VI Sem Mech - CAD&M Practical Drawings(CAD) and Procedure _ M Scheme

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AutoCAD 3D - Introduction

WCS and UCS

There are two coordinate systems: a fixed system called the world coordinate system (WCS) and a movable system called the user coordinate system (UCS). By default, these two systems are coincident in a new drawing.

By default when we start a new (blank) drawing we use the World Coordinate System (WCS). This is (0,0,0) point. The square in the crosshairs of UCS indicates the World Coordinate System. Normally in 2D views, the WCS X axis is horizontal and the Y axis is vertical. The WCS origin is where the X and Y axes intersect (0,0). All objects in a drawing file are defined by their WCS coordinates. However, it is usually more convenient to create and edit objects based on the movable UCS.

Moving or rotating the UCS can make it easier to work on particular areas of a drawing.

We can relocate the user coordinate system by UCS command

• Move the UCS by defining a new origin point.
• Align the UCS with an existing object.
• Rotate the UCS by specifying a new origin point and a point on the new X axis.
• Rotate the current UCS a specified angle around the Z axis.
• Revert to the previous UCS.
• Restore the UCS to be coincident with the WCS.
• View makes the ucsicon parallel to drawing screen.

Region

Regions are two-dimensional areas we create from closed shapes or loops. Closed polylines, lines, and curves are valid selections. Curves include circular arcs, circles, elliptical arcs, ellipses, and splines.

Regions are two-dimensional enclosed areas that have physical properties such as centroids

Creating 3D Solids

Presspull

Click inside bounded areas to press or pull and drag the mouse in the required Z direction and enter the height

We can create a new solid or surface by sweeping an open or closed planar curve (profile) along an open or closed 2D or 3D path.of bounded areas

EXTRUDE

Select the objects or edge subobjects to extrude.

Specify the height and taper angle or select the path

Closed polylines, circles and regions are only extruded to 3d solids

SWEEP

Creates a 3D solid or surface by sweeping a 2D object(region) along a path.

LOFT

Creates a 3D solid or surface in the space between several cross sections. To create a solid by lofting, first create a set of cross sections. Then click the Loft button on the Modeling Toolbar.

REVOLVE

Select a closed region or closed polyline to revolve.

To set the axis of revolution, specify one of the following: The start and endpoint. Click to points on the screen to set the axis orientation. ...

Press Enter. To create a 3D solid the angle must be 360 degrees.

SLICE

Select the 3D solid or surface objects to slice. Press Enter.

Specify two points to define the cutting plane.

Specify which side of the sliced object to retain, or enter b (Both) to retain both sides.

UNION

Combines selected 3D solids, surfaces, or 2D regions by addition.

SUBTRACT

Select the objects that you want to keep, press Enter, then select the objects that you want to subtract. Objects in the second selection set are subtracted from objects in the first selection set.

INTERSECT

Create a 3D solid from the common volume of two or more existing 3D solids, surfaces, or regions.

 VISUALSTYLES

Creates and modifies visual styles and applies a visual style to a viewport.

Create 3D Solid Primitives

•  Box  

Create a rectangular or cubical solid box.

•  Wedge

Create a solid wedge with rectangular or cubical faces.

•  Cone

Create a pointed or frustum of a cone with a circular or elliptical base.

• Cylinder

Create a solid cylinder with a circular or elliptical base.

•  Sphere

Create a solid sphere using one of several methods.

•  Pyramid

Create a solid pyramid with up to 32 sides.

•  Torus

Create a ring-shaped solid that resembles the inner tube of a tire.

Solview

This command automates the manual process of creating views, layers, and layout viewports for 3D models.

Note SOLVIEW must be run on a layout tab. If the Model tab is current, the last active layout tab is made current.

Enter an option [Ucs/Ortho/Auxiliary/Section]: Enter an option or press Enter to exit the command

SOLVIEW places the viewport objects on the VPORTS layer, which it creates if it does not already exist. The view-specific information that is saved with each viewport you create is used by SOLDRAW to generate the final drawing view.

SOLVIEW creates layers that SOLDRAW uses to place the visible lines and hidden lines for each view, view name-VIS, view name-HID, view name-HAT, and a layer where you can place dimensions that are visible in individual viewports, view name-DIM.

Soldraw

After using SOLVIEW, visible and hidden lines representing the silhouette and edges of solids in the viewport are created and then projected to a plane perpendicular to the viewing direction.

Select viewports to draw ...

Select objects: Select the viewports to be drawn

SOLDRAW can only be used in viewports that have been created with SOLVIEW.

3DROTATE : In a 3D view, displays the 3D Rotate gizmo to aid in revolving 3D objects around a base point.

3DARRAY : For 3D rectangular arrays, in addition to columns and rows, you also specify the number of levels in the Z direction.

For 3D polar arrays, you specify the axis of rotation with any two points in space.

Enter the number of items in the array

Specify the angle to fill (+=ccw, -=cw) <360>

The specified angle determines how far the objects are arrayed about the axis of rotation. A positive number produces a counterclockwise array rotation. A negative number produces a clockwise array rotation.

