be used. When the production volume is not large, a simple equipment can be made by converting the alternating current of rectifier into direct current. According to the structure of the parts, the special fixture (tool cathode) similar to the part shape is made of brass or red copper and other conductive materials. The unprocessed parts are coated with epoxy resin for isolation protection. The commonly used electrolytes are NaCl, NaNO2 > and nano > 3.

This method is suitable for nonferrous and ferrous metal parts, especially for parts with complex shape and burr on inner hole, cross hole and inner surface which are difficult to remove by mechanical and manual methods. It can remove the burr of extra hard parts such as molybdenum, nickel, titanium and quenched parts. Put the cleaned metal parts into the chemical solution (50 ℃), and the metal on the surface of the parts will be transferred to the solution in the form of ions. These ions gather on the surface of the workpiece and form a layer of sticky film with high resistance and low conductivity through chemical reaction to protect the workpiece surface from corrosion. The burr protrudes from the surface, and the chemical action will remove the burr. When processing, only one slot can be used. According to the different materials of deburring workpiece, different chemical solutions are used. The main components of the base can be hydrochloric acid, phosphoric acid, sulfuric acid, diphenylaniline hydrochloride and water. Chemical deburring is suitable for small metal parts, and can remove fine burr with thickness less than 0.07 mm.

Milling: refers to the use of rotating multi edge cutting tools to cut workpiece, is a high efficiency processing method. When working, the tool rotates (as the main motion), and the workpiece moves (as the feed motion), and the workpiece can also be fixed, but at this time, the rotating tool must also move (complete the main motion and feed motion at the same time). There are horizontal milling machine or vertical milling machine and large gantry milling machine. These machine tools can be ordinary machine tools or CNC machine tools.

1) Plane parts

The characteristics of plane parts are shown in that the machining surface can be parallel to or perpendicular to the horizontal plane, and can also form a fixed angle with the horizontal plane. At present, most of the parts processed on the CNC milling machine belong to the plane type parts, and the plane parts are the simplest type of parts in the NC milling process. Generally, only the two axis linkage or three axis of the three-dimensional CNC milling machine is needed Linkage can be processed. In the process of machining, the machining surface is in contact with the cutter, and the end mill or nose cutter can be used for rough and finish machining.

(2) Curved surface parts

The feature of curved surface parts is that the machining surface is a spatial surface, and the machining surface and milling cutter are always in point contact in the process of machining. Ball end milling cutter is often used for surface finishing.

Computer gong processing milling machine

The milling machine used in machining is very complex, and there are many kinds of milling cutters. “Milling” workpiece is: the workpiece is placed on the worktable and clamped with fixture, and the milling cutter is installed on the spindle. The spindle drives the cutter to rotate at high speed (main motion). The workpiece is driven by the worktable, which can realize the horizontal and vertical movement (feed motion). Under the joint action of the main motion and feed motion of the machine tool, the redundant part of the workpiece is removed. It can process plane, groove and curved surface on milling machine. The strengthening methods of aluminum alloy are as follows:

Solution strengthening

The addition of alloy elements into pure aluminum forms aluminum based solid solution, which causes lattice distortion, hinders the movement of dislocations, and plays a role of solution strengthening, which can improve its strength. According to the general law of alloying, when forming infinite solid solution or high concentration solid solution alloy, not only high strength, but also excellent plasticity and good press workability can be obtained. Al Cu, Al Mg, Al Si, Al Zn, Al Mn binary alloys can generally form finite solid solutions and have high limit solubility (see table 9-2), so they have great solution strengthening effect.

Another strengthening effect of alloying elements on aluminum is achieved by heat treatment. However, the transformation of aluminum during heat treatment is different from that of steel because there is no isomeric transformation of aluminum. The heat treatment strengthening of aluminum alloy is mainly due to the high solid solubility of alloy elements in the aluminum alloy, which decreases sharply with the decrease of temperature. Therefore, the supersaturated aluminum based solid solution can be obtained after the aluminum alloy is heated to a certain temperature and quenched. When the supersaturated aluminum based solid solution is placed at room temperature or heated to a certain temperature, its strength and hardness increase with time, but the plasticity and toughness decrease. This process is called aging. Aging at room temperature is called natural aging, and aging under heating conditions is called artificial aging. The phenomenon of increasing the strength and hardness of aluminum alloy during aging is called aging strengthening or aging hardening. The strengthening effect depends on the aging hardening phenomenon in the aging process.

Excess phase strengthening

If the amount of alloying elements in aluminum exceeds the limit solubility, there will be a part of the second phase which can not be dissolved into the solid solution, which is called excess phase. In aluminum alloys, these excess phases are usually hard and brittle intermetallic compounds. They hinder dislocation movement in the alloy and strengthen the alloy, which is called excess phase strengthening. This method is often used to strengthen cast aluminum alloy and heat resistant aluminum alloy in production. The more the amount of excess phase and the more dispersed the distribution, the greater the strengthening effect. However, if there are too many excess phases, the strength and plasticity will be reduced. The more complex the structure of the excess phase and the higher the melting point, the better the thermal stability at high temperature.

Refine the structure and strengthen it

Many aluminum alloys are composed of α solid solution and excess phase. If the microstructure of aluminum alloy can be refined, including refining α solid solution or refining excess phase, the alloy can be strengthened.

Because of the coarse structure of cast aluminum alloy, modification is often used to refine the alloy structure in actual production. Computer gong machining | mechanical parts processing | CNC machine tool processing | Dongguan high-speed computer gong machining modification is to add 2-3% modifier (commonly used sodium salt mixture: 2 / 3naf + 1 / 3nacl) to the molten aluminum alloy before pouring, so as to increase the crystal core and refine the microstructure. After modification, fine and uniform eutectic and primary α solid solution structure can be obtained, which can significantly improve the strength and plasticity of aluminum alloy.

