Crank And Slotted Lever Mechanism Engineering Essay

Crank And Slotted Lever Mechanism Engineering Essay In a kinematic chain when one link is fixed, then that chain is known as mechanism. It may be used for transmitting or transforming motion for example engine indicators, typewriters etc.[1] A mechanism which has four links is known as simple mechanism, and a mechanism which has more than four links is known as complex mechanism. A mechanism which is required to transmit some particular type of work is knows as machines. In certain cased the elements have to be designed to withstand the forces safely. A mechanism is a kinematic chain in which kinematic pairs are connected in such a way that first link is joined to the last link to transmit a predetermined constrained motion The various parts of the mechanism are called as links or elements. When two links are in contact and a relative motion is possible, then they are known as a pair. An arbitrary set of a link which forms a closed chain which is capable of relative motion and that can be made into a rigid structure by adding a single link is known as kinematics chain. To form a mechanism from a kinematics chain one of the link must be fixed. The technique obtaining different mechanism by fixing the various link in turn is knows as inversion. [2] Fig 1.1-Chart illustrating kinematic pair makes up a machine CHAPTER 2 KINEMATIC PAIRS Two links that can move with respect to each other by a mechanical constraint between them, with one or more degrees of freedom The relative motion between two links of a pair can take different form. Three types of pair are identified as lower pairs and these are the commonly occurring ones. Sliding: Such as occurs between a piston and a cylinder Turning: Such occurs with a wheel on an axle Screw Motion: Such as occurs between a nut and a bolt All other cases are considered to be combination of sliding and rolling is called higher pairs. Screw pair is higher pair as it combines turning and sliding. 2.1 Classification of Kinematic Pairs Since kinematics pairs deals with relative motion between two links then can be classifies based on the characteristics of relative motion between two bodies. The type of relative motion between the elements The type of contact between the elements The type of closure[1] The type of relative motion between the elements The kinematic pair according to type of relative motion can classified as below Sliding Pair Turning Pair Rolling Pair Screw Pair Spherical Pair 2.1.2 The type of contact between the elements The kinematic pair according to type of contact between the elements can be classified Lower Pair Higher Pair 2.1.3 The type of closure The kinematic pair according to type of closure between the elements can be classified as Self -Closed Pair Force -Closed Pair 2.2 GRUBLERS CRITERION FOR PLANAR MECHANISM The Grublers criterion applies to mechanism with only single degree of freedom joints where the overall movability of the mechanism is unity.Subtituting n=1 and h=0 in kutzbach equation we have [3] F= 3 (n-1) 2j h The equation is known as Grublers criterion for plane mechanisms with constrained motion. 2j-3n+h+4=0 Where, F=number of degrees of freedom of a chain j= number of lower kinematic pairs h = number of higher kinematic pairs n= number of links When F=1, the linkage is called a mechanism. When F=0 it forms a structure. That is an application of external force does not produce relative motion between any links of a linkage When F>1 the linkage will require more than one external driving force 2 obtain constrained motion When F 2.3 KINEMATIC CHAIN A Kinematic Chain is defined as a closed network of links, connected by kinematic pairs so that the motion is constrained. First a network of links to give constrained motion, certain conditions are to be satisfied. Minimum number of three links is required to form a closed chain .The three links are connected with turning pairs. Fig.2.1 (a) A Five-Link Kinematic Chain (b) Six-Link Kinematic Mechanism 2.3.1 Types of kinematic chains The most important kinematic chains are those which consists of four lower pairs, each pair being a sliding pair or a turning pair Four Bar Chain or Quadric Cyclic Chain Single Slider Crank chain Double slider crank chain 2.3.2 Inversions Inversion is a method of obtaining different mechanisms by fixing different links in a kinematic chain. A particular inversion of a mechanism may give rise to different mechanism of practical unity, when the proportions of the link are changed [2]. CHAPTER 3 SLOTTED LINK QUICK RETURN MECHANISM Slotted link mechanism which is commonly used in shaper mechanism. The mechanism which converts rotary motion of electric motor and gear box into the reciprocating motion of ram which is the most simple and compact machine.