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

CNC machining should learn to operate according to machining characteristics The process design of Shenzhen CNC precision processing plant must be completed before the programming is started, because the programming is based only after the process plan is determined. The quality of the process plan will not only affect the efficieCNCy of the machine tool, but also directly affect the processing quality of the parts. Analyze according to a large number of machining examples. Inadequate consideration of process design is one of the main reasons for CNC machining errors Therefore, it is very necessary to make process analysis and planning before programming. CNC machining process design mainly iCNCludes the following contents: (1) Select the parts suitable for machining on the CNC machine tool, and determine the process content (2) Analyze the drawings of the parts to be processed, define the processing content and technical requirements, and determine the processing scheme of the parts. Formulate CNC processing route. Such as division of processes, connection between processing and non CNC processing processes, etc Machining workpiece (Processing workpiece) (3) Design of processing procedures and steps. For example, the positioning datum of the selected parts, the determination of the fixture and auxiliary equipment scheme, the determination of the cutting parameters, etc. (4) Adjustment of CNC machining program. Select tool setting point and tool change point, determine tool compensation, and determine processing route (5) Allocate machining allowaCNCe in CNC machining. (6) Process some process instructions on CNC machine tools. (7) First article trial processing and on-site problem handling.

Non-standard equipment parts processing process will present tool wear accelerated, poor processing appearance integrity, chip removal difficulties and other common problems, seriously affect the quality of such material precision parts processing, production cycle and processing costs. Non-standard equipment parts processing needs to get super-lubricated processing appearance and high processing accuracy, which requires the knife has a high standard life, the tool is not worn, will be based on the quality of the processed appearance is not reduced super poor. Diamond tool standard life is very high, high-speed cutting tool wear is also very slow. Therefore, ultra-precision cutting, cutting speed is not subject to the constraints of tool life, which is different from the general cutting rules.   Non-standard equipment parts processing practice selected cutting speed, is often based on the use of ultra-precision machine tools and dynamic characteristics of the cutting system to select the dynamic characteristics, that is, to select the minimum vibration speed. Because at this speed the appearance of the smallest roughness, the highest quality machining. Obtaining a high quality non-standard machined appearance is the primary concern in the machining of non-standard equipment parts. The use of good quality, especially the dynamic characteristics of good, small vibration of the ultra-precision machine tools can use high cutting speed, can improve the power of processing. The selection of non-standard equipment parts processing parameters include the selection of the cutting tool point of view, the selection of cutting speed and depth of cut and feed rate selection. From the past experience we know that in the processing of plastic materials, if you select a larger front angle of the tool can be useful to press down the composition of the chip tumor, which is the front angle of the tool increases, the cutting force is reduced, cutting deformation is small, the tool and chip contact length becomes shorter, reducing the basis for the composition of the chip tumor.

First, a large number of reduction in the number of tooling, processing the shape of complex parts do not require complex tooling. If you want to change the shape and size of the parts, only need to modify the parts processing procedures, suitable for new product development and reshaping. Second, stable processing quality, high machining accuracy, high repeatability, adapt to the processing requirements of the aircraft.   Third, multi-species, small batch production in the case of high productivity, can reduce production preparation, machine tool adjustment and process inspection time, and due to the use of the best cutting volume and reduce the cutting time. Fourth, can be processed by conventional methods difficult to process the complex surface, and can even process some unobservable processing parts.

First, the transmission device in the actual operation of the probability of danger is relatively large, the machine tool transmission is generally composed of gear parts, drive chain and drive belt, if these parts are not fully considered when the design of safety, no design protection layer, the rotating part of the exposed, then it is very likely that the worker's hand, or clothing stranded into the device, thus causing injury. Second, pressure machinery pressure parts may cause danger, generally common punching machines, crushers, molding machines, shear beds, etc. belong to the pressure machinery, because most of this equipment requires manual operation, and personnel operation can not avoid human error because of personnel fatigue or mood swings, so it is also very easy to happen injury accidents. Third, the danger from the machine tool is also a danger, because the machine tool is mostly high-speed cutting machinery, so its danger is great, the tool, splash, the operator stands inappropriate position leading to impact and other factors may lead to personal injury accidents.