Rotate arrayed objects? [Yes/No] <Y>: Enter y or n, or press Enter

3D Mirror.

Select the object to mirror.

Specify three points to define a mirroring plane.

Press Enter to retain the original objects, or enter y to delete them.

Align.

Select the objects that you want to align.

Specify a source point and then the corresponding destination point. To rotate the object, specify a second source point followed by a second destination point.

            Press Enter to end the command

Geneva wheel

Aim :

             To draw the geneva wheel 3d drawing in AutoCad

Procedure :

1. Hub:

Draw  2 concentric circles of radius 15 mm and 20 - Circle  with center point,  radius option.

Draw the keyway (10 mm X 3 mm) - Line,  Offset, Trim

2. Wheel

Draw the top half of  slot at 25 mm from the center of the  hub(2.5 mm 30 mm x  2.5 mm ). - Line,  Offset, Trim

Fillet  the inner end with radius 2.5.

Mirror  the bottom half.

Make a polar array of   8 slots.

Draw the circular arc between two successive slots. (Line at  22.5 degree, line of 55 mm =radius of geneva wheel & vertical line from last line, Circle, Trim)

Make a polar array of   8  arcs.

3. 3D Solid Modeling View toolbar  à SE Isometric view

Modeling Toolbar à Presspull Presspull the the hub by clicking inside between  two circles to half thickness ( 10 mm ) in Z direction

Presspull the the wheel by clicking inside between  hub and outline  to half thickness ( 5 mm ) in Z direction

View  toolbar  à Front  view Mirror  the bottom  half

Modeling Toolbar à Union Union the two halves. View toolbar  à SE Isometric view

Visual Styles Toolbar à Conceptual , 2D wireframe,  3D Hidden etc

4. Isometric  view & Orthographic views  SOLVIEW  must be run on a layout tab. If the Model tab is current, the last active layout tab is made current To create isometric view  , Set UCS à View and give Solview à Ucsà Current Ucs Change view to main view (Front or Top view) in Model Tab To create Orthograpic & Sectional views  . SOLVIEW  àUcs/Ortho/Auxiliary/Section] SOLDRAW to generate the final drawing views.

RESULT :

 The geneva wheel 3d drawing is drawn  in AutoCAD

                                                      Bearing block

Aim :

             To draw the bearing block 3d drawing in AutoCAD

Procedure :

Bottom portion of  block

1.View toolbar à  Front View

2. Draw two lines from a point A à at -45 degree and at  -135 degree.

3. Draw three concentric circles of  radius 45, 55, and 25 mm , with intersection point A as centre.

4. Trim the circles outside the two lines

5. Draw circles with 2P – 2 Point option to connect circles of radii 25, 45 mm.

6. Draw three circles of 20 mm radius with the centres of last drawn circles(R10) and “A” point as  centres. Draw a circle of 5 mm radius with “A” point as centre

7. Fillet the 20 mm radius circles on the left side and right side – with Radius = 15 mm.

8. Draw the rectangle of 15 mm x 8 mm, at the top symmetrically.( Line, Offset and Trim commands)

9. Trim the unnecessary edges.

10. View toolbar à  SE isometric View . Presspull - click  between outer and inner edges and pull to Z-Thickness of 22 mm.

Middle and top portion of block.

11. View toolbar à  Right side View

12. Draw a series of lines :: 60 mm to the right , 35 mm to the top, 5 mm to the left, 35 mm to the top, 45 mm to the left, 35 mm downwards, 10 mm to the left and 35 mm downwards.

13. With midpoint of 45 mm line as centre, draw concentric circles of 22.5 mm and 10 mm radii.

14. Erase 45 mm line.

15. View toolbar à  SE isometric View. Presspull - click  inside the middle portion and pull to Z-Thickness of 15 mm. Presspull - click  between outer and inner circles  and pull to Z-Thickness of 35 mm

16. Move the the top portion 5 mm the right.

17. Union the Middle and top portions.

Assembly

18. Assemble and union the portions – Move and Union 

19. Isometric  view & Orthographic views creation :SOLVIEW  must be run on a layout tab. If the Model tab is current, the last active layout tab is made current.To create isometric view  , Set UCS à View and give Solview à Ucsà Current Ucs.Change view to main view (Front or Top view) in Model Tab

To create Orthograpic & Sectional views  . SOLVIEW  àUcs/Ortho/Auxiliary/Section]

SOLDRAW to generate the final drawing views.

RESULT :

 The bearing block 3d drawing is drawn  in AutoCAD

Bushed bearing

Aim

             To draw the bushed bearing 3d drawing in AutoCAD

Procedure :

Half Block (or) Half  Body

1.View toolbar à  Front View

2. Draw  a rectangle of 112 x 15 (Command : Rectang , Explode(X) or Line)

3. Draw two concentric circles of radius 25 and 16 mm at a height of 35 from the base of rectangle.

4. Draw vertical lines from the horizontal quadrant points of the 25 mm radius circle downwards.

5. Fillet with Radius 5 mm on both sides

6. View toolbar à  SE isometric View . Presspull - click  between outer circle  and bottom rectangle  and pull to Z-Thickness of 20 mm.(half thickness)------bottom of body

7.  Presspull - click  between circles   and pull to Z-Thickness of 25 mm.(half thickness)

--------- top of body.

