Machine Design Lab-I
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Transcript of Machine Design Lab-I
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area, weight, volume, centre of gravity and moment of inertia. In FEA the object is
divided into large number of finite elements which form an interconnecting network
network concentared nodes. By using a computer with significant computational
Capabilities, the entire object can be anlysed for stress- strain, heat transfer coefficient
at nodes. By determining the inter relating behaviours of all nodes in the system, the
behaviour of the entire object can be assessed.
Design review & Evaluation:Checking the accuracy of the design can be accomplished conveniently on the graphical
terminal. Semiautomatic dimensioning and tolerance routines which assign size specification to
surface indicated by the user help you to reduce the possibility of dimensioning errors. The
designer can zoom in on part design details and magnify the image on the graphics screen for
close scrutiny. One of the most important evaluation feature available on some computer aided
design systems is KINEMATICS. The available kinematics packages provide the capability to
animate the motion of the simple designed mechanisms such as hinged component & linkages.
Commercial kinematics software available is ADAMS (Automatic Dynamic Analysis ofMechanical Systems).
Automated Drafting:It involves the creation of hard-copy engineering drawings directly from the CAD data base.
Most of the CAD systems are capable of generating as many as six views of the parts.
Engineering drawings can be made into company drafting standard by programming the
standards into the CAD system. Implementation of computer in the design stage becomes the
subset of design process. Once the conceptual design materializes in the designer mind the
geometric model starts by the appropriate CAD software. The choice of geometric model to
CAD is analogous to the choice of a mathematical model to engineering analysis. A valid
geometric model is created by definition translator, which converts the designer input into theproper database format. In order to apply engineering analysis in geometric model, interface
algorithms are provided by the system to extract the required data from the model database to
perform the analysis. In case of FEA, these algorithms from the finite element modeling
package of the system. Design testing & evaluation may require changing the geometric model
before finalizing it. When the final design is achieved the drafting & detailing of the model
starts, followed by documentation & production of final drawings.
Geometric modelling:
A geometric modeling is defined as the complete representation of an object that includes in
both graphical and non-graphical information. In computer-aided design, geometric modelingis concerned with the computer compatible mathematical description of the geometry of an
object. The mathematical description of the geometry of an object to be displayed and
manipulated on a graphics terminal through signal from CPU of the CAD system. The software
that provides geometric modeling capabilities must be designed for efficient use of both by the
computer and the human designer. To use geometric modeling, the designer construct the
graphical image of the object on the CRT screen of the IGS system by inputting three types of
commands to the computer. The first type of command generates basic geometric elements
such as points, lines, and circles. The second command types is used to accomplish scaling,
rotation or other transformations of these elements. The third type of command causes the
various elements to be joined into desired shape of the object being created on the ICG system.
During this geometric modeling process the computer converts the commands intomathematical model, stores it in the computer data files and displays it as an image on the
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screen. The model can be subsequently being called from the data files for review, analysis or
alteration. The most advanced method of geometric modeling is solid modeling in three
dimensions. This method uses solid geometry shapes called primitives to construct the object.
Basically there are three types of modelling, They are:
a. Wire Frame Modelingb. Surface Modeling
c. Solid Modeling
Wire frame model Introduction:This is the basic form of modeling; here the objects drawn will be simple but more verbose,
geometric model that can be used to represent it mathematically in the computer. It is
sometimes referred as a stick figure or an edge representation of the object. Typical CAD/CAM
system provides users with possibly three modes to input coordinates: Cartesian, Cylindrical or
Spherical. Each mode has explicit or implicit inputs. Explicit input could be absolute or
incremental coordinates. Implicit input involves user digitizes..A wire frame model consists ofpoints, lines, arcs, circles &curves. Early wire frame modeling techniques developed in 1960s
were 2-dimensional. They are not centralized &associative. Later in 1970s the centralized,
associative database concepts enabled modeling of 3D objects as wire frame models that can be
subject to 3-dimensional transformations.
Wire frame entities:Wire frame Entities are divided into 2 types are:
a. Synthetic Entities: Splines & Curves
b. Analytic Entities: Points, lines, Circles, arcs, conics, fillet, chamfer
Surface Modelling:A surface model of an object is more complete and less ambiguous representation than it wire
frame model. It is also richer in associated geometric contents, which make it more suitable for
engineering and design applications. Surface model takes one step beyond wire frame models
by providing information on surfaces connecting the object edges. Creating a surface have
some quantitative data such as point & tangents & some qualitative data like desired shape &
smoothness. Choice of surface form depends on type of application.