[3] Fig 3.1 : Slotted link mechanism The slotted link mechanism which is mainly divided into seven main parts .They are A Clamping nut B Ram C Link D D Crankpin A E Slotted crank B F Bull Wheel G Glot Slotted link mechanism gives ram the higher velocity during the return stroke (i.e. Non cutting stroke) .Then the forward stroke which reduces the wasting during the return stroke. [4] When the bull wheel is rotated the crank pin A is also rotated side by side through the slot the crank B. This makes the slotted crank B.This makes the slotted crank to oscillate about one end C.The oscillation motion of slotted crank makes ram to reciprocate. The intermediate D is required to accommodate the rise and fall of the crank. Crank Pin A decides the length of the strokes of the shaper. The further its away from the center of the bull wheel longer is its stroke. The cutting stroke of the ram is complete while crank pin moves from A to A1 and slotted link goes from left to right. During return stroke pin moves from A1 to A and link moves from right to left Cutting Time/Idle Time = Angle of AZA1/ Angles of AZA2 3.1 SHAPER MECHANISM The working of a shaper mechanism is that it has two stokes. One is forward stroke and the other is return stroke. Clearing up more about these two strokes is that in the forward stroke the material is feeded, where as in the return stroke is an idle stroke when no material is feeded.[6] Fig 3.2 : Shaper Mechanism Shaping process which involves only short setup time and uses only inexpensive tools. Shaping is used for the production of gears ,splined shafts racks etc. it can produce one or two such parts in a shaper less time that is required to setup for production. Other alternatively equipment with a higher output rate is required. [5] The cost per cubic cm of metal removal by shaping may be as five times more than that of the removal by milling or broaching. Shaping machines are mainly used in tool rooms or model shops. 3.2 SHAPER CUTTING SPEED The cutting speed depends on The type of material used. The amount of material removed. The kinds of tool material. The rigidity of machine. 3.4 DIFFERENCE BETWEEN WHITHWORTH AS WELL AS QUICK RETURN MECHANISM Maximum pressure is holding the ram down the slides so that steadying is most necessary on entering the cut In Whitworth motion, the main pressure is in the correct place, less pressure is required in center of stroke. Slotted link motion is opposite to all the points explained above. Not withstanding the recompense stated above for the Whitworth motion, constructional difficulty make it more suitable for traversing head shaping machines and slotting machines, so that the crank motion, despite its restrictions finds universal adaptation for the pillar style of shaping machines.[6] CHAPTER 4 DESIGN OF CRANK AND SLOTTED LEVER MECHANISM Design and fabrication of crank and slotted lever mechanism and also doing the structural and thermal analysis of crank shaft. Drawing the velocity diagram of the mechanism. Fig 4.1 : Dimensions for the components using AutoCAD DESIGNING USING CATIA The design of different components is explained here using Catia. SLOTTED LEVER Slotted lever connected to the crank shaft which provides the forward and backward motion of the tool post. The drawing is done as per the dimensions shown above. Different view of the slotted lever is also explained Fig 4.2: Design of slotted lever FIG4.3: Different angle view of slotted lever CRANK SHAFT Crank shaft which is connected to flywheel with the help of a motor , which provides the rotation of the crank shaft as well as the rotation of the slotted lever connected to it. The drawing is done as per the dimensions shown above. Different view of