Parts in the process of processing, due to the influence of various factors, easily lead to its own existence of certain defects, such as the appearance of substandard, limited scope of use, etc.. The existence of these defects will inevitably bring certain problems to the use of parts, in order to overcome these problems and give full play to the unique value of the parts, precision parts machining is the best choice. The choice of precision parts machining can not only effectively improve the quality of materials, parts accuracy, play its function, but also make the durability of the parts greatly improved, and contribute to the improvement of the quality of the entire machinery. Precision machining is also good for improving the dimensional accuracy of the parts, so the most direct effect is that it can make the parts reach interchangeability, which in turn increases the wear resistance and service life of the parts. It is because of all these advantages that precision machining of parts is so popular, and there are more suitable fields to be used when assembling equipment, so that its value can be maximized. Thus, it seems that we must pay attention to the precision parts processing link. After the processing of different parts we can get more suitable for their own parts, so in order to make these products better for their own service, to play its most extreme value, so many people are less precision machining this important link.

In understanding the premise of precision shaft machining process, we should first have a deeper understanding and knowledge of its function, structural characteristics and technical requirements, and then analyze the process for different blank materials, then I will introduce the process of precision shaft machining of precision hardware machining to you! First, the function, structural characteristics and technical requirements of precision hardware shaft parts   Precision hardware shaft is one of the typical parts frequently encountered in the machine. It is mainly used to support the transmission parts, transfer torque and bear the load. Shaft parts are rotating body parts, its length is greater than the diameter, generally by the concentric axis of the outer cylindrical surface, tapered surface, bore and thread and the corresponding end face composed of. According to the different structural shapes, shaft parts can be divided into light shaft, stepped shaft, hollow shaft and crankshaft, etc..   The shaft with length-diameter ratio less than 5 is called short shaft, more than 20 is called slender shaft, and most of the shafts are in between.   Precision hardware shafts are supported by bearings, and the shaft section that fits with the bearings is called journal. Journals are the assembly benchmark of the shaft, their accuracy and surface quality are generally required to be high, and their technical requirements are generally formulated according to the main function and working conditions of the shaft, which usually have the following items.   (A) Dimensional accuracy   In order to determine the position of the shaft, the journals that play a supporting role usually require high dimensional accuracy (IT5~IT7). The dimensional accuracy of the journals of assembled transmission parts is generally required to be lower (IT6~IT9).   (II) Geometric shape accuracy   The geometric shape accuracy of precision hardware shaft mainly refers to the roundness and cylindricity of journal, outer taper surface, Morse taper hole, etc. The tolerance should be generally limited to the dimensional tolerance range. For the inner and outer circular surfaces with high accuracy requirements, the allowable deviation should be marked on the drawing.   (C) Mutual position accuracy   The position accuracy requirement of precision hardware shaft is mainly determined by the position and function of the shaft in the machinery. Usually, the coaxiality requirement of the journal of the assembled transmission parts to the supporting journal should be ensured, otherwise it will affect the transmission accuracy of the transmission parts (gears, etc.) and generate noise. Ordinary accuracy of the shaft, the radial runout of the mating shaft section to the support journal is generally 0.01~0.03mm, and the high precision shaft (such as spindle) is usually 0.001~0.005mm.   (D) Surface roughness   The surface roughness of the shaft diameter that generally fits with the transmission parts is Ra2.5~0.63μm, and the surface roughness of the support shaft diameter that fits with the bearing is Ra0.63~0.16μm. Second, the precision hardware shaft blanks and materials   (A) Precision hardware shaft blanks   Precision hardware shaft can be used in the form of bar, forging and other blanks according to the use requirements, production type, equipment conditions and structure. For shafts with a small difference in outer diameter, bar stock is generally used; for stepped shafts or important shafts with a large difference in outer diameter, forgings are often used to save materials and reduce the workload of machining, and also improve mechanical properties.   According to the different scale of production, there are two kinds of forging methods for blanks: free forging and die forging. Small and medium batch production more free forging, a large number of mass production using die forging.   (B) Material of precision hardware shaft   Precision hardware shaft should be used according to the different working conditions and use requirements of different materials and different heat treatment specifications (such as tempering, normalizing, quenching, etc.) to obtain a certain strength, toughness and wear resistance. 45 steel is a common material for shaft parts, it is cheap after tempering (or normalizing), can get better cutting properties, and can obtain higher strength and toughness and other comprehensive mechanical properties, quenched surface hardness up to 45 ~ 52HRC. 40Cr and other alloy structural steel is suitable for medium precision and high speed shaft parts, such steel after quenching and tempering, has a good overall mechanical properties.   Bearing steel GCr15 and spring steel 65Mn, after tempering and surface high-frequency quenching, the surface hardness can reach 50 ~ 58HRC, and has a high fatigue resistance and good wear resistance, can be manufactured with high precision shaft.   Precision machine tool spindle (such as grinding wheel shaft, coordinate boring machine spindle) can choose 38CrMoAIA nitride steel. This steel after tempering and surface nitriding, not only can obtain a very high surface hardness, and can maintain a softer core, so good impact resistance toughness. Compared with carburizing and quenching steel, it has the characteristics of little heat treatment deformation and higher hardness.

