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Cutting Force and Surface Roughness in Cryogenic Machining of Elastomer

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Cutting Force and Surface Roughness in Cryogenic Machining of Elastomer
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  Proceedings of the 2 nd  International Conference on Current Trends in Engineering and Management ICCTEM -2014 17 – 19, July 2014, Mysore, Karnataka, India   151   CUTTING FORCE AND SURFACE ROUGHNESS IN CRYOGENIC MACHINING OF ELASTOMER Rajesh Nayak 1 , RavirajShetty 2   1 (Assistant Professor, Mechanical, Manipal University, India) 2 (Professor, Mechanical, Manipal University, India) ABSTRACT Most products based on elastomers are produced by some kind of molding and curing process. This paper deals with a new method of elastomer machining. A series of cutting experiments under different rake angle, cutting speed, feed and constant depth of cut has been conducted on cutting force and surface roughness under ambient and cryogenic condition. From experimental data it can be clearly seen that increase of cutting force become more significant with higher cutting speeds for cryogenic cutting. Cryogenic machining showed remarkable reduction in surface roughness compared ambient machining especially at high rake angle. Keywords: Cryogenic Machining, Cutting Force, Elastomer, Surface Roughness. 1. INTRODUCTION Elastomers have been used as an engineering material for nearly 180 years in various military equipment’s and industries in applications such as liner layers of armored vehicles, tires, springs, shock isolators, noise and vibration absorbers, seals, and electrical and thermal insulators. An elastomer can be defined as, “a macromolecular material, which, at room temperature, is capable of recovering substantially in shape and size after removal of a deforming force [1-3]. Most elastomer parts are manufactured using a molding rather than machining process, to manufacture elastomer parts with complicated shapes, such as tire and footwear tread patterns, a set of molds must first be produced. However, there are many disadvantages associated with molding elastomers including high cost, labor-intensive and time consuming process of mold fabrication and the inflexibility of a mold to design changes. For these reasons, machining offers an attractive alternative for manufacturing elastomer components. Most elastomer parts are manufactured using a molding rather than machining process. In the molding process, raw polymeric materials are mixed with other additives and then heated, melted, and pressed into a mold. Inside the mold, the polymer material is subjected to a controlled temperature-pressure-time cycle. The material is cured, vulcanized, and cooled to produce the desired properties and geometry. To manufacture elastomer parts with complicated shapes, such as tire and footwear tread patterns, a set of molds must first be produced. However, there are many disadvantages associated with molding elastomers including high cost, labor-intensive and time consuming process of mold fabrication and the inflexibility of a mold to design changes. For these reasons, machining offers an attractive alternative for manufacturing elastomer components, which would be especially useful for manufacturing low volume custom or prototype parts and other applications requiring a complex shape and frequently modified designs. Potential applications of elastomer machining include prototype tire and footwear tread patterns, custom seals for biomedical applications, specialty vibration dampers, and scrap tire recycling equipment.   INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 5, Issue 9, September (2014), pp. 151-156 © IAEME: www.iaeme.com/IJMET.asp Journal Impact Factor (2014): 7.5377 (Calculated by GISI) www.jifactor.com   IJMET   © I A E M E    Proceedings of the 2 nd  International Co This current work deals with cry rake angle, cutting speed, feed and consta under ambient and cryogenic condition. F become more significant with higher cutti reduction in surface roughness compared a 2. LITERATURE REVIEW Very little research on elastomer elastomers and the complexity of the machi variety of carbide end mills of various si Norbornone rubber, and silicone rubber at high speeds yields smoother