China Shenzhen Perfect Precision Product Co., Ltd. company news

Precision parts processing, not any material can be precision machining, precision parts processing on the material requirements are very strict. So we know what materials are generally used for precision parts processing? Next, let me share with you! For precision machining materials are divided into two categories, metallic materials and non-metallic materials.   For metal materials, the hardness of stainless steel is the largest, followed by cast iron, followed by copper, and finally aluminum. The processing of ceramics, plastics, etc. is the processing of non-metallic materials.   First of all, the hardness of the material requirements, for some occasions, the higher the hardness of the material is the better, but only limited to the hardness of the processing machine requirements, the processing of the material can not be too hard, if harder than the machine is unable to process.    Secondly, the material is soft and hard, at least one grade lower than the hardness of the machine, but also depends on the role of the processed device is to do what with a reasonable selection of materials for the machine parts.   In short, precision machining requirements of the material or some, not what material is suitable for processing, such as too soft or too hard material, the former is not necessary for processing, and the latter is impossible to process. Therefore, the most basic one is, before processing must pay attention to the density of the material, if the density is too large, equivalent to the hardness is also very large, and if the hardness is more than the hardness of the machine (lathe turning tool), it is impossible to process, not only will damage the parts, but also cause danger, such as turning tool flying out of the crash injury. Therefore, in general, for mechanical processing, the material material should be lower than the hardness of the machine tool, so that it can be processed.

In the process of machining mechanical parts, the reasonable arrangement of heat treatment process can make the cold and hot process better together, to avoid the deformation brought about by heat treatment. So we know how to reasonably arrange the heat treatment process location? Next by the editor to share! 1、Preparatory heat treatment The purpose of the preparatory heat treatment is to eliminate the internal stress generated during the manufacturing process of the blank, improve the cutting performance of metal materials, and prepare for the final heat treatment. Belonging to the preparatory heat treatment are tempering, annealing, normalizing, etc., generally arranged in the rough machining before, after. Arranged in the roughing before, can improve the cutting performance of the material; arranged in the roughing after, conducive to the elimination of residual internal stress.   2, the final heat treatment should generally be arranged in the roughing, semi-finishing machining, finishing before and after. Deformation of larger heat treatment, such as carburizing quenching, tempering, etc., should be arranged before finishing, in order to correct the deformation of heat treatment in finishing; deformation of smaller heat treatment, such as nitriding, etc., can be arranged after finishing.   3, aging treatment The purpose of aging treatment is to eliminate internal stress, reduce the deformation of the workpiece. Aging treatment is divided into natural aging, artificial aging and ice cold treatment three categories. Ageing treatment is generally arranged after roughing, before finishing; for high precision parts can be arranged after semi-finishing and then an ageing treatment; ice-cooling treatment is generally arranged after tempering or finishing or the last of the process.   4, surface treatment in order to surface anti-corrosion or surface decoration, sometimes need to surface plating or bluing and other treatment of this surface treatment is usually arranged at the end of the process. Production process refers to the entire process from raw materials (or semi-finished products) into products. For machine production, it includes transportation and storage of raw materials, preparation of production, manufacture of blanks, processing and heat treatment of parts, assembly, and commissioning of products, painting and packaging. Modern enterprises use the principles and methods of system engineering to organize production and guide production, and view the production process as a production system with input and output. It can make the management of the enterprise scientific and make the enterprise more resilient and competitive.   In the production process, the process of directly changing the shape, size and performance of raw materials (or blanks) into finished products is called the process. It is the main part of the production process. For example, the billet casting, forging and welding; heat treatment to change the properties of materials; parts of mechanical processing, etc., are part of the process. Processes are composed of one or several sequential processes.   The process is the basic unit of the process. A process is the part of the process that is completed continuously at a workplace for a workpiece or group of workpieces. The main characteristics of a process are that it does not change the object, equipment or operator, and that the process is completed continuously.

