Design and Manufacturing of a holding fixture to test the tensile strength of a flat specimen

Transcription

1 Design and Manufacturing of a holding fixture to test the tensile strength of a flat specimen Joginder Singh Associate Professor, Department of Mechanical Engineering, Dr. M.R.Tyagi Professor, Department of Mechanical Engineering, Mr. Ajit Associate Professor, Department of Mechanical Engineering, Gianender Assistant Professor, Department of Mechanical Engineering, Rinki Yadav Assistant Professor, Department of Mechanical Engineering, Abstract Flat specimen of hot rolled carbon steel sheet and strip (HR1) is designed and manufactured as per the standard of ASTM E8. UTM to be used for the tensile testing of the specimen. But there is no provision to hold the flat specimen of 4 mm thickness. Therefore, we designed a holding fixture to solve the purpose. CATIA software is used for the 3D Modeling and Drafting of the fixture. DFM, DFA and DFT are used for the optimization of manufacturing, assembly and testing. Tolerances are applied at necessary places. Different conventional machines are used for the manufacturing of fixtures like lathe, milling, shaper, grinding and drill machines. Special attention given towards the diameter of the holding fixture to be manufactured. Because every UTM has different provision to hold the shaft. There are minimum and maximum limit of diameter that UTM can accommodate. Therefore, we manufactured the fixture at maximum limit. Because material reduction is easy than material increasing. Diameter of the shaft can obtained at any stage using lathe machine. The fixture so obtained seemed to be satisfactory for further tensile testing. basically related to 2D Design, 3D Design and Manufacturing of a specimen holding fixture [2]. Limitation of the UTM is that it can hold only round specimen, but our specimen is flat one. So there is a need of fixture which can be used in the same UTM to hold the flat specimen. Design Design is the foundation of a Product, Building, Pipe Line, Power Plant, Dam, Factory and so many. If design is correct then everything will go smooth and output will be the best. If design goes wrong, then many thing goes waste like timing, money, efforts and one has to think again from the scratch and also creates frustration. Once the design and analysis is confirmed only then we proceed to manufacturing [1]. Same thing is elaborate with the help of a flowchart Figure 1. Keywords: CATIA, DFM, DFA, DFT, Tolerance, ASTM, UTM, Milling, Shaper, Lathe, Drill, Grinding. Introduction There are many verticals in mechanical engineering department like 2D and 3D design, virtual and physical analysis, conventional and non-conventional manufacturing, development, inspection, welding, planning, purchasing, marketing, heat treatment, coating, painting, piping and so many. Every vertical has its own importance. This paper is Figure 1: Flow Chart from Concept to Manufacturing 1

2 Different techniques are used to make the process more stronger like DFM, DFA and DFT. Purpose of these technique is to make assure that whatever we manufacturing, assembling or testing that should be correct and solve the purpose [3]. Design For Manufacturing, Assembly and Production DFM is used so that each and every part can be manufactured at lowest possible cost. For the optimization of cost, we refer Design To Cost (DTC). Cost of manufacturing, assembling and other processes should be least to sustain in the market. We are not referring to Design For Production (DFP) because we are not going to mass produce the fixture [2]. All this, we can understand with the help of a flow chart as shown in Figure 2. Figure 3: Mandrel Designed in PDM Figure 4: Cover Plate Designed in PDM Figure 2: Flow Chart of Design For Manufacturing (DFM) CAD Design of the Fixture CATIA Software is used for the 3D Modeling and Drafting of the fixture. Different modules used are Sketcher, Part Design, Assembly and Drafting. Sketcher Module Whenever we want to design a part either in Part Design, Generative Shape Design, Generative Sheet Metal Design, etc., we have to use Sketcher module. It is the base to design a part. The different sketcher commands which we used for the creation of the part are line, constraint, circle, rectangle, axis, point, corner, trim, quick trim, sketch analysis, etc. Part Design Module A part can be of plastic, casting, sheet metal, forging, etc. Accordingly, we should select the module like Part Design, Generative Shape Design, Generative Sheet Metal Design, etc. Part Design Module is the used frequently because most of the parts are solid like casting, machining, forging, etc. Commands of part design are classified into Sketch-Based Features, Dress-Up Features, Surface-Based Features, Transformation Features, Boolean Operations and Advanced Dress-Up Features. The different part design commands which we used for the creation of the part are Pad, Pocket, Shaft, Fillet, Chamfer, Hole, User Pattern, Apply Material, etc. All parts of this fixture are created in part design only. There are mainly three parts in this fixture i.e. Mandrel, Cover and Shim 4 mm which are shown below. Product Module Figure 5: Shim 4 mm Designed in PDM Product module is a module in which all individual parts are assembled as per the requirement. The different commands which we used for assembly are fix, coincidence constraint, offset constraint, contact constraint, angle constraint, manipulation, etc. The assembled view is shown in Figure 6. Figure 6: Assembly of Fixture in Product Module 2