machined surf Shih et al [3] investigated the m conditions and reported that proper selecti grooves can be machined in elastomers. It in achieving a smooth machined surface. Strenkowski et al [4] carried out machining parameters on chip morphology, significant effect on the types of chips gen corresponding smooth machined surfaces Strenkowski et al [5] have developed wed prior to material separation. Shih et al [6] have done analysis design of the workpiece fixture was foun elastomers because of the low elastic modul Dhokia et al [7] have discovere development of a process control system fo 3. EXPERIMENTAL SETUP Nitrile Rubber (NBR) is commonl industries. NBR is actually a complex fami elastomer with the appropriate acrylonitril NBR in a wide variety of application areas used in fuel and oil handling hose, seals an 40C to +125C, NBR materials can withsta specimens known as Nitrile rubber was copolymers of acrylonitrile and butadiene. mm. The experiments were carried out in a PSG Fig.1.  Cryogenic cutting The Elastomers have a very low Elastomers exhibit large elastic deformation ference on Current Trends in Engineering and Manage 17 – 19, July 2014, Myso 152   genic elastomer machining. A series of cutting experi nt depth of cut has been conducted on cutting force an rom experimental data it can be clearly seen that incr ng speeds for cryogenic cutting. Cryogenic machining bient machining especially at high rake angle. machining has been conducted because of the complex ning process itself. Jin and Murakawa, [2] have carried es and helix angles to mill grooves in three types of arious cutting speeds .They have reported that at high h ces and lower forces. chining of elastomers with sharp woodworking tools on of end mill geometries, process parameters, and fi as also shown that cryogenic cooling of an elastomer w orthogonal rubber cutting experiments and examined t machined surface roughness. Feed rate and rake angle rated during orthogonal cutting. Long and continuous r were produced for high feed speed conditions and lar e indentation models to investigate chip formation dur on rubber workpiece to study its stiffness using ANS to be a critical factor in achieving good surface fini us. the novel concept of cryogenic CNC machining of cryogenic CNC machining. y considered the workhorse of the industrial and autom ly of unsaturated copolymers of acrylonitrile and butadi e content in balance with other properties, the rubber requiring oil, fuel, and chemical resistance. In the auto d grommets, and water handling applications. With a te d all but the most severe automotive applications [2]. E used for this research. NBR is actually a complex fa ach rubber tube had an outside diameter of 60 mm and a A141 lathe (2.2 KW) using the set up shown in Fig.1. condition Fig.2.  Fixture design lastic modulus (1~10 MPa) as compared with 200 GPa before rupture. Based on previous end milling and ortho   ent ICCTEM -2014 re, Karnataka, India   ents under different d surface roughness ase of cutting force showed remarkable material response of ut experiments with elastomers; H-NBR, lix angle cutters and nd under cryogenic ture stiffness, clean rkpiece is beneficial e effects of various ere found to have a ibbon-like chips and ge rake angle tools. ing incipient cutting S. In this work, the h in end milling of elastomers and the tive rubber products ene. By selecting an ompounder can use motive area, NBR is perature range of – lastomer work-piece mily of unsaturated wall thickness of 15 for AISI 1020 steel. gonal cutting tests, it  Proceedings of the 2 nd  International Co has been shown that a stable fixture is ne achieve a stable condition for the elastomer The stretched workpiece provided force was further increased by applying a mandrel with through screws for workpiece of the flexible workpiece. The machining e cryogenic conditions. In cryogenic conditi nitrogen before conducting the turning tes with three factors and three levels per facto Table 1: Levels Rake a 1 2 3 The selected cutting tool for this st varying rake angles were used in experimen The surface roughness of the instrument Surtronic 3+ (112/1590).The le range of 10µm, 100µm and 500µm.Reso selectable cut off value of 0.25mm, 0.8mm measure the surface roughness. The fig.4 sh . Fig.3.  