In the field of mechanical parts processing industry, surface roughness is a very important index. So do you know how to choose the surface roughness when machining mechanical parts? Next, let me share with you! Surface roughness is an important technical index reflecting the error of the microscopic geometry of the surface of the part, is the main basis for the inspection of the surface quality of the part; it is reasonable to choose or not, directly related to the quality of the product, service life and production costs. Mechanical parts surface roughness selection method has three kinds, namely, calculation method, test method and analogy method. In the mechanical parts design work, the most common application is the analog method, this method is simple, fast and effective.   Application of the analog method requires sufficient reference materials, the existing mechanical design manuals provide more comprehensive information and literature. The most commonly used is the surface roughness that corresponds to the tolerance level. In general, the smaller the size tolerance requirements of mechanical parts, the smaller the surface roughness value of mechanical parts, but there is no fixed functional relationship between them. For example, some machines, instruments on the handle, hand wheel and health equipment, food machinery on the surface of some mechanical parts of the finishing, their surface requirements are processed very smooth that is, the surface roughness requirements are very high, but the size tolerance requirements are very low. Mechanical parts processing in general, there are dimensional tolerance requirements of the parts, the tolerance level and surface roughness values between or have a certain correspondence.

Shaft parts, which are one of the common parts in machines, are also very important parts, which can play a supporting role for transmission parts and can transmit torque. So do you know what the mechanical processing technology of shaft parts is about? Let me share with you next! The technical requirements and processing of shaft parts is an important thing for us to know about large machining, so what exactly is it about? Then please see the following content.   Shaft parts of the technical requirements, generally have the following aspects, for. 1. Diameter accuracy, geometric shape accuracy On the shaft, the support journal and fit journal is very important, its diameter accuracy of IT5-IT9 level, and shape accuracy, should be controlled within the diameter tolerance, and its requirements are higher than the diameter accuracy. If the shaft is ordinary accuracy, then its radial circular runout, if it is to fit journal to support journal, is generally regarded as 0.01-0.03mm. while the high accuracy shaft is 0.001-0.005mm. if there is special requirement, then it should be specified clearly.   2.Surface roughness Because of the machine precision, running speed and other factors, the surface roughness requirements of shaft parts are also different. The surface roughness of the bearing journal is 0.16-0.63um, and that of the mating journal is 0.63-2.5um.   3. Spindle materials, blanks and heat treatment The common material used for shaft parts is 45 steel, which is normalized, annealed, tempered and quenched to obtain certain strength, hardness, wear resistance and toughness. For high speed shaft parts, alloy structural steel can be used because it will improve the wear resistance and fatigue resistance after heat treatment. Blanks for spindles are usually forgings and round steel, which can reduce the amount of cutting and machining, and can improve the mechanical properties of the material.

1、 What is stamping? Stamping is a forming processing method of workpieces (stamping parts) with required shape and size by applying external force on plates, strips, pipes and profiles by press and die to cause plastic deformation or separation. The car body, chassis, fuel tank, radiator sheet, boiler drum, container shell, motor, electrical iron core silicon steel sheet, etc. are all processed by stamping. Instruments, household appliances, bicycles, office machinery, household utensils and other products also have a large number of stamping parts. According to the stamping processing temperature, it can be divided into hot stamping and cold stamping. The former is suitable for sheet metal processing with high deformation resistance and poor plasticity; The latter is carried out at room temperature, which is a common stamping method for thin plates. Sheet metal, die and equipment are the three elements of stamping processing. Sheet metal: The surface and internal properties of the sheet metal used for stamping have a great impact on the quality of the finished stamping products. 6 points for requirements of stamping materials ① The thickness is accurate and uniform. ② The surface shall be smooth and clean without spot, scar, scratch, surface crack, etc. Prevent scrap generation. ③ The yield strength is uniform without obvious directivity. In order to reduce defective products or waste products ④ High uniform elongation. To prevent uneven deformation. ⑤ Low yield ratio. In order to improve the accuracy of bending parts. ⑥ Low work hardening. To prevent future deformation Die: The precision and structure of die directly affect the forming and precision of stamping parts. Die manufacturing cost and life are important factors that affect the cost and quality of stamping parts. Equipment: According to the transmission structure: manual punch, mechanical punch, hydraulic punch, pneumatic punch, high-speed mechanical punch, CNC punch According to machining accuracy: ordinary punch, precision punch According to the scope of use: ordinary press, special press Processing characteristics 1. The stamping process has high production efficiency, convenient operation, and is easy to realize mechanization and automation. 2. The stamping quality is stable, the interchangeability is good, and it has the characteristics of "identical". 3. Stamping strength and stiffness are high. 4. The cost of stamping parts is low.

