DESIGN AND FABRICAION OF METAL SPINNING WITH LATHE CARRIAGE

Transcription

1 DESIGN AND FABRICAION OF METAL SPINNING WITH LATHE CARRIAGE Mandar Sawant 1, Amey Dhuri 2, Prasad Gawade 3, Gauresh Arolkar 4, Devendra Dicholkar 5 1 Professor, SSPM s college of engineering, Kankavli, Maharashtra, India 2,3,4,5, Student, SSPM s College of Engineering, Kankavli, Maharashtra, India ABSTRACT This paper presents improvement in manual metal spinning process. The machine carriage is modified mainly for the purpose of reduction in requirement of a skilled workforce. The spinning machine consists of a mandrel mounted onto the headstock spindle. A work piece on which operation is to be performed is clamped in between this mandrel and the tailstock (dead centre). Final component formed by pressing blank over the mandrel. The operation is performed by a hand tool on a spinning lathe. It is tedious process. Lots of human effort required for this process. The metal spinning machine with lathe carriage is a modification of the manual machine. By using roller tool & lathe carriage aids to control the entire operation, in order to reduce requirement of skilled labour, to improve overall efficiency in the current process, improving consistence and repetitiveness along with an overall reduction in cost. Also in this we find out effect of roller tool radius on surface finish of final component. For trial purpose we design various roller tools & make modification in lathe carriage. Keywords: Spinning, Roller, Mandrel, Blank. 1. INTRODUCTION Metal spinning is one of the oldest method of chip-less formation. Metal spinning is a term used to describe the forming of metal into seamless, axisymmetric shapes by a combination of rotational motion and force. Metal spinning is the technique to produce axisymmetrical part or component over rotating mandrel with the help of rigid tool known as roller. During the process both the mandrel and blank rotated while the spinning tool contract the blank and progressively induce a change according to the profile of the mandrel. Spinning process helps to produce a lightweight component. The components of metal spinning are cylinders, drums, Domes, hemispheres, cones, cups etc. Alternatives to spinning such as press forming are also used for the production of axisymmetric sheet metal components. However, spinning has a number of advantages when compared with these manufacturing methods. Localised deformation of the material under the roller requires low forming forces. Moreover, simple and nondedicated tooling provides flexibility and has the potential for net shape forming. Lastly, formed components have high quality surface finish and improved strength. 2. METAL SPINNING PROCESS 2.1 Conventional metal spinning process A mandrel is mounted on head stock which is the driving section of the lathe. A metal disc is then clamped in between the mandrel and the pressure pad which is further attached to the tailstock. The mandrel is then rotated at high speed which causes the disc clamped against it to be rotated as well. A force is applied onto the work piece which causes the plastic flow of the work piece material over the mandrel. The tool, mostly a duck bill applies force on rotating material. During spinning process, the wooden butt of the tool is placed in one's armpit such that one's body weight provides the force and one's arms are free to guide the tool. So it is heavy and effortful. If the bending process is repeated for a long period of time it will be tedious work to the operator. Moreover it can cause injury to the operator. By using this lathe carriage the forces required to be applied by the operator will be substantially decreased, thus preventing injuries and increasing efficiency of work. Volume 5, Issue 4, April 2017 Page 1

2 2.1.1 Tools for conventional spinning process Figure 1 Conventional metal spinning process Figure 2 Tools The primary tools are the Sheep's nose used for most of the forming, and the Duck's bill used for finishing the fully formed piece. The hooked nose of the Sheep's nose is ideal for forming tight radii as well as having a decreasing radius that makes it easy to form the metal over a variety of curves. The Duck's bill has a flat side for finishing straight surfaces and a rounded side to finish curved surfaces. The tool post is essentially a rounded pin protruding from a boring bar mounted on the crossfeed such that the pin acts as a fulcrum around which the hand tool can be leveraged. The tool post is moved as the part forms down the mandrel so that a consistent lever arm is maintained Design tooling parameter a) Roller diameter[2] Roller acts as a tool which applies the force on the metal sheet over the mandrel. Rollers are available in different diameter and different thickness. This roller deforms the metal sheet over the mandrel in several no of passes. According to Hayama low mandrel speed, small roller diameter and low viscosity lubricant give low surface finish. Roller diameter can be calculated by using the following formula. Dr= 0.1D+ (120±60) mm Where, Dr= Roller diameter in mm D = Original diameter of blank in mm D=300mm Dr=0.1*300+(120-60)=90mm Volume 5, Issue 4, April 2017 Page 2

3 b) Roller nose radius[2] Roller nose radius has a significant effect on a dimensional accuracy. Large the nose radius result in uniform thickness distribution and low surface roughness. Which is applicable for conventional spinning. Nr = (0.012~0.05) D By using this formula we calculate a nose radius. Where, Nr = Nose radius in mm D = Blank diameter in mm Nr= ( )*300= 18.6mm Figure 3 CAD model of Roller tool c) Forces[5] Force between the work piece and Roller generated during shear forming can be resolved into three mutually perpendicular component, namely the axial (Fa), Radial (Fr) & Tangential (Ft). It has been experimentally observed that tangentially force is smaller than axial & radial forces. Although most of the power is supplied by the motors driving the chuck is translated through the tangential component. Feed ratio, mandrel speed, sheet thickness, roller diameter, roller nose radius affect the tool forces. Mandrel rotational speed has an optimum value. Slater and chan et al both report that there is a mandrel speed at which tangential force is negligible. For sheet thickness there is a linear directly proportional relationship exist between thickness and all three forces. The influence of roller diameter and roller nose radius on tool force was examined by avitzur and yang he report that the tangential force decrease with increase in both parameter, whereas axial and radial forces increases.[2] d) Mandrel[5] Mandrel is a supporting as well as rotating part in the metal spinning set up. Blank is clamped between the mandrel and the tailstock. This blank is deforming over the mandrel by applying the force with the help of roller. The material used for mandrel is mild steel of medium grade. Mandrels must be statically balanced, and when used at high speed and the mandrels should also dynamically balance. The actual mandrel material selection depends on the design, part material and desired life. As we want to produce a skillet having range 220mm to 260mm diameter according to this requirement we design the mandrel having outside diameter 260mm and height 100mm Design Process Parameter a) Feed Ratio[4] Feed ratio is known as the ratio of roller feed rate to spindle speed. High feed ratio causes rough surface finish and material failures. Original blank diameter is maintained with high feed ratio. Fluctuating feed ratio has major effect on various parameters such as wall thickness and tool forces. Low feed ratio is preferred prior to high feed ratio in spinning process as it is a better option since a good surface and no any failure of the component takes place. For Aluminium feed ratio is 0.9 mm/rev and for mild steel feed ratio is 1.8 mm/rev. b) Feed Rate[3] One of the major parameter in this process is roller feed rate. It is the parameter which affects the formability and forming quality. Technically it is the distance of the tool that advances into or along the work piece each time is. It is Volume 5, Issue 4, April 2017 Page 3

