Tutorial Exercise Pattern1. DWG
Purpose this tutorial is designed to use geometric commands to construct a one-view drawing of Pattern1 such as the one in Figure-3-239. Refer to the following for special system setting and suggested command sequences.
System Settings
Begin a new drawing called “Pattern1”. Use the UNITS command to change the number of decimal places past the zero from four to two. Keep the remaining default unit values. Using the LIMITS command, keep 0,0 for the lower left corner and change the upper right corner from 12,9 to 21.00,16.00.
Layers
Create the following layer with the format:
Name Color Linetype Object White Continuous Center Yellow Center
Dim Yellow Continuous
Suggest Commands
Begin constructing this object by first laying out four points, which will be used as centers for circles. Use the CIRCLE-TTR command to construct tangent Arcs to the circles already drawn.
Use the TRIM command to clean up and partially delete circles to obtain the outline of the pattern. Then add the 2.00 diameter holes followed by the center markers using the DIMCENTER command.
Whenever possible, substitute the appropriate command alias in place of the full AutoCAD command in each tutorial step. For example, use “Co” for the COPY command, “L” for the LINE command, and so on. The complete listing of all command aliases is located in Unit 01 on pages 1-9 and 1-10.
Step #1
Use the PDMODE command to change the point style to a value of 2. This will form a “plus sign” when using the POINT command. An alternate method of selecting different points is through the Point Style dialog box which can be found in the pull-down menu under the headings of Format > Point Style.
Locate one point at absolute coordinate 7.50, 7.50. Then use the COPY command and the dimensions in Figure 3-240 as a guide for duplicating the remaining points.
Command: PDMODE
New value for Pdmode <0>: 2 Command: POINT
Point: 7.50,7.50 (Locates the point at “A”)
Figure 3-239
Command: COPY
Select objects: L (This should select the point) Select objects: (Press enter to continue)
<Base point or displacement>/multiple: M Base point: Nod of (select the point at “A”)
Second point of displacement: @2.25, -3.00 (Locates point “B”) Second point of displacement: @4.50,1.00 (Locates point “C”) Second point of displacement: @5.25,3.50 (Locates point “D”) Second point of displacement: (Press to exit this command) Step #2
Use the CIRCLE command to place four circles of different sizes from points located at “A,”
“B,” “C,” and “D” as shown in Figure 3-241. When you have completed drawing the four circles, use the ERASE command to erase points “A,” “B,” “C,” and “D,”
Command: CIRCLE
3P/2P/TTR/<Center point>: Nod of (select the point at “A”) Diameter/<Radius>: 2.50
Command: CIRCLE
3P/2P/TTR/<Center point>: Nod of (select the point at “B”) Diameter/<Radius>: 2.00
Command: CIRCLE
3P/2P/TTR/<Center point>: Nod of (select the point at “C”) Diameter/<Radius>: 1.50
Command: CIRCLE
3P/2P/TTR/<Center point>: Nod of (select the point at “D”) Diameter/<Radius>: 1.75
Command: CIRCLE
Select objects: (Pick the four point labeled “A”, “B”, “C, and “D”) Select objects: (Press to execute this command)
Step #3
Use the CIRCLE-TTR command to construct a 4.00 radius circle tangent to the two dashed circles in Figure 3-242. Then use TRIM command to trim away part of circle “C”.
Command: CIRCLE
3P/2P/TTR/<Center point>: TTR
Enter Tangent spec: (select the dashed circle at “A”)
Enter second Tangent spec: (Select the dashed circle at “B”) Radius: 4.00
Command: TRIM Select cutting edges…
Select cutting edges: (Projmode = UCS, Edgemode = No extend) Select objects: (Select the two dashed circles shown in Figure 3-242) Select object: (Press enter to continue)
<Select object to trim>/Project/Edge/Undo: (Select the large circle at “C”)
<Select object to trim>/Project/ Edge/Undo: (Press Enter to exit this command) A built-in undo is provided if a mistake is made during the trimming process.
Step #4
Use the CIRCLE-TTR command to construct a 6.00 radius circle tangent to the two dashed circles in Figure 3-243. Then use TRIM command to trim away part of circle “C”.
