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

In machining, shaft parts are one of the main parts in the machine. It plays the role of supporting transmission, transmitting torque and bearing load. It is an indispensable part of mechanical equipment. However, in the process of production, shaft parts will wear out after working for a long time, so the maintenance method of porridge parts is very important. Maintenance of general shaft 1. Wear of small shaft and shaft sleeve: replace with new parts, repair the small shaft as shaft sleeve or repair the shaft sleeve with small shaft. 2. Journal wear: for the wear of general transmission journal and cylindrical surface, the clearance fit or transition fit between shaft and shaft sleeve should be repaired or replaced if its accuracy exceeds half of the original fit tolerance, and the size reduction after repair should not exceed half of the nominal size; For the wear of shaft journals of transmission parts such as bearings, gears and pulleys, chrome plating or metal spraying shall be used to restore the size. 3. Wear of keyway: (1) appropriately increase the width of keyway or convert to another milling keyway when the strength allows; (2) The keyway on the shaft is reworked after surfacing. 4. Shaft end thread damage: (1) under the condition of not affecting the strength, the shaft end thread can be appropriately turned smaller; (2) Weld the threaded part of the shaft end and turn it to the size requirements. 5. The cylindrical conical surface on the shaft is damaged: (1) grind off the damaged surface according to the original taper, and grind it as little as possible; (2) The unimportant conical surface can be turned into a cylindrical shape and then fitted with a conical surface sleeve. 6. Wear of conical hole: (1) wear off the damaged part of the conical surface according to the original taper; (2) Boring into a cylindrical hole, complete with welding, and machining according to the original conical hole. 7. Pin hole damage: (1) ream the original pin hole and re allocate the pin; (2) Fill the transposition and reprocess the pin hole. 8. Flat head, end hole damage: (1) surfacing repair; (2) Reduce the size appropriately. Maintenance of main shaft 1. The journal is worn, and its roundness and taper are different (1) Repair and grind the journal, pay attention to maintaining the hardness layer on the surface of the shaft, shrink the inner hole of the bearing and grind it to the requirements or replace it with a new bearing; (2) The shaft neck shall be polished, chrome plated or metal brush plated, and then externally ground to the requirements. The thickness of chromium plating layer shall not exceed 0.2mm. 2. Wear of journal installed with rolling bearing Repair by local chrome plating, brush plating or metal spraying, and then fine grinding to restore the journal size; The maximum grinding amount of carburized main shaft journal shall not be greater than about 0.5mm; The maximum grinding amount of nitriding and cyaniding main shaft journal is about 0.1mm, and the surface hardness after grinding should not be lower than the lower limit value required by the original design. 3. Wear of spindle taper hole There are burrs and bumps in the taper hole of the spindle, which can be removed with a scraper; If there is slight wear and the runout of the taper hole is still within the tolerance, it can be polished by grinding. If the accuracy of the taper hole is out of tolerance, it can be placed on a precision grinder to grind the inner taper hole. 3、 Maintenance of crankshaft 1. Local bending (1) Press correction method: support the crankshaft on two V-shaped irons, press the convex surface with the press, and the amount of over correction should be greater than a certain multiple of the deflection, and maintain the load for a certain time. After straightening, conduct artificial aging. (2) Knock the concave surface of the crankshaft with a hammer. The number of times to knock the same point should not be too many. The tapping point should be on the non machined surface. 2. Journal wear (1) Grind down the journal, and the reduction of the journal shall not exceed 2mm. (2) Large amount of wear can be repaired by spraying, bonding and other methods, but the strength must be checked before repair.