The thread is the most common method for connecting mechanical parts, and the processing of threaded holes is often at the end of the entire production process. Once the processing is unqualified, it will lead to the scrapping of components or more troublesome reprocessing, so it puts forward higher requirements for the safety of the process. There are various tools for machining threaded holes, including thread turning tools, taps, extrusion taps, thread milling cutters, etc. How to select the correct machining tool? The selection of tools is actually the selection of processing methods. Each processing method uses different tools. For the processing of threaded holes, there are several common ways: tapping, turning, extrusion molding, and thread milling. Now let's first understand the advantages and disadvantages of various processing methods and the use restrictions. In actual production, we can analyze which tool to use from the technical and economic perspective according to the characteristics of these processing methods. 1. Tooth tapping Tapping is a widely used method in the processing of threaded holes. It can determine the forming of thread with the aid of the geometric shape of the cutter, so no special machine tool is required for processing, and it can be used on ordinary machine tools, production line special machines and machining centers. The tapping process is that the tap rotates forward to cut, reverses when it reaches the bottom of the thread, leaves the workpiece, cuts in a very narrow space and discharges the chips. For different processing conditions and different processing materials, the types of taps selected are also different. Tap tapping is often used in small diameter and mass production. 2. Turning Turning thread refers to turning with indexable inserts. For triangular threads commonly used in production, the shape of the cutting part of the thread turning tool should conform to the axial section of the thread. When turning, the turning tool must move a lead (single head thread, lead=pitch) longitudinally for each rotation of the workpiece to process the correct thread. There are three common methods for turning triangular threads: A. Thread turning with straight method. When turning the thread, after the test cutting check that the workpiece and the thread pitch meet the requirements, the radial direction is perpendicular to the workpiece axis and the feed is repeated for many times until the thread is properly turned. The tooth profile of this turning method is more accurate. Because the two edges of the turning tool cut at the same time and chip removal is not smooth, the turning tool is easy to wear due to large force, and the chip will scratch the thread surface. B. Thread turning by oblique method. When the thread pitch of the workpiece is greater than 3MM, the oblique method is generally used to turn the thread. The oblique method is that the turning tool feeds along the thread profile side in the radial direction while making the axial feed. After several times of cutting, the thread is processed. Finally, the straight method is used to eat the tool to ensure the accuracy of the thread profile angle. C. Left and right knife entry method. In an ordinary lathe, this method uses the scale of the horizontal carriage to control the vertical feed of the thread turning tool, and uses the scale of the small carriage to control the left and right micro feed of the turning tool. When the thread is close to cutting, the nut or thread gauge shall be used to check whether the thread size and processing accuracy are qualified. This method is easy to operate, so it is widely used. Turning thread is generally applied to holes with large diameter, and the workpiece can be firmly clamped on the lathe for rotary processing. 3. Extrusion processing Extrusion processing belongs to chip free processing. The processing process is the same as tapping, the extruding tap is screwed into the pre drilling hole, and the material is extruded in the axial and radial direction, thus forming a unique tooth shaped thread profile. Thread extrusion is applicable to materials with good plastic deformation. The range of materials is relatively small. Generally, the fracture elongation of materials is required to be greater than 7%, and the maximum tensile strength is less than 1300N/MM. It is widely used in aluminum alloy processing. 4. Thread milling The process of thread milling is as shown in the figure below. The thread milling cutter generally descends to the bottom of the threaded hole, approaches the workpiece by means of spiral interpolation, rotates 360 degrees along the threaded hole, rises a pitch in the Z direction, and then leaves the workpiece. The torque of thread milling cutter is small, which increases the safety of the process. It also has a wide range of applicability, and can process various materials. In the case of the same pitch, a tool can be used to process threads with various thread diameters or tolerance ranges. Disadvantages: the machine tool is required to be a three coordinate CNC machine tool. In addition, compared with the tap, its processing efficiency is relatively low and the tool cost is relatively high, so it is suitable for processing large diameter threaded holes in small batch production. As we mentioned just now, the tap is the most widely used tool for machining small diameter threaded holes, and tapping is a relatively complex processing process, so there are many problems encountered in the processing process. Common problems of tap include fracture, chipping, wear, etc. The fracture is mainly along the whole cross section of the tap. The appearance of edge chipping is that the cutting edge is chipped off. The wear of the tap refers to that the cutting edge of the tap and die is worn off when the tap and die have not been used for a long time, making the tooth size smaller and unusable. The taps that fail in these three ways are far from reaching their normal service life. After these problems occur in tap processing, we can focus on the following aspects for analysis. 