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Module 1: Machining of Advanced Materials

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Cutting Fluids in Grinding Process

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Video 1: Cutting fluids in Grinding ProcessWe are discussing about the abrasive processes. In this abrasive processes till now we haveseen the grinding process, in which grind introduction to grinding grinding wheel specificationbelt grinding, what are the problems? What are the solutions of the grinding wheels andall those things? Now, we proceed to the grinding fluids, thatis also a part of our syllabus that is called machining fluids. So, in this aspect we arestudying the grinding fluids. The grinding fluids basically if you see in a machiningoperation other surface grinding, here in this region you can see lot of spark is generatedbecause of the friction that is between the grinding wheels as well as the workpiece surface.So, in order to reduce the temperate generation and the heat affected on the workpiece andall those things always people will use the grinding fluids ok .Grinding fluids can be lubricate based or it can be coolant base. So, both are theredepend on what type of application, whether you are going for high speed or whether youare going for very low speed or whether you are going for medium this will decide whichtype of cutting fluids you are going to use in the particular bending operation.But as you have already seen the grinding wheel specification in this one, which isthe most important one that will have influence with respect to the grinding fluids that wehave to see as abrasive type you do not have any much thing because whether it is aluminaor a silicon carbide or diamond whatever the things. So, whether is a grid size you knowit will have much effect because what are the grid size you are using whether it isyou are using medium or coarse or something. So, grid grid is the bonding between abrasiveparticle and the bonding material that is called wheel bonding material. So, whetherhard bonding or soft bonding so, it do not it also do not have structure. The structureif you see what is happening if you see the structure the structure is nothing, but openstructure and dense structure. If you are going to apply the cutting fluid are the grindingfluid basically it tries to enter or it will tries to help the grinding wheel to not load.And it also helps the grinding wheel in terms of cooling and all those things that is whymost important factor whenever we considered about the grinding fluids, you can say thestructure is the only parameter that can have some influence compared to other. Anyhow thebonding different bonding's are there vitrified bonding to the shellac bonding rubber bondingand all that those also do not have much fluid well only particular specification that iscalled the structure, which is having some influence whenever you apply the grindingfluid. The grinding fluid significance the presenceof boundary layer are air around the periphery if you do not use the cutting fluid normallywe consider it as air will be there between if you see this region you have workpieceas well as the grinding wheel. So, the air can penetrate into this one. If you are applyingcutting fluid normally if if you see the cutting fluid plays a major role in terms of a burningof a workpiece it will reduce the burning effect and chip burnishing. At the same timeit also cools down the machining region and all those things lubricates a machining region.So, that the temperature generation is very less and all those things.There are varieties of cutting fluid application people can go for a one nozzle applicationor people can go for the multiple nozzle also, here you can see here multiple nozzles . So,this will enhance the particular grinding operation efficiency by dislodging the wheelloading and all those things, wheel loading as you have seen the chip materials are cloggingbetween the 2 successive abrasive grinds ok that is called wheel loading. So, the grindingfluids will help to not clog the materials. Applications of cutting fluid in grindingit is generally accepted that the heat generation is a limiting factor in the grinding processdue to is the thermal damaging and what will happen, if there is a heat generation in thegrinding process there will be thermal damage with respect to the workpiece heat combatenergy transfer, because the thermal energy transfer takes place. And whenever you usethe cutting fluid what will happen the thermal energy it will extract from the machine region.So, this cutting fluid also remove limit amount of energy transfer to the workpiece throughdebris flushing, and lubrication, and the cooling effect. What will happen it will takethe temperature generation in the machining region by debris flushing; that means, thatyou are flushing the debris that is between the your grinding wheel as well as the workpieceand the cutting fluid also help to dislodge the clog material, it will help in terms oflubrication because the proper lubrication if you provide what will happen the frictionbetween ah the grinding wheel as well as the workpiece will reduce. So, the heat generationwill be less the cooling effects the workpiece has to be cooled. So, that the it would notgo for thermal softening region and all those things ok.There have been many new and existing systems of so; that means, that not this cooling applicationslike there are many varieties of techniques are there flood cooling is there multi-nozzlethat we have seen in the previous slide single nozzle. So, nozzle