More and more people can't live without plastic. Plastic is widely used in production and life because of its good performance. In the process of plastic processing, technology is the basis to guide our plastic processing and production. So, what is the CNC processing technology of plastic mold? For plastic mold CNC processing technology, let's make a specific introduction below. Process analysis of plastic parts 1. Ingredients In addition to polymers, the raw materials used in plastic processing also need to add various plastic auxiliary agents, such as plasticizers, stabilizers, lubricants and fillers, in order to improve the forming process and the use performance of products, so as to reduce the processing cost of products. 2. Shaping This is the key link in plastic processing. In this link, the plastic will be reasonably used through the forming method according to its thermoplastic, thermosetting, initial form, product shape and size, so as to achieve the desired effect. The main methods of processing thermoplastic include extrusion, injection molding, calendering, blow molding and thermoforming. The main methods of processing thermosetting plastics are molding, transfer molding, and injection molding. Similar to plastic processing, rubber can also be processed by the above method. In addition, raw materials can also be cast with liquid monomers or polymers. In these plastic mold processing methods, the most commonly used are extrusion and injection molding, which are also the two most basic plastic forming methods. 3. Machining The mechanical processing of plastics requires the help of metal, wood and other processing methods, which can produce products with accurate size but small quantity. However, due to the great difference between the properties of plastic and metal and wood, the thermal conductivity of plastic is relatively poor, and the coefficient of thermal expansion and the amount of elastic mold are low. Therefore, when the fixture or pressure is too large, deformation will occur, and attention should also be paid to melting and adhering to the tool during cutting. Therefore, when machining plastics, the cutting tool and cutting speed should conform to the characteristics of plastics. 4. Join There is a big gap between the methods of joining plastics and other materials. The most commonly used ones are welding and bonding. Welding is hot-air welding with welding rods. Bonding is to use adhesive as required. 5. Surface finish This is to make plastic products more beautiful. The commonly used decoration methods are Mechanical finishing: it is to use some mechanical tools to remove burrs and burrs on plastic products, so as to achieve the purpose of trimming dimensions. Finishing: apply paint on the surface to brighten the surface, and stick the surface of products with patterned film. 6. Assembly The assembly process of plastic processing is to use the methods of bonding, welding and mechanical connection so that plastic parts can be assembled into the required shape.

Bearing is one of the important parts in machining equipment. The accuracy of bearing has a great impact on the accuracy and quality of products. Therefore, according to different needs, bearing manufacturers will also provide products with different accuracy requirements. How to divide the accuracy grade of bearings is described in detail below. The accuracy grade of rolling bearings can be divided into two types, one is dimensional accuracy, the other is rotational accuracy. The accuracy grade standard of bearings is mainly divided into six grades: grade 0, grade 6x, grade 6, grade 5, grade 4 and grade 2. The bearing grade standard is raised from grade 0 in turn. For general workpiece processing, grade 0 can meet the requirements, but in some occasions or processing requirements, bearings of grade 5 or higher accuracy are required. These accuracy levels are formulated according to ISO standards, but their names will change greatly due to the influence of national standards. Dimensional accuracy of bearings This mainly refers to the items related to the installation of shaft and housing. 1. The inner diameter, outer diameter, width and assembly width will deviate. 2. Deviation is also allowed for the inner and outer diameter of the roller set. 3. Allowable limit value of chamfer size. 4. The width also allows for variation. Rotation accuracy of bearing This is an item related to the runout of the rotating body. 1. The inner and outer rings can allow axial and radial runout. 2. The inner ring can have lateral runout 3. Allowable variation of inclination of outer diameter surface 4. Allowable variation of thrust bearing raceway thickness 5. Allowable deviation and allowable variation of conical hole Selection of bearing accuracy 1. The placement body is required to have high jumping accuracy It is mainly used for sound, affecting equipment and its main shaft; Rotation axis of radar and parabolic antenna; Machine tool spindle; Electronic computer, disk spindle; Aluminum foil roll neck; Multi stage rolling mill support bearing. The applicable accuracy levels are: P4, P5, P2, ABEC9. 2. High speed rotation Mainly used for supercharger; Main shaft and auxiliary engine of jet engine; Centrifugal separator; Liquefied natural gas pump; Turbine molecular pump main shaft and protective bearing; Machine tool spindle; Tension wheel. The applicable accuracy levels are: P4, P5, P2, ABEC9. 3. Small friction and friction change are required It is mainly used to control machines (synchronous motor, servo motor, gyro gimbal; measuring instrument; machine tool spindle. The applicable Accuracy grades are: P4, P5, P2, ABEC9, ABMA 7p. 4. General accuracy It can be mainly used in small motors, gear drives, cam drives, generators, low induction synchronous servo motors, pressure rotors, printers, copiers, and testing instruments. The applicable Accuracy grades are: P0, p6.

