OBJECTIVES:

After this tutorial you will be able to:

1. Convert a two-dimensional object to polylines;
   
   
2. use the EXTRUDE command to create a solid from an object made of Polylines;
   
   
3. use the REVOLVE command to create a solid from an object made of Polylines; and
   
   
4. apply the practice of Revolution Conventions to the multiview representation of a model.

STEP 1

     In this tutorial, you will create an advanced solid model, and convert the model to a multiview drawing through the Solview and Soldraw commands. FIGURE 1 provides a preliminary view of the model you will construct, with the subparts identified.

FIGURE 1

To begin this tutorial, locate and open the classtemplate file you have used before.

Now, save your file under the name tutorial5.

Finally, move to Model space by clicking on the Model tab.

STEP 2

    To construct this model, you will create a series of two-dimensional elements that can be converted to a solid to form the first part of the model, the Base Plate. The first element you need for the Base Plate is a circle. This circle's center should should be located at the 0,0 point and have a radius of 80mm. See FIGURE 3.

FIGURE 3

To the large circle, add a 5mm radius circle that is vertically aligned with the center of the larger circle and 65mm above it. See FIGURE 4.

FIGURE 4

With the small circle in place, you will use a new command, called Array, to make multiple copies of the small circle. There are two Array commands in AutoCAD, one for 2D elements and one for Solids. Each Array command is capable of producing two types of arrays, Rectangular and Polar. To access this command, type array at a Command: prompt or select Array on the Modify menu. Look at FIGURE 5 which provides a view of the Array dialogue box that will appear after Polar Array is selected. The items in this dialogue box that you need to interact with or change are numbered to match the directions below it.

FIGURE 5

1. In the Array dialogue box, select the button next to Polar to indicate you wish to create this type of array.
   
   
2. Next, click on the button to the right of this that is labeled, Select an object. AutoCAD will return you to your drawing so that you can select the item or items you wish to array. Click on the edge of the smaller circle you added and press Enter. You will return to the Array dialogue box.
   
   
3. On the dialogue box, locate the button to the Right of the Y selection window for Center point:. Again you will return to the drawing. This time use the Center Osnap to select the center of the large circle as the center of the array. You will again return to the dialogue box.
   
   
4. Now, locate the window labeled: Number of items: and type 20 in the window. Leave the Angle of fill: at 360 so that the array will be full circle. Click on OK to complete the array and exit the dialogue box. The completed array will look like FIGURE 6.

FIGURE 6

Looks like a good time to save!

With the array completed, you will use the Extrude command to convert the circles to solid cylinders.

The Extrude command can only be used with Polyline (plines) objects that have a "closed path." These include objects like circles and polygons, objects constructed as polylines that have a closed path, and 2D drawings that have been converted to polylines that have a closed path. By "closed path" I mean that each element in the figure is linked to the end of another element without any gaps. See the EXAMPLE to the Right. You may recall that it was necessary to explode the hexagon you added in Tutorial 2 before you could remove two of its sides. This was because AutoCAD used Polylines to construct polygons.

You can extrude more than one item at a time as long as they should be the same height. Read the information on the Extrude command and then extrude all the elements you have created so they have a positive thickness of 10mm and are NOT tapered.

When you are finished, the figure will not look any different on the screen. To see the extrusion, you need to change your view point. Use the Vpoint command and ROTATE your view to 300 degrees IN the XY Plane and 35 degrees FROM the XY Plane. The image on the screen should now match the one in FIGURE 7.

FIGURE 7

To complete the Base Plate, subtract the small cylinders from the large cylinder using the Subtract command. If needed, you can use the link to review the procedures for this command.

Again, the model will not look any different than the one in FIGURE 7. To check your model, use either the Hide or Render command and then convert it back to its normal wire frame appearance with regen.

Your Base Plate is now complete.

STEP 3

     The second part of the model is the Bearing Base. Before beginning the construction of this part, change your Vpoint to 270 degrees IN the XY Plane and 90 degrees FROM the XY Plane. The model will again look like FIGURE 6.

Use the Realtime Zoom (if needed) so you have room on the screen to draw this part of the model to one side of the Base Plate.

The Bearing Base will again be created as a 2D object that you extrude; however, this part will begin as a series of 2D elements that will be edited and then converted to Polylines with the Pedit command.

To construct this part, move to a blank region of AutoCAD's drawing area, to the left of the Base Plate, and construct a circle with a 10mm Radius. Use a left mouse click, in a blank spot of the drawing area, to locate the center of this circle.