1. The requirements of precision hardware shaft for matching machine parts   Since the precision of the precision hardware shaft itself is within 1μm, it is required to have high dimensional accuracy and shape accuracy of its mating parts (shaft, bearing seat, end cap, retaining ring, etc.), especially the accuracy of the mating surface should be controlled at the same level as the bearing, which is crucial and most easily ignored.   Must also pay attention to the precision hardware shaft of the matching machine parts if it fails to meet the above requirements, often make the precision hardware shaft in the installation than the original bearing error occurs several times, or even 10 times more than the error, completely does not become its precision hardware shaft, the reason is that the error of the matching machine parts is often not simply superimposed on the error of the bearing, but with a different multiplier amplification added to the. 2、Precision hardware shaft fit   In order to ensure that the bearing does not produce excessive deformation after installation, it must do the following.   (1) The roundness of the shaft and the seat hole and the verticality of the retaining shoulder should be required in accordance with the corresponding accuracy of the bearing.   (2) To accurately calculate both the amount of interference of the rotating collar fit and the amount of suitable fit of the fixed collar.   Rotating collar burning interference amount in the possible range is also appropriate to obtain a small. As long as the effect of thermal expansion at operating temperature and the effect of centrifugal force at the highest speed is practically guaranteed, it will not cause creep or sliding of the tightly fitted surface. Fixed collar according to the size of the working load and bearing size, choose a very small gap fit or interference fit, too loose or too tight are not conducive to maintain the original precise shape.   (3) bearing such as in high-speed conditions, and high working temperature, should pay special attention to the rotating collar fit can not be too loose to prevent eccentric vibration, as well as fixed collar fit can not appear clearance, in order to prevent the collar under load deformation and excitation vibration.   (4) the fixed ring to take a small interference with the condition of the matching surface both sides have high shape accuracy and small roughness, otherwise it causes installation difficulties and disassembly more difficult, in addition, also need to consider the impact of spindle thermal elongation.   (5) use pairs of angular contact ball bearing spindle, most of the load is lighter, its fit interference such as large, then its internal axial preload will be significantly larger, resulting in adverse effects. The use of double row short cylindrical roller bearing spindle and tapered roller bearing spindle, the load is relatively large, so its fit interference is also relatively large. 3、Ways to improve the actual fit accuracy   In order to improve the actual fit accuracy of the bearing installation, we must use the measurement method and measurement tools that do not deform the bearing, the actual precision measurement of the bearing bore and outer circle with the size of the surface, you can measure the inner diameter and outer diameter of the measurement items are measured, and the measured data to make a comprehensive analysis, based on this, precision for the shaft and seat hole bearing installation parts of the size. The actual measurement of the corresponding size and geometry of the shaft and housing should be carried out under the same temperature conditions as when the bearings are measured. In order to ensure a high practical fit, the roughness of the surfaces of the shaft and the seat bore with the bearing should be as small as possible.   In the above measurement, should be in the bearing of the outer circle and bore, and the corresponding surface of the shaft and seat hole, in close to the assembly chamfer on both sides, respectively, to show the maximum deviation direction of the two groups of marks, so that in the actual assembly, so that the maximum deviation of the two parties to align the same orientation, so that after the assembly, the deviation of both sides can be partially offset.   The purpose of making two sets of orientation marks is that the compensation of deviation can be considered comprehensively, so that the respective rotational accuracy of the two end supports can be improved, and the coaxiality error of the seat hole and the two end journals between the two supports can be partially eliminated. The implementation of surface strengthening measures on the mating surface, such as sandblasting treatment, with a slightly larger diameter precision plug plug once the bore, etc., are conducive to improving the accuracy of the mating.

