DRAWING CIRCLES KNOWLEDGE AND UNDERSTANDING After completing this module, you will know and understand the theory regarding: different methods of creating circles in CAD graphics. APPLICATION OF KNOWLEDGE After completing this module, you will be able to: draw circles in CAD graphics using appropriate methods. ASSESSMENT After completion of this module, you will be assessed on: your knowledge and understanding of different methods of creating circles in CAD graphics your ability to create circles in CAD graphics using appropriate methods your saved and printed drawing (Drawing Tutorial 10L) your updated portfolio. Marks will be given for neatness, completeness, correctness and presentation. (Refer to the chapter on portfolios for further details). Chapter 19 - Drawing Circles 123
DRAWING CIRCLES There is more to drawing circles than just providing a centre point and a radius. Circles that are created must be placed in relation to existing objects. You must learn to apply the various means of drawing circles within given parameters. center, diameter Once you have specified the centre point, you will be prompted to enter a diameter. You must then enter a distance or drag the circle to the desired size. The value used for the diameter is divided in half, creating a default radius value. A USING AUTOCAD The CIRCLE command The CIRCLE command can be activated by typing circle on the command line or by clicking the circle icon on the Draw toolbar. The command from the toolbar and the command line operate the same. You are presented with a few options and then guided through the process. Read the prompts very carefully, take your time to learn the many variations and you will reap the fruits later. Alternatively you can use the Draw menu to activate the CIRCLE command. You will then be presented with the various options on a drop-down menu. The menu provides you with the following options: two points Select the first point by entering coordinates, or by choosing a point in the drawing window. Select the second endpoint by dragging the circle or by entering coordinates on the command line. The distance between the two points you give will be the diameter of the circle. three points Enter the points one at a time. To establish the point locations, enter the coordinates or select the points in the display window. A C B center, radius (This is also the option given to you when you click on the Circle icon.) AutoCAD prompts you by default to enter a centre point. (At this point you are also given the option to use the two point, three point or tangent, tangent, radius options. Just type 2P, 3P or TTR on the command line and enter it.) tangent, tangent, radius Select the first line, circle, or arc. It will automatically provide you with a tangent snap. Snap to it, then to the second line, circle, or arc. Then enter a value for the radius. Once you have specified the centre point, you will be prompted to enter a radius. (At this point you can switch to entering a diameter by typing a d and entering it.) You can either enter a value for the radius or drag the circle to the desired size. The radius you specified now becomes the new default for future CIRCLE commands. A B tangent, tangent, tangent This option is only available from the menu. You draw the circle by using tangential snaps to three selected objects. The circle will fit itself to the three snap points. 124 CAD for EG&D - Grade 10
USING ALLYCAD AllyCAD does not use a single command with many variations the way that AutoCAD does. Rather, it provides many different drawing methods that can each be accessed with a single click. Using commands from the Geometry menu or toolbar A Geometry line is a type of construction line that allows you to position objects prior to actually drawing them. Geometry objects display in a faint dotted line. Geometry circles must be traced over to create circles. The following Geometry circle draw commands are available: Circle- (or Left-click the icon) - Draw Geometry circles with the centre and a point on the diameter Circle Diameter (or Right-click the icon) - Draw up to five concentric Geometry circles with the centre and the diameters Circle 3 Point - Draw a Geometry circle through three points Circle Tan LPtRad (or Left-click the icon)- Draw a Geometry circle tangent to a line and through one point on the radius Circle Tan CPtRad (or Right-click the icon)- Draw a Geometry circle tangent to a circle and through one point on the radius Circle Tan LL (or Left-click the icon)- Draw a Geometry circle tangent to two lines Circle Tan 3L (or Right-click the icon) - Draw a Geometry circle tangent to three lines Circle Tan CC (or Left-click the icon)- Draw a Geometry circle tangent to two circles Circle Tan LC (or Right-click the icon)- Draw a Geometry circle tangent to line and a circle Using commands from the Draw menu or toolbar Using the Draw menu or Draw toolbar allows you to draw circles or to create circles from Geometry circles. The following circle draw commands are available: Circle (or Left-click the icon) - Draw a circle with the centre point and a point on the diameter Circle Diameter (or Right-click the icon) - Draw up to five concentric circles with the centre and the diameters Circle2 Point (or Right-click the icon) - Draw a circle by two points on the diameter Fill Geometry - Draw entities by tracing over Geometry lines and circles Fill Geometry Circle (or Left-click the icon) - Draw a circle by tracing over a Geometry circle Chapter 19 - Drawing Circles 125
Drawing Tutorial 10L: Drawing Circles Templates TIME ALLOCATION: 1 HOUR 1. Start a new drawing using the template you created in 10J. 2. Name it and save it in the correct location. 3. Update your title block. 4. Choose an appropriate scale. 5. Draw the templates as shown on the next page by using the appropriate techniques for drawing circles. (Choose from: Center-radius, Center-diameter, 2-point, 3-point, Tangent-tangent-radius, and Tangent-tangent-tangent.) 6. Make full use of all your layers. 7. Make sure that you save regularly. 8. Show all dimensions and annotations. 9. Adhere to the SANS regarding mechanical drawing. 10. Print and save the final drawing. 11. Update your portfolio. 126 CAD for EG&D - Grade 10
Drawing Tutorial 10L Drawing Circles Templates Name of Learner Name of FET Institution Scale Date Chapter 19 - Drawing Circles 127
NOTES 128 CAD for EG&D - Grade 10