the crank shaft is also explained Fig 4.4: DESIGN of crank shaft Fig 4.5: Different angle view of crank shaft TOOL POST Tool post which is connected to slotted lever, where the tool is connected to it which is used for the cutting of materials. The drawing is done as per the dimensions shown above. Different view of the Tool post is also explained Fig 4.6: Design of tool post Fig 4.7: Different angle view of tool post TOOL CUTTER Tool cutter is connected to the tool which is used to cut the material. The design is done as per assumed dimensions. Different view of the Tool is also explained. Fig 4.8: Design of tool Fig 4.9: Different angle view of tool 5.2 FABRICATION OF CRANK AND SLOTTED LEVER With the help of above design of different components it has been combined together to form a crank and slotted lever mechanism which is seen mainly in shaper machines. Fig4.10: Design of crank and slotted lever mechanism The final fabrication model will be represented as shown below. Fig4.11: Final Design of crank and slotted lever mechanism 4.3 MODEL FABRICATION To conclude my Assigned project I hereby affix few photos of crank and slotted quick return mechanism indicating the functioning the same. Fig 4.12: FABRICATED MODEL OF CRANK AND SLOTTED LEVER Fig 4.13: SLOTTED LEVER CONNECTED TO THE LEVER CHAPTER 5 STRUCTURAL AND THERMAL ANALYSIS OF CRANK SHAFT Crank and slotted lever mechanism, crank shaft which acts as the rotating device which helps the slotted lever forward and backward movement. Therefore analyzing the different propertied which take place in a crank shaft 5.1 STRUCTURAL ANALYSIS Fig 5.1: Crank shaft used for analysis Units TABLE 1 Unit System Metric (m, kg, N, s, V, A) Degrees rad/s Celsius Angle Degrees Rotational Velocity rad/s Temperature Celsius Model (C4) Geometry TABLE 2 Model (C4) > Geometry Object Name Geometry State Fully Defined Definition Source C:UsersPATRICKDesktopPAPArollcageSUDEEPPart1.CATPart Type Catia5 Length Unit Millimeters Element Control Program Controlled Display Style Part Color Bounding Box Length X 2.e-002 m Length Y 0.20055 m Length Z 0.19999 m Properties Volume 6.2904e-004 m ³ Mass 4.938 kg Scale Factor Value 1. Statistics Bodies 1 Active Bodies 1 Nodes 3258 Elements 556 Mesh Metric None Preferences Import Solid Bodies Yes Import Surface Bodies Yes Import Line Bodies No Parameter Processing Yes Personal Parameter Key DS CAD Attribute Transfer No Named Selection Processing No Material Properties Transfer No CAD Associatively Yes Import Coordinate Systems No Reader Save Part File No Import Using Instances Yes Do Smart Update No Attach File Via Temp File Yes Temporary Directory C:UsersPATRICKAppDataLocalTemp Analysis Type 3-D Mixed Import Resolution None Enclosure and Symmetry Processing Yes TABLE 3 Model (C4) > Geometry > Parts Object Name Part 1 State Meshed Graphics Properties Visible Yes Transparency 1 Definition Suppressed No Stiffness Behavior Flexible Coordinate System Default Coordinate System Reference Temperature By Environment Material Assignment Structural Steel Nonlinear Effects Yes Thermal Strain Effects Yes Bounding Box Length X 2.e-002 m Length Y 0.20055 m Length Z 0.19999 m Properties Volume 6.2904e-004 m ³ Mass 4.938 kg Centroid X 1.e-002 m Centroid Y -1.9072e-004 m Centroid Z -1.9565e-004 m Moment of Inertia Ip1 2.4661e-002 kg ·m ² Moment of Inertia Ip2 1.2451e-002 kg ·m ² Moment of Inertia Ip3 1.2537e-002 kg ·m ² Statistics Nodes 3258 Elements 556 Mesh Metric None Coordinate Systems TABLE 4 Model (C4) > Coordinate Systems > Coordinate System Object Name Global Coordinate System State Fully Defined Definition Type Cartesian Ansys System Number 0. Origin Origin X 0. m Origin Y 0. m Origin Z 0. m Directional Vectors X Axis Data [ 1. 0. 0. ] Y Axis Data [ 0. 1. 0. ] Z Axis Data [ 0. 0. 