Now, you will use a new command, Copy, to create a second circle the same size. NOTE: The Copy command can copy single or multiple items. Read the information on the Copy command and make a copy of the last circle you created. Locate the copy to the LEFT of the original, align it HORIZONTALLY with the original, and 96mm away from the original. See FIGURE 8.

FIGURE 8

Add a construction line connecting the centers of the two circles. Use this line to place a 25mm radius circle at the line's midpoint so that it is centered between the smaller circles. See FIGURE 9.

FIGURE 9

Keep the line used to add the larger circle. You will use it later to place the Bearing Base on top of the Baseplate.

Finally, add tangent lines (use the Tangent Osnap) that connect each small circle to the larger circle, as shown in FIGURE 10. Review the Osnap Tangent command before adding these lines.

FIGURE 10

Trim the circles so they match FIGURE 11.

FIGURE 11

With the circles trimmed, it is time to turn this figure into a closed set of Polylines with the Pedit command. Read the information on the Pedit command and use its Join option to convert the Bearing Base to Polylines (except for the line down the middle). You now have a polyline 2D object with a closed path. The figure will appear the same when you are done, but you can check it by clicking on one line in the figure. If the figure is a polyline, the whole figure should select.

Before you Extrude the figure, change the Vpoint back to 300 degrees IN the XY Plane and 35 degrees FROM the XY Plane so that you can see the figure as a 3D object after it is extruded. See FIGURE 12.

FIGURE 12

With the drawing converted to Plines, use the Extrude command to convert it to a solid that has a positive height of 20mm and no taper. See FIGURE 13.

NOTE: Remember, if you wanted to extrude the figure in the opposite direction, you would use a negative number for the height. Height is always along the Z-axis.

If your object will not extrude, zoom in close to inspect the intersections of the lines. AutoCAD will not extrude a figure, even if you used Pedit, if there are any gaps in the figure's edge or lines that extend past the intersections. Because of the way a computer monitor displays an image, they may not show at a smaller view of the figure. If this is the problem, undo the Pedit, fix the lines, use Pedit again, and try the Extrude command once more.

FIGURE 13

FIGURE 14

Now that you have a solid Bearing Base, you need to place it on top of the Base Plate. Read the information on the Move command and use it to move the Bearing Base so that it is centered with the TOP of the Baseplate.

HINT: Use the Midpoint of the horizontal construction line (used to locate the large circle during the Bearing Base's construction) as its basepoint and an absolute coordinate for the Bearing Base's new location. The absolute coordinate should be 0,0,10, since the Bearing Base must sit on top of the Baseplate, and the top of the Baseplate's center is 10mm above the 0,0 point. See FIGURE 14.

STEP 4

     For the last part of the model, you will create a cylinder with a chamfered counterbored hole by revolving a 2D Polyline 360 degrees to form a solid. The Revolve command can be used to create a circular or arched shape from any set of closed plines.

First, you need to set your UCS to a FRONT orientation.

You will begin the construction of the Counterbored Cylinder the same way you began the last one, as a series of lines that you will convert to a Polyline.

Change your Vpoint to 270 degrees IN the XY Plane and 0 degrees FROM the XY plane. You should now be looking directly at the FRONT surfaces of the Baseplate and Bearing Base. This is also a good time to see if the Bearing Base is properly oriented to the Baseplate. If they are not correctly aligned, use the Move command to reposition the Bearing Base.

Look at FIGURE 15, which shows a diagram of the 2D figure you will create and provides the dimensions to create it. Again, construct this figure in blank space on AutoCAD's drawing area. It will be moved into place after you convert it to a solid.

FIGURE 15

Using the diagram in FIGURE 15, create this structure. If you need to review the Relative Rectangular or Relative Polar coordinates, use the LINKS in the LEFT PANEL. See FIGURE 16 for a view of the 2D figure when you are done.

FIGURE 16

Notice that you were asked to add a line to the right side of the "closed" figure, which was 5mm from it. This is a construction line you will use as the axis of rotation when you rotate the figure. This will create an opening through the Chamfered-Counterbored Cylinder.

Once the figure is complete, convert it to a "closed" Polyline path with the Pedit command.

Read the information on the Revolve command and follow the directions below.

1. Activate the Revolve command.
   
   
2. Select the figure you just converted to Polylines.
   
   
3. Use the default option for the Axis of revolution of <Start point of axis> and an Osnap to select one end of the construction line that is 5mm away from the structure.
   