1. Machine tool problems Check whether the machine tool operates normally, whether the spindle runout is too large, whether the machine tool spindle is coaxial with the bottom hole, and whether the processing program is correct. 2. Workpiece material Check whether the material strength of the workpiece is too high, whether the material quality is stable, and whether there are pores, residues, etc. 3. Diameter and depth of threaded bottom hole Check whether the diameter of the thread bottom hole is correct. If the diameter of the bottom hole is too small, the root of the tap will contact the workpiece during cutting, which is easy to cause the tap to break. The diameter of the thread bottom hole is marked in the tap sample, or the formula (bottom hole diameter=thread diameter - thread pitch) can be used to obtain the bottom hole diameter. For extrusion taps, the diameter of the thread bottom hole is different from that of the cutting tap. The approximate bottom hole diameter can also be calculated according to the formula (bottom hole diameter=thread diameter - thread pitch/2). For blind holes, the depth of the bottom hole should also be considered. Since there are several cutting teeth at the front end of the tap, and the diameter of these cutting teeth is relatively small, they cannot be considered as effective threads, so the depth of the bottom hole should also consider the depth of the cutting teeth and the size of the sharp corner at the front end of the tap. In production, there are also cases where the bottom hole is not deep enough and the front end of the tap touches the bottom of the hole, causing the tap to break. 4. Whether the correct tap type is selected As mentioned earlier, for different processing conditions and different processing materials, the types of taps selected are also different. First of all, for the two different processing conditions of through hole and blind hole, the types of cutting taps selected are different. For materials with long chips, such as steel, in the case of through holes, select a straight slot tap to discharge chips downward, and in the case of blind holes, select a spiral tap to discharge chips upward. For short chip materials, such as cast iron, iron chips are chips that can be contained in the chip removal slot, so through holes and blind holes can be processed with straight slot taps. In another case, the chips formed by the left hand tap are separated. This tap is suitable for situations where the workpiece is close to the tooling and the chip removal space is insufficient. mash welder In production, we often see that it is an incorrect method to use the spiral groove tap in the processing of through holes. There are three reasons: First, the spiral groove tap discharges chips upward. In order to achieve this effect, the structure of the tap itself is complex, the rigidity is not good, and the chip transmission stroke is long, so it is easy to get stuck during the spiral groove transmission process, causing blade breakage or fracture. Second, the number of cutting teeth in front of the two taps is different. The spiral groove tap generally has 2-3 cutting teeth, while the straight groove tap has 3-5 cutting teeth. The life of the tap is proportional to the number of cutting teeth. Third, the spiral groove tap is more expensive than the straight groove tap, which is not economical. On the other hand, for cutting taps, we should choose taps with different grooves for processing different materials. There are various angles on the tap, such as front angle, rear angle, guide angle, blade inclination, etc. The design of these angles is based on the characteristics of different materials. For example, for steel parts and cast iron, the front angle of the tap is larger because the chips of steel parts are longer, while the iron chips of cast iron are generally chips, and the front angle is smaller, even 0 ° front angle. The tool company will give different recommended taps for different workpiece materials. For taps processing steel, aluminum alloy, cast iron, stainless steel and other common materials, different color rings may be used to distinguish the handle. 5. Cutting parameters Cutting parameters are very important. Different types of taps, different processing conditions, and different workpiece materials should choose different parameters. For example, under the same conditions, the linear speeds of high-speed wire taps and cemented carbide taps differ greatly. This speed has a certain range. The linear speed of high-speed wire taps is generally within 20M/MIN (the feed of the tap is fixed, that is, the pitch). Too fast or too slow will lead to tap failure. Selecting appropriate cutting parameters can ensure production efficiency and achieve relatively high tool life. 6. Cooling and lubrication As we mentioned earlier, the tap is used to cut in a very narrow space and discharge the chips, which will generate a lot of heat during the processing. Therefore, cooling and lubrication are very important. For materials with high toughness, the concentration of coolant can be increased or oily coolant can be used.