positions also can be variedwhether you can go from 0 degrees, whether you can for 15 20 or 30 or something and thesame time standard distance between the wheel as well as the nozzle and solid lubricantalso used minimum quantity lubricant it is called sustainable grinding also can be usedin the cutting fluid applications. Cooling mechanisms in the grinding if yousee, the need of cutting fluid the cooling mechanisms the need of the cutting fluid ifyou see the cooling mechanisms, type of fluid health is you can divide into 3 segments.Then the cutting fluid application. So, useful fluid application normally common nozzle designsis the one at the same time uncommon nozzle is basically whenever you are going for thesolid lubricants are floating nozzle there are some varieties of nozzles are there.So, this type of uncommon nozzles also will be there. So, you have to choose accordingto your requirement what is your requirement; what piece my requirement? Whether it is whetherI want to remove the material in a bulk amount, whether I want remove the material for thesurface finish, whether I have to do the form grinding or normal grinding or centralizedgrinding, which type of grinding that I want to use depend on that you have to choose yournozzle as well as the cutting fluid. So, the types of nozzles if you see the firstone is the basic shoe nozzle this is the one of the common and commercial type of ah thing,where if you see normally this shoe nozzles are very effective because they are they ableto maximise the amount of cutting fluid passing through the cutting zone ok this is the cuttingzone. So, this a workpiece interface and the grinding wheel interface. So, that it canpass through the grinding fluid and it maximise on the periphery of the machining region.The other variety is floating type of nozzles here the floating type of nozzles will havethe tension springs will be there. So, that it can float as per the requirements of thatone so, that you can send the cutting fluid into the machining region. Nozzle positionsin the grinding if you see there are some researchers working on or worked already onthe nozzle positions, you can use tangential position at the same time you can use intermediateposition because you need certain boundary basically what will happen if you are usinghere the cutting fluid goes like this. So, it will occupy the machining region if youuse here what will happen it comes through the boundary and goes like this ok.If you are using here what will happen it goes like this. So, the nozzle stand up distance;that means, that how far you are keeping this is one of the thing at the same time, howincline you are keeping this a nozzle. So, that the cutting fluid carry all the peripheryof the grinding wheel also studied by many researchers ok.The cutting fluid contributed significantly to improve the surface finish of the samplesbecause the cutting fluid the conventional grinding process is considered to be one ofthe finishing process that is why people uses it for the finishing. So, the output ah asa operator that I will look is I have to kept a good surface finish on my product, thatis that is why normally you play with the nozzle. It also appeared that the decreasednozzle distance from the wheel that is nothing, but the stand-up distance how far your nozzleis standing away from the wheel, at the same time flexible hose to the positioning of thenozzle.
Video 2: MQCF/MQL in Grinding ProcessSo, sustainable whenever I was telling many times that the course title says machiningconditioning fluids. So, at last what I want to say is whether whenever I teach about machiningas well as whether I would teach about machining fluids at last my ambition is towards sustainable,how sustainability I can incorporate. So, that a better output can come at the sametime I can also help the operator in order to safeguard him as well as in order to makehim healthy with respect to the emissions and all those things.Even though emissions are there how to protect that was one of the concern if there is, ifI cannot generate or if I do not generate any emissions that will be better that iswhy always I try to emphasis for the sustainability aspects. Here also I am going to talk aboutthe minimum quantity lubricant or minimum quantity cutting fluid in the grinding process.Here you can see here in this grinding wheel is there at the same time the workpiece isalso moving that is table feed will be there. So, in in the previous one what will happenthe cutting fluid is a liquid, which may not penetrate into the machining region betweenthe grinding wheel and workpiece. That is why, if I can send the atomized cutting fluidthat can penetrate into the machining region and extract the heat by forced convictionas well as it also can lubricate that region that is what the intention of MQL.So, minimum quantity lubrication if you see. So, to avoid the adverse effect of the cuttingfluid the minimum quantity lubrication or the minimum quantity cutting fluid techniquesare came into existence, the minimum quantity lubrication refers to use of very minimalcutting fluids that is 5 ml per hour to 500 ml per hour. So, normally people will talkabout 50 ml per hour and all those things. So, ml 50 ml per hour means very very lessquantity with respect to the flood cooling where you spend per a minute half a litreof something ok. Here per hour you are spending half a litreso, maximum. So, this is about the minimum quantity over 2 billion gallons of cuttingfluid is wasted per every year. So, in order to keep the resources for the next generations,we have