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Module 1: Tool Wear and Tool Life

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Types and Application Techniques of Cutting Fluids

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Video 1: Categories of Cutting Fluids
The solid cutting fluid or the solid lubricantsbasically ok. So, here air will be used as a cooling agent and the solid particles likea graphite, molybdenum disulphide, calcium dichloride and ah tungsten (Refer Time: 01:14)sulfide like that we will be taking. And if you see in the schematic the compressed airis coming from here and the solid lubricant powder current case assume that the graphiteis there. So, graphite is fit like this. So, both will mix and come out as a solid lubricantjet basically it will come as a jet. So, the air assists in terms of pressurizingat the same time. So, the particles will also go into the chip tool interface and ah workpiecetool interface indirectly I mean to say the machining region. The basically how the graphiteact as a lubricant. So, if you see the graphite there is layer by layer formation is therewhere ah between the layers of the carbon atoms are held by the weak Van der waal forcesok. You can see the layers in between the layers we have a Van der waal forces theseare the Van der waal forces. So, among the carbons between the carbonsin this one layer there will be a strong covalent bonding ok. So, whenever it falls in the machiningregion what is the advantages that layer by layer shearing takes place. So, this layerwill share of assumed that it may rebind on the one surface it will shear also becauseby the breakage of Van der waal bonding which is a weak bond. This is how it will act asa lubricant as we have already seen that ah graphite is a self you begin in terms of castiron. So, they are normally the cutting fluid is not used ok.If you see the some other also as you have seen in the previous slide solid lubricantpossess laminar structure. So, laminar structure in terms of ah not only graphite we will takesome other common example because they are carbon based are there at the same time someof the carbons present in the work pieces also some of the work pieces here some othervariety that is called MoS 2 molybdenum disulfate. Here this is also MoS 2, ah CaF 2, W s 2 andother one thing that can be used is PTFE normally polytetrafluoroethylene is also used. If yousee this is one of the coatings normally used in the common utensils which are used in themess or I mean to say in the kitchen ok. So, just I we will speak about the MoS 2 structure.MoS 2 also will have laminar structure as it is specified laminar structure is thereand here the shading takes place, whenever the shearing takes place in the in terms ofgraphite or in terms of MoS 2 layers by layers will goes off. Here also if you clearly seethere is a weak sulfur sulfur bonding allows easy sliding of these layers ok.So, sulfur assist in the MoS 2 to act as a lubricant because the bonding between sulfursulfur is very weak that is what. In the graphite among the carbon there is a covalent strongbonding, another one between the layers of graphene there is a Van der waal weak bonding.So, whenever the chip tool goes off like this what will happen the Van der waal force breaksand the top graphite layer goes off and bottom graphite layer may stay ok, because of thesevere plastic deformation and shearing action. So, here it is slightly different becausethe bonding among mo and s is good, but inter bonding between sulfur and sulfur is veryweak. So, the sulfur assist in the form of solid lubricant, so that it will goes offa by shearing ok. This is about the solid lubricant ok.Now, we will move to the nano cutting fluids. As I said nano cutting fluid, if you see theseare the fluids that are developed at our laboratory just for ah the introduction purpose and justgiving you what ah normally we do is we take ah cutting fluid either it can be a mineraloil based cutting fluid are and green cutting fluid or something. For example, we are takingone liquid type of a fluid and then we mix with the nanoparticles. In the current casewe have mixed MoS 2 molybdenum disulfate that is why I have slightly explained you in theprevious slide about MoS 2. So, MoS 2 is cutting fluid is there plus MoS2 particle ok, MoS 2 particles are there if you mix it what will happen it will form thethe particle size should be nano. So, that it form a nano fluid ok I mean to say nanocutting fluid ok. So, this is the combination, but.If you see there is a slight difference between two things that is at t equal to 0 hour andt equal to 24 hours this is the sonication time. Normally the sedimentation problem lotof the collide this is normally a collides basically. So, there will be always