With the continuous progress of optical fiber laser technology and the continuous decline of laser processing cost, an obvious trend has emerged in the sheet metal processing market, which is to gradually transfer the products below the medium batch that were originally used for CNC punching to CNC laser cutting machines. However, people in the industry also clearly realize that the CNC punching machine still has its irreplaceable advantages, which are mainly embodied in the following aspects: sheet metal processing combined with CNC stamping forming; Large batch of non trimming punching type sheet metal processing; Sheet metal processing of dense mesh. At present, these three kinds of sheet metal processing are closely dependent on the characteristics of CNC punch, and still produce huge economic benefits in the process of sheet metal processing. Solution This paper discusses how to finish high quality dense mesh stamping under the condition of reasonable operating cost. technical requirement Mesh parts generally include the following types of products: ventilation door panels of cabinet base stations, ordinary wall panels and ceilings of subway tunnels, screens of fluid equipment, and sound attenuation wall panels of public facilities such as theaters and venues. Technical requirements for mesh punching of different products: ⑴ The mesh of the cabinet category requires greater ventilation efficiency, so there is a higher requirement for density; (2) Tunnel wallboard and ceiling are relatively for limited noise reduction and weight reduction, so there are more requirements for flatness to facilitate on-site assembly; (3) In addition to the requirements for passing efficiency, the fluid screen also has high requirements for the rigidity of parts due to the pressure brought by the fluid itself; (4) Silencing wallboards for public facilities often require smaller hole diameters, and have high requirements for product surface quality. It can be seen from the above that the dense mesh punching we discussed is not a simple "screen punching", but an efficient sheet metal processing process with a certain technical content, and will cause massive economic losses due to the negligence of the processing manufacturer on some technical requirements. These losses are not only reflected in the large amount of rapid loss of ordinary molds, but also in the secondary and tertiary processing that has to be carried out for this purpose, And the resulting unexpected defective rate and scrap rate. special requirements Typical group hole punching cases and corresponding technical requirements. ⑴ The customer is not allowed to level the dense mesh plate for the second time (Fig. 1). The technical difficulties of this kind of perforated plate mainly lie in the huge deflection after multi hole punching and the plate collision accident during the punching process caused by the plate warping. Fig. 1 Punching without leveling (2) Dense perforated plate with hole spacing very close to the plate thickness. The technical difficulty of this kind of mesh plate is the material between the mesh holes. Because of the torsion caused by too close hole spacing, it is easy to cause the scrapping of the whole mesh plate. (3) Dense perforated plate with aperture close to the plate thickness. The technical difficulty of this kind of perforated plate is that the hole diameter is almost close to or even less than the plate thickness, which causes frequent needle breakage of the die during the stamping process, making the entire stamping efficiency too low, leading to high costs. (4) Dense perforated plate with relatively hard material. The technical difficulty of this kind of perforated plate is that due to the large shear strength of the plate material, it causes rapid wear of the die punch pin, and increases the frequency of broken pins, leading to ultra-high product scrap rate and die consumption rate. (5) Dense mesh plate made of aluminum/aluminum alloy. The technical difficulty of this kind of perforated plate is that a large amount of aluminum chips will be produced during the aluminum plate stamping process, which will stick to the mold surface and the inside of the mold guide sleeve, causing rapid wear and even scrapping of the mold in the repeated rolling process.

