Brief introductionCentral abrasive and a binder resin made of a circular abrasive through hole. Abrasive wheel is the most widely used as a maximum amount, the use of face, high-speed rotation, can the outer, inner circle, plane type and various other metal or non-metal surface of the workpiece when using coarse grinding, fine grinding and half grooving and grinding and cutting and so on. Wheel variety. The press can be divided into ordinary abrasive abrasive (corundum and silicon carbide) abrasive grinding wheel and the natural and super abrasive (diamond and cubic boron nitride) grinding wheel; according to the shape can be divided into flat-shaped grinding wheel, bevel wheel, cylindrical grinding wheel, cup wheel, disc wheel and so on; press binding agent can be divided into ceramic wheel, resin wheel, rubber wheel, metal grinding wheel. The main parameters of the abrasive wheel, viscosity, hardness, binding agents, shape, size and so on. Since the wheel typically operate at high speed, before turning test should be carried out so that the use of (guaranteed wheel at the maximum operating speed, do not break) and static balance test (when working to prevent vibrations caused by the machine). Grindstone at work for some time, it should be trimmed in order to restore the grinding performance and the correct geometry.PrecautionsWheel using a certain degree of risk. For everyone's safety, are listed below using precautions:Grinder is one of the most commonly used mechanical plant equipment, its installation is reasonable, whether compliance with safety requirements; the use of it is correct, whether compliance with safety rules. These problems are directly related to the safety of every employee, so in actual use must draw our attention.
1 installation process Precautions
First of all to secure the quality of the grinding wheel while installing the detection method, the Nepalese velvet hammer (can also be pen) tapping the side of the wheel, the sound is crisp, no problem.Orientation grinder installed in any position, is the question we must first consider the installation process, only the selected reasonable and suitable location, we can carry out other tasks. Grinder prohibit installed facing or near the equipment and operating personnel often been in the past where, generally larger workshop should set up a dedicated wheel room. If indeed due to terrain limitations plant can not set up a dedicated wheel room, shall be installed in the front of the wheel height of not less than 1.8m protective bumpers and bumpers require a solid and effective.Unbalanced balance wheel mainly by the grinding wheel manufacture and installation of inaccurate center of gravity so that the wheel does not coincide with the rotary shaft caused. Harm imbalance mainly manifested in two aspects, one at the wheel rotating at high speed, causing the vibration, could easily lead to the workpiece surface polygonal oscillation marks; on the other hand, accelerated the unbalance vibration of the spindle and bearing wear, serious when the wheel will cause rupture and even cause accidents. Therefore, requires a lot greater than or equal straight fitted chucks should be static balance wheel during trimming after shaping or imbalance found in the work, it should be repeated static balance 200mm sand office.Matching matching problem mainly refers to the chuck and the wheel mounting support issues. According to standards, not less than the diameter of the wheel chuck is mounted sand office diameter of 1/3, and the corresponding provisions of wheel wear to a diameter of 10mm diameter larger than the chuck should be replaced with a new wheel. This presents a problem matching the chuck and the grinding wheel, otherwise there will be such a situation, the "big horse car" wasteful equipment and materials; "small horse cart" do not meet the safety requirements, could easily lead to accidents. Therefore, a reasonable match with the chuck wheel, on the one hand can save the device, cut about material; on the other hand meet the requirements for safe operation. Further, between the grinding wheel and chuck chuck should install a larger diameter than the diameter of 2mm, 1mm ~ 2mm thick cushion.Protective shield problem is the main grinding machine guards, whose role is: When the wheel for some reason undermine the job, effectively covering the wheel debris, to ensure the safety of personnel. Wheel shape shield round and square, its maximum opening angle must not exceed 90 °; shield material is not less than the tensile strength of 415N / mm2 steel. When replacing a new wheel, shield installation should be solid and reliable, and the guards can not be demolished or do not discard.Quiet block panel is one of the main protective accessory grinder, shield above the level of the main shaft opening is greater than or equal to 30 must reset this device (when. Its main function is to block the grinding process flying quiet to avoid harming operator. it is attached to the positive terminal of the protective hood opening, the width should be greater than the width of the wheel guard, and should be firmly secured in a protective cover. in addition, the surface of the wheel peripheral clearance requirements baffles should be less than 6mm.Bracket bracket problem is one of the commonly used grinder attachment, according to the provisions wheel diameter of 150mm or more grinders must be set adjustable bracket. The distance between the wheel and the bracket should be less than the workpiece to be ground to make the smallest form factor of 1/2 inch, but the maximum should not exceed 3mm.Grounding grinder using power lines, and therefore housing of the device must have a good grounding protection device. This is easily one of the important factors in the accident.