   
4. When asked for the End of the Axis:, use an Osnap to select the opposite end of the same construction line.
   
   
5. When asked for the Angle of revolution:, use the default of <360>.

Your figure should now look like a cylinder with a counterbored hole and a chamfered edged as it would appear from a FRONT view (see FIGURE 17).

FIGURE 17

To see the Counterbored Cylinder as a 3D object, change your viewpoint to 300 degrees IN the XY plane and 35 degrees FROM the XY plane (see FIGURES 18).

FIGURE 18

STEP 5

     In this step you will combine the Counterbored Cylinder, the Bearing Base, and the Baseplate into one model. When placing the Counterbored Cylinder on top of the Bearing Base, you will need to be sure you are selecting the correct basepoint on the solids so they will be correctly aligned.

See FIGURE 19.

Use the Move command and select the Center of the BOTTOM of the Counterbored Cylinder as the basepoint for this move. When asked for a second position, select the Center of a TOP EDGE of one of the larger arcs on the Bearing Base. See FIGURE 18 to view the Counterbored Cylinder placed correctly in relationship to the other two solids.

HINT: To select the center of these features, you must place your cursor on the circle's edge. Be careful to place the cursor on the correct circles. It can sometime be tricky to select the correct circle when the model is in wireframe. You can always use the Hide command first to make sure you are selecting the correct elements.

FIGURE 19

To check the placement of the Counterbored Cylinder, change your viewpoint to 270 degrees IN the XY plane and 0 degrees FROM the XY plane (a front view). If the Cylinder is not correctly placed, you can see that it either sits above the Bearing Base or extends down into it. It should look like FIGURE 20.

Because you are viewing the solids as wireframes, which saves computer resources, it is not always easy to tell where the solids intersect with each other. Changing your viewpoint is one strategy you can use to check this. Accuracy counts, and it pays to "measure twice and cut once" before you combine the parts into a single model.

FIGURE 20

If the parts are correctly aligned, change your Vpoint back to 300 and 35, and use the Union command to merge the three parts into one.

NOTE: Notice that you were not told to combine the three solids until they were all complete. If you union or subtract parts of a model and later discover that the placement of some features are incorrect, they can be hard to fix. Keep things as individual items and union or subtract them after you are sure that all the elements of the model are correctly constructed and positioned.

With one solid to work with:

1. Change the UCS back to a WORLD orientation.
   
   
2. Use the Cylinder command to create two 5mm radius cylinders, concentric with the smaller arcs on each end of the Bearing Base, that have a height of 20mm. See FIGURE 21. HINT: Use the Center Osnap to locate the cylinders; however, if you select the arcs at the top of the figure to locate the cylinders, you must use a negative height.
   FIGURE 21
   
   
3. Now, subtract the cylinders from the Bearing Base.
   
   
4. Add another cylinder that continues the smaller center hole in the Chamfered-Counterbored Cylinder through the rest of the model. This cylinder should start at the BOTTOM of the existing small hole in the Counterbored Cylinder, have a radius of 5, and have a height of 30. See FIGURE 22.
   Should you use a positive or negative height in this case?

FIGURE 22

In the last step, you could have used a height that was more than needed. Since you will be subtracting this cylinder, a larger height does not matter.

Use the Subtract command to remove the cylinder you just added to create a through hole.

STEP 6

     With the model complete, you will then use Solview to create a front, top and right side multiview orientation of the figure, followed by Soldraw to extract the 2D images.

Below is a brief list of things to help you remember the steps for this conversion. You can also refer to the list of AutoCAD Commands Explanations in the area to the LEFT of this screen if the hints are not enough to get you through this process. I would suggest you first try to proceed on your own, since you learn more that way. If you need more help, you can refer to Tutorial 4 to complete these tasks.

Solview & Soldraw:

1. Change to a FRONT UCS.
   
   
2. Change to Layout1 and remove the viewport that AutoCAD automatically places there by clicking on the edge of the viewport and using the Erase command.
   
   
3. Activate the Solview command by typing solview at a Command: Prompt.
   
   
4. For the FRONT view, use the Ucs option, and a scale of .5.
   
   
5. Place the view in an appropriate location for a front view. Remember you can change its position several times until you are satisfied.
   
   
6. When specifying the corners of the viewport that surround this view, make sure it is large enough to accommodate the addition of center lines. NOTE: If you get the viewports too small, you can stretch them later.
   
   
7. Name the Front view FRONT.
   
   
8. After the Front view is placed, use the Ortho option of Solview to place the other two views. Name the Top view TOP and the Right Side view SIDE.