For the machining accuracy level, people's requirements are getting higher and higher. Therefore, in order to achieve the product quality control of mechanical parts and meet the requirements of customers for mechanical parts, the machining level of mechanical parts has been standardized in the field of mechanical manufacturing. This specification is applicable to the processing of most mechanical parts and is one of the reference materials for customer inspection product standards. So, what is the general mechanical parts processing level specification? 1. Machined surface of mechanical parts (1) Class a surface: attach great importance to the decorative surface, and there are high requirements for the surface during the use of parts. (2) Grade B surface: pay more attention to the decorative surface, and only occasionally see the surface in the use of parts. (3) Grade C surface: the decorative surface is not required to be high, and only appears inside the part. 2. Machining accuracy requirements for mechanical parts (1) Materials of machined parts: it needs to meet the drawing requirements provided by customers and the national standards for materials. Common specifications include stainless steel material specification, aluminum alloy material specification and carbon structural steel material specification. (2) If the drawings of machined parts provided by customers are not marked with dimensional tolerances, they can be inspected with reference to the requirements of gb/t1804-f for unmarked tolerances of national standard linear dimensions. (3) If the drawing does not identify the angle tolerance, refer to the unmarked tolerance gb/t11335-m of the national standard angle for inspection. (4) Angle tolerance can be checked by referring to the unmarked tolerance gb/t1184-h of national standard shape and position. 3. Quality control of machined parts (1) For drawings: if you find that the representation on the drawings is unclear, fuzzy, wrong and other problems after receiving the drawings, you should contact and communicate with the customer in time to confirm the solution of the problems. (2) The process of parts processing needs to be formulated in advance and strictly observed in the processing process. (3) During the processing of parts, if there is a processing error or the size exceeds the tolerance range, it is necessary to communicate with the process personnel to let the process personnel confirm whether the parts are available. (4) If the parts need to be scribed before processing, the traces should be removed in time after processing. (5) After parts are processed, deburring, chamfering and rounding off of edges and corners after drilling are required (except for special requirements). 4. Control of appearance of machined parts (1) Mechanical bumps and surface scratches similar to those caused by improper operation are not allowed on the surface of class a surface, and a small amount of class B and C can exist. (2) Deformation and cracks are not allowed on surfaces a, B and C, which will seriously affect the subsequent work of the parts. (3) If the surface of parts needs surface treatment, oxide layer, rust and uneven defects are not allowed on the surface. 5. Quality inspection of machined parts (1) Appearance inspection: carefully observe the surface, and it is not allowed to have cracks, scratches, bumps, unevenness, warpage and deformation on the surface. At the same time, the roughness of the surface should meet the requirements. (2) Material inspection: materials are the basis of products, so the inspection of materials needs to meet the relevant regulations and requirements of the state and customers. (3) Dimension and tolerance inspection: inspect in strict accordance with the drawings. (4) Thread and hole inspection: with the help of tooth gauge, plug gauge or screw inspection, the bottom hole of the thread is not greater than 0.1mm of the standard bottom hole.