First, cnc precision machining order   When the mold is very large and deep, the rough machining and semi-finishing before quenching is done with soft machining, and the finishing after quenching is done with hard machining; small and shallow molds can be milled at once after quenching. If the mold wall is very thin and the cavity is very deep, electric machining is used.   If the mold cavity has a large, flat bottom surface, rough machining is done with a one-piece milling disc followed by corner clearing with a round-nose milling cutter, which has good cutting strength and disperses heat. Round nose milling cutter in the processing of the need to clear the root of the parts faster than the flat bottom cutter efficiency, not easy to collapse the edge Second, the choice of cnc precision machining tools   When cnc precision machining hardened mold, the correct choice of milling cutter is very important. Usually, the choice of high rigidity body design, high temperature resistance, wear-resistant coating, super hard material production tool is preferred, Zhongshan Elang precision tools launched high-speed and high hardness H series to achieve high-speed and high hardness HRC70 processing. In addition, the rigidity of the tool is important, in order to increase the rigidity of the small diameter milling cutter, the diameter of the shank is made much larger than the diameter of the tool to improve the machining finish and extend the tool life; the overhang length of the tool clamping should be as short as possible. On the other hand, the choice of new coatings, so that the tool can withstand higher cutting temperatures, such as Tisin and Cygnus-X coating with acidification temperature of 1300 ℃, surface hardness Hv3700, coating thickness of 4um so they are more suitable for high-speed and hardening quenching mold processing Third, cnc precision machining toolholder selection and tool clamping   The toolholder should be dynamically balanced or choose sintered toolholder, while the shape of the toolholder should be adapted to the structure of the mold. Usually a half degree clearance should be maintained between the milling cutter and the side of the workpiece, for example, if the side of the workpiece is 3° bevel, the shape of the toolholder is made 5/2 to get the maximum rigidity. If the side of the workpiece is 90° straight, the shank should be of thin neck construction.   It is important to clamp the milling cutter, which involves the tolerance of the toolholder, the fit of the toolholder and the tool holder, and the diameter jump after installation. For this reason, the manufacturing tolerance of the toolholder should be -0.0025mm to -0.005mm, or the application of heat shrinkable clamping to clamp the tool. Fourth, nc precision machining machine selection and NC programming points   The use of good rigidity, high precision machine tools to achieve good results. Machining high hardness mold programming tool cutting into the mold path should be used spiral interpolation, so that the cutting process is smoother. In cases where cutting from the side or spiral cannot be used, oblique wave cutting should be used to avoid axial cutting. Programming also determines the size of the radial travel and depth of cut.