to minimise the cutting fluids utilisation also at the same time 17 percent of the manufacturinggoes to the product basically. So, if I can minimise the cutting fluid I can be competitivein the market by selling my product at minimal price. This is a known slide to you becauseI explained already whenever I was talking about minimum quantity lubricant are cuttingfluid. So, there you have 2 things one is the easyaccessibility of the air one side at the same time high convective heat transfer coefficientof the cutting fluid is mixed and form a mist and it is injected between the grinding wheel,as well as the workpiece you can see here say the mist is coming in and in between theworkpiece as well as grinding . So, the this mist will help not only in termsof providing lubrication cooling, because of this force velocity, because of this highvelocity particulates are the molecules, because of the high velocity of this z what will happenthe clogging also can be removed that is reloading will be minimised.The advantages is environmental friendly one the see there is no maintenance are the costor the waste lower thermal shocks less clogging of the wheel I I was saying that if thereis any clogging it can penetrate and it can take out the clogging. So, in this way youcan enhance the grinding efficiency of any particular process compared to our normalprocess. This is how you can see here the grindingwheel and the minimum quantity lubrication the fluid is occupying here and the abrasiveparticles will be there and this will remove the workpiece material ok. These slides aretaken from one of the senior professors from IIT Madras so, thankful to the professor.So, the researchers also studied about the droplet size they experimentally validatedthe droplet size the question is whenever I am sending the cutting fluid and air compressedair, and I mixing it internally and I am sending it what will happen I am sending a atomizedgas which is having high convective heat transfer. Now the problem is how to calculate the dropletus this is the biggest question for the purpose. Malvern analyser is there. So, you can ifyou have that equipment you can measure the particle size or the droplet sizes the dropletvelocity also can be measured using high speed camera ok. So, if you see here in the figureone this is an least jet is there the jet is falling in the grinding operation you cansee from the other view in the figure number 2 and the velocity can be calculated by highspeed camera at the same time you can also measure the droplet size by Malvern analyseronce you have done. Once you know the physics if the people whoare having some knowledge about fluid and all those things who works in the fluid andthermal area not only the manufacturing they can simulate the droplet sizes. So, they cancheck the droplet sizes as well as they can also simulate using the standard software'sand they can validate it.
Video 3: Conventional Abrasive Processes - Honing ProcessNext we move on to the conventional abrasive processes the thereare other conventional abrasive processes are there.Which we see now is we have till now seen the grinding process, wherein grinding wehave seen the grinding fluids we have seen. Now we move on to the honing process, thenfollowed by lapping, super finishing, drag finishing, vibratory finishing, sand blasting,and if time permits we also see some of the introduction to advanced abrasive finishingprocesses. Move on to the honing process honing processis one of the conventional finishing processes exclusively this is used to finish the cylinderliners and cylinders. Honing is a finishing process in which tool is called hone ok. Thetool which you go in to see in upcoming slides that is called hone it will have a rotaryas well as reciprocating motions, while the workpiece does not perform any type of motionworkpiece will be stationary and the tool will not only reciprocate it rotates and goesinside and rotates and come inside this helical path it will follow.So, most honing done in internal cylinder surfaces such as automobile cylindrical walls,mostly the application of this one is in terms of automobiles cylindrical and cylindricalline it is application. Where I will tell you why you have to use this the honing stonesare held against the workpiece with controlled light pressure, because these are loaded bythe spring load and you can vary the this pressure and you can perform the finishingoperation. The honing head not guided externally, butinstead floats are being guided in the workpiece inside itself the honing stones should notleave the work surface and this stroke length must cover the entire work length normallyif your cylinder liner is this much big it has to go throughout and it has to come thethroughout. So, that it can do the complete workpiece.This is called the hone basically honing processes is an abrasive process. The small amount ofmaterial is removed; that means, the specific energy requirements is. So, high like grindingprocess mainly internal holes are done ok. The tool the honing are done by the honingstones honing head with honing stones that is nothing, but the hone and whatever youare seeing here is a tool honing tool honing stones are made up of abrasive material adjustablepushing springs, basically this hone will have the honing sticks where these are loadedby the spring loads and you can vary the this spring loads on this.Various honing stones it is called a single stone with the small bore normally you willhave only single stone that is going to finish because it will goes rotates and goes insidereciprocate. So, you