For the machining accuracy level, people's requirements are getting higher and higher. Therefore, in order to achieve the product quality control of mechanical parts and meet the requirements of customers for mechanical parts, the machining level of mechanical parts has been standardized in the field of mechanical manufacturing. This specification is applicable to the processing of most mechanical parts and is one of the reference materials for customer inspection product standards. So, what is the general mechanical parts processing level specification? 1. Machined surface of mechanical parts (1) Class a surface: attach great importance to the decorative surface, and there are high requirements for the surface during the use of parts. (2) Grade B surface: pay more attention to the decorative surface, and only occasionally see the surface in the use of parts. (3) Grade C surface: the decorative surface is not required to be high, and only appears inside the part. 2. Machining accuracy requirements for mechanical parts (1) Materials of machined parts: it needs to meet the drawing requirements provided by customers and the national standards for materials. Common specifications include stainless steel material specification, aluminum alloy material specification and carbon structural steel material specification. (2) If the drawings of machined parts provided by customers are not marked with dimensional tolerances, they can be inspected with reference to the requirements of gb/t1804-f for unmarked tolerances of national standard linear dimensions. (3) If the drawing does not identify the angle tolerance, refer to the unmarked tolerance gb/t11335-m of the national standard angle for inspection. (4) Angle tolerance can be checked by referring to the unmarked tolerance gb/t1184-h of national standard shape and position. 3. Quality control of machined parts (1) For drawings: if you find that the representation on the drawings is unclear, fuzzy, wrong and other problems after receiving the drawings, you should contact and communicate with the customer in time to confirm the solution of the problems. (2) The process of parts processing needs to be formulated in advance and strictly observed in the processing process. (3) During the processing of parts, if there is a processing error or the size exceeds the tolerance range, it is necessary to communicate with the process personnel to let the process personnel confirm whether the parts are available. (4) If the parts need to be scribed before processing, the traces should be removed in time after processing. (5) After parts are processed, deburring, chamfering and rounding off of edges and corners after drilling are required (except for special requirements). 4. Control of appearance of machined parts (1) Mechanical bumps and surface scratches similar to those caused by improper operation are not allowed on the surface of class a surface, and a small amount of class B and C can exist. (2) Deformation and cracks are not allowed on surfaces a, B and C, which will seriously affect the subsequent work of the parts. (3) If the surface of parts needs surface treatment, oxide layer, rust and uneven defects are not allowed on the surface. 5. Quality inspection of machined parts (1) Appearance inspection: carefully observe the surface, and it is not allowed to have cracks, scratches, bumps, unevenness, warpage and deformation on the surface. At the same time, the roughness of the surface should meet the requirements. (2) Material inspection: materials are the basis of products, so the inspection of materials needs to meet the relevant regulations and requirements of the state and customers. (3) Dimension and tolerance inspection: inspect in strict accordance with the drawings. (4) Thread and hole inspection: with the help of tooth gauge, plug gauge or screw inspection, the bottom hole of the thread is not greater than 0.1mm of the standard bottom hole.

Metal cutting is the most basic processing method in the manufacturing industry. It is the process of using cutting tools to cut off excess materials of machined parts, so as to obtain qualified parts. The selection of appropriate tool materials plays a vital role in machining efficiency and machining quality. High quality cutting tools should have high hardness and wear resistance, sufficient strength and toughness, high heat resistance, good processability and economy, good thermal conductivity and small expansion coefficient. In all kinds of materials, there may be different performances for the above aspects, which requires the processing personnel to comprehensively analyze the requirements of all aspects and choose the most ideal matching result. Commonly used tool materials are mainly divided into four categories: tool steel, cemented carbide, ceramics and ultra hard tool materials. Let's see what the