HSS tools with varying 4. RESULTS AND DISCUSSIONS 4.1 Cutting Force The rake angle is the most imp performance dramatically. Fig.5 to Fig.10 orthogonal cutting conditions. It is observe cutting conditions. As shown in Figure larger cutting of rubber at lower temperatures. In contrast This is because the increased rigidity of ru the tool clearance surface. In contrast, unde tool during cutting, which would apply a Lower vertical forces are beneficial in m because the tool usually has a small include ference on Current Trends in Engineering and Manage 17 – 19, July 2014, Myso 153   cessary for producing a smooth surface finish for mac workpiece, a mandrel was designed as shown in Fig.2. adequate contact force between the workpiece and the vacuum through the series of small holes. The elastom stability. The lathe chuck grabbed the mandrel in order periments were carried out using High Speed Steel (HS on, the rubber stiffness was increased by cooling the s. Based on previous studies [5, 6] the machining para , as indicated in Table 1. Levels of variables used in the experiment (A) ngle (degree) (B) Cutting speed (m/min) (C) Feed (mm/rev10 68 0.11 30 109 0.18 50 150 0.25 udy provided the variable experimental conditions. Ther ts as shown in figure3. achined workpieces were measured using Taylor H ngth for which roughness test was carried out was 6m ution used to carry out the experiment was 0.5µm.T and 2.50mm. Skid pick up stylus with diamond tip radiu ows the photographic view of surface roughness measure rake angles Fig.4.  Photographic view of surt rtant geometric parameter for cutting tools, and its v shows the measured cutting force as a function of ra that the cutting forces are decreasing with increasing r forces are produced during cryogenic cutting. This is du , decreasing vertical forces were observed when cryogen bber at lower temperatures leads to less workpiece mate r ambient temperatures rubber is more flexible and easie larger force on the tool clearance surface in the positi aintaining cutting stability and achieving a good mac angle which results in a low tool rigidity   ent ICCTEM -2014 re, Karnataka, India   ined rubber [6]. To andrel. The contact er tube is fixed to a o avoid deformation ) under ambient and ork piece in liquid eters were selected )   fore, HSS tools with bson manufactured .It had a selectable e instrument had a of 5µm was used to ment conducted. onic 3+ lue affects the tool e angle for various ake angle for similar to a larger modulus ically cutting rubber. rial flow underneath r to flow beneath the e vertical direction. hined surface finish  Proceedings of the 2 nd  International Conference on Current Trends in Engineering and Management ICCTEM -2014 17 – 19, July 2014, Mysore, Karnataka, India   154   10203040507580859095100105110115120125130    C  u   t   t   i  n  g   F  o  r  c  e   (   N   ) Rake Angle (Deg) Feed (0.11 mm/rev Feed (0.18 mm/rev) Feed (0.25 mm/rev) 102030405090100110120130140150160170180190    C  u   t   t   i  n  g   F  o  r  c  e   (   N   ) Rake Angle (Deg) Feed (0.11 mm/rev Feed (0.18 mm/rev) Feed (0.25 mm/rev)   Fig.5.  Cutting force with rake angles under Fig.6.  Cutting force with rake angles under ambient condition at 68m/min cryogenic condition at 68m/min 1020304050859095100105110115120125130135140145150    C  u   t   t   i  n  g   F  o  r  c  e   (   N   ) Rake Angle (Deg) Feed (0.11 mm/rev Feed (0.18 mm/rev) Feed (0.25 mm/rev) 102030405095100105110115120125130135140    C  u   t   t   i  n  g   F  o  r  c  e   (   N   ) Rake Angle (Deg) Feed (0.11 mm/rev Feed (0.18 mm/rev) Feed (0.25 mm/rev)   Fig.7.  Cutting force with rake angles under  Fig.8.  Cutting force with rake angles under ambient condition at 109m/min cryogenic condition at 109m/min 10203040506065707580859095100105110115120    C  u   t   t   i  n  g   F  o  r  c  e   (   N   ) Rake Angle (Deg) Feed (0.11 mm/rev Feed (0.18 mm/rev) Feed (0.25 mm/rev) 1020304050707580859095100105110115120125130    C  u   t   t   i  n  g   F  o  r  c  e   (   N   ) Rake Angle (Deg) Feed (0.11 mm/rev Feed (0.18 mm/rev) Feed (0.25 mm/rev)   Fig.9. Cutting force with rake angles under Fig.10.  Cutting force with rake angles under ambient condition at 150m/min cryogenic condition at 150m/min

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Jul 23, 2017
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