1. ] Mesh TABLE 5 Model (C4) > Mesh Object Name Mesh State Solved Defaults Physics Preference Mechanical Relevance 0 Sizing Use Advanced Size Function Off Relevance Center Coarse Element Size Default Initial Size Seed Active Assembly Smoothing Medium Transition Fast Span Angle Center Coarse Minimum Edge Length 2.e-002 m Inflation Use Automatic Tet Inflation None Inflation Option Smooth Transition Transition Ratio 0.272 Maximum Layers 5 Growth Rate 1.2 Inflation Algorithm Pre View Advanced Options No Advanced Shape Checking Standard Mechanical Element Midside Nodes Program Controlled Straight Sided Elements No Number of Retries Default (4) Rigid Body Behavior Dimensionally Reduced Mesh Morphing Disabled Pinch Pinch Tolerance Please Define Generate on Refresh No Statistics Nodes 3258 Elements 556 Mesh Metric None Static Structural (C5) TABLE 6 Model (C4) > Analysis Object Name Static Structural (C5) State Solved Definition Physics Type Structural Analysis Type Static Structural Solver Target ANSYS Mechanical Options Environment Temperature 22.  °C Generate Input Only No TABLE 7 Model (C4) > Static Structural (C5) > Analysis Settings Object Name Analysis Settings State Fully Defined Step Controls Number Of Steps 1. Current Step Number 1. Step End Time 1. s Auto Time Stepping Program Controlled Solver Controls Solver Type Program Controlled Weak Springs Program Controlled Large Deflection Off Inertia Relief Off Nonlinear Controls Force Convergence Program Controlled Moment Convergence Program Controlled Displacement Convergence Program Controlled Rotation Convergence Program Controlled Line Search Program Controlled Output Controls Calculate Stress Yes Calculate Strain Yes Calculate Results At All Time Points Analysis Data Management Solver Files Directory F:ansyshallo_filesdp0SYS-1MECH Future Analysis None Scratch Solver Files Directory Save ANSYS db No Delete Unneeded Files Yes Nonlinear Solution No Solver Units Active System Solver Unit System mks TABLE 8 Model (C4) > Static Structural (C5) > Rotations Object Name Rotational Velocity State Fully Defined Scope Geometry All Bodies Definition Define By Vector Magnitude 200. rad/s (ramped) Axis Defined Suppressed No Fig 5.2 : Graph showing rotational velocity TABLE 9 Model (C4) > Static Structural (C5) > Loads Object Name Frictionless Support State Fully Defined Scope Scoping Method Geometry Selection Geometry 1 Face Definition Type Frictionless Support Suppressed No Solution (C6) TABLE 10 Model (C4) > Static Structural (C5) > Solution Object Name Solution (C6) State Solved Adaptive Mesh Refinement Max Refinement Loops 1. Refinement Depth 2. TABLE 11 Model (C4) > Static Structural (C5) > Solution (C6) > Solution Information Object Name Solution Information State Solved Solution Information Solution Output Solver Output Newton-Raphson Residuals 0 Update Interval 2.5 s Display Points All TABLE 12 Model (C4) > Static Structural (C5) > Solution (C6) > Results Object Name Total Deformation Minimum Principal Elastic Strain Stress Intensity Middle Principal Stress Equivalent Stress State Solved Scope Scoping Method Geometry Selection Geometry All Bodies Definition Type Total Deformation Minimum Principal Elastic Strain Stress Intensity Middle Principal Stress Equivalent (von-Mises) Stress By Time Display Time Last Calculate Time History Yes Identifier Use Average Yes Results Minimum 8.5255e-009 m -8.1173e-006 m/m 5.3895e+005 Pa -4.8689e+005 Pa 5.3642e+005 Pa Maximum 7.9016e-007 m -8.1177e-007 m/m 3.0171e+006 Pa 1.2909e+006 Pa 2.7325e+006 Pa Information Time 1. s Load Step 1 Substep 1 Iteration Number 1 TABLE 13 Model (C4) > Static Structural (C5) > Solution (C6) > Results Object Name Shear Stress Vector Principal Elastic Strain Strain Energy State Solved Scope Scoping Method Geometry Selection Geometry All Bodies Definition Type Shear Stress Vector Principal Elastic Strain Strain Energy Orientation XY Plane By Time Display Time Last Coordinate System Global Coordinate System Calculate Time History Yes Use Average Yes Identifier Results Minimum -3.4345e+005 Pa 5.6327e-007 J Maximum 3.4345e+005 Pa 1.1931e-005 J Information Time 1. s Load Step 1 Substep 1 Iteration Number 1 Material Data Structural Steel TABLE 14 Structural Steel > Constants Density 7850 kg m^-3 Coefficient of Thermal Expansion 1.2e-005 C^-1 Specific Heat 434 J kg^-1 C^-1 Thermal Conductivity 60.5 W m^-1 C^-1 Resistivity 1.7e-007 ohm m TABLE 15 Structural Steel > Compressive Ultimate Strength Compressive Ultimate Strength Pa 0 TABLE 16 Structural Steel > Compressive Yield Strength Compressive Yield Strength Pa 2.5e+008 TABLE 17 Structural Steel > Tensile Yield Strength Tensile Yield Strength Pa 2.5e+008 TABLE 18 Structural Steel > Tensile Ultimate Strength Tensile Ultimate