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ENGT 122 - CAD I

ENGT 122 - CAD I. Chapter 4 - Drawing Aids. Objectives. • Learn the UNITS command for drawing unit setup. • Learn to input engineering, architectural, and metric units. • Learn to plot a drawing to scale. • Set up layers and assign colors and linetypes to them.

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ENGT 122 - CAD I

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  1. ENGT 122 - CAD I Chapter 4 - Drawing Aids

  2. Objectives • Learn the UNITS command for drawing unit setup. • Learn to input engineering, architectural, and metric units. •Learn to plot a drawing to scale. • Set up layers and assign colors and linetypes to them. • Set up Grid, Snap, and Ortho modes based on the drawing requirements. • Use Object Snaps and understand their applications. • Use Autotracking and Polar Tracking. • Determine local (CELTSCALE), and global (LTSCALE) linetype scaling factor for plotting.

  3. Drawing Units • In AutoCAD, drawings should always be created full size; (1 unit in drawing = 1 unit on actual part) Scaling only come into play when its time to plot to paper. • Before you start a drawing, decide what value each drawing unit will represent based on what you plan to draw and what system of measurement you plan to use. Metric Ex: 1 unit = 1 mm on an actual part. Imperial Ex: 1 unit = 1 inch on an actual part. • The easiest way to set the system of units (Metric or Imperial) is to select the appropriate template: • acad.dwt for English Units • acadiso.dwt for Metric Units

  4. Drawing Units • Important: Be sure to start your drawing with the correct template according to the units you intend to use (acad.dwt for inches, adadiso.dwt for mm). • Once you start, its difficult to switch to a different set of units because of numerous system variables set in the templates. • If you use the wrong template, a last resort is to copy your objects to the correct template. Ex: If you start a drawing in Imperial inches and want to work in Metric millimeters, copy all objects to a metric template. In some cases (i.e. title blocks) you may have to scale some objects by a scale factor.

  5. Drawing Units • The UNITS command controls the format and precision of units in AutoCAD and determines the following; • What format for coordinate input is allowed. • How your coordinates and distance inputs are interpreted by AutoCAD. • How coordinates and distances are displayed. • Command Line • Coordinate Tracker • Inquiry Commands • And that’s all…It does not switch from Metric to English or vice versa, and It does not affect dimension display.

  6. Units Format • Units Command – sets the format for length and angle units in your drawing. • Command:UNITS • Application Menu:Draw Utilities > Units This does NOT switch your units, so don’t use it!

  7. Units Format • Length Type: • Architectural 27’-2 ¼” • Decimal326.25 • Engineering 27’-2.25” • Fractional 326 ¼ • Scientific3.2625E+02 • For Scientific, Decimal, or Fractional, coordinates may be entered in any of these 3 formats but not Architectural or Engineering (inch ” & feet ’ symbols not allowed). • If Architectural or Engineering are selected, coordinates may be entered in any format (the inch symbol ” is optional).

  8. Units Format InputtingArchitectural,Engineering, andFractionalUnits: • The input for these unit types is NOT the same as the format they are displayed by AutoCAD. AutoCADStandardOptionalExample: DisplayInputInput • Architectural 27’-2 ¼” 27’2-1/4” 27’2-1/4 • Engineering 27’-2.25” 27’2.25” 27’2.25 • Fractional326 ¼ 326-1/4 • The inch symbol can be dropped; Numbers without foot symbol are assumed to be inches. 326-1/4 or 326.25

  9. Units Format • Length Precision:- determines number of decimal points or smallest fraction that is displayed.

  10. Units Format • Angle Type: • Decimal Deg. 34.50 • Deg/Min/Sec 34d30’0” • Grads won’t use • Radians 0.6021r • Surveyor N34dE • Regardless of type selected, all formats may be used for input. Requires using the appropriate suffix and symbols, or defaults to selected input method.

