The fundamental of grinding reachs its process capability

  • Time:
  • Click:196
  • source:SHERBURNE CNC Machining
Article author Dr. Stuart Salmon is the United States " association of advanced production science and technology " chairman. He thinks, grinding treatment is inside a lot of domains, go up from the technology no matter or economically, can machine photograph compare with cutting, some domains are only treatment method even. But at present manufacturing industry a lot of people think grinding treatment efficiency is low, wasteful, do not grant to use as far as possible accordingly. Salmon thinks, the main reason that produces this kind of opinion is right grinding principle reachs his immanent latent capacity lacks understanding. The purpose of the article should help author compose the concerned personage of business circles understands correctly and use grinding technology namely. Current manufacturing industry is seeking the plan that replaces grinding agog. A few using those who raise a spare parts manufacture efficiency in the experiment " new " plan includes: Wear-resisting coating cutting tool and hard cutting, dry cutting, high speed cutting. But should point out, "High speed " two words are not new to grinding. The linear velocity of groovy moving surface of emery wheel amounts to 1829m/min, the production that high speed exceeds hard abrasive emery wheel is economic speed amounts to 4572 ～ 10668m/min, and in the lab in grinding the speed on special device can achieve 18288m/min -- only a bit under velocity of sound. The partial matter that is versed in industry does not like grinding is right it does not understand. Exceed craft of grinding of feed of hard abrasive gentle to look from technology or economic angle no matter, can cut with milling, broaching, dig and the turning photograph compare below certain circumstance. But there are a lot of people in production enterprise, their knowledge stays on level of traditional processing technique, often take repellent attitude to grinding. But the propulsion as new material (if pottery and porcelain, brilliant needs aggrandizement metal and aggrandizement group material, multilayer metal and press metalloidly add up to material) , grinding often is exclusive and feasible treatment method. If use proper bond, can make grind bead to be mixed in the desquamation in machining a process get controlling from whetstone process. And emery wheel changes blunt or when load of shape of occurrence pink bits, can go up in the machine tool nap. These advantages are being achieved hard in the treatment method of other. The quantitative class that emery wheel can make the public errand that machines the surface reachs number (micron class) , still can make the surface bright and clean at the same time spend and cutting grain achieves groove. Inopportune is, long-term since, grinding is regarded to be all the time a kind " artistic " . The 40 ～ till recently 50 years, machine a process continuously to undertake study to grinding through researcher, developed new, system of improvement abrasive, binder and all sorts of grinding fluid. The taking of these achievement, make grinding treatment entered scientific kingdom. The phyletic abrasive of abrasive can divide it is two kinds big: Common abrasive (wait like alumina, carborundum) and exceed hard abrasive (diamond, cubic nitrogen changes the) such as boron. CBN and Jin Zeshi are harder than common abrasive, more wear-resisting, but very costly. In the meantime, exceeding hard abrasive is good heat conduction system (the 6 times) that the thermal conductivity of diamond is copper, and common abrasive is material of pottery and porcelain, it is adiabatic so. Exceed hard abrasive to still have very tall thermal diffusion sex, have namely come loose quickly hot ability. This one character makes exceed hard abrasive to have " cold cutting " nature. The anti-wear properties that exceeds hard abrasive can also greatly excel is common abrasive, but these character that exceed hard abrasive to have also do not mean them to apply to all grinding working procedure. Every kinds of abrasive has its properest use field, the characteristic that understands every kinds of abrasive so is very important. For example, abrasive of alumina pottery and porcelain -- call brilliant to plant sometimes gel (SG) abrasive or abrasive of pottery and porcelain -- compare melt normally (common) alumina has better anti-wear properties and appearance to maintain a gender. But abrasive of pottery and porcelain also has its properest use field. Alumina: Al2O3 is the cheapest abrasive. The function when hard steel of grinding temper by dipping in water is very good, below the condition of successive nap, also can grinding