4 measured in mm/sec or mm/ min. Due to the high feed rate rough surface finish & wrinkling may be occur. A low feed rate gives a high surface finish while a high or increased feed rate will make a work piece fit to mandrel. Due to high feed rate rough surface finish and wrinkling occurs this is the main drawback of high feed rate. c) Spindle Speed[2] According to hayama the effect of mandrel speed on to the tool forces is very less, almost negligible. Due to this negligence a wider range of feasible mandrel speed is possible. The influence of rotational speed on the variation of axial and radial forces is negligible. For aluminium material we take Spindle speed 800 to 900 rpm. On an average, the best quality of most of the components is achieved at high spindle speeds. N= (9500~320000)/Do Where, N=Mandrel speed in RPM Do= original blank diameter in mm N=270000/300=900 rpm d) Lubricants[5] A lubricant is used for providing lubrication between two surfaces under friction which produces an immense amount of heat. A lubricant is almost always used during spinning. The fluid used serves as both a lubricant and coolant..when spinning aluminium, stainless steel or titanium, the work pieces or mandrels or both are sometimes coated with the lubricant before spinning. The lubricant must continue to adhere to the rotating preform during spinning. Most of the time cup grease is used. Viscosity is an important parameter of a lubricant. To reduce the viscosity, a lubricant can be heated. Reduced viscosity helps in easy application of the lubricant. 3. EXPERIMENTAL SETUP FOR TRIAL TABLE 1: PARAMETERS FOR PROCESS Material workpiece Al1100 Roller nose 19 radius(mm) Blank diameter(mm) 300 Spindle speed(rpm) 900 Blank Thickness(mm) 2 Feed rate(mm/rev) 1 Roller diameter 90 Mandrel diameter(mm) 260 In the figure below we can see mandrel, chuck, tailstock live centre and tailstock. The mandrel is held in the chuck and tailstock live centre is held in the tailstock. The use of chuck is to rotate the mandrel with certain speed & tailstock live centre support the mandrel. Tool posts are used to hold the tool & travel the tool in direction of workpiece. Roller is the tool which is contact with the workpiece and it is held in tool post. The blank is clamp between mandrel male and live centre female part. When spindle speed is given to mandrel then mandrel and blank start rotating together along with live centre at high speed. The roller is then passed on the blank and in turn forces are generated on the sheet of workpiece. This flows over the mandrel and obtains the same shape as that of the mandrel. Figure 4 Experimental setup Volume 5, Issue 4, April 2017 Page 4

5 IPASJ International Journal of Mechanical Engineering (IIJME) Volume 5, Issue 4, April 2017 ISSN Figure 5 Roller tools 4. RESULT By making the modification in the setup we take a trial and produce final component without any crack and wrinkle. The final component is shown in Figure 6. Figure 6 Final component 5. CONCLUSION In conventional process the worker had to apply a lot of force while in process with carriage, worker s efforts are reduced and a very less force is to be applied. Also using above design parameters we have to reduce the defect & failure occurs in metal spinning operation performed with lathe carriage. The accuracy of the process also increases considerably with using the new process with carriage. Using large nose radius provides high surface quality. If a good machine is available then the working time is also reduced highly. Skilled worker can produce components or final products with very good surface finish and high accuracy. If the carriage movement and tool movement is automated then a very perfectly precise product can be obtained. Acknowledgements We thank Mr. Bandekar (Proprietor- Laxmi metal industry, Kudal MIDC) for providing us with this opportunity to work in the development of this machine. We also thank employee Mr. Lad for sharing with us his valuable knowledge and experience. We also would like to thank our guide Pr. M.T. Sawant for his constant support and Volume 5, Issue 4, April 2017 Page 5

6 encouragement. Lastly, we thank all those who have directly or indirectly helped us in the development of this machine. References B.P.Bewlay, Spinning, ASM Handbook, volume 14B, pp J.M Allwood, A review of mechanics of metal spinning, Journal of Material Processing Technology 210(2010), pp.3-23 Wang Lin, Analysis of material deformation and wrinkling failure in conventional metal spinning, Durhan University (2012), pp C.C.Wong, A review of spinning, shear forming and flow forming processes, International journal of Machine tool & Manufacture 43(2003), pp Amol Jadhav, Design of metal spinning parameter for general lathe, International journal of Engineering Development & Research(2014), pp AUTHOR Mandar Sawant completed the B.E. degree from Rajendra Mane College of completed M.E. degree in CAD/CAM/CAE from KIT College. Engineering and Technology and Volume 5, Issue 4, April 2017 Page 6