a sedimentalproblem, there is agglomeration problem and all those things to avoid all these thingswhenever we want to do the machining text. Normally this these are used in the machiningsystem before that using we how to treat them for proper mixing. So, you can clearly isvisible comparison can be taken from the two pictures, if you see this one and this onethere is a slight difference. In the second one what will be the uniformmixing is taking place, and these are not agglomerated and sub placed uniformly ok.So, that is what we want before we used in the machining process ok. How this nano fluidslook like in the schematic ways? Nano fluid as I said it contains the CF 2 cutting fluidplus MoS 2 particles assume that I have a any particle. So, cutting fluid liquid isa plus we are using MoS 2 as a nano particle. So, we have to use some other dopants alsobecause like emulsifiers, stabilizers, functionalizers and many more as I said know in the previousthing we have to use rust inhibitors and all those things. So, those are all have to use.At the same time we have to in this particular thing we have we have use the emulsifiers,we have used the stabilizers, because this particle should uniformly dispersed at thesame time it should I mean to say it should not agglomerate among the particles itself.For that purpose at the same thing it has two stable at particular location, for thatpurpose normally we will use the stabilizers and all those things ok.So, if you ah see the another advantage of nano fluid is contact angle ok. So, normallythe contact angle if it is more what will happen? So, the area of contact is very less.So, if for that purpose normally we should go for better wettability. Normally if thecontact angle is less ; that means, that the fluid has a proper wettability.Assume and that I have this surface and I have this wettability and another case I havethis wettability. So, in circumstances the area of wetting and other things is you cancalculate and all those things ok.. So, area of wetting is most important in terms of machiningarea ok. So, if ah I want to take the heat from themachining area the contact available it falls it should have a proper contact area; thatmeans, minimum contacted; that means, at maximum wetting area. So, that I can take the heatout of that machining surface or the machining zone. At the same time if the two things iffrom this point of you I can say two things one is if the wettability area is increasingwhat will happen better cooling, cooling will be done and better lubrication also will bedone ok. So, these are the two advantages that ah youwill get if you have a proper wetting surface ok. Whenever you add this one what this isthe case one is before adding and case two is after adding the nanoparticles to the cuttingfluid. This is before and after, I mean to say cuttingfluid with ah cutting fluid plus nanoparticle ok this is cutting fluid only ok. So, contactangle. So, other advantage is if you see the onlymeeting surfaces tribological conditions just I want to explain you from the tribologicalconditions where the surface is only mating surfaces. In the second case normally youwill have a normal lubricant or the cutting fluid wherever the application is there.In the third case whenever we see about this nano fluids it forms a thick and strong protectivefilm in the tribological application in either bearings another tribological coordinations.If this is the benefit in the tribological conditions we can also impart by mixing withah suitable cooling fluids in the machining process and you can use it ok. That is thebeauty about the nano cutting fluid ok. So, the thing is many researchers are workingnowadays on the nano fluids in the machining. So, if any researchers who want to take upthe research in terms of nano fluids or nano cutting fluids as your thing you can takeup because, only thing that you should take care is what type of nanoparticles I am using.As I said in the previously that ah some people are using metal nano particles, ceramic nanoparticles,and solid lubricant nanoparticles and other particles.So, based on your application, based on your workpiece material, based on your tool material,based on what type of cutting fluid composition that you have ok you have to decide thesenanoparticles. That nano particle should have chemical compatibility whenever you are mixingit and you should be very careful about these thermal properties of this nano particle beforeand after, how the thermal conductivity of the fluid is increasing or decreasing, whetherthe contact angle is increasing or decreasing, whether the thermal conductive heat transfercoefficient of this fluid is increasing or decreasing is all to be measured before yougo to the experimentation in the machining process.