Surface Entities:Similar to wire frame entities, existing CAD / CAM systems provide designers with both
analytic and synthetic surface entities. Analytic entities include plane surface, ruled surface,surface of revolution, and tabulated cylinder. Synthetic entities include the bicubic Hermite
spline surface, B spline surface, rectangular and triangular bezier patches, rectangular and
triangular Coons patches, and Gordon surface. The mathematical properties of some of these
entities are covered in this chapter for two purposes. First, it enables users to correctly choose
the proper surface entity for the proper application. For example, a ruled surface is a linear
surface and does not permit any twist while a B spline surface is a general surface. Second
users will be in a position to better understand CAD/CAM documentation and the related
modifiers to each surface entity command available on a system. The following are
descriptions of major surface entities provided by CAD/CAM systems
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Solid Modeling:A solid model of an object is more complete representation than its surface model. It is unique
from the surface model in topological information it stores which potentially permits functional
automation and integration. Defining an object with the solid model is the easiest of the
available three modeling techniques. Solid model can be quickly created without having to
define individual locations as with wire frames. The completeness and unambiguity of solidmodels are attributed to the information that is related database of these models stores
(Topology: It determines the relational information between objects.) To model an object
completely we need both geometry & topological information. Geometry is visible, whereas
topological information are stored in solid model database are not visible to user. Two or more
primitives can be combined to form the desire solid. Primitives are combined by
Boolean Operations. Different Boolean operations are:
1. Union(U)
2. Intersection(n)
3.Difference(-)
Solid entities:There are a wide variety of primitives available commercially to users. However, the four most
commonly used are the block, cylinder, cone, and sphere. These are based on the four natural
quadrics: planes cylinders, cones, and spheres.
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EXPERIMENT 1
Aim: To create a rectangle using extrude base/boss command.
Procedure:1. Open the new part drawing.
2. Select the front plane.
3. Go to normal to the selected plane and select sketch.
4. Go to sketch and pick up the rectangle drawing tool.
5. Now, go to the center of the selected plane and keeping the center as the midpoint, draw
a rectangle.
6. Select the smart dimension tool.
7. Select the breadth side of the rectangle and enter the dimension as 20mm.
8. Now, select the length side of the rectangle and enter the dimension as 40mm.
9. Now, go to exit sketch.
10. Select the extrude base/boss tool.11. Enter the extrude dimension as 20mm.
12. Click on ok.
Result: The specified drawing is complete.
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EXPERIMENT 1
Aim: To create a rectangle using extrude base/boss command.
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EXPERIMENT 2
Aim: To create a hollow rectangular block using extrude boss/base and extrude cut command.
Procedure:1. Open the new part drawing.
2. Select the top plane.
3. Go to normal to the selected plane and select sketch.
4. Go to sketch and pick up the rectangle drawing tool.
5. Now, go to the center of the selected plane and keeping the center as the midpoint, draw
a rectangle.
6. Select the smart dimension tool.
7. Select the breadth side of the rectangle and enter the dimension as 20mm.
8. Now, select the length side of the rectangle and enter the dimension as 40mm.
9. Now, go to exit sketch.
10. Select the extrude base/boss tool.
11. Enter the extrude dimension as 20mm.
12. Click on ok.
13. Now go to the sketch tab and select the top plane for sketching.
14. Select the rectangle tool.
15. Select the center of the plane and draw a rectangle such that the center of the rectangle
and the plane coincide.
16. Now, select smart dimension and set the dimensions equal to 10X30 mm.
17. Exit sketch mode and go to the features pane.
18. Select the extrude cut tool and select the sketch.
19. In the extrude cut option panel select the cut through all option.20. Click ok.
Result: The specified drawing is complete.
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EXPERIMENT 3
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Aim: To create a hexagonal bolt using swept boss/base command and chamfer command.
Procedure:
1. Open the new part drawing.2. Select the front plane.
3. Go to sketch and select hexagon tool.
4. Select the center of the plane and draw a hexagon.
5. Use smart dimension to make the sides of hexagon equal to 20mm. .
6. Now, exit sketch and go to extrude tool.
7. Extrude the hexagon to 20mm. .
8. Go to sketch and select circle tool.
9. Draw a circle such that the center of the circle and the center of the center of plane and
hexagon coincide.
10. Use smart dimension to make the diameter equal to14mm. .
11. Exit sketch and go extrude command.12. Extrude the circle by 100mm. .
13. Now, select the top plane on the tip of the circular stem of the bolt and select sketch.
14. Go to the circle command and draw a circle of 14mm diameter on the plane.
15. Exit sketch and go to the feature tab and select helix/spiral tool under the curves
command.