  11. Units Format • Angle Precision:- determines number of decimal points for displayed angles.

  12. Exercise 1 • Set your units to a format that allows all unit types shown to be used for input (Architectural or Engineering). • Draw the green objects. Hint: input for 5’-2 ¼” is5’2-1/4” Hint: input for 5’-1.25” is5’1.25 Global Coordinates (0,0)

  13. Scaling CAD Drawings • One more time…CAD drawings are always created full size! That means: Full Scale, Full Size, 1:1, 12”=1’, etc. • However, to put your full size drawing on a sheet of paper requires scaling… As Part of Your Plot Routine! • The method we use for scaling is the easiest that I know. It requires making a title block border and using it as a gage to determine the proper plot scale. • To use this method requires 2 new commands: • DIST • SCALE

  14. Preparation for Plotting to Scale 2 new commands required to plot a CAD drawing to scale. • Distance Command – gives the distance between 2 points. Command:DIST Specify first point: Specify second point: Distance = 3.7640… • Scale Command – changes the size of selected objects by a specified scale factor. Command:SCALE Select objects: pick objects to scale Specify base point: Specify scale factor or [Copy/Reference] <2.0000>: *Note: format and precision of DIST is controlled by UNITS command.

  15. DEMO – DIST & SCALE • Open new drawing. • Create a 10” x 7 ½” border. • Show DIST command. • Show how UNITS affects precision. • Show SCALE command.

  16. Exercise 2 • Open a new drawing using English units (acad.dwt). • The standard BTC border for an A-size (11” x 8.5”) sheet is 10” x 7.5”. Create a rectangle 10” long by 7.5” wide as shown in A. This will represent an A-size border. • Use the DIST command to approximately verify the length & width of your border. • Use the SCALE command to double the size of your rectangle as shown in B. Then verify the approx. dimensions using the DIST command. B 15” A 7 ½” 10” 20”

  17. Scaling CAD Drawings • One more time…CAD drawings are always created full size! That means: Full Scale, Full Size, 1:1, 12”=1’, etc. • However, to put your full size drawing on a sheet of paper requires scaling… Within the Plot Routine! • General procedure for scaling a plot is the same regardless of drawing type, however there are slight differences for each of the following; • Machine drawings in English Units • Machine drawings in Metric Units • Architectural drawings

  18. Scaling – English Units - Machine Method for Scaling:- The following method is the easiest I know. Step 1: • Start a new drawing using English units (acad.dwt). • Create your drawing Full Size using as many views as required.

  19. Scaling – English Units - Machine Step 2: Determine sheet size to use. Varies according to;  Assignment instructions Physical size of part  Company standards  Amount of detail on part  Paper/plotter availability  Etc. U.S. Standard (in) International (mm) LetterSheetsizesize A 8.5 x 11 B 11 x 17 C 17 x 22 D 22 x 34 E 34 x 44 LetterSheet sizesize A4 210 x 297 A3 297 x 420 A2 420 x 594 A1 594 x 841 A0 841 x 1189 BTC uses U.S. Standard lettered sheet sizes for all plots including metric

  20. Scaling – English Units - Machine Step 3: In your drawing, generate a rectangular Border with dimensions equal to that of the Standard BTC title block border. • BTC uses ½” border margins, so Border dimensions will be 1” smaller than sheet size. Rectangle Border Dim:

  21. 12 15 Scaling – English Units - Machine Step 4: Estimate the Plot Scale. • All plots must conform to a standard scale. • The following are some standard plot scales for an English (inch) machine drawing – remember this from drafting? • Use DIST to estimate the length & width of your drawing. Then select a scale you think will fit the objects within the border.

  22. Scaling – English Units - Machine Step 4 Continued: Estimate the Plot Scale. • If you forget the standard plot scales you can refer to the standard scales in the AutoCAD plot dialog box. • Choose a plot scale that would reduce/enlarge your model so it fits within the full size border rectangle. Or start by choosing a plot scale closest to 1:1, either1:2 to reduce the drawing or 2:1 to enlarge the drawing.

  23. Scaling – English Units - Machine Step 5: Determine the Plot Scale Factor . • Based on the Plot Scale you selected, calculate the Plot Scale Factor – remember this from drafting? • Plot Scale written A:B • Plot Scale Factor is A / B Example: Plot Scale is 1:2 Plot Scale Factor = 0.5 Example: Plot Scale is 4:1 Plot Scale Factor = 4

  24. Scaling – English Units - Machine Step 6: Scale the border rectangle. • Use the SCALE command to scale the border rectangle by the inverse of your Plot ScaleFactor. • Use the MOVE command to center the border around the drawing objects and see if sizing is acceptable. • The drawing objects should fill the border but allow a margin (i.e. at least ½” gap between border and objects on all sides). • If border sizing is correct you are ready to plot, skip to Step 9. Otherwise continue. Original Border Plot Scale = 1:2 PSF = 1/2 Scaled Border 2X Original