Video 2: Adverse Effects of Cutting Fluid
But adverse effects of cutting fluid on operator as well as environment I will talk in a bigway; however, ah I am just giving you some glimpse because just now I am talking aboutthe different different types of cutting fluids. So, I will just talk about what are the basicproblems because of these cutting fluid emissions what are the things comes to the operatoras well as environment ok. So, I am already saying the elaborative specialclass about this chemical what are there and what are the emissions and all those thingsI will talk ah in upcoming classes ok. So, just I will give you the first glimpseor whatever the cutting fluid falls on a operator what will happen. So, if a operator is operatingthere is a assume that the workpiece is rotating with the high speed those flashing alwaystakes place because the machining region is a part of ah workpiece rotation and all thoseinteraction between tool and workpiece. So, because of which what will happen if it fallsin the hand it causes the contact dermatitis where the epidermis and outerdernis of (ReferTime: 24:18) of the operator. If it is prolong exposure to the cutting fluid these type ofproblems you can see on the hand ok. So, though this is about the one of the problem.This is a common problem because if you see the operator most of the operators ah thisah splashing will takes place. So, in order to prevent all these things one has to weara apron, one has to take care of the ah gloveses with they before they are going to the operationor before going to do the machining operation I mean to say machining operation I am not[laugher] about the operation that we do ah the doctors do, ok. So, whenever do the machiningoperation they should be properly interest from the top to bottom so that ah it can becontact should be prevented ok, because that is why I am taking about this is a contactwith dermatitis. Contact dermatitis means whenever the prolongedcutting fluids falls on the operators skin that is epidermis ok, so this will affectok, this will come because of the contact that me that is why this is called as contactdermatitis ok. So, the second one is a thin normally whatis here shown is a thin section of computer tomography that is CT scan. Many of the youknow about CT scan showing the mild bronchitis and interstitial lunges diseases ok. Theseare CT scan of the lungs where ah particles are entered into the olivia region or thelungs region of the operator. I will come in the next slide how these particles willenter and all those things. So, then I will come back to you ok.So, at the same time some of the chemicals in the cutting fluid always some of the likenitrides and nitrates and all those things this. These are ah come into the cutting fluidbecause of whenever you add some additives like corrosion inhibitors, monocytes, emulsifiersand all those things. But if the quantity that one has to add this type of additivesto the cutting fluid if it a exceeds beyond the specified limitation by the national instituteof health organizations and all those things. What will happen? It may lead to the uncontrolledcell culture that is ah cell growth in which is also called as a cancer and all those thingsok. One should be careful about all these things ok.So, now, I have just to talk about what is there at the middle. In the next slide ifyou see this one mold mild bronchiectasis and all those things. What about the, howthis will be come to the operator ok? So, whenever the cutting fluid mists is therecutting fluid mists are aerosols; that means, that when the cutting fluid falls on a machiningregion where the temperature is very high what will happen it try to evaporate ok. Somepart of things you have evaporate ok. Comprises of liquid particles less than twenty micronsnormally different sizes are there. So, aerosols may be suspended in the air forseveral hours, even several days possibly in the work breathing zone. Assume that ifa person if the operation is going on; that means, a machining operation is going on inthat circumstances what will happen there is a spectrum of the cutting fluid aerosolswill be developed ok. So, that ranges from some few microns to some hundreds of micronsok. So, like ah it maybe less than 20 microns,less than 10 microns, approximately 2 microns, 2.5 microns and all those things. But thesame time these are the aerosols which are like a small small nano particle or microparticle airs which may suspend in atmospheric air or if a person is operating like thisassume that a operator is bending and the experiment machining operation is going onin this way. So, it will splashes and it may go into the nostrils of the operator ok.So, in that case the normally inhaling acceptability of the human is less than ten microns of aerodynamicdiameter of the particle. If the particle or the aerosol size is less than 10 micronsit can go into the nose and deposit in various regions of the respiratory system by the complexaction of different deposition mechanisms ok. That means, operator can inhale this oneok; that means, that it will go into the nose not into the lungs ok that should be no getpoint here ok. If you see if the particle size is below 2.5microns of aerodynamic define it can go into olivia region of the lungs ok which is a sensitivepart of it ok. If it is 10 microns or less than time microns that I mean to say between10 to 2.5 micrometers you can breathe, but less than 2.5 microns or equal to 2.5 micronsit can enter into your olivia region of your lungs which is more sensitive ok.Anyhow I will show a picture in the next slide because of the material here I am unable toshow I will show in the this mists droplet us can cause throat pancreas rectum and prostatecancers ok. You, we will this occupies and causes a lot of ah different different cancersto the operator. Now, I will come to the point ah where lessthan 2.5 microns particles are aerosols will go into and occupy the olivia region of yourlungs ok. These are the lungs and if you just zoom ityou will find the olivia region and if the aerosols goes and occupies