nickel base super alloy, al2O3 has very good adaptability to all sorts of grinding conditions, if be mixed softly hard data, light cutting and heavy cut, can wear a very fast face bright and clean degree. Alumina of pottery and porcelain: Intensity of alumina of pottery and porcelain is very high, so most the circumstance with the cutting power higher load that applies to every to wear bead. Alumina of pottery and porcelain is outer when round grinding and hard steel of temper by dipping in water of grinding of big planar move back and forth, its effect is very good. But it is unwell at cutting arc long, odd the part with a minor force of the bear that wear bead, be like inside the circle is ground, delay feed is ground etc. But through " drawing " change the alumina of pottery and porcelain that make to wear bead, below the circumstance that grows in cutting arc even, also can use at machining alloy of agglutinant stainless steel, high temperature to wait, the appearance that wears bead right now is compared (long broadness is compared) achieve 5. Alumina of pottery and porcelain grinds the function of bead to be able to pass the melt alumina that joins partial brittleness to form compound abrasive emery wheel to get ameliorative. Right now, need the cutting arc length that knows emery wheel to go up in workpiece to spend, so that have specific aim land,affirmatory emery wheel deserves to compare. Carborundum: SiC abrasive has natural and sharp figure. Comfortable at grinding horniness material (be like hard alloy) . Because its are sharp, make it comfortable also at processing very weak data, mix like aluminous, polymer, balata and low intensity steel, copper alloy plastic wait for weak data. Diamond: Natural can use at grinding with making synthetic diamond. Diamond is configuration of hardness of a kind of freeboard, because it has to iron,add up to a gender in person (the alloy that steel is iron and carbon) and form wear away quickly, so unwell at processing black metal data, but diamond is special the grinding treatment that applies to nonferrous metal material, titanium, pottery and porcelain and cermet. Cubic nitrogen changes boron: CBN resembling diamond is same, it is a kind of very costly abrasive. A value that exceeds hard abrasive emery wheel wants than the emery wheel of common abrasive 50 times more expensive above, but its service life wants than common emery wheel 100 times taller above, although grinding is the hardest steel, also have only slight wear away. CBN is the most comfortable at processing black metal data, carry the circumstance of emery wheel appearance for long in the requirement especially, be like the grinding of the raceway inside bearing. Additional, CBN is more comfortable at often changing the working procedure of emery wheel, because small lot and emery wheel change, want nap when installation, this is the main factor that brings about emery wheel to use up. Because CBN is when high temperature,with water the contact wants to have reaction, wear away quickly, want to use glycol or oil so. Bond is common the bond of emery wheel, can use pottery and porcelain, resin or plastic, the metallic matrix that exceeds the bond of hard abrasive to be able to use agglomeration or with eletroplate the method of nickel layer enclothes emery wheel to go up. This kind of emery wheel is not of ooze water, also do not have empty. Metallic bond and eletroplate the grinding fluid of emery wheel should choose carefully, in case emery wheel skids. What generation is in in cutting arc when skidding is tremendous and dynamic hydraulic pressure, meeting top lifts emery wheel, cause work bright and clean degree of aggravation and accelerate emery wheel to wear away. Closely related the choice with bond and both abrasive. It is to ask to appearance maintains during emery wheel is being used like the use field syncretic of CBN for example changeless, and till use up,just all get off from the machine tool. Because the thermal conductivity of CBN is very good, use metallic bond so more advantageous. Both union rises the condition that offerred cold cutting. Because heat in metal cutting passes abrasive and emery wheel to conduct, follow the rate that cooling fluid takes away again, more than entering workpiece to should be gotten quickly. Metallic bond has two kinds of forms: Eletroplate and agglomeration. Eletroplate emery wheel is not of nap, they make correct appearance at the beginning, use to all the time extinct. Agglomeration metal emery wheel uses electric spark nap normally, resemble eletroplating next emery wheel is installed in that way use to the machine tool. Agglomeration and eletroplate the radial after emery wheel installs main shaft is jumpy should be less than 0.