Recently, many new members of the society have posted questions about how to get started in the mechanical design industry. Based on what they have read over the years, I think that to learn a good industry, we should first determine the direction, then have a clear outline, how to learn, and what to learn first and then what to learn from that subject; Of course, in the process of continuous learning and accumulation, there will be a lot of technical materials, so it is necessary to reasonably classify and summarize them. The following is the outline for personal summary of large machinery knowledge: Standards related to mechanical drawing, limit and fit, mechanical engineering 1. General representation and selection of mechanical drawings (1) Types and selection of drawings, drawing frames and title blocks (2) Drawing view and surface layout, drawing scale, drawing line, section symbol and line type and their selection (3) Stipulation and use of simplified drawing method 2. Drawing and marking of standard parts and common parts (1) Screw drive and fasteners (external thread and internal thread, taper thread, internal thread and external thread connecting thread fasteners) (2) Gear, rack, worm, worm gear and sprocket (gear rack, worm, worm and sprocket meshing gear) (3) Spline (rectangular external spline, rectangular internal spline, involute spline connection) (4) Cylindrical spring (cylindrical helical compression spring cylindrical helical tension spring cylindrical helical torsion spring spring in assembly drawing) (5) Rolling bearing 3. Marking and selection of drawing size, limit and fit, geometric tolerance and surface roughness (1) Drawing size (basic specification marking method) (2) Limits and fits (basic concept, standard tolerance, limit fit, priority fit, geometric tolerance) (3) Surface roughness (selection of marking symbols and code values of evaluation parameters) 4. Drawing and marking of part drawings and assembly drawings (1) Part drawing (view selection, dimensioning, process structure and technical requirements) (2) Assembly drawing (the view represents the size and the part represents the technical requirements) 5. Relevant standards and applications of mechanical engineering (1) Standards and standardization (standardization of standards) (2) National standard (general basic standard for standard system formulation, national standard related to mechanical engineering) (3) Industry standards and enterprise standards (mechanical industry standards and their system formulation principles, enterprise standards) (4) International standards and foreign advanced standards (ISO, IEC EN, advanced enterprise standards of national standards association/group standards of countries with developed European standards industry) (5) Product standardization review (technical documents and drawings) 2、 Engineering materials 1. Classification and performance of engineering materials (1) Classification of engineering materials (metal ceramic polymer composite) (2) Properties of engineering materials (mechanical properties, physical properties, chemical properties, process properties) 2. Metal materials and their heat treatment (1) Crystal structure of metal (characteristics of crystal Crystal structure of metal Crystal structure of metal Phase structure of pure metal in solid state (2) Iron carbon alloy phase diagram (analysis of crystallization process of typical iron carbon alloys The effect of carbon on the equilibrium structure and properties of iron carbon alloys Application of iron carbon phase diagram) (3) Chemical composition analysis, metallographic analysis and nondestructive testing of metal materials (4) Heat treatment of metal materials (application examples of heat treatment of typical parts of steel, cast iron, non-ferrous metal and alloy heat treatment equipment) (5) Common metal materials (steel, cast iron, non-ferrous metals and alloys) (6) Basis for selection of metal materials (service performance, process performance and economy) 3. Engineering plastics, special ceramics and composite materials (1) Engineering plastics (commonly used thermoplastics Engineering plastics Processing of commonly used thermosetting engineering plastics Engineering plastics Application of engineering plastics) (2) Special ceramics (properties of special ceramics and processing of applied ceramic materials) (3) Composite materials (performance category application) 3、 Mechanical product design 1. New product design procedure (1) Feasibility analysis (feasibility analysis report of market research product positioning) (2) Conceptual design (functional analysis scheme design specification) (3) Technical design (work content and requirements: mechanism motion design, mechanical structure design) (4) Design evaluation and decision-making (evaluation objective criteria evaluation method) 2. Introduction to Mechanical System Design (1) Machine and mechanism (2) Friction, wear and mechanical efficiency in mechanical systems (friction and mechanical efficiency methods to reduce friction and wear Mechanical self-locking) (3) Design criteria for mechanical parts (strength, stiffness, life, heat dissipation, reliability criteria) (4) Manufacturing process design (part manufacturing process design machine assembly process design) (5) Mechanical vibration and noise (vibration and noise source and hazard prevention and measures to reduce harmful vibration and noise) (6) Safety (principle of safety design protection design) (7) UoM and preferred number system (UoM standard number system standard) 3. Mechanical parts and components design (1) Mechanical transmission (gear drive worm drive belt drive chain drive screw drive linkage cam mechanism) (2) Connecting piece (interference connection of bolt key pin coupling) (3) Shaft and bearing (shaft sliding bearing rolling bearing) (4) Operating adjustment and control parts (spring clutch brake) (5) Frame piece and guide rail (box frame piece guide rail) (6) Retarder and Governor Design (Retarder Governor)