this region thatis slightly dangerous ok. So, that should be taken care ok. That is why and at the sametime it will also causes some of the asthma, irritation in the breathing and all thosethings ok. So, these about the operator and the surroundingsok. If you see the surroundings normally what the people will do? In the workshop you areusing the cutting fluid you are recycling it, recycling it, recycling it again againand again and again and again what will happen the cutting fluid will destroy its lubricationproperty goes bad its cooling property goes bad and all other properties goes to bad notonly this it will also start emitting very dangerous vapors ok. That is why after sometime whenever the workshop people or other people wherever they feel that it has to bethrown what will happen the first thing what they will do is they will just dump into thenearby water bodies that causes the water pollution. If you see a portion of this oneok, so it will causes the lot of water pollution. The what about the fishes whatever the fronswhatever the ah living organisms that are there in the this one this will affect lotof things. And if some people will if we consumes that fishes or frons and all those things,so it may also affect the humans who are around that water bodies. Some of the people alsodo they just dig the earth in the premises of the company and all those things and theyjust dump it into that one. So, that causes the soil pollution. So, water pollution, soilpollution at the same thing because of the vapors and operator, so environment, becauseof this there is an environmental pollution pollution and water pollution is there, andsoil pollution all the pollutions are there ok.So, in order to save all these things what are the thing, one one has to take care whatI mean to say is, why I am explaining all these things tomorrow you may be a staff ina certain company and ah workers will be there I mean to say the supporting staff who arethe operators you should ah help them in protecting from all these problems. So, if you do notwear all these things if you you may get these type of problems and all those things thatok. Elaborately when we I will teach there, butmy concern is if you are ah watching or not watching that particular lecture sometimessome people may miss that ah some that particular lecture. I just appeal to you is ah the humanah life has a good value because a operator is working in a company. So, he has his ownfamily something happens to him its family will be in a difficult situation. So, if hehe may be a major earning member in the live in the family. So, you always as a engineerit is our primary responsibility to give the safety to the operator. So, at the same timehelp the company in not dumping in the like a water pollution or ah soil pollution andah hope you ah help the operators also ok. So, these are the problem forces some of thealternative ways ok. So, why these problems comes? Whenever you are using huge amountof cutting fluid then only these problems comes. So, either can you reduce the cuttingfluid by having the same performance if that is so, that is good. Can I do not use cuttingfluid if I can do the machining operation there is also fine. So, this comes that theanother variable that is called ah cutting fluid application technique. So, whether howto overcome all these things or which process is not good which cutting fluid techniqueis suitable for what application which cutting fluid technique is suitable for what applicationand all those things ok. So, which cutting fluid technique will give lot of emissionsand all those things also we will see ok.
Video 3: Cutting Fluid Application Techniques
Cutting fluid applications, the first oneis the flood cooling application where normally 400 to 600 ml per minute consumption of cuttingfluid huge amount of cutting fluid will be used here ok. So, this is one of the culpritany how we will talk about this one. So, cutting fluid jet application that iscalled where ah still more higher cutting fluid is used, but you will send with thehigh pressure ok. In the flood cooling it is by the virtue of gravity air jet applicationnormally instead of liquid type of cutting fluid some people they will use air jet whichI have seen in the hot air and cold air application. Another applications are cutting fluid mistapplication that is ah mixing of cutting fluid with the air and you are carrying out theoperation. Some people they will called as a minimum quantity cutting fluid process,minimum quality lubrication is one of the famous word that you can see in the minimumand some people they say micro lubrication. And some people they contradict MQL is notah micro lubrication micro lubrication and MQL are both are different. Some people saythat the pseudo dry machining, some people they say near dry machining, why they saynear dry is instead of using 400 to 600 ml the air they will be using ah 5 to 10 ml,ml per minute. Even some of the cases ah research papersare there where they have ah used ah 1 to 5 ml per minute ok. In this circumstancesif somebody is using 1 ml per minute where 600 ml is a maximum and 1 ml it is approximatelyminimal that is why it is near to dry machining that is why the name came near dry machiningprocess ok. So, do not confuse between ah MQL near dry machining process. Some otherpapers you also see pseudo dry green machining. So, a paper is they are all with the nameok that is also similar to this one ok. So, the first one is flood cooling where youcan see the coolant or the lubricant that is flowing like a water that if you pour waterfrom a glass it is ah ok. So, by virtue of gravity it falls ok. So, it falls in the machiningregion by the virtue of gravity ok. So, normally I said it is 400 to 600 ml perminute is the consumption, it is the consumption. If if you see in that way it is average onaverage it is 500 ml per minute which is a huge amount of the cutting fluid that is goinginto the machining region and we use it recirculating. The basic problem here is ah free convectiontakes place because the solid body is there a fluid that