0125mm. To metallic bond emery wheel, it is very important to reduce main shaft to beat. The space that because wear bead,extends from bond is very little, if beat,achieve 0.

025mm, the one aspect of the matter that can produce emery wheel already load is too heavy and cause excessive wear away, additional one end criterion negative charge is very small and still very sharp. Certain eletroplate emery wheel can make a radius of very small outline circular arc (about 0.

125mm) . But majority eletroplates the radius of outline circular arc of emery wheel is more than 0.

5mm. Normally, eletroplate emery wheel is applied at high speed grinding, and metallic agglomeration emery wheel is comfortable at material of grinding pottery and porcelain. Integral metal bond is vibration of arenaceous wheel pair, jumpy the accommodation that waits for working requirement with cooling fluid discharge is very small. If the tigidity of grinder, workpiece and clamping apparatus is poorer, or the bearing condition of old machine tool not beautiful, and there is equalizer on the machine tool, use below this kind of condition eletroplate emery wheel can cause emery wheel life, work bright and clean degree of problem with exterior grain respect. Wait for particular case according to the vibration of the machine tool and stability, use colophony bond emery wheel to be close friends sometimes a few. Colophony bond has very strong damp capacity to vibration. Of course, of colophony emery wheel corrective the equipment that involves with nap and time, can raise cost. Bond of pottery and porcelain is used most general. Because the emery wheel of this kind of bond takes hole, make cutting fluid enters grinding arc effectively, have bigger empty accommodate worry bit. In the meantime, use diamond tool can repair emery wheel of bond of pottery and porcelain conveniently mix to correct figure grind acute. Add: Common abrasive and exceed hard abrasive applicable by treatment material limits: Alumina abrasive: Hard steel of temper by dipping in water, nickel radical is super abrasive of alumina of cermet of alloy, high temperature alloy, black: Hard steel of temper by dipping in water, nickel radical is super alloy, agglutinant abrasive of carborundum of alloy of stainless steel, high temperature: Stone mill of polymer of hard alloy, aluminium and titanium, balata, copper alloy, plastic King Kong expects: Nitrogen of cubic metre of hard alloy, aluminium and titanium, pottery and porcelain, cermet changes boracic abrasive: The prepares emery wheel preparation of emery wheel of metal of super alloy, black includes hard steel of temper by dipping in water, nickel radical: Installation, balance, finishing and nap. Emery wheel preparation is bad, the source that after becoming, problem of a lot of grinding arises. Above all, want to install emery wheel according to the instructor of emery wheel manufactory, the primitive balance position with make sure emery wheel is in before nap better and the smallest jumpy. The 2nd, want to lest meet the opening inside emery wheel,be operated carefully when installation. The aperture inside emery wheel is in immense stress bears when high speed rotates, carry and installing improper often is the cause that blowout causes when emery wheel is started. The 3rd, when installing emery wheel of bond of pottery and porcelain, must use paper gasket. The 4th, spend with smooth torque and degree of tightness on close flange dish. After installation ends, emery wheel should ordinal make thick balance, nap, balance with essence of life, next resumptive grinding. If emery wheel savagery is very lopsided and jumpy very big, often need add nap to reach balance again. The balance with good emery wheel can make grinding surface keeps good and bright and clean continuously degree, make life is lengthened. In the meantime, correct nap can make emery wheel holds stable grinding surface and grinding action. The sharp degree of emery wheel reachs the nap method of emery wheel of be decided by of its appearance precision. So, any moment should make device of emery wheel nap is in good working position, this nods diamond nap to sheet implement or the diamond gyro wheel of electric machinery drive is same. Only place diamond revises the commonly used method that is emery wheel of bond of nap pottery and porcelain, regular meeting of method of this kind of nap brings about emery wheel function to be not stabilized, so the method of nap and program otherwise are broken adjust accordingly. When grinding workpiece, typical method is: Emery wheel kibble machines allowance certainly, change nap parameter next, again essence of life grinds workpiece. Normally the practice is, thick when repairing emery wheel, the circle outside diamond edge emery wheel makes fast and transverse feed, and when essence of life is repaired, amend implement transverse feed speed is decelerated greatly, in order to gain bright and clean emery wheel surface and workpiece face. One kind is called " build receive form " or " partial jackknife type " nap method, can assure correct, stable nap. For example, one diameter is 406.

The emery wheel of 4mm, speed is 6000sfm(1828m/min) , only place diamond is amended implement circular arc radius 0.

254mm makes kibble nap, the nap quantity of every journey is 0.

