STUDY OF SURFACE INTEGRITY BY SURFACE GRINDING USING VEGETABLE OIL THROUGH MINIMUM QUANTITY LUBRICATION

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1 STUDY OF SURFACE INTEGRITY BY SURFACE GRINDING USING VEGETABLE OIL THROUGH MINIMUM QUANTITY LUBRICATION V. Gopalakrishna 1, P.Chaitanya 2 and M. Avinash 3 1,2,3 Department of Mechanical Engineering, SVCE, Nellore Abstract - Components produced through operations involving the removal of material display surface irregularities resulting not only from the action of the tool itself, but also from other factors that contribute to their superficial texture. This texture can exert a decisive influence on the application and performance of the machined component. There are now several types of metalworking fluids in the market and the most common can be broadly categorized as cutting oils or water-miscible fluids. Vegetable oils have become identified world over as a potential source of environmentally favorable metal working fluids due to a combination of biodegradability, renewability and excellent lubrication performance.our paper analyzes the behavior of the minimum quantity lubricant (MQL) technique using vegetable oil for surface grinding operation and compares it with the conventional cooling method. Keywords Surface grinding, cutting fluid, vegetable oil, Minimum Quantity Lubrication, Surface integrity I. INTRODUCTION A lubricant is a substance used to facilitate relative motion of solid bodies by minimizing friction and wear between interacting surfaces. In addition to the primary purpose of reducing friction and wear, lubricating oils are also required to carry out a range of other functions, including removal of heat, corrosion prevention, transfer of power, providing a liquid seal at moving contacts and removal of wear particles. Conventional metal working fluid delivery system provide fluids to work zone in volumes which flood the work area these fluids are filtered then re-circulated through the system. Micro lubrication delivery system provides extremely low volumes of fluids to the process. Micro lubrication is also known as MQL or near dry machining. It is observed that completely dry cutting, as compared to flood cutting, lowers the required cutting force and power on the part of the machine tool as a result of increased cutting temperature. However, achievable tool life and part finish often suffer under completely dry condition. Under these considerations, the concept of minimum quantity lubrication presents itself as a possible solution for grinding in achieving slow wear of grinding wheel while maintaining cutting forces/power at reasonable levels, provided that the minimum quantity lubrication parameters can be strategically tuned. This paper aims to evaluate the performance of the MQL technology compared with conventional cooling, applied in very small flow rates as an environmentally correct alternative to the cutting fluid utilized in cylindrical plunge grinding. The small amount of lubricant is pulverized in a compressed air flow, reducing the undesirable effects involved in supplying lubrication and cooling. The evaluation of the MQL technique in the grinding process consisted of analyzing the surface integrity (roughness). Surface grinding is used to produce a smooth finish on flat surfaces. It is a widely used abrasive machining process in which a spinning wheel covered in rough particles (grinding wheel) cuts chips of metallic or nonmetallic substance from a work piece, making a face of it flat or smooth. The surface grinder is composed of an abrasive wheel, a work holding device known as a chuck, and a reciprocating table. The chuck holds the material in place while it is being worked on. It can do this one of two DOI: /IJMTER AC9BR 10

2 ways: ferromagnetic pieces are held in place by a magnetic chuck, while non-ferromagnetic and nonmetallic pieces are held in place by vacuum or mechanical means. Depending on the work piece material, the work is generally held by the use of a magnetic chuck. This may be either an electromagnetic chuck, or a manually operated, permanent magnet type chuck. The chuck used in the project was a manually operated magnetic chuck. Aluminum oxide, silicon carbide, diamond, and cubic boron nitride (CBN) are four commonly used abrasive materials for the surface of the grinding wheels. Of these materials, aluminum oxide is the most common. Because of cost, diamond and CBN grinding wheels are generally made with a core of less expensive material surrounded by a layer of diamond or CBN. II. EVOLUTION OF CUTTING FLUIDS Until the mid 19th century, essentially all lubricating oils were based on natural oils, i.e. animal fats, vegetable oils and marine oils, which are triglycerides of mixed C8-C22 linear fatty acids. Industrial development during the 19th century rapidly increased the need for lubricants, which exceeded the supply of natural oils. However, the increased exploitation of petroleum as a fuel source also provided a new material possessing lubricant properties; mineral oil, which was co-produced, when crude oil was refined for gasoline production. This led to the availability of mineral oil in large quantities and at competitive prices. Mineral oils are found to be more stable than natural oils; also they are cheaper and available in a wide range of viscosities. They are extremely complex mixtures of C20- C50 hydrocarbons containing a range of linear alkanes (waxes), branched alkanes (paraffins), alicyclic, olefinic and aromatic species. They also contain a significant concentration of hetero atoms, mainly All rights Reserved 11