3 Drafting Module Drafting module is used to create 2D drawing of the parts and assemblies. We can create Front View, Top View, Bottom View, Left Side View, Right Side View, Isometric View, Section View, Detail View, Clipping View, Broken View, etc. There is always a link between the 3D and 2D. As we update the 3D, drawings get updated by clicking the Update command. The different drafting commands which we used for the creation of the part are Front View, Projection View, Isometric View, Linear Dimensions, Angular Dimensions, Radius Dimensions, Diameter Dimensions, Chamfer Dimensions, Thread Dimensions, Text, Tolerance Description, etc. 2D drawing of Mandrel is shown below in Figure 7. Lathe Lathe machine is basic of workshop. It is used to manufacture the Mandrel. The operation covered by this machine are plain turning, step turning, chamfering, filleting, etc. with the help of a single point cutting tool. As the material is mild steel, chips produced during the operation were continuous type. Such types of chips can harm the worker. We use chip breaker to discontinue the chips [5]. Figure 8: Chip Breaker in Lathe Figure 7: 2D Drawing of Mandrel in Drafting Module Weight of Fixture as per CAD Mandrel, Cover and Shim are manufactured with Mild Steel material. It is the most common material used in industry. Total weight of the fixture as per the CAD is shown in the table. Table-01 Part Name Isometric View of Part Part Weight (Kg) Quantity Weight (Kg) Mandrel Cover Plate Shim Figure 9: Machining operation on Lathe Milling Milling machine is also known as M1TR. It can be of two types i.e. horizontal and vertical. We performed the operations on vertical milling machine like facing, chamfering, etc. Multiple Point cutting tools are used in this machine except for boring. As the tools are multiple point, so there is no requirement of chip breaker because of interruption machining [5]. HSHCS Bolt Total Weight of the fixture (Kg) Manufacturing In manufacturing, we convert raw material into finished parts with the help of conventional and non-conventional manufacturing system. We used different conventional manufacturing machines like lathe, milling, grinding, shaper, drilling, etc. Figure 10: Machining operation on Milling 3

4 Power Hacksaw Power Hacksaw is used to remove the bulk material where accuracy is not required. Cutting blade is the tool for this machine and it breaks frequently, so it needs to be replace again and again. This is machine is shown in Figure 10. Figure 11: Machining operation on Shaper From the DFM technology, we easily manufactured the fixture as per the design without using non-conventional machines. Cutting Points in a tool Cutting tools that we used in workshop have cutting points which varies as per the machine to be used. In lathe and shaper machine, we uses single point cutting tool, milling machine we uses 2, 4 6 or 8 point cutting tool, power hacksaw we uses multiple point cutting tool, grinding machine we uses infinite number of cutting point tool [4]. It can be shown in table as below: Table-02 S.No. Cutting Tool Picture of 1 Lathe 2 Shaper 3 Milling 4 Power Hacksaw 5 Grinding Single Point Cutting Tool Single Point Cutting Tool 2, 4, 6 or 8 Point Cutting Tool Finite Number of Cutting Point Tool Infinite Number of Cutting Point Tool Cutting Tools Following is the graph between the type of machine and number of cutting point is as follows: Figure 12: Machining operation on DM Figure 13: Machining operation on GM Graph 01: Type of machine vs Number of cutting point Design of Flat Specimen Flat specimen design as per the standard of ASTM E8 with the help of CATIA software in PDM and Drafting Module. Figure 14: Manufacturing of Internal Threading by Tap Set Manufacturing of Specimen Flat specimen is manufactured by Wire EDM only to get the burr free part so that testing can perform on it. We also tried to manufacture with conventional machine but not able to get the accuracy because burrs were coming on the edges because of that it can break at stress concentration zones. 4

5 Figure 15: 2D Drawing of Flat Specimen in CATIA Software Figure 19: Total Assembly of fixture with specimen Figure 16: Wirecut EDM Figure 17: Flat Specimen manufactured with Wirecut EDM Assembly After accurate manufacturing of individual parts, we easily assembled the child parts with the help of DFA technology. We can easily assembled and disassembled the parts. Figure 18: Assembly of one half of the fixture Benefits of Newly Developed Fixture New developed fixture can hold specimen of different thickness and different materials as shown in the above figure. By replacing Shim of different thickness, we can use same fixture for different specimen. Comparison of Old and New Concept Fixture S.No. Old Concept Fixture 1 It can hold only round specimen only. 2 Flat specimen cannot hold. Conclusions New Concept Fixture By this we can use both flat and round specimen. Same fixture can be used for different thickness of specimen by replacing shim of different thickness. Design of the fixture is good enough to take the load during the tensile testing on UTM machine. After considering the DFM and DFA, fixture is easily manufactured and assembled. The same fixture can be used for other specimen by just replacing the shim of different thickness. Acknowledgment This work supported by Mr. Balbir Singh (Workshop Supervisor, Faridabad) and his team. Director Brijesh Kumar Sharma (Owner of a Mechanical Workshop, Faridabad) also appreciated for his guidance and support. 5

6 Nomenclature DFM DFA DFP DTC DFT PDM ASTM References International Journal of Applied Engineering Research ISSN Volume 13, Number 6 (2018) pp. 1-6 : Design For Manufacturing : Design For Assembly : Design For Production : Design To Cost : Design For Testing : Part Design Module : American Society for Testing and Materials [1] Ibrahim Zeid and R Sivasubramanian, CAD/CAM, Revised First Edition, The McGraw-Hill companies, 2007, [2] George E. Dieter, Engineering Design, A Materials and Processing Approach, Third Edition, McGraw-Hill International Editions, Mechanical Engineering Series, International Editions 2000, 32 (ASTM), (CAD), 270 (CAD/CAM), (FEM), 385 (DFP), (DFM), (DFA), (DTC), (CAE). [3] [4] Cyril Donaldson, George H LeCain, V C Goold, Tool Design, Tata McGraw-Hill Edition, Third Edition, 33 Reprint 2003, (Tooling Materials), (Design of Fixtures). [5] HMT Bangalore, Production Technology, Tata McGraw- Hill Edition, 33 rd Reprint 2011, cutting tool material (21), drilling (121), milling (185), grinding (247), threading (393), cutting fluids (437) and tool standards (523). 6