The disassembly of rolling bearing is one of the important disassembly contents in mechanical maintenance. The disassembly must follow the basic rules of bearing disassembly, and different disassembly tools and methods should be used for different bearings. When the bearing is tight fit with the shaft and loose fit with the seat hole, the bearing and shaft can be removed from the housing together, and then the bearing can be removed from the shaft with a press or other removal tools. Here are some common bearing disassembly methods: 1. Removal of inner/outer ring. Dismantle the outer ring of interference fit, set several screws for extruding the outer ring screw on the circumference of the shell in advance, tighten the screw evenly on one side, and disassemble at the same time. These screw holes are usually covered with blind plugs, tapered roller bearings and other separate bearings. Several notches are set on the housing shoulder, and cushion blocks are used to disassemble them with a press or by tapping gently. 2. Removal of cylindrical hole bearing It is easiest to pull out with a press. At this time, pay attention to let the inner ring bear its pulling force. The inner ring of large bearing is disassembled by oil pressure method. The oil pressure is applied through the oil hole arranged on the shaft to make it easy to pull. For bearings with large width, oil pressure method and drawing fixture can be used together to remove them. The inner ring of NU and NJ cylindrical roller bearings can be disassembled by induction heating. It refers to the method of heating parts in a short time to expand the inner ring and then drawing. 3. Removal of tapered hole bearing Remove the relatively small bearing with tight sleeve, support the inner ring with the stop fastened on the shaft, turn the nut back several times, and then use the cushion block to knock it with a hammer for removal. For large bearings, it is easier to disassemble the bearing by using oil pressure. It is a method of disassembling the bearing by pressurizing the oil hole on the tapered hole shaft to make the inner ring expand. During operation, there is a danger that the bearing will suddenly come out. It is better to use the nut as a stop. 4. Knockout method Knocking is the simplest and most common method of disassembly. It is a disassembly method that uses the force of hammering to make the matched parts move and separate from each other to achieve the purpose of disassembly. The machine structure is relatively simple, and the parts are solid or some unimportant parts. Most of them are disassembled in this way. Before disassembly, in order to reduce friction, always soak the joints with lubricating oil. Knocking is a simple and easy method of disassembly. The commonly used tools for striking and disassembling are hand hammers, namely ordinary bench workers' hand hammers, punches and cushion blocks. The punch is made of steel, and the top of the hammered part is processed into a sphere, so that the end in contact with the workpiece is usually inlaid with soft metal, such as copper, aluminum, etc., and made into a flat or suitable shape for the workpiece, so as to protect the workpiece surface from damage. Different methods and steps shall be taken according to different machine structures during striking. The sleeve of sliding bearing and the outer sleeve of rolling bearing belong to interference fit in the hole, and they are usually taken out by striking. When removing, the end face of the bushing hammered shall be padded with cushion blocks. When removing the bushing with small diameter, it is better to use a step punch. The small diameter of the punch is just matched with the inner hole of the bushing. The large diameter of the punch is about 0.5mm smaller than the outer diameter of the bushing. For the disassembly of large diameter bushings and rolling bearings, bushings are often used. The removal of ordinary small bearing covers usually adopts the method of symmetrically driving inclined pads to open the bearing covers. 5. Press and pull Press unloading and pull unloading have many advantages over blow unloading. They apply uniform force, and the force size and direction are easy to control. They can remove large parts and components with large interference, and this method of disassembly has less chance to damage parts. However, press and pull unloading require corresponding machinery and tools. Pressure machine tools are required for pressing and unloading. Common pressure machine tools include mechanical press, friction press and hydraulic press. The drawing die is often used for pulling and unloading. The drawing die can be divided into fixed arm and movable arm, as well as two claws and three claws. The tension applied by the drawing die claw should be applied to the inner ring of the bearing. If the structure is special and it is unable to pull the inner ring, the outer ring can be pulled.