Bush (Draw full bush)

8. View toolbar à  Front View

9. Draw two concentric circles of  radius 12.5 and 16 mm

10.  View toolbar à  SE isometric View . Presspull - click  between circles   and pull to Z-Thickness of 50 mm.(half thickness).

Full Block 

11. View toolbar à  Right Side View or Top View

12. Mirror the other half of block .

13. Union the the halves of block .

Slot & fillet at Rectangular Base

14. View toolbar à  Front View . Draw the slots at top of  rectangular base at both ends

15. View toolbar à  SE isometric View . Presspull - click  in the slot area and press downwards to make slot.

16. Fillet the rectangular base at both ends.

Oil hole

17. Make oil holes for block (Cone, Cylinder and union or two circles and loft) and  bush (Cylinder) with extra length at the bottom side at the top UCS in the SE Isometric view.

18. Move the oil holes to block and bush repectively and Subtract.

Assembly

19. Move bush to block.

20.  Isometric  view & Orthographic views creation : SOLVIEW  and SOLDRAW

RESULT :

 The bushed bearing 3d drawing is drawn  in AutoCAD

4. Gib and Cotter Joint

Aim :

             To draw the Gib and Cotter Joint 3d drawing in AutoCAD

Procedure :

1. View toolbar à  Front View

2. Draw the fork rod, square rod, gib and cotter.(Commands: Line, Rectang, Fillet, Offset, Trim, Mirror)

3. View toolbar à  SE isometric View .

4. Presspull - click  inside the fork area  and pull to Z-Thickness of 38 mm

5. Presspull - click  inside the square rod area  and pull to Z-Thickness of 38 mm.

6. Presspull - click  inside the gib area  and pull to Z-Thickness of 12 mm.

7. Presspull - click  inside the cotter area  and pull to Z-Thickness of 12 mm.

8. View toolbar à  Top View

9. View toolbar à  SE isometric View        (Or) UCS II toolbar à  Top UCS (Or) World UCS

10. Draw a rectangle for slot in the fork rod and square rod. Copy the rectangle to top face of the fork rod and square rod. Presspull - click inside the rectangle and press downwards outside the solid ---- in the fork rod. (Separately for the square rod)

Assembly

11. Move the square rod to the fork rod. Move gib and cotter

12. Isometric  view & Orthographic views creation : SOLVIEW  and SOLDRAW

RESULT :

 The Gib and Cotter Joint 3d drawing is drawn  in AutoCAD

5. Screw Jack

Aim :

             To draw the Screw Jack 3d drawing in AutoCAD

Procedure :

1. View toolbar à  Front View

2. Create body of the Screw Jack :

 Construct the half of the cross section and an axis line for revolution.

 Use Region (Reg) command to create the closed 2d area.

 Use Revolve (Rev) command to create the 3d solid.

Select the region and press enter

Specify the start point of axis

Specify  the end point of axis

Specify angle of revolution <360> : press enter

3.  Similarly create all other parts

v Nut

v Screw Spindle

v  Cup

v Special washer

v Set Screw

v Tommy Bar

4. Create a hole in the screw spindle (A) at top

                         Copy the shank of the set screw (b)at the top of the screw spindle

Subtract: select A first, press enter and select B next and press enter. (A-B)

5. Create a hole in the screw spindle at side.

                         Make a cylinder. Move the cylinder to the screw spindle

                         Subtract this cylinder from the screw spindle

6. Similarly draw the half circular slots in the cup and slot in the set screw.

7. Assembly :

             Move the nut to the body.(align bottom of center of the collar of the nut à top center of body).

             Move the screw spindle to the nut.(align top center of the nut à bottom  center of screw spindle head) and again move the screw spindle upwards by 10 mm.

             Move the cup to the screw spindle (align bottom center of the cup à top  center of screw spindle head)

             Move the washer and set screw.

8. Isometric  view & Orthographic views creation : SOLVIEW  and SOLDRAW

RESULT :

The Screw Jack 3d drawing is drawn  in AutoCAD.

6. Connecting Rod

Aim :

             To draw the Connecting Rod  3d drawing in AutoCAD

Procedure :

1. View toolbar à  Front View

2.  Draw the big end and bush

     Draw the small end and bush

     Draw the I section  connecting big end and small end

3.  View toolbar à  SE Isometric  View

4.  Presspull  all the parts to half thickness.

             Presspull big end

             Presspull big end bush

             Presspull small end

             Presspull small end bush

             Presspull the I-section flange

             Presspull the I-section web or rib

5. View toolbar à  Right Side View or Top view

             Mirror all the parts

             Union

6. View toolbar à  SE Isometric  View

   UCS II toolbar à Right UCS

             Make holes in top and bottom of the big end

7 Split the big end by Slice (SL)  command.

8. Make bolts and join the ends.

9. Isometric  view & Orthographic views creation : SOLVIEW  and SOLDRAW

RESULT :

The Connecting Rod  3d drawing is drawn  in AutoCAD.