16. Under the helix/spiral options, select height and pitch type of helix.
17. Enter the height as 100mm and pitch as 6mm. .
18. Now, select the tip of the helix and draw a triangular geometry on the tip of height 3mm
and base 5mm.
19. Go to the swept boss/base tool and then select the geometry and the helix as the path.
20. Click ok.21. Draw a circle on the top side of bolt which touches all the polygon sides internally.
22. Select fillet option in feature tab, in fillet select chamfer and enter distance 3mm and
angle 60.
23. Chamfer is done on hexagonal bolt.
Result: The specified drawing is complete.
EXPERIMENT 3
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Aim: To create a hexagonal bolt using swept boss/base command and chamfer command.
EXPERIMENT 4
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Aim: To create a helical gear using loft boss/base command.
Procedure:1. Open the new part drawing.
2. Select the front plane.
3. Go to sketch and select circle tool.
4. Select the center of the plane and draw two circles.
5. Use smart dimension to make the circle of diameter equal to 10mm.
6. Now, exit sketch and go to extrude tool.
7. Extrude the circle by 3mm.
8. Go to sketch and select center line tool.
9. Draw a geometry specified in the drawing using the line tool on the surface of the
extruded circle.
10.Now, select the copy entities tool and select the opposite side of the extruded part and
copy the geometry to that side and select delete relationship.
11.Select the rotate tool and rotate the geometry on one side of the extruded part by 10o.
12. Exit sketch and go to the loft boss/base command.
13. Select the two geometries and loft the two geometries.
14. Now, select the circular geometry tool and select the lofted teeth.
15. Select the circular plane as the plane for pattern, and enter the number of patterns as 22.
16.Select the rectangle tool and make a rectangle of the specified on the inner circle of
diameter 4mm of the gear, for creating a notch.
17. Go to the extrude cut tool and select the rectangle and then select the cut through all
option.
18.Click ok.
Result: The specified drawing is complete.
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EXPERIMENT 4
Aim: To create a helical gear using loft boss/base command.
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EXPERIMENT 5
Aim: To create a simple spring using helix and spiral command.
Procedure:
1. Open the new part drawing.
2. Select the top plane.
3. Go to sketch and select circle tool.
4. Draw a circle of diameter 20mm.
5. Now exit sketch and go to the reference geometry tool in the features tab.
6. Select the helix and spiral tool and then select the circle.
7. Give the height of helix as 100mm and the pitch as 6mm.
8. Now, go to the circle tool and draw a circle of diameter 4mm at the tip of the helix such
that the tip of the helix is the center of the circle.
9. Go to the swept boss/base command and select the circle as the reference geometry and
the helix as the path.
10.Click ok.
Result: The specified drawing is complete.
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EXPERIMENT 5
Aim: To create a simple spring using helix and spiral command.
Image:
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EXPERIMENT 6
Aim: To create an Allen key using swept boss/base command.
Procedure:1. Open the new part drawing.
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EXPERIMENT 6
Aim: To create an Allen key using swept boss/base command.
Image:
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EXPERIMENT 7
Aim: To create a base of a plumber block.
Procedure:
1. Open the new part drawing.
2. Select the front plane and select the line tool.
3. Draw the specified geometry.
4. Now, use smart dimension and make the sides of the geometry as specified in the
drawing.
5. Select the center line tool and draw a center line.
6. Make the distance between the center line and the inside of the geometry equal to20mm.
7. Now exit sketch and go to the revolve boss/base command.
8. Select the geometry as the entity to be revolved and then select the center line as the
axis.
9. Click ok.
Result: The specified drawing is complete.
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EXPERIMENT 7
Aim: To create a base of a plumber block.
Image:
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EXPERIMENT 8
Aim:To analyze a hook using Simulation Express.
Procedure:1. Open the new part drawing.
2. Go to the tutorials section and open the Simulation Express.
3. Open the hookdrawing given as example in the tutorial.
4. Select the simulation express tool and start it.
5. Now, select the fixtures on the hook and click next.
6. Apply the load on the hook at the specified point and also give the amount and direction
of force. Enter the amount of force as 1500N in reverse direction.
7. Now, select the material of the hook. Set it to Alloy Steel.
8. Run the simulation.
9. Play the simulation and check if the hook is deforming as you had planned.
10. Now, select the Von Mises graph and print it.
11. Select the displacement graph and print it.
Result:The analysis is complete.
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EXPERIMENT 8
Aim:To analyze a hook using Simulation Express.
Image:
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Displacement analysis graph
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Von Mises stress analysis graph