can do and the multiple also. So, in whatever you have seen in theprevious slide where there are 4 that is called multiple type. So, you can if at all I wantto remove more amount of material you have to go for multiple storms.The honing head it will have a rotating motion it will have a reciprocating motion honingstones are pushed to the surfaces by the spring loading honing sticks ok. So, that you canapply whatever the required amount of pressure is required, because if at all I want theseare adjustable basically if I want more amount of material to remove you have to adjust accordingto it if I want very less amount you have to adjust according to that.So, as I said this is called reciprocating motion will be there as well as rotary motionalso will be there, because of which you will form the crosshatch pattern you can see herethe crosshatch patterns are clearly visible here. So, this is called the honing processwhy you required the crosshatch pattern in engine cylinders, whenever if you would havegone to the patrolling stations in olden days what will happen they use to fill the petrolas well as they use to fill the engine oil also that is lubricating oil also.What will happen, the engine the piston motion will be taking place inside the cylinder whatin that circumstances this lubricating oil will come between the piston as well as thecylinder walls and smooth functioning will be taking place; that means, the reciprocationmotion of the piston will be smooth for that particular application you will have the crosshatchpatterns what will happen it is not only finishing process honing process is not only the finishingprocess, it is also generate the crosshatch pattern and this lubricant goes and sit inbetween the surface lay that is lay is nothing, but predominance surface direction.So, this crosshatch micro grows or the Nano grows are there along with the surface finishthis will go and sit there and helps the piston for the smooth functioning, that is why alwaysif you see the these are all these particular honing process is used in the cylinder linersfinishing How you can give or the impart the rotarymotion and as well as the reciprocation motion, rotary motion is transferred with respectto gears this gear 1 to gear 2 to gear 3. So, that you can transfer this to the gear4 and you can transfer to the gear 5, but the same time reciprocation motion you aregoing to get from this ok. So, indirectly you are going to get the rotary motion aswell as reciprocation motion, then if you can synchronise both you will get a helicalpath. If you see here F t is the tangential forceas well as F r is the radial force and if you can combine normally V c is nothing, butF c is the cutting force electric motors are normally used for the rotary motion as wellas hydraulic systems are used for the reciprocation motion. So, that you can get the helical pathand at the same time the it will come in a reverse direction also.Surface roughness if you see as I said the crosshatch pattern will be generated on theengine cylinders or the cylinder liners, whatever you are seeing here this is the lay that isnothing, but predominance direction of the surface roughness or the surface finish youcan see the this is reverse direction and this is going direction.So, that you can get the crosshatch pattern, why was talking about the lubricant staysin this crosshatch patterns. He as I said this is not only a finishing process it alsogenerate certain pattern and finishing always helps in piston motion in a freeway, at thesame time this crosshatch pattern helps to retain the lubricant. So, that proper motionof the piston takes place. If you can see here this particular area ofah the liners cylinder liners, this if you see here what will you can clearly see thecrosshatch patterns ok. This crosshatch patterns will help the engine cylinder liners. Applicationsas you can see this is the honing process it will go rotates as well as reciprocatesin a engine. So, you can do the honing process. As well as I was telling every previouslypeople use to do the engine cylinders itself directly, but it is a costly process becausebecause of the piston motion the engines wear out and you have change for that purpose peoplefind the some other solution that is called cylinder liners, what they will do they willdo the honing process in the cylinder liners, these are the cylinder liners and this theyjust go and fit in the cylinders. So, if there is a wear out of the cylinderliners just take out the cylinder liner and replace the with a new cylinder liners. Thisis the advantage and it is a cost effective method also. In this way if you have sometime are nearby this companies are there engine cylinder manufacturers are there, please visitah the honing process some of the colleges are some of the universities you may not havethe facility of honing, but some many of the institutes will have you can just go nearbybig institutes and can visit our, if there is a small industry who manufactured the enginecylinders and all those things you can go and visit that company, for visualising theor for seeing the practical thing and all those things.For seeing the how the honing process practically works and all those things you can feel andyou can also see the surface roughness measurement here, I want to say some other thing alsonot only surface finish surface lay that is crosshatch pattern, but also you will requireout of roughness that is nothing, but you should have get a perfect circle if you aregoing to get a abnormal what will happen your piston will the life of the engine goes verybad; that