Strength Pa 4.6e+008 TABLE 19 Structural Steel > Alternating Stress Alternating Stress Pa Cycles Mean Stress Pa 3.999e+009 10 0 2.827e+009 20 0 1.896e+009 50 0 1.413e+009 100 0 1.069e+009 200 0 4.41e+008 2000 0 2.62e+008 10000 0 2.14e+008 20000 0 1.38e+008 1.e+005 0 1.14e+008 2.e+005 0 8.62e+007 1.e+006 0 TABLE 20 Structural Steel > Strain-Life Parameters Strength Coefficient Pa Strength Exponent Ductility Coefficient Ductility Exponent Cyclic Strength Coefficient Pa Cyclic Strain Hardening Exponent 9.2e+008 -0.106 0.213 -0.47 1.e+009 0.2 TABLE 21 Structural Steel > Relative Permeability Relative Permeability 10000 TABLE 22 Structural Steel > Isotropic Elasticity Temperature C Youngs Modulus Pa Poissons Ratio 2.e+011 0.3 Fig 5.3 : Middle Principal Stress Fig 5.3: Principal Stress Fig 5.4: Strain Energy Fig 5.5: Minimm Principal Elastic Strain Fig 5.6: Stress Intensity Fig 5.7: TOTAL Deformation Fig 5.8: VECTOR Principal Elastic Strain 5.2 THERMAL ANALYSIS Thermal Analysis is the heat developed in crank shaft. Units TABLE 1 Unit System Metric (m, kg, N, s, V, A) Degrees rad/s Celsius Angle Degrees Rotational Velocity rad/s Temperature Celsius Model (D4) Geometry TABLE 2 Model (D4) > Geometry Object Name Geometry State Fully Defined Definition Source C:UsersPATRICKDesktopPAPArollcageSUDEEPPart1.CATPart Type Catia5 Length Unit Millimeters Element Control Program Controlled Display Style Part Color Bounding Box Length X 2.e-002 m Length Y 0.20055 m Length Z 0.19999 m Properties Volume 6.2904e-004 m ³ Mass 4.938 kg Scale Factor Value 1. Statistics Bodies 1 Active Bodies 1 Nodes 3258 Elements 556 Mesh Metric None Preferences Import Solid Bodies Yes Import Surface Bodies Yes Import Line Bodies No Parameter Processing Yes Personal Parameter Key DS CAD Attribute Transfer No Named Selection Processing No Material Properties Transfer No CAD Associativity Yes Import Coordinate Systems No Reader Save Part File No Import Using Instances Yes Do Smart Update No Attach File Via Temp File Yes Temporary Directory C:UsersPATRICKAppDataLocalTemp Analysis Type 3-D Mixed Import Resolution None Enclosure and Symmetry Processing Yes TABLE 3 Model (D4) > Geometry > Parts Object Name Part 1 State Meshed Graphics Properties Visible Yes Transparency 1 Definition Suppressed No Stiffness Behavior Flexible Coordinate System Default Coordinate System Reference Temperature By Environment Material Assignment Structural Steel Nonlinear Effects Yes Thermal Strain Effects Yes Bounding Box Length X 2.e-002 m Length Y 0.20055 m Length Z 0.19999 m Properties Volume 6.2904e-004 m ³ Mass 4.938 kg Centroid X 1.e-002 m Centroid Y -1.9072e-004 m Centroid Z -1.9565e-004 m Moment of Inertia Ip1 2.4661e-002 kg ·m ² Moment of Inertia Ip2 1.2451e-002 kg ·m ² Moment of Inertia Ip3 1.2537e-002 kg ·m ² Statistics Nodes 3258 Elements 556 Mesh Metric None Coordinate Systems TABLE 4 Model (D4) > Coordinate Systems > Coordinate System Object Name Global Coordinate System State Fully Defined Definition Type Cartesian Ansys System Number 0. Origin Origin X 0. m Origin Y 0. m Origin Z 0. m Directional Vectors X Axis Data [ 1. 0. 0. ] Y Axis Data [ 0. 1. 0. ] Z Axis Data [ 0. 0. 1. ] Mesh TABLE 5 Model (D4) > Mesh Object Name Mesh State Solved Defaults Physics Preference Mechanical Relevance 0 Sizing Use Advanced Size Function Off Relevance Center Coarse Element Size Default Initial Size Seed Active Assembly Smoothing Medium Transition Fast Span Angle Center Coarse Minimum Edge Length 2.e-002 m Inflation Use Automatic Tet Inflation None Inflation Option Smooth Transition Transition Ratio 0.272 Maximum Layers 5 Growth Rate 1.2 Inflation Algorithm Pre View Advanced Options No Advanced Shape Checking Standard Mechanical Element Midside Nodes Program Controlled Straight Sided Elements No Number of Retries Default (4) Rigid Body Behavior Dimensionally Reduced Mesh Morphing Disabled Pinch Pinch Tolerance Please Define Generate on Refresh No Statistics Nodes 3258 Elements 556 Mesh Metric None Steady-State Thermal (D5) TABLE 6 Model (D4) > Analysis Object Name Steady-State Thermal (D5) State Solved Definition Physics Type Thermal Analysis Type Steady-State Solver Target ANSYS Mechanical Options Generate Input Only No TABLE 7 Model (D4) > Steady-State Thermal (D5) > Initial C