025mm. The commonly used transverse feed speed when be being amended commonly often passes fast, make emery wheel surface has one part to be not repaired. And although can make emery wheel surface is repaired,use the route for many times, but the surface is rough. Performance of grinding of this kind of emery wheel is higher, but wear away fast and inhomogenous. Emery wheel nap falls in grinding job rate commonly undertake. Only exception is to make blow when pressing plastic nap, in 300sfm(91.

Undertake below the low speed of 44m/min) . Transverse feed speed should according to nap implement diamond dimension and to the requirement of emery wheel surface computation are affirmatory, general kibble uses 2 ～ 3 times to build receive, essence of life is ground need 4 ～ 6 times to build receive. Amend implement the computational: of transverse feed speed?  of account of egret of  thing gate of a lane not " ＝ of?XB of cutting of the feet 0.

015 ″ ) , diamond approach (0.

001 ″ ) , 1400rpm of emery wheel rotate speed. Distance CB calculates as follows: Because of XB ＝ 0.

015 ″ , CX ＝ 0.

015 ″ - 0.

001 ″ ＝ 0.

014 ″ . CB ＝ 0.

00735, and ＝ of AB ＝ 2CB 0.

0147 ″ . Got diamond so the feed pitch that every turn, assure not to stay to did not build a part in emery wheel surface. Conversion arrives ＝ of minutely 1400rpm of × of feed speed AB 20.

58ipm. This speed makes nap enclothes diamond surface of whole emery wheel. If nap asks 2 times to build,receive, criterion feed speed halve, for 10.

29ipm. Relatively ideal to thick nap. Nap of essence of life needs 4 ～ 6 times to build receive, feed speed should decrease accordingly. When if be built 4 times,be being received, be 5.

14ipm. The uses grinding liquid correct application of grinding fluid is very fundamental to successful grinding. The action of grinding fluid is right cutting arc area undertakes cool and lubricating. The action of fluid of water radical grinding basically is cooling, also have certain lubricant effect. And the action of cooling oil basically is lubricant, have bit of cooling effect. The water that synthesizes additive completely base grinding fluid, most apply to sharp heavy-cut grinding emery wheel, arc of the cutting when this kind of emery wheel works normally is longer, need is better erode action. Synthesize the grinding fluid of additive partly, most apply to grinding complex form and requirement lubricity can be good, in order to prevent the situation of burn. Pure fat dose is comfortable at grinding complex form, cutting arc shorter, grinding is bright and clean the circumstance with degree of higher demand. And glycol base grinding fluid is applied to use cubic nitrogen to turn boracic emery wheel and the situation that should avoid to use pure oil agent. Choosing grinding fluid is a difficult task: Want to consider the initiative price of grinding fluid already, want to consider the charge that its manage and processes again. Alleged to environmental hurtless " green " cooling fluid, it is a kind of deceit only. Have the fresh cooling fluid of some of bucket outfit, OK even and drinkable, but once grinding breaks end polluted a liquid, can become harmful to the environment waste material. Grinding fluid once make choice of, answer its to undertake filter and maintaining. Want to consider its cleanness to spend not only, control its chroma, conductivity and PH cost even. The experiment of newest grinding fluid makes clear, grinding fluid chroma is not linear relation to the influence of grinding process. Long-term since, people thinks, increase as grinding fluid pH indicator, grinding process can become scale ground improvement, actually this is incorrect. For example, grinding fluid chroma is in 7.

5% ～ 8% when, its function not as good as chroma of 5% good, but increase to 10% ～ when chroma 12% when, function gets ameliorative again. The test result to fluid of grinding of 50 kinds of water radical very much the same. Nevertheless, below some circumstances, the trend is not apparent; And fall in another some of circumstance, 7.

The grinding fluid chroma of 5% arrived to cause the rate of machine tool stall simply; And chroma 5% work with the grinding fluid of 10% the case is good. After choosing proper grinding fluid to reach its to run a system, next first issue is how an area of correctly grinding of grinding fluid infuse. Grinding fluid should note cutting arc area, is not simple ground notes the combinative department to workpiece and emery wheel, normally pouring cooling fluid enters cutting arc area partly rarely only. Gyral emery wheel is blowy like implement in that way, throw grinding liquid from the circle outside emery wheel go out. The hole of emery wheel can hold bit already, can develop the function that carries grinding fluid again. such, grinding fluid relies on belt of emery wheel itself to cutting arc area. So, below appropriate rate, grinding fluid is pouring can take to the circle outside emery wheel to cutting arc area. In addition, nozzle should make special design, make grinding fluid is nodded in correct infuse with proper speed spray. Nozzle dimension should enclothe width of whole emery wheel, when width is foregone, the mouth height of nozzle (D) can be obtained through computation. If nozzle width is 1.