characteristics of these four categories are. Tool steel cutter Tool steel used to make cutting tools includes carbon tool steel, alloy tool steel and high-speed steel. Its main characteristics are poor heat resistance but high bending strength, low price, and good welding and grinding performance. Forming tools, which are widely used in medium and low speed cutting, are not suitable for high-speed cutting. Carbon tools belong to special quality non alloy steel, with good machinability and low price. They are used in a large amount in tool steel. Carbon tool steel can obtain high hardness after heat treatment, but when the cutting temperature is higher than 250 to 300 ℃, martensite will decompose and reduce the hardness. In addition, its carbide distribution is uneven, its deformation after quenching is large, it is easy to produce cracks, and its hardenability is poor, and its hardening layer is thin. It is only suitable for low-speed cutting tools, such as files, hand saw blades, etc. Alloy tool steel is a kind of steel that heats chromium, tungsten, vanadium and other alloy elements on the basis of carbon tool steel to improve its hardenability, toughness, wear resistance and heat resistance. The thermal hardness reaches 325 to 400 degrees Celsius, and the allowable cutting speed is 10 to 15 meters per minute. Therefore, it is mainly used for low-speed machining tools such as taps, dies, etc. High speed steel is a tool steel with high hardness and wear resistance, which contains more tungsten, molybdenum, chromium, vanadium and other elements. It has good comprehensive properties and is a tool material with the widest range of applications. After heat treatment, the hardness of high-speed steel reaches 62 to 66hrc, the bending strength is 3.3gpa, the heat resistance is about 600 degrees Celsius, and the heat treatment deformation is small, it can be forged, and it is easy to grind out sharp edges. It is commonly used to manufacture forming tools and hole processing tools with complex structures. Carbide cutter Cemented carbide is an alloy material made of hard compounds of refractory metals and bonding metals by powder metallurgy. It is higher than tool steel in hardness, strength, toughness, heat resistance, wear resistance and corrosion resistance. It is one of the most important tool materials today. The cutting speed of cemented carbide tools is 4 to 7 times faster than that of high-speed steel, and the service life is 5 to 80 times higher, but the disadvantage is that they are brittle and cannot be made into integral tools with complex shapes, so they are often made into blades, which are then installed on the tool body or die by welding, bonding, mechanical clamping and other methods. Ceramic cutting tool In recent years, with the deepening of the research in the field of high-temperature structural ceramics, the performance of silicon nitride ceramics has been greatly improved, so that silicon oxide ceramic tools have developed rapidly, and become a new tool with faster cutting speed and more wear-resistant than cemented carbide tools. Ceramic cutting tool is a cutting tool material made of alumina or silicon nitride as the matrix, and then a small amount of metal is added, which is sintered at high temperature. It has the characteristics of high hardness, good wear resistance, strong heat resistance, stable chemical properties, low friction coefficient, low strength and toughness, and low thermal conductivity. Therefore, it is suitable for cutting tools for fine machining hard materials at a high speed. Super hard tool Ultra hard cutting tools are made of diamond, cubic boron nitride and other materials. They have excellent mechanical and physical properties, and their hardness is much higher than the above three cutting tool materials. Cubic boron nitride has high hardness, heat resistance and stability, and is inert to iron group elements. Therefore, it is most suitable for making tools for cutting all kinds of hardened hard steel, such as carbon tool steel, alloy tool steel, high-speed steel, as well as all kinds of iron-based, nickel based, cobalt based and other thermally sprayed parts. Diamond tool is the material with the highest hardness in nature. The tool made of it has a wider range of applications and can process all kinds of difficult and non difficult materials. However, natural diamond is expensive and is mainly used in precision machining of non-ferrous metals and non-metallic materials. With the progress of modern society and the rapid change of science and technology, mechanical material processing has higher and higher requirements for the materials of cutting tools. Therefore, mastering and understanding the use of various cutting tools and the characteristics of materials can better select and correctly use cutting tools and manufacture more accurate parts.