2 Precautions during use
Side grinding problem in everyday use grinders, we often can find some operator, regardless of the type of grinding machines, regardless of the type of wheel, optionally grinding wheel on the use of the side, which is a serious breach of security operations operating procedures illegal behavior. Procedures used by the circumferential surface of the face do not use the side wheel for grinding large radial strength of this wheel, axial strength is small, it will cause the wheel broken, even wounding the operator the force is too large, the actual the use of the process should prohibit such behavior.Positive operational problems in everyday use, many operators always used to facing the grinding wheel to operate, because this direction can pull its weight, in fact, this behavior is a grinder operating behavior should be particularly prohibited. Follow the rules, the use of grinders grind the workpiece, the operator should stand on the side of the wheel, the front wheel must not operate so as not to fail the wheel, or the wheel broken wheel fly flying wounding.Operational problems in the use of force grinder, some operators, especially the younger operators, for the sake of grinding speed, force too much too fast, this is a very unsafe practices. Any wheel body has a certain level of strength, doing so is likely to cause a broken wheel, and even flying out of wounding, but also a should be prohibited.Common operational problems in the actual daily operation, but also this happens, someone to catch production tasks, grab working hours, the two share a grinder while operating, which is a serious violation of operating behavior should be strictly prohibited. A grinder is not enough time, you can add grinder solution, and definitely not at the same time share a grinder.
3 replacement process Notes
Any wheel wear problems it has certain requirements for the use of wear, the wear reaches a certain level must be re-replacement of the grinding wheel. Not in order to save material, it requires the use of ultra-wear, which is a very unsafe violations. A general rule, when the wheel wear to diameter ratio of diameter 10mm chuck should be replaced with a new wheel.Validity of the problem from the Treasury brought a new wheel is not necessarily qualified wheel, new wheel even buy from the manufacturers are not necessarily qualified wheel. Any wheel has its certain expiration date, under the terms of use, which is qualified grindstone; use over the period, it is not necessarily qualified wheel. Rules of "the use of the wheel should be within the validity period, resin and rubber bonded grinding wheel storage must be approved by turning test, those who pass before after one year."Texture problems in the course, if you find a local wheel cracks, stop using it immediately, replace the new wheel, wheel to avoid crushing injury accident.
4 Other considerations should
Environmental issues in general should set up a dedicated grinder wheel room, and the room is strictly prohibited in the vicinity of the wheel grinder or stacking flammable items, to avoid fire or explosion, or other components should not be misplacing objects in the vicinity of the grinder.Management grinder should be the person responsible for this non-unit personnel who want the grinder when grinding on the object, subject to full-time person in charge of licensing and compliance with safety procedures strictly prohibited without the consent of the responsible officer, the indiscriminate use of unauthorized outsiders grinder. In addition, the replacement of the grinding wheel is also the person responsible should prevent others from unauthorized replacement, install the wheel.Off the problem of car operator stops working, you should immediately turn off the car. Prohibition grinder idle in the absence of use, unattended situation. Furthermore, it should be kept clean after use shortwave turbine.ScheduleAbrasive wheel is the central and the binding agent made of a circular abrasive through hole.Determined by properties of the abrasive grinding wheel, grain size, hardness, binding agents, shape and size and other factors, we are presented below, respectively.