means, that you have to frequently change the your cylinder liners that is whyyou have to take care about the out of roughness of that particular liner also.There are many varieties of hones one is solid type of things if you can see here whateveryou have seen in the previous slides and all those things there are the flexible typesalso there. So, where you have a spherical balls will be there and you can reciprocateit through so, that you can do the honing process also. So, there are varieties of honesare there these are only 4 are there as we you can see like conventional, single pointcutting tool grinding is a abrasive millions of multipoint cutting tool.Similarly, the technology is growing in the honing process also the people are using thistype of things and people also use this type of multipoint cutting tools also. So, youcan go for whichever is required, and whichever is economic, whichever is causing less pollution,whichever is sustainable you can choose according to your requirement.The lubrication are the cutting fluids in honing process mostly the cutting fluids herewe will be used is lubricants, as you can see here these are all mostly lubricant typeof cutting fluids will be used. So, water base cutting fluids are not used if at allused very less amount of water base, because a cooling is not a criteria here the lubricationis the major thing that the people want here. That is why always if you see the lubricantbased cutting fluids are there; that means, friction is the main culprit here to reducethe friction to reduce the heat generation in the honing process, this particular lubricanttype of cutting fluid will be used and it is a dominating one not the coolant type of;that means, if you see the table where the lubricant and coolant is there there peopleare going to use mostly mineral oil based cutting fluids, people who want to work onthis one there are very less papers on sustainable cutting fluids for honing applications.So, if you have expertise on sustainable green cutting fluid development, you can also checkthose cutting fluids for the honing process also that is can be a good area to take upas your masters are PHD thesis this is about the honing process.The advantages of this particular process is it improves the geometrical accuracy andsetting certain surface pattern that mean that to crosshatch pattern, it can generateat the same time this will help in terms of lubrication at the cylinder piston interactionregion. Same materials like grinding stones you canuse that is nothing, but a silicon carbide CBN or polycrystalline diamond you can usesimilar type of grinding particles on the hones, that is called honing sticks. Moreprecise shape smaller grain you can use so, you what are the difference here is you cango for precise shapes at the same time more finer because you need to get the fine surfacesat the same time fine crosshatch patterns. That is why normally the people goes for finesize of abrasive particle size you might have seen the abrasive size in the grinding wheelspecification. So, coarse medium and fine is there. So, people will go medium to finerather than coarse if you go for coarse the surface roughness wills very high the pistoncannot move as per the requirement. So, the piston will fail the complete automobile willfail for that purpose you have to go for the finer or a smaller grains or abrasive particles.Cutting fluids are used for the lubrication that is nothing, but dominating the lubricatingcharacteristics not the cooling characteristics ok, you have to choose lubricant not the coolantif at all you want to go for very high speeds of reciprocation as well as rotation in thatcircumstances, you can go for very minimal amount of water addition to heat if at allrequired, but normally it is not recommended. Expensive and time-consuming because thisprocess takes lot of time this is the disadvantage of this particular process because the materialremoval rate is too less, because you have a fine particles and the low spring relaxationwill depend on your requirement with the abrasive particles will remove very very minuet chips;that means, that time for finishing will be very high.Summary of today's class we have seen the grinding fluids after the grinding processand fluid application angles whether conventional fluid, you can use whether it can be usedto tangentially 15 degrees or 30 degrees or what is the stand-off distance how far youhave to keep and all those things we have seen.The type of cutting fluids whether people have use liquid type of cutting fluid ah solidlubricants also people used MQCF that is called sustainable grinding process is one of theconcept nowadays people are working. So, people you can also work especially those peoplewho want to do research they can go for MQCF in the grinding operation for machining ofadvanced materials like aerospace alloys or biomaterials or something.Wetting angle and wetting surface calculations as well as software developed particle sizesthat is droplet size validation and all those things we have been that is in the MQL whatis the droplet size experimentally people have validated using Malvern experiment atthe same time they have also validated using the software's by simulating it, and the honingprocess we have seen and the lubricants that are used in the honing process also we haveseen. So, honing process keep in mind that it is lubricant type of cutting fluids youhave to use not the cooling type of cutting fluids.So, thank you for today's class and we will see some of the other conventional finishingprocesses in the next class .