Metal cutting is the most basic processing method in the manufacturing industry. It is the process of using cutting tools to cut off excess materials of machined parts, so as to obtain qualified parts. The selection of appropriate tool materials plays a vital role in machining efficiency and machining quality. High quality cutting tools should have high hardness and wear resistance, sufficient strength and toughness, high heat resistance, good processability and economy, good thermal conductivity and small expansion coefficient. In all kinds of materials, there may be different performances for the above aspects, which requires the processing personnel to comprehensively analyze the requirements of all aspects and choose the most ideal matching result. Commonly used tool materials are mainly divided into four categories: tool steel, cemented carbide, ceramics and ultra hard tool materials. Let's see what the characteristics of these four categories are. Tool steel cutter Tool steel used to make cutting tools includes carbon tool steel, alloy tool steel and high-speed steel. Its main characteristics are poor heat resistance but high bending strength, low price, and good welding and grinding performance. Forming tools, which are widely used in medium and low speed cutting, are not suitable for high-speed cutting. Carbon tools belong to special quality non alloy steel, with good machinability and low price. They are used in a large amount in tool steel. Carbon tool steel can obtain high hardness after heat treatment, but when the cutting temperature is higher than 250 to 300 ℃, martensite will decompose and reduce the hardness. In addition, its carbide distribution is uneven, its deformation after quenching is large, it is easy to produce cracks, and its hardenability is poor, and its hardening layer is thin. It is only suitable for low-speed cutting tools, such as files, hand saw blades, etc. Alloy tool steel is a kind of steel that heats chromium, tungsten, vanadium and other alloy elements on the basis of carbon tool steel to improve its hardenability, toughness, wear resistance and heat resistance. The thermal hardness reaches 325 to 400 degrees Celsius, and the allowable cutting speed is 10 to 15 meters per minute. Therefore, it is mainly used for low-speed machining tools such as taps, dies, etc. High speed steel is a tool steel with high hardness and wear resistance, which contains more tungsten, molybdenum, chromium, vanadium and other elements. It has good comprehensive properties and is a tool material with the widest range of applications. After heat treatment, the hardness of high-speed steel reaches 62 to 66hrc, the bending strength is 3.3gpa, the heat resistance is about 600 degrees Celsius, and the heat treatment deformation is small, it can be forged, and it is easy to grind out sharp edges. It is commonly used to manufacture forming tools and hole processing tools with complex structures. Carbide cutter Cemented carbide is an alloy material made of hard compounds of refractory metals and bonding metals by powder metallurgy. It is higher than tool steel in hardness, strength, toughness, heat resistance, wear resistance and corrosion resistance. It is one of the most important tool materials today. The cutting speed of cemented carbide tools is 4 to 7 times faster than that of high-speed steel, and the service life is 5 to 80 times higher, but the disadvantage is that they are brittle and cannot be made into integral tools with complex shapes, so they are often made into blades, which are then installed on the tool body or die by welding, bonding, mechanical clamping and other methods. Ceramic cutting tool In recent years, with the deepening of the research in the field of high-temperature structural ceramics, the performance of silicon nitride ceramics has been greatly improved, so that silicon oxide ceramic tools have developed rapidly, and become a new tool with faster cutting speed and more wear-resistant than cemented carbide tools. Ceramic cutting tool is a cutting tool material made of alumina or silicon nitride as the matrix, and then a small amount of metal is added, which is sintered at high temperature. It has the characteristics of high hardness, good wear resistance, strong heat resistance, stable chemical properties, low friction coefficient, low strength and toughness, and low thermal conductivity. Therefore, it is suitable for cutting tools for fine machining hard materials at a high speed. Super hard tool Ultra hard cutting tools are made of diamond, cubic boron nitride and other materials. They have excellent mechanical and physical properties, and their hardness is much higher than the above three cutting tool materials. Cubic boron nitride has high hardness, heat resistance and stability, and is inert to iron group elements. Therefore, it is most suitable for making tools for cutting all kinds of hardened hard steel, such as carbon tool steel, alloy tool steel, high-speed steel, as well as all kinds of iron-based, nickel based, cobalt based and other thermally sprayed parts. Diamond tool is the material with the highest hardness in nature. The tool made of it has a wider range of applications and can process all kinds of difficult and non difficult materials. However, natural diamond is expensive and is mainly used in precision machining of non-ferrous metals and non-metallic materials. With the progress of modern society and the rapid change of science and technology, mechanical material processing has higher and higher requirements for the materials of cutting tools. Therefore, mastering and understanding the use of various cutting tools and the characteristics of materials can better select and correctly use cutting tools and manufacture more accurate parts.