Computer gong processing – spindle

It is found that there is abnormal sound in the spindle and gearbox when the spindle speed is below 500r / min. observing the power meter of the motor, it is found that the output power of the motor is unstable and the pointer swings greatly. However, the abnormal sound disappeared when it was used above 1201r / min. After startup, the power meter of the motor will swing automatically without rotation command, and the motor will drift and rotate automatically. After normal operation, the braking time is too long, and the machine tool has no alarm.

According to the phenomenon observed, the main shaft controller may be out of control, and the mechanical transmission or motor can not be eliminated. Due to the heavy workload of dismantling the mechanical part, the spindle controller of the electrical part is checked first. The controller is Siemens 6sc-6502. First, check the preset parameters in the controller, and then check the control board, all of which are normal. After checking that the circuit board is dirty, clean the circuit board according to the requirements, but after it is installed, the machine fails as usual. Therefore, the fault causes in the controller can be eliminated temporarily. In order to determine whether the fault is in the motor or in the mechanical transmission part, it is necessary to separate the motor from the machinery. After the separation, it is found that when the motor speed command is close to 450R / min, the abnormal sound starts to appear continuously, but when the instruction of 1201r / Min is given, the abnormal sound disappears again. For this reason, we analyzed the spindle part. The original 450 R / min command given at low speed and 4500r / min command at high speed are the same to the motor at the highest speed, but the gear decelerates at low speed, so the fault can be basically determined in the motor part. After analysis, the abnormal sound may be caused by poor bearing.

When the motor was disassembled for inspection, it was found that the bearing was damaged. When the bearing was stuck at high speed, the load was increased, which made the power meter swing and deflect. But after stopping, the motor drifted and the brake was too slow. After checking, the encoder disc was scratched. After replacing the bearing and encoder, all the faults were eliminated. This fault is mainly due to the abnormal sound when the spindle rotates. Therefore, it is necessary to find out the sound source before checking. Abnormal sound is common for mechanical rubbing, jamming and bearing damage.

CNC machining center spindle orientation usually adopts three ways: magnetic sensor, encoder and mechanical orientation. When using magnetic sensor and encoder, in addition to adjusting the position of components, it can also adjust the machine parameters. There is no alarm when the orientation error occurs, and it can only be detected when there is an interruption in the process of tool change.

Once in a refitted CNC machining center, there was a fault of inaccurate orientation. At the beginning, the machine tool was often interrupted in the work, but the frequency was not many. The machine could work again after restarting, and the fault occurred repeatedly. After careful observation of the machine tool after the fault occurred, it was found that the real cause of the fault was the position deviation of the spindle after orientation. It is strange that if the spindle is touched by hand after orientation (similar to the situation when the tool is inserted into the spindle during tool change), the spindle will drift in the opposite direction. Check the electrical part without any alarm, and the mechanical part is very simple.

The orientation of the machine tool uses encoder, so from the fault phenomenon and possible parts, the possibility of electrical part is relatively small, the most important mechanical connection. Therefore, it was decided to check the mechanical connection part. When checking the connection of the encoder, it was found that the set screw of the coupling sleeve on the encoder was loose, which caused the coupling sleeve to retreat, resulting in excessive clearance between the coupling part and the spindle, and the rotation was not synchronous. The failure was eliminated after the set screw was fixed as required. In case of spindle orientation failure, the analysis and treatment shall be carried out according to the specific structure of the machine tool. The electrical part shall be checked first, and then the mechanical part shall be considered if it is confirmed to be normal.

Domestic die steel and imported die steel

China’s mold industry has experienced rapid development in recent years, and the achievements have been considerable, especially since the beginning of the year, under the guidance of the national twelfth five year plan, the industry vigorously develops high-end precision equipment, and constantly promotes the steady progress of China’s mold industry.

According to experts, due to the development of die and mold industry in recent years to a larger, more precise, more complex and more economic and rapid direction, so the requirements for the miniaturization and precision of its products are higher, which urges China’s mold industry to constantly improve and upgrade technology to adapt to the changing market environment. According to relevant data, in terms of precision plastic mold, China has been able to produce plastic parts mold for camera and mobile phone, multi cavity small module gear mold and 7800 cavity plastic sealing mold with accuracy of 5 μ M.

In recent years, domestic die steel production has made great progress. At present, many domestic steel mills are mass producing some steel grades with strong universality or excellent performance internationally, such as 4Cr5MoSiV1 (equivalent to aisih13), 3Cr2Mo (equivalent to aisip20), 10ni3mncaal, Cr12MolV1 (equivalent to aisid2), etc. Among them, 4Cr5MoSiV1 and 3Cr2Mo are relatively large in production and use, and their research and improvement are also in-depth.

Reducing material cost and improving performance price ratio have become the focus of new die steel development in advanced die steel production enterprises. For example, when Hitachi Metal Co., Ltd. and Datong Special Steel Co., Ltd. introduced their products at the technical exchange meeting during the exhibition, they all agreed to develop dac-magic hot working die steel, hpm-magic and cena1 plastic mold steel and dha-world die-casting die steel to cope with the financial crisis and more fierce market competition.

Generally speaking, some well-known die steel manufacturers abroad still have obvious advantages in the production means, variety specifications, serialization degree, after-sales service and awareness and effect of developing new steel grades. CNC machine tool processing of domestic die steel serialization degree and quality stability is still to be improved; the proportion of production and application of some good performance die steel is still low, the application of most new steel is still small, at the same time, there is a lack of effective means of promotion and sales, post-sale service needs to be improved; in addition, some new steel grades with special performance need to be developed. Improving and perfecting the above shortcomings will still be the main task of die steel development in China in the future.

报错笔记