   Remember, the hidden lines will not appear until you complete Soldraw.

NOTE: If you need to ZOOM across all of the views, make sure you are in the PAPER side of Paper Space before you Zoom. If you accidentally Zoom in the MODEL side of Paper Space you will need to use Zoom XP to return the images to the same scale, and Mvsetup to realign the views.

FIGURE 23

Activate Soldraw, to convert the views on the screen to 2D images by typing soldraw at a Command: prompt. When asked to select the objects, you can type in all to select all of the viewports or click on the edge of each one until they are all selected.

After Soldraw is completed, you must change the color of some layers, the lineweigths of some layers and add three new layers.

Click on the Layer toolbutton next to the Layer Status Window to access the Layer Properties Manager dialogue box.

—In this dialogue box, change the color of the -HID layers by clicking on the Color setting in the property listing of these layers and selecting a new color on the Color Select dialogue box.

—While still in the Layer Properties Manager dialogue box, click on the word Default under the Lineweight heading in the layer properties of the -VIS layers to access the Lineweight dialogue box. In the Lineweight dialogue box, change the lineweight.

— Create a Front-cen, Side-cen, and Top-cen Layer and change their color.

Have you saved lately????

STEP 7

     With Soldraw completed, you need to make a few modifications before printing the drawing.

While in the PAPER side of Paper Space, Zoom into the FRONT View.

Change to the MODEL side of Paper Space by clicking on the PAPER button on the end of the Status Bar. See illustrations below.



.

Be careful not to Zoom at this point or you will change the size of the Front view relative to the other two views.

In FIGURE 24, you will notice that only three holes are represented by hidden lines in the Base Plate area of the Front view, the two small holes on the left and right and the taller hole that extends from the bottom of the counterbore. If you examine your drawing, you will see a huge number of hidden lines in the Base Plate that represent the edges of the arrayed holes. Simplifying this type of view is a common practice in technical graphics known as REVOLUTION CONVENTIONS. Removing most of these hidden lines creates a simpler drawing that is easier to understand.

FIGURE 24

To apply the concept of REVOLUTION CONVENTIONS to your drawing, you will erase all of the hidden lines in the Base Plate except the two for the tall center hole, which extends from the bottom of the Counterbored Cylinder, and the hidden lines that form the outside holes on either end.

FIGURE 25

How do you know which they are? I'll tell you.

Erase most of the hidden lines in the Base Plate area of the model except:

—the short lines on the outside edges of the Baseplate,

— the third short line in from the outside edges of the Baseplate, and

—the two that extend from the base of the Counterbored Cylinder.

Repeat this process for the Right side view. Refer to FIGURE 25 to check your modifications.

Now, add center lines where needed. Use Center Marks (select this command on the Dimensioning Menu) for the small holes in the Top view. See FIGURE 26. REMINDER: Be sure to change to the appropriate -CEN layer for the view when adding center lines. Lines placed in the wrong layer will cause headaches later when using VPLAYER to freeze the center lines in the other views.

1. Use ltscale (Line type Scale) to change the length of the dashes in the hidden and center lines to a factor of .5.
   
   
2. Use Vplayer for each viewport to freeze the center lines placed in other viewports so they are not displayed.
   
   NOTE: If you find that the wrong center lines disappear during Vplayer, undo the last steps, and check to see if they were drawn in the correct layer. This is easy to do through the Layer Status Window (see FIGURE below). Select a line, and the name of the layer on which that line was drawn will appear in the Layer Status Window. If you need to move the line to a different layer, select it, and then select the layer name in the Layer Status Window drop-down menu. Press Ecs.
3. To make the Floating Viewport borders invisible, change to the PAPER side of Paper Space and click on the light bulb located by it on the Layer Status Window.

   FIGURE 26

   
   

Now, Explode the titleblock, if necessary, and use ddedit to edit the text. Remember that you used a .5 scale when placing this views in Solview, so what scale should you list in the titleblock for the drawing?

Finally, print the drawing according to the specifications we have used in the past.

Well you completed another one!

Pat yourself on the back for a good job.

There is only ONE more AutoCAD Tutorial left on dimensioning.

AutoCAD is a registered trademark of AutoDesk, Inc.

AutoCAD Tutorial 5: For Release 2000i was written by:
Dr. Alice Y. Scales, Ed.D.
Graphic Communications Program
Department of Mathematics, Science and Technology Education
NORTH CAROLINA STATE UNIVERSITY

This work is copyrighted and the property of Alice Y. Scales and is not to be copied without permission of the author.

9/21/01

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