NC machining is the most widely used machining method at present, and it is also the basic skill that every machining worker must master. After startup, workpiece clamping, workpiece touch number, tool preparation and processing parameter setting, it enters the startup processing link. In this link, we will summarize what problems need the attention of operators. Tool and feed speed Before starting to execute each program, all tools must be carefully checked to ensure that they are consistent with the tools specified in the programming instructions. At the beginning of processing, the feed speed should be adjusted to the minimum, and the methods of single section execution, rapid positioning and tool dropping should be adopted. Attention must be paid to the feeding, and the hand should be placed on the stop key. If problems are found, it must be stopped immediately. During machining, pay attention to the moving direction of the tool to ensure safe feeding, and then slowly increase the feeding speed until it reaches the appropriate value. At the same time, add coolant or cold air to the tool and workpiece to reduce the cutting temperature. Precautions for rough machining When rough machining the workpiece, the position of the operator should not be too far away from the control panel, so as to ensure that the machine can be shut down and checked in time in case of abnormal phenomena. Pull the table again after roughening to make sure that the workpiece is not loose. If there is any, the workpiece must be corrected and touched again. In the processing process, we should constantly optimize the processing parameters according to the processing conditions to achieve the best results. Because roughening is a very critical process, after processing, the main dimension value should be measured to see whether it is consistent with the drawing requirements. It can be removed after passing the self inspection, and must be sent to the inspector for special inspection. Precautions for drilling processing Drilling on the machining center is divided into three steps. First, the center drill must be used to locate the hole, then drill with a drill bit 0.5 to 2 mm smaller than the hole size in the drawing, and finally finish machining with a suitable drill bit. Precautions for reaming Similar to drilling, reaming the workpiece is also divided into three steps. First, locate the hole with a central drill, then drill with a drill bit 0.5 to 3 mm smaller than the hole size in the drawing, and finally ream with a reamer. When reaming, pay attention to control the spindle speed within 70 to 180 revolutions per minute, neither lower than the lower limit nor higher than the upper limit. Precautions for boring processing Boring the workpiece is divided into four steps. The first step is to use the center drill for positioning, the second step is to use a drill bit that is 1 to 2 mm smaller than the hole size in the drawing, the third step is to use a rough boring cutter or milling cutter to process to a machining allowance of only about 0.3 mm on one side, and the last step is to use a fine boring cutter with pre adjusted size for fine boring, and the fine boring allowance cannot be less than 0.1 mm. Precautions for direct NC operation Before DNC NC machining, the workpiece should be clamped, the zero position should be set, and then the machining parameters should be set. Open the processing program for data transmission processing in the computer for inspection, then let the computer enter the DNC state, and enter the file name of the correct processing program. Next, press the "tape" key and the program start key on the machining machine tool, and then the machine tool controller will display the flashing words "LSK". At this time, press the enter keyboard on the computer to carry out DNC data transmission processing.