Shot blasting is to use the high-speed rotating impeller to throw small steel shot or small iron shot out of the high-speed impact part surface, so it can remove the oxide layer on the part surface. At the same time, steel shot or iron shot strikes the part surface at high speed, causing lattice distortion on the part surface and increasing surface hardness. It is a method of cleaning the part surface. Shot blasting is often used to clean the casting surface or strengthen the part surface. Generally, shot blasting is used for regular shape, with several heads up and down, left and right, high efficiency and little pollution. Shot blasting and sand blasting are widely used in repair and shipbuilding. However, both shot blasting and sand blasting use compressed air. Of course, it is not necessary to use high-speed rotating impeller for shot blasting. In the repair and shipbuilding industry, shot blasting (small steel shot) is generally used for steel plate pretreatment (rust removal before painting); Sand blasting (mineral sand is used in repair and shipbuilding industries) is mostly used in formed ships or sections to remove old paint and rust on steel plates and repaint them. In the repair and shipbuilding industry, the main role of shot blasting and sand blasting is to increase the adhesion of steel plate coating paint. In fact, the cleaning of castings is not only by shot blasting. For large pieces, the drum sand cleaning is generally carried out first, that is, the riser of castings is cut off and rolled in the drum. Parts collide with each other in the drum, and most of the sand on the surface is removed before shot blasting or shot blasting. The size of shot blasting ball is 1.5mm. Research shows that, in terms of damage, it is much easier to damage metal materials when there is tensile stress on the surface than compressive stress. When there is compressive stress on the surface, the fatigue life of materials is greatly improved. Therefore, shot peening is usually used to form surface compressive stress for parts that are prone to fatigue fracture, such as shafts, to improve product life. In addition, metal materials are very sensitive to tension, which is why the tensile strength of materials is much lower than the compressive strength, This is also the reason why metal materials generally use tensile strength (yield, tension) to express material properties. The working surface of the steel plate of our daily car is strengthened by shot peening, which can significantly improve the fatigue strength of the material. Shot blasting is to use the motor to drive the impeller body to rotate. With the effect of centrifugal force, shot with a diameter of 0.2~3.0 (including cast shot, cut shot, stainless steel shot, etc.) is thrown to the surface of the workpiece, so that the surface of the workpiece can reach a certain roughness, making the workpiece beautiful, or changing the welding tensile stress of the workpiece to compressive stress, so as to improve the service life of the workpiece It is almost used in most fields of machinery, such as ship building, automobile parts, aircraft parts, guns, tanks, surfaces, bridges, steel structures, glass, steel plates, pipes, etc. Sand blasting (shot blasting) is to use compressed air as power to spray sand with a diameter of 40~120 mesh or shot with a diameter of about 0.1~2.0 to the surface of the workpiece, so that the workpiece can achieve the same effect. Shot sizes are different, The treatment effect achieved is different. It is emphasized that shot peening can also play a role in strengthening. Now domestic equipment has entered a misunderstanding that only shot peening can achieve the purpose of strengthening. Enterprises in the United States and Japan use shot peening for strengthening! Each has its own advantages. For example, for a workpiece such as a gear, the shot blasting angle cannot be changed, and the initial speed can only be changed by frequency conversion However, it has a large amount of treatment and a fast speed, while shot peening is just the opposite. The effect of shot blasting is not as good as shot peening Sand blasting is a method of using compressed air to blow quartz sand out at high speed to clean the surface of parts. It is also called sand blowing in the factory. It can not only remove rust, but also remove oil, which is very useful for painting. It is commonly used for derusting the surface of parts; Surface modification of parts (small wet sand blasting machines sold in the market are used for this purpose. The sand is usually corundum and the medium is water); In the steel structure, it is an advanced method to use high-strength bolts for connection. Because high-strength connection uses the friction between the joint surfaces to transmit force, the quality of the joint surface is required to be high. At this time, the joint surface must be treated with sand blasting. Sand blasting is used for complex shape, easy to remove rust manually, with low efficiency, poor site environment and uneven rust removal. General sandblasting machines have sandblasting guns of various specifications, which can be put in and cleaned as long as the box is not too small. The head, an auxiliary product of pressure vessel, is sandblasted to remove the oxide skin on the surface of the workpiece. The diameter of quartz sand is 1.5mm-3.5mm One kind of processing is to use water as a carrier to drive the emery to process parts, which is sandblasting. Both shot blasting and sand blasting can clean and decontaminate the workpiece, so as to prepare for the following sequence, that is, to ensure the roughness requirements of the next process, or to ensure the consistency of the surface, shot blasting can strengthen the workpiece, so the sand blasting is not obvious. Generally, shot blasting is small steel ball and sand blasting is quartz sand. Number of items according to different requirements. Sand blasting and shot blasting are used almost every day in precision casting.