  25. Scaling – English Units - Machine Step 7: If border sizing is unacceptable, the Plot Scale Factor must be recalculated: • Choose the next closest Plot Scale A:B = 1:4 or A:B = 4:1 • If the border must be increased: • Choose plot scale A:B = 1:4 • The Plot Scale Factor = A / B = 1/4 • If the border must be reduced: • Choose plot scale A:B = 4:1 • The Plot Scale Factor = A / B = 4

  26. Scaling – English Units - Machine Step 8: Re-Scale the border using the inverse of the newPlot Scale Factor. Then test to see if sizing is acceptable. • Before re-scaling, the border must be returned to its original size: • Use SCALE command or • Redraw original border rectangle • The drawing objects should fill the border but allow a margin (i.e. at least ½” gap between border and objects on all sides). • If border sizing is correct you are ready to plot, continue to Step 9. Otherwise, return to Step 7 and repeat the procedure again using the next closest plot scale to 1:1.

  27. Scaling – English Units - Machine Step 9: Plot the drawing. • The scaled border should be centered about your drawing. • Issue the PLOT command • Select a printer and the sheet size determined earlier. • DONOT click OK until results are verified with Preview button. • Retrieve your plot and Write the Plot Scale on the Sheet!!!

  28. Scaling – English Units - Machine Step 9: Plot the drawing.

  29. Scaling CAD Drawings Essence of Scaling Procedure: • In essence, we are using the the border as a ScalingGage to determine which standard plot scale makes our full size drawing fit onto the selected sheet size. • The original border size is designed to fit the physical paper sheet. • In the drawing, we scale the border with the SCALE command to fit the full size drawing using the inverse of a standard Plot Scale Factor. • If the border fits, then the drawing is plotted at the selected Plot Scale and the border is scaled back down by the Plot Scale Factor in the plot routine, returning to its original size.

  30. Scaling CAD Drawings Essence of Scaling Procedure: Original border (10x7½) Designed to fit 11x8½ sheet Scale border in drawing to fit full size objects  Use SCALE command at 1/Plot Scale Factor Re-Scale border & object by plotting  Use PLOT command at Plot Scale Factor -returns border to original size

  31. End Lecture 10

  32. DEMO – English Plot Scale • Load file English Scale Demo.dwg. • Show use of DIST command. • Show methods for plotting to scale.

  33. Exercise 3A: Create and plot the following drawing to scale (see steps 1-9). Step 1:Make the drawing using English units. Step 2: Assume sheet will be A-size. Step 3:Draw a border rectangle. Step 4: Estimate the Plot Scale. Step 5&6: Determine the Plot Scale Factor & scale the border. Step 7&8: If necessary, repeatedly recalculate Plot Scale Factor & re-scale border. Step 9: Plot your drawing to the appropriate scale and Write the Scale on Your Plot! Step 10: Verify your plot size by measuring with a ruler.

  34. Scaling CAD Drawings • General procedure for scaling a plot is the same regardless of drawing type, however there are slight differences for each of the following; • Machine drawings in English Units • Machine drawings in Metric Units • Architectural drawings • Next we look at the difference for aMachine drawing in Metric Units.

  35. Scaling – Metric Units Step 1: • Start a new drawing using Metric units (acadiso.dwt). • Create your drawing Full Size.

  36. Scaling – Metric Units Step 2: Determine sheet size to use. Varies according to;  Assignment instructions Physical size of part  Company standards  Amount of detail on part  Paper/plotter availability  Etc. U.S. Standard (in) International (mm) LetterSheetsizesize A 8.5 x 11 B 11 x 17 C 17 x 22 D 22 x 34 E 34 x 44 LetterSheet sizesize A4 210 x 297 A3 297 x 420 A2 420 x 594 A1 594 x 841 A0 841 x 1189 BTC uses U.S. Standard lettered sheet sizes for all plots including metric.