Abrasive belt grinding is composed of abrasive belt, contact wheel, tension wheel, workbench and other basic components. The function of the contact wheel is to control the contact pressure of the abrasive belt particles on the workpiece and make the abrasive belt particles cut. The tensioning wheel plays the role of tensioning the sand belt. It is a roller made of cast iron or steel. Next, this paper will introduce the mechanism and characteristics of abrasive belt grinding of mechanical parts. 1、 General mechanism of abrasive belt grinding The function of the contact wheel is to control the contact pressure of the abrasive belt particles on the workpiece and make the abrasive belt particles cut. The contact wheel is usually made of steel or cast iron with a layer of hard rubber poured on it. The harder the rubber is, the higher the metal removal rate is, and the softer the wheel surface is, the lower the grinding surface roughness value is. The tensioning wheel plays the role of tensioning the sand belt. It is a roller made of cast iron or steel. When the tension is large, the grinding efficiency is high. Because the abrasive grains of the abrasive belt are arranged neatly and evenly, with small negative front angle and large rear angle, and the abrasive grains can participate in cutting at the same time, it has high efficiency, less grinding heat generation and good heat dissipation effect. Similar to wheel grinding, the formation of chips also has three stages: elastic friction deformation, scoring and cutting. However, due to the above advantages, the surface residual stress and work hardening depth of grinding workpiece are much lower than that of wheel grinding. 2、 Characteristics of abrasive belt grinding 1. Abrasive belt grinding has high efficiency and high metal removal rate. Its efficiency has reached 10 times that of milling and 5 times that of ordinary grinding wheel. Due to less heat generated by friction and long heat dissipation interval of abrasive particles, it can effectively reduce workpiece deformation and burns, which is known as "cold" grinding. Generally, the machining accuracy can reach the machining accuracy of ordinary grinding wheel grinding, and some dimensional accuracy can reach ± 0.005mm, the maximum can reach 0.0012mm, and the flatness can reach 0.001mm. 2. The abrasive belt is in flexible contact with the workpiece, which has good running in and polishing effects, and can grind all kinds of complex forming surfaces. The surface roughness of the workpiece can reach 0.8-0.2 microns. 3. It has strong adaptability, and can be used in ordinary lathes, vertical lathes, gantry planers, etc. to grind external circles, internal circles, planes, etc. with abrasive belt grinding heads. 4. The equipment structure is simple. The contact wheel is rarely worn, which can keep the sand belt at a constant speed; The transmission chain is short, which increases the stability of grinding, and the power utilization rate of the machine tool is more than 85%. 6. The auxiliary time is less. After the workpiece is positioned once, the abrasive belt can be replaced many times to complete all processing, without balancing and dressing like the grinding wheel. 7. It is easy to operate, convenient to maintain, safe and reliable, and the machine tool has high seismic resistance.

When installing and turning eccentric workpieces, the axis of the eccentric shaft (sleeve) should be crossed first, and then installed on the two center or four jaw single acting chuck. Now take the eccentric shaft as an example to introduce the machining and marking method of eccentric workpiece. 1. First turn the workpiece blank into an optical axis, so that the two end faces are perpendicular to the axis. Attention should be paid to avoid errors in production, because their errors will directly affect the alignment accuracy, determine the surface roughness, and then paint a layer of blue display agent on the two end faces and the surrounding outer circle of the shaft, and put it in the V-shaped frame of the flat plate after it is dry. 2. Use the vernier caliper to draw the tip of the needle to measure the highest point of the optical axis, and record the data, then move the vernier of the vernier height gauge down to half of the actual measured diameter of the workpiece, and gently draw a horizontal line on one section of the bow and arrow, then turn the workpiece 180 degrees, still use the height just adjusted, and then draw another horizontal line on this section. Check that the front and rear lines coincide. If they coincide, it is the horizontal axis of the workpiece; If it does not coincide, the vernier height gauge needs to be adjusted, and the vernier moves down by half of the distance between the two parallel lines. Repeat until the two lines coincide. 3. After finding out the axis of the workpiece, you can draw a circle line on the section and around the workpiece. These lines are the horizontal section of the axis and the intersection line of the workpiece, which plays a great role in later production. 4. Turn the workpiece 90 degrees, use a flat teaching ruler to draw the end line, and then use the vernier height ruler just adjusted to draw a circle line on the shaft section and around, so as to get two mutually perpendicular circle lines on the workpiece, which is the simplest and convenient way to draw a circle line. 5. Move the vernier of the vernier height gauge up by an eccentric dimension, and also draw a circle line on the end face and around the shaft. 6. After the center line of the eccentricity is drawn, the two ends of the eccentricity center are respectively punched. The center position of the punching hole is required to be accurate, and the hole pit should be shallow, small and round. If two centers are used to turn the eccentric shaft, the central hole shall be drilled first according to the same punching; If four jaw single action chuck is used for clamping and turning, an eccentric circle should be drawn first according to the same punching. Colleagues must also punch several sample punching holes evenly and accurately on the eccentric circle for alignment.