First, CNC precision machining machine maintenance   1, half an hour before work every day to clean and maintain the machine If you use an air gun or oil gun to clean the chips, the spindle must have a knife.   2, prohibit the use of air guns or oil guns to blow the spindle taper hole, to avoid chips and other tiny particles of debris are blown into the main shaft hole, affecting the cleanliness of the spindle.   3、Check whether the lubricator is working normally, whether the lubricant is sufficient, and turn on the machine according to the normal order.   4, in the machine tool before the official work to start the spindle (speed of 501R / M) in order to carry out spindle warm-up. Second, CNC precision machining machine operation   1, before the machine against the program list to confirm the processing blank type, size and machining allowance and the blank to sand and polish processing.   2, on the machine to confirm the placement of workpieces, as well as the processing process sequence, complete the more table action   3、Distribution, such as the need for "distraction bar" distraction speed of 501R/M, such as the use of knife distraction speed depends on the tool, in this process should also pay attention to the same height must be taken to ensure the accuracy of the distraction, the distraction is available after the end of the "G0 G54 X0 Y0" for inspection   4, formal processing before checking to confirm the placement of the workpiece and take the number of correct Third. CNC precision machining precautions   1、Before processing each program, you need to strictly confirm whether the tool is consistent with the program   2、When loading the tool, you should confirm the length of the tool and the suitability of the chosen clamping head.   3、Keep the tool in the same workpiece in the same area every time to ensure the accuracy of the tool connection.   4、Use air blowing in the roughing program as much as possible, and spray oil in the light tool program   5、Before oil spraying in the light knife need to clean the machine tool aluminum slag to prevent aluminum slag oil absorption   6, in the cnc precision machining operation by itself, the operator shall not leave the machine tool or regularly check the machine tool running condition, if you need to leave midway, you must designate the relevant personnel to look at the check   7, in the process of processing, such as found that the machining allowance is too much, you must use the "single section" or "pause" to X, Y, Z value zero after the manual milling off and then shake back to the "zero point "Let it run on its own   8, the processing process, such as found in the case of collision tool operator must immediately stop, such as pressing the "emergency stop" button or "reset button" button or the "feed rate" to zero, etc.   9, in the machine operation is prohibited to open the door to avoid flying knife or flying workpiece   10. The workpiece must be cleaned and deburred in time after the machine   11. At the end of the shift, the operator must do a timely and accurate handover to ensure that subsequent processing can be carried out normally   12. Before shutting down the machine, ensure that the tool magazine is in the original position, XYZ axis is stopped in the center position, and turn off the power supply and general power supply on the machine operation panel in turn.   13. When encountering heavy thunderstorms, the power must be cut off immediately to stop work

The main surface of all kinds of precision hardware shaft parts is the outer surface of each journal, the accuracy of the bore of the hollow shaft is generally not required, and the accuracy of the secondary surfaces such as threads, splines and keyways on the precision hardware shaft is also relatively high. Therefore, the machining process route of shaft parts mainly considers the processing order of the outer circle and intersperses the processing of secondary surfaces reasonably. I will introduce you to the following, the production of different precision, different materials commonly used in the machining process route of various types of precision hardware shaft parts:. (1) general carburized steel precision hardware shaft parts processing process route: preparation - forging - normalizing - playing top hole - rough turning - semi-finish turning, finish turning - carburizing (or carbonitriding) - quenching, low-temperature tempering - rough grinding - secondary surface machining - finish grinding.   (2) General precision quenched steel precision hardware shaft processing process route: preparation - forging - normalizing (annealing) - playing the top hole - rough turning - quenching - semi-finishing turning, finishing turning - surface quenching, tempering - rough grinding - secondary surface machining - finishing grinding.   (3) precision nitrided steel shaft parts processing process route: preparation - forging - normalizing (annealing) - playing the top hole - rough turning - eight quality - semi-finish turning, finish turning - low-temperature aging - rough grinding - nitriding treatment - secondary surface processing - finish grinding - light grinding.   (4) the overall quenching precision hardware shaft parts processing process route: preparation - forging - normalizing (annealing) - playing the top hole - rough turning - tempering - semi-finish turning, finish turning - secondary surface processing - overall quenching - rough grinding - low-temperature aging - finish grinding.   General precision hardware shaft parts, the final process using fine grinding is sufficient to ensure the quality of processing. Precision shaft parts, in addition to finishing, should also be arranged for finishing processing. For shaft parts other than the overall quenching, the finishing process can be arranged in accordance with the specific circumstances of the different quenching and heat treatment before, or arranged in the quenching and heat treatment after the secondary surface processing before. It should be noted that the quenched parts, can not use the general tool, shaft parts of the main surface is the outer surface of each journal, hollow shaft bore accuracy is generally not high, and precision spindle threads, splines, keyways and other secondary surface accuracy requirements are relatively high. Therefore, the machining process route of shaft parts mainly considers the machining sequence of the outer circle, and the machining of secondary surfaces is reasonably interspersed.