Command: CIRCLE
3P/2P/TTR/<Center point>: TTR
Enter Tangent spec: (select the dashed circle at “A”)
Enter second Tangent spec: (Select the dashed circle at “B”) Radius: 6.00
Command: TRIM Select cutting edges…
Select cutting edges: (Projmode = UCS, Edgemode = No extend) Select objects: (Select the two dashed circles at the right)
Select object: (Press enter to continue)
<Select object to trim>/Project/Edge/Undo: (Select the large circle at “C”)
<Select object to trim>/Project/ Edge/Undo: (Press enter to exit this command)
Step #5
Use the CIRCLE-TTR command to construct a 6.00 radius circle tangent to the two dashed circles at the right. Then use TRIM command to trim away part of circle “C”. See Figure 3-244 Command: CIRCLE
3P/2P/TTR/<Center point>: TTR
Enter Tangent spec: (select the dashed circle at “A”)
Enter second Tangent spec: (Select the dashed circle at “B”) Radius: 6.00
Command: TRIM Select cutting edges…
Select cutting edges: (Projmode = UCS, Edgemode = No extend) Select objects: (Select the two dashed circles shown in Figure 3-244) Select object: (Press to continue)
<Select object to trim>/Project/Edge/Undo: (Select the large circle at “C”)
<Select object to trim>/Project/ Edge/Undo: (Press enter to exit this command)
Step #6
Use the CIRCLE-TTR command to construct a 0.75 radius circle tangent to the two dashed circles in Figure 3-245.Then use TRIM command to trim away part of circle “C”.
Command: CIRCLE
3P/2P/TTR/<Center point>: TTR
Enter Tangent spec: (select the dashed circle at “A”) Enter second Tangent spec: (Select the dashed circle “B”) Radius: 0.75
Command: TRIM
Select cutting edges…
Select cutting edges: (Projmode = UCS, Edgemode = No extend) Select objects: (Select the two dashed circles shown in figure 3-245) Select object: (Press enter to continue)
<Select object to trim>/Project/Edge/Undo: (Select the large circle at “C”)
<Select object to trim>/Project/ Edge/Undo: (Press to exit this command)
Step #7
Use the TRIM command, select all dashed arcs in Figure 3-246 as cutting edges, and trim away the circular segments to form the outline of the pattern1 drawing.
Command: TRIM Select cutting edges…
Select cutting edges: (Projmode = UCS, Edgemode = No extend) Select objects: (Select the four dashed arcs shown in figure 3-246) Select object: (Press enter to continue)
<Select object to trim>/Project/Edge/Undo: (Select the circle at “A”)
<Select object to trim>/Project/Edge/Undo: (Select the circle “B”)
<Select object to trim>/Project/Edge/Undo: (Select the circle “C”)
<Select object to trim>/Project/Edge/Undo: (Select the circle “D”)
<Select object to trim>/Project/Edge/Undo: (Press to exit this command)
Step #8
Your drawing should be similar to the in Figure 3-247.
Step #9
Use the CIRCLE command to place a circle of 2.00 unit diameter at the center of are “A”. Then use the COPY command to duplicate the circle at the center of arcs “B” and “C”. See Figure 3-248.
Command: CIRCLE
3P/2P/TTR/<Center point>: Cen of (select the arc at “A”) Diameter/<Radius>: D
Diameter: 2.00 Command: COPY Select objects: Last
Select objects: (Press to continue)
<Base point or displacement>/Multiple: M Base point: Cen of (Select the arc at “A”) Second point of displacement: Cen of (Select the arc at “B”)
Second point of displacement: Cen of (Select the arc at “C”) Second point of displacement: (Press to exit this command)
Step #10
Use the LAYER command to set the new current layer to center. Change the variable Dimcen from a value of 0.09 to 0.12. This will place the center marker identifying the centers of circles and arcs when the DIMCENTER command is used. Figure 3-249.
Command LAYER
?/Make/Set/New/ON/OFF/Color/Ltype/Freeze/Thaw/Lock/Unlock: Set New current layer <0>: Center
?/Make/Set/New/ ON/OFF/Color/Ltype/Freeze/Thaw/Lock/Unlock: (Press to exit this command) Command: DIMCEN
Current value<0.09> New value:-0.12 Command: DIMCENTER
Select arc or circle: (select the arc at “A”) Command: DIMCENTER
Select arc or circle: (select the arc at “B”) Command: DIMCENTER
Select arc or circle: (select the arc at “A”) Command: DIMCENTER
Select arc or circle: (select the arc at “D”)
Step #11
Dimensions may be added. Place them on the layer “Dim” as shown as Figure 3-250