5 ″ , criterion the area of nozzle mouth is: 1.

5din2. Set grinding speed to be 5500(1676m/min) , conversion becomes inch of beard to multiply 12, get 66000in/min, so, the grinding fluid velocity of flow that spout manages is: (1.

99000din3/min of ＝ of 5din2) × 66000in/min. If oil pump pressure is 110psi(0.

758MPa) , minutely liquid discharge is 58gpm(minutely 58 gallon, it is about 219.

554 litres / cent) , and 231 cubic metre of 1 gallon ＝ inch  , so oil pump discharge is: 13398in3/min of ＝ of 231in3 × 58gpm. Apparent, the discharge that oil pump is imported and exports should be equal, namely 13398 should be equal to 99000d. Then but D of height of cipher out spout is: 0.

135 ″ (13398/99000) . The nozzle mouth height that chooses actually can is worth than computation slightly a bit smaller, because grinding fluid leaves after nozzle,speed can be reduced somewhat. When nozzle frame-up fall to the circumstance of emery wheel, it is important to consider this element blame to be. So, dimension of the nozzle in this exemple is taken 0.

12 ″ × 1.

5 ″ are better. The pressure of oil pump is to drive a liquid to be in pipeline system midstream is moved. Sometimes systematic obstruction may exceed oil pump forehead to decide pressure 110Psi. Because often produce nozzle to make incorrect, arm of pipeline, connect, activity have twist or block sluggish appearance. If go up,the block sluggish element that states influence flow exists, flow speed can be reduced. Accordingly, should detect via often coming with discharge agent the change of velocity of flow, light looks manometric it is insufficient. Appendix: ? A main index in subtling チ of Lei  material frightens ǘ magpie to be troubled by  ? to exceed the standard of emery wheel technology of hard abrasive is chroma. Industrial group constant chroma 100 misunderstanding are 100% , actually otherwise, chroma the definition of 100 is: In 1 cubic metre inch there is 72 carats abrasive inside bulk. So, chroma 50 it is to show every are cubic inch in have 36 carat abrasive, the granuality size of abrasive has a lot of kinds, and the abrasive of distinct size can have identical chroma. It is the oppose of granuality of two kinds of abrasive of 75 to compare likewise with chroma now. One kind is 60 granuality (beautiful mark, similarly hereinafter) , another kind is 200 granuality, they every are cubic inch abrasive content is 54 carat, to the abrasive of 60 granuality, every carat has 6900, and every carat has the abrasive of 200 granuality 262000. So the abrasive of 60 granuality, in every cubic metre inch there are 372600 to wear bead in emery wheel, and the abrasive of 200 granuality, this number achieves 14148000. When granuality means different abrasive to be the same as in chroma photograph, of fine granuality wear bead (left) amount the grinding of over thick granuality grain. Assume wearing bead is distributinging equably inside emery wheel, criterion afore-mentioned every cubic metre inch after the medium number that wear bead opens cubic metre, can get the number wearing bead on every inches of length. To 60 granuality character, it is every inches 72, and 200 granuality are every inches 242, the reciprocal of afore-mentioned numbers grinds a span namely. To 60 granuality character, span is 0.

014 ″ , to 200 granuality, span is 0.

004 ″ . If the cutting arc length in grinding is spent,be 0.

013 ″ , the emery wheel of 60 granuality, abrasive span is longer than it, working without abrasive on cutting arc sometimes so, and the emery wheel to 200 granuality, the span that wear bead is 0.

004 ″ . Place grinds bead to work on cutting arc with having 3 at least. From afore-mentioned contrast derivative a commonly used regulation, when choosing emery wheel namely, should assure to there are 4 ～ on cutting arc length 10 wear bead working. CNC Milling CNC Machining