(1) abrasives and abrasive selection is the main raw material to manufacture grinding wheel, which bears the cutting work. Thus, the abrasive must be sharp and have high hardness, good heat resistance and a certain toughness. The name commonly used abrasive, code, characteristics and uses are shown in Table 1.Table 1 Common abrasivesCategory names Use Code features oxide corundum A (GZ) containing 91 to 96% alumina. Brown, high hardness, good toughness, cheap grinding carbon steel, alloy steel, malleable iron and hard bronze corundum WA (GB) containing 97 to 99% alumina. White, higher than the corundum hardness, low toughness, good self-sharpening, grinding less heat when grinding hardened steel, high carbon steel, high-speed steel and carbide black silicon carbide thin-walled parts C (TH) containing more than 95% silicon carbide. Black or dark blue, shiny. Higher hardness than corundum, brittle and sharp, good thermal and electrical conductivity of grinding cast iron. Brass, aluminum, refractory materials and non-metallic materials green silicon carbide GC (TL) containing more than 97% of silicon carbide. Green, hardness and brittleness higher than TH, thermal and electrical conductivity, good grinding carbide, optical glass, precious stones, jade, ceramic, honing engine cylinder liner wear high hardnessDepartment of synthetic diamond material D (JR) colorless or light yellow, yellow-green, black. High hardness, brittle than natural diamond properties. The price is better than other abrasive grinding times more expensive carbide gemstones high hardness materials cubic boron nitride CBN(JLD) cubic crystal structure, slightly lower than the hardness of diamond, high strength, good thermal conductivity grinding, grinding, honing a variety of hard and tough hardened steels and high molybdenum, high alumina, high cobalt steel, stainless steelNote: The code in brackets are the old standard code.(2) Select the size and granularity refers to the size of the abrasive granule. Grit and powder particle size groups. Abrasive Grain screening classification, which mesh aperture medium grain size number to one inch over the length of the number to represent. E.g., abrasive grit # 60, by instructions per inch mesh has perforations 60, and not through the perforations 70 per inch sieve. The classified powder by microscopic measurement, its actual size abrasive grit to be represented (W). Various grit grit size shown in Table 2.Table 2 and a particle size of the abrasive gritAbrasive grit abrasive powder particle size (um) grit particle size (um) grit particle size (um) 14 # 1600 ~ 1250 70 # 250 ~ 200 W40 40 ~ 28 16 # 1250 ~ 1000 80 # 200 ~ 160 W28 28 ~ 20 20 # 1000 ~ 800 100 # 160 ~ 125 W20 20 ~ 14 24 # 800 ~ 630 120 # 125 ~ 100 W14 14 ~ 10 30 # 630 ~ 500 150 # 100 ~ 80 W10 10 ~ 7 36 # 500 ~ 400 180 # 80 ~ 63 W7 7 ~ 5 46 # 400 ~ 315 240 # 63 ~ 50 W5 5 ~ 3.5 60 # 315 ~ 250 280 # 50 ~ 40 W3.5 3.5 ~ 2.5Note: more than 14 # coarse grains and fine powder finer than W3.5 rarely used, it is not listed in the table.Grit size selection, mainly with surface roughness and productivity related.When rough grinding to a large margin, the required surface roughness is large, coarse grains should be used. Because coarse grains, large pores, grinding depth can be larger wheel clogging and fever. When grinding, the balance is small, requiring a lower roughness values, you can select finer grit. In general, the more fine abrasive grinding surface roughness better.Different size wheel applications are shown in Table 3.Table 3 different wheel size rangeWheel size wheel size range generally used generally range 14 ~ # 24 # mill steel ingot, billet cutting, grinding and casting burrs 120 # ~ W20 grinding, honing and thread grinding 36 # 60 # general grinding plane, cylindrical, inner circle and centerless grinding W20 or less mirror grinding, honing fine 60 # to 100 # grinding and tool sharpening, etc.(3) binding agents and their selection for bonded abrasive grinding wheel substance called binder. Wheel strength, impact resistance, heat resistance and corrosion resistance is mainly determined by the performance of a binding agent. Commonly used types of binding agents, properties and uses are shown in Table 4.Table 4 Common binding agentName code performance Use vitrified V (A) water, oil, acid, alkali corrosion, to maintain the correct geometry. Porosity and a large grinding rate, greater strength, toughness, flexibility, vibration resistance is poor, can not withstand lateral forces V wheel <35m / s grinding, this binding agent most widely used, can be made into a variety of mill tools for form grinding and thread grinding, gear, crankshaft and other resin binder B (S) strength and elastic, not afraid of the impact, can work at high speed. Friction polishing action, but strong resistance and heat resistance than the ceramic binder is poor, not acid, alkali, porosity is small, easy to plug the V round of> 50m / s high-speed grinding, grinding wheel can be made thin groove, sharpening the tool rake face. Precision grinding. When wet milling cutting fluid alkali content should be <1.5% binding agent rubber R (X) greater elasticity than the difference between the binder resin, strength is also large. Porosity is small, easy to fall off abrasive, poor heat resistance, not oil, not acid, but also the smell of manufacturing grinding wheel bearing channel and centerless grinding wheel, guide wheel and a variety of slot and sheet cutting grinding wheel, polishing wheel made of soft metal such as binding agents(Bronze, nickel plating) J toughness, formability, strength, self-sharpening poor performance of manufacturing all kinds of diamond abrasive, long lifeNote: The code in brackets are the old standard code.