3 III. MINIMUM QUANTITY LUBRICATION MQL means Minimum Quantity Lubrication. This is a new machining method that delivers the required minimum quantity of lubricant mixed with air and performs machining through a continuous supply of this oil/air mixture to the tool tip. This method is also called semi dry machining, near dry machining (NDM), and MMKS. This method for machining and the mixture are called MQL. MQL makes it possible to reduce the amount of lubricant to nearly zero. MQL generally uses vegetable oil or ester oil as the cutting fluid. These high-performing oils have excellent lubrication and natural dissolving properties. Furthermore, they are environmentally friendly. Many advantages are realized through the use of MQL and the reduction of cutting oil consumption. These include improvement of the plant environment; improvements in chip recycling, reduction of electricity consumption, increased tool life, a "greener" environment, and a decrease of machine maintenance due to contamination by coolant. In conventional manufacturing of mass-produced parts that typify automotive parts (engine, transmission, brake, etc.), a large volume of cutting fluid (coolant) is used to improve productivity and machining accuracy. Recently, the negative effects of cutting fluid upon people and the environment have become a serious problem so the reduction of coolant is strongly required. Minimum-quantity lubrication system lubrication involves a loss of Consumption lubrication, i.e. the lubricant is used up almost completely during processing so that a preparation is not necessary in the cycle. An air current with finely distributed oil drops, so-called aerosol, lubricates the friction spots between the tool and the chips running off in the chip grooves. The minimum-quantity lubrication system assures effective lubrication of cutting processes using smallest amounts of lubricant. The arduous task of cleaning and disposing large amounts of lubricant and cooling lubricant is, if necessary at all, made much easier. IV. EXPERIMENTAL SET UP The material used in these tests was EN31 steel (Carbon %,Manganese %, Chromium % Sulphur 0.050% max, Silicon %, Phosphorous 0.050% max.). The work piece of 135*135*35 mm in dimension was used for the project and this work pieces were cut into 4 equal parts marked using a scriber and scale and then these marked work pieces were cut using a the hacksaw. To record the temperature of the material during the grinding process a J-Type thermocouple was used and in order to place the thermocouple into the workpiece material a hole of size 6mm was made using a lathe machine. The tests were carried out with aluminum oxide (Al2O3) grinding wheels with specification of 200 x 12 x 31.75mm AA60K Construction Of MQL All rights Reserved 12

4 The main aim of MQL equipment is to mix the air and oil and spray it in the form of mist. For this a gas welding torch was taken and the acetylene passage of the gas torch was closed and the air inlet is connected to the air compressor and the torch is connected with a thin nozzle and the whole equipment was mounted on the surface grinding machine.for the oil flow measurement a burette is taken and it was fixed on to the grinding machine at a certain height. A pipe was connected to the burette outlet and the other end of the pipe was connected with a thin nozzle and the nozzle is held together with the gas torch nozzle such that the oil nozzle and the air nozzle come in contact with each other. When the air lever was opened the air comes through a certain pressure and when the oil valve of burette was opened the air comes in contact with the oil such that a fine spray of oil was formed. PROCEDURE The experiment was done on the work piece considering three cases. Dry Grinding Wet Grinding (Water) Minimum Quantity lubrication (Vegetable Oil) Minimum Quantity Lubrication (MQL): The experiment using the MQL equipment was carried down considering three parameters 1. Varying Coolant Quantity 2. Varying Feed Rate/Speed 3. Varying Depth of Cut All rights Reserved 13

5 VI. CONCLUSION The MQL(minimum quantity lubrication)is employed to increase the machining productivity and quality of metal cutting. While operating the operator feels uncomfortable during the operation due to the occurrence of sparks and toxic gases. By this method the fine spray of mixture nullifies all All rights Reserved 14

6 toxic gases while doing the operation. There will be a fine finish on the surface of the material as it is practically proven in the surface roughness test device. The cost of the equipment and the vegetable oil used is very low and the operation is user friendly. The test results have proved the above points. An analysis of the experimental data of this study led to the following conclusions regarding the EN 31 steel: The MQL technique can be applied efficiently in the surface grinding process, providing environmentally correct and technologically relevant gains. The Ra values were substantially reduced with the use of the MQL technique, probably due to excellent properties of lubricity. No significant clogging of the grinding wheel pores was found with the MQL technique. The use of MQL did not negatively affect the surface integrity and it does not effect the health of the operator. This technique reduces the affect the environment. REFERENCES [1] Analysis of surface integrity for minimum quantity lubricant MQL in Grinding. Leonardo Roberto da Silvaa,_, Eduardo Carlos Bianchib, Ronaldo Yoshinobu Fusseb, Rodrigo Eduardo Cataic, Thiago Valle Franc-ab, Paulo Roberto Aguia [2] D. Sahm, T. Schneider, The production without coolant is interesting and must be more known, Machines and Metals Magazine (367) (1996) [3] F. Klocke, G. Eisenbla tter, Dry cutting, Annals of the CIRP 46 (2) (1997) [4] C. Dunlap, Should you try dry?, Cutting Tool Engineering 49 (1) (1997) [5] O. Novaski, J. Do rr, Machining without coolant, Machines and Metals Magazine 399 (1999) [6] A.R. Machado, A.E. Diniz, Advantages and disadvantages of the use of the cutting fluids, Machining Congress 2000, Sa o Paulo, SP, Brazil, [7] U. Heisel, D. Lutz, R. Wassmer, U. Walter, The minimum quantity lubricant technique and its application in the cutting process, Machines and Metals Magazine (386) (1998) 22 All rights Reserved 15