  37. Scaling – Metric Units Step 3: In your drawing, generate a rectangular Border with dimensions equal to that of the Standard BTC title block border. • Since you are working in mm, the border size must be converted to mm (1 inch = 25.4 mm). • BTC uses ½” border margins, so Border dimensions will be 1” smaller than sheet size But in mm! Rectangle Border Dim:

  38. Scaling – Metric Units Step 4: Estimate the Plot Scalesame as for English drawing. Step 5: Determine the Plot Scale Factorsame as for English drawing. Step 6: Scale the border rectangle by the inverse of the Plot Scale Factorsame as for English drawing. Step 7: If border scaling is incorrect, the Plot Scale Factor must be recalculated same as for English drawing. Step 8: Re-Scale the border using the inverse of the newPlot Scale Factor. Then test to see if sizing is acceptable. same as for English drawing.

  39. Scaling – Metric Units Step 9: Plot the drawing same as for an English drawing except for the following: • The sheet size will default to a metric sheet, but select a U.S. standard Letter sheet size (i.e. A-size: Letter or B-size: 11 x 17). • BEFORE setting the plot scale, use the down arrow to select mm rather than inches. Then select the plot scale (i.e. 1:4). • The dialog box should then show 1 mm = 4 units which is correct! First: Select mm units Then: Set plot scale

  40. DEMO – Metric Plot Scale • Load file Metric Scale Demo.dwg. • Show methods for plotting to scale.

  41. Exercise 3B: Create and plot the following drawing to scale (see steps 1-9). Step 1:Make the drawing using Metric units. Step 2: Assume sheet will be A-size. Step 3:Draw a border rectangle. Step 4: Estimate the Plot Scale. Step 5&6: Determine the Plot Scale Factor & scale the border. Step 7&8: If necessary, repeatedly recalculate Plot Scale Factor & re-scale border. Step 9: Plot your drawing to the appropriate scale and Write the Scale on Your Plot! Step 10: Verify your plot size by measuring with a ruler.

  42. End Lecture 11

  43. Scaling CAD Drawings • General procedure for scaling a plot is the same regardless of drawing type, however there are slight differences for each of the following; • Machine drawings in English Units • Machine drawings in Metric Units • Architectural drawings • Next we look at the difference for anArchitectural Drawing.

  44. Scaling – Architectural Units Step 1: • Start new drawing using English units (acad.dwt). • Change your Units to Architectural format with 1/16” precision. • Create your drawing Full Size.

  45. Scaling – Architectural Units Step 2: Determine sheet size to use. • Same as for English Machine drawing. Step 3: In your drawing, generate a rectangular Border with dimensions equal to that of the Standard BTC title block border. • Same as for English Machine drawing.

  46. 21’-0” 31’-0” Scaling – Architectural Units Step 4: Estimate the Plot Scale. • Architectural drawings must conform to a standard Architectural scale. • Below are some standard Architectural plot scales. • Use DIST to measure the length & width of your drawing. Then select a scale you think will fit the objects within the border.

  47. Scaling – Architectural Units Step 4 Continued: Estimate the Plot Scale. • If you forget the standard plot scales you can refer to the standard scales in the AutoCAD plot dialog box. • Guesstimate a plot scale that would reduce your model to fit within the full size border rectangle.

  48. Scaling – Architectural Units Step 5: Determine the Plot Scale Factor. • Based on the Plot Scale you selected, calculate the Plot Scale Factor. • Plot Scale written A:B • Plot Scale Factor is A / B • Example: • Plot Scale is 1/64” = 1’-0” • Plot Scale Factor = (1/64) / 12 • Plot Scale Factor = 1 / 768 • Example: • Plot Scale is ¼” = 1’-0” • Plot Scale Factor = (¼)/12 • Plot Scale Factor =1/48

  49. Scaling – Architectural Units Step 6: Scale the border rectangle by the inverse of the Plot Scale Factorsame as for English Machine drawing. Step 7: If border scaling is incorrect, the Plot Scale Factor must be recalculated same as for English Machine drawing. Step 8: Re-Scale the border using the inverse of the newPlot Scale Factor. Then test to see if sizing is acceptable same as for English Machine drawing. Step 9: Plot the drawing same as for English Machine drawing except choose the appropriate Architectural Scale in the form; A” = 1’-0”

  50. DEMO – Architectural Plot Scale • Load file Arch Scale Demo.dwg. • Show setting UNITS. • Show methods for plotting to scale.

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