(4) Select the wheel hardness and hardness is the degree of difficulty on the abrasive grinding wheel surface under the force of falling. Wheel hardness soft, showing grit wheel off easily, the hardness of the wheel hard, abrasive grains showing off more difficult. Abrasive grinding wheel hardness and hardness are two different concepts. With an abrasive wheel may be made of different hardness, which is mainly determined by the binding agent performance, as well as the number of wheel manufacturing processes. Significant differences between the grinding wheel and the cutting is "self-sharpening", select the hardness of the wheel, in fact, is to choose self-sharpening wheel, hoping to further sharp abrasive grains do not fall off too early, and do not fall off not blunt the .According to regulations, common wheel hardness level in Table 5.Table 5 Common Wheel hardness levelHardnessGrade Large stage soft soft hard hard in the small stage soft 1 soft 2 Soft 3 soft 1 soft 2 1 2 1 Hard 2 Hard Hard Hard 1 Hard 2 Generation 3 No. G(R 1) H(R 2) J(R 3) K(ZR 1) L(ZR 2) M(Z 1) N(Z 2) P(ZY 1) Q(ZY 2) R(ZY 3) S(Y 1) T(Y 2)Note: The code in brackets are the old standard code; ultra-soft, hard not included; Tables 1, 2, and 3 in order of increasing hardness.Selection of grinding wheel hardness general principle is: the processing of soft metals, in order not to make premature loss of abrasive, then use a hard wheel. When machining hard metal, in order to make timely blunt abrasive grains fall off, thereby exposing new abrasive grains with sharp edges (ie, self-sharpening), use soft grinding wheel. The former is because the soft material grinding wheel abrasive wear is very slow work, without departing too early; the latter because when grinding hard materials, abrasive wear wheel work faster, you need fast update.When grinding, grinding in order to ensure the accuracy and roughness, should be used slightly harder wheel. Poor thermal conductivity of the workpiece material, burns and easy to produce cracks (such as grinding carbide, etc.), use the wheel to be softer.(5) the shape and size of the machine structure and select the desired grinding wheel made of various shapes and sizes. Table 6 are several kinds of wheel shape, size, and application code.The outer diameter of the wheel should be as the election was bigger, in order to improve the peripheral speed of the wheel, so to improve productivity and grinding surface roughness favorable. In addition, under conditions of the machine rigidity and power permit, such as the selection of the width of the larger wheel, you can also receive increase productivity and reduce the effect of roughness, but high grinding heat-sensitive materials in order to avoid burns and the workpiece surface cracks, wheel width should be appropriately reduced.Table 6 Common wheel shape and purposeWheel size code name schematic representation of the main purposes flat-shaped grinding wheelP P D × H × d for cylindrical grinding inner circle, plane and centerless grinding wheel biconcavePSA PSAD × H × d-2-d 1 × t 1 × t 2 for cylindrical grinding, centerless grinding and sharpening knives double bevel wheelPSX PSX D × H × d for grinding gears and threaded cylindrical grinding wheelN N D × H × d for vertical flat end mill sand wheel discD D D × H × d for sharpening knives in front of a bowl-shaped grinding wheelBW BW D × H × d for rail grinding and grinding toolsFor example, the meaning of numbers41-A30Q4BF MAX SPEED R.P.M41According to international practice refers T41- parallel grinding wheel cutting wheel T27- T42- cymbals cymbals grinding wheelAAbrasive: A- C- BC corundum WA- corundum silicon carbide GC GreenAC SA- mixing abrasive corundum crystal BA- MA- microcrystalline corundum corundum black corundum ZA-PA- chrome corundum corundum SG- FA- half brittle ceramic corundum SC- cubic boron carbide BC- Diamond D-30Abrasive particle size: min 16, 20, 24, 30, 36, 40, 46, 54, 60, 70, 80, 90, 100, 120, 150, 180, 220.240 (referred to as a fine powder)QWheel hardness scale: F, Q, H, J, K, L, M, N, P, Q, R, S, T, Y4Organization number: abrasive grinding wheel according to product volume ratio of share points0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12BBinding agent typeFEnhancedMAX SPEEDMaximum permissible line speed m / sR.P.MThe maximum permissible speed r / min