liquid is falling and it is takingaway some of the heat it is not because it is not going into the ah machining interiorzones. So, it takes away partially the heat. So, what will happen? So, thermal crackingwill takes place, in proper combustion will takes place, and all those things at the sametime it is falling by virtue of gravity it is free conviction ok. So, the free convictionmeans the convective ah the heat transfer with conviction is low force convection itwill better ok. So, the cutting fluid account 17 percent ofthe product cost this is another big drawback of this process is ah if my product cost is100 rupees, 17 rupees will go for the cutting fluid consumption itself. So, if I can minimizethe cutting fluid or if we can drop the cutting fluid then I can ah be competitive in themarket by selling my product of the economic price compared to other people who are usingthe cutting fluid ok. So, I can sell at even less price still I am at the profit ok. Thatis why this process is a not a good process. However, most of the industries currentlyin India are using this process ok. So, second one is jet application cuttingfluid ah jet application ok. So, where you you can see here where the high pressure jetis send or into the chip tool interface. If you see here chip tool interface it is sendingin the machining region. Normally here in the flood cooling it is by virtue of the gravityit is falling here you are pumping with very high pressures, so the convection will behigher side to the flood cooling. But the advantage here is forced convection ok ok.So, the advantage that you are going to get is there in the flood cooling it is free convectionhere it is the forced convection. So, heat transfer will be better in this way. At thesame time the drawback of this one is consumption of cutting fluid is still higher comparedto flood cooling. So, the the another one is air jet coolingsince I am talking about high pressure jet. So, some people they also send the cold airor cold water also they will send and ah hot air also some people they are ah using hotair as a cutting fluid in machining of ah titanium alloys also, ok. So, you can useif at all somebody people are working because the as I said that titanium ah temperatureconducting is very low. So, the temperature that you are sending by hot air or somethingwill stay on the surface itself ok you can do the machining process very easily. So,this is about the air jet. The advantage if you see with the air jetand flood cooling. The flood cooling you have a cutting fluid or a high pressure coolingyou have a cuttings fluid where convective heat transfer coefficient is very high, butit cannot penetrate into the interior zones of the ah machining zone. On other side youhave a air; that means, compressed air where ah it can easily enter into the intricateregions. If I combine both normally what I will get is minimum quantity lubrication orminimum quality cutting fluid. Let me explain you in one case what I am gettingis easy accessible capabilities of air into intricate shapes; that means, I am using ahighly compressed air which has can enter into the intricate regions of the my metalcutting I mean to say if this is the metal cutting. So, it can enter like a jet ok itcan enter like a jet. So, on other condition I have a cutting fluidwhose convective heat transfer coefficient is very high , but it cannot enter. Here conductiveheat transfer coefficient is low, h value is low, h value is high , but it can penetrateeasily , but it cannot penetrate easily. So, advantage of penetration, advantage of highconvective heat transfer coefficient whether we can combine both or not is the question.If we can combine these then we are at the good condition where you can penetrate intothe intricate regions at the same time you can also get the heat out of it ok. That iscalled mist cooling or minimum quantity lubrication or minimum quantity cutting fluid ok.So, what I am taking here is here I am taking the easy accessibility of the cutting fluid,I am taking at the same time convective heat transfer coefficient of cutting fluid I amtaking, I am mixing and I am atomizing and I am sending into the machining region ok.So, whatever I am sending here is a jet that is atomized jet ok, it is an atomized jet.So, atomized jet can penetrate into the intricate regions and it can extract the heat becausethe convective heat transfer coefficient because I am sending atomized particles of the cuttingfluid whose convective heat transfer coefficient is very high. At the same time since I amsending any pressure I am extracting the heat by forced convection.There are three advantages one is penetration into intricate regions, second one is ah highconvective heat transfer coefficient, third one is an extracting by the forced convection.Because of this this process has a huge application, and many other papers you can see alreadymany people published in terms of ah milling in terms of ah drilling in terms of turningprocess in even in terms of grinding process also many people have ah published work ok.So, in the normal condition is high pressure ah cutting fluid jet this one if you use ahMQCF jet ok. So, you can see here normally the it will be a liquid here, here it willbe a atomized jet, ok, well good, ok. So, you can here another advantage is normallythe consumption of cutting fluid is ah less. Here the cutting fluid consumption will bemore than 600 ml per minute about 600 ml, here normally it will be like ah 5 to 10 mlper minute. So, advantage that you are going to get is the product that you can sell inthe market will be at competitive price ok and the quality of the product will also bewill be good ok. So, these are the beauty and advantages ofthis one. However, the initial investment of getting this ah minimum quantity lubrication,nozzles and the pump maybe a costly; however, many of the researchers has already demonstratedthat you can develop your own nozzles. There are internal mixing nozzles, there are externalmixing nozzles and you can also develop these nozzles in your small small workshops also.