Computarized Engineering Graphics ENGR 2220

1. Computarized Engineering Graphics ENGR 2220 Department of Mechanical Engineering Inter American University of Puerto Rico Bayamon Campus Dr. Omar E. Meza Castillo omeza@bayamon.inter.edu http://www.bc.inter.edu/facultad/omeza

2. Course Objectives • Upon successful completion of the course, the student will be able to: • Identify types of software and hardware used for computer-aided design. • Clearly represent and control mental images. • Graphically represent technical designs, using accepted standard practices. • Use plane and solid geometric forms to create and communicate design solutions. • Describe the engineering design process. • Understand concepts and applications of 3-D modeling. • Understand the theory, techniques and standards of multiviews. • Apply the concept of cutting planes to create section views and sectioned 3-D .CAD models. • Apply the standard dimensioning practicing for mechanical drawings. • Apply tolerances to dimensions

3. Tentative Lecture Schedule

4. Reference • Bethune, James. Engineering Graphics with AutoCAD 2009, Prentice Hall, 2009. • Earle James. Engineering Design Graphics, 11th Ed., Pearson Prentice Hall. 2005.

5. "Lo peor es educar por métodos basados en el temor, la fuerza, la autoridad, porque se destruye la sinceridad y la confianza, y sólo se consigue una falsa sumisión” Einstein Albert Chapter 2: Instrument for Engineering Graphics Technical Drawing Tools

6. Scales (scale rulers) are used to measure distances on technical drawings. • There are many different scales. The most important ones are Metric, Civil and Architect’s. We also have Mechanical Engineering or Combination that we don’t review in this course. • An architect’s scale is used to create drawings of structures, such as a building or a factory floor layout. • The civil engineer’s scale is a decimal scale divided into multiple units of 10 and is called a fully divided scale.

7. Metric Scales Civil Scales Architect’s Scales

8. Metric scale: • The international organization that established the metric standard is the International Standards Organization (ISO). The system is called the International System of Units or SystemeInternationale, abbreviated SI. The metric scale is used to create scaled technical drawings using SI units.

9. A standard ruler measurement is usually about a foot long, or in metric terms, about 30 centimeters. You will find the ruler marked with lines which are designated with numbers from 1 to 30 and between each set of numbers, there are smaller lines which indicate the number of millimeters. Ten millimeters or mm equal 1 centimeter or cm, hundred cm equals one meter and so on. To measure the length between two points on a paper or other medium, place the ruler with the first centimeter line (which can be tagged as zero) on the first point. Mark the number at which the second dot on the paper corresponds to the centimeter reading, on the ruler. For example, with one point placed against the zero mark and the second point shows a reading of 3. In this case, the distance in centimeters between the two points is 3cm. If the point is actually placed at a point beyond 3 but well within the line depicting 4, count the smaller lines which show the millimeter scale and count the number of lines at which the point rests, say at the 5th small line, in which case the distance between the two points is 3.5cm or 35mm. 3.5 cm=35 mm Goes to 30 cm 3 cm=30 mm

10. The metric scale ruler has 3 sides and there are 6 different scales on this scale. The number on each corner refers to the scale on the drawing. For example 1:125 on this scale means: every millimeter on the drawing is equal to 125 millimeters in real life. We write this scale as 1 mm=125 mm or Scale = 1/125

11. Metric scales: There are 6 scales to use.

12. How long is this match? Every 10 divisions on this scale are 10 mm (as shown). The match is longer than 20 mm. You have 6 divisions after 20, which are equal to 6 mm. So it is 26 mm long! What is the scale? Scale is 1 or 1 mm=1 mm

13. How long is this screw? Every 10 divisions on this scale are 200 mm (as shown). So every division is 20 mm. The screw is longer than 400 mm. You have 2 divisions after 400 mm which are equal to 2x20=40 mm. So it is 440 mm long! What is the scale? 1/20 or 1 mm=20 mm

14. How long is this knife? Every division on this scale is 5 mm (as shown in the corner). So every 20 division are equal to 100 mm (shown for the first number). The knife is longer than 300 mm. You have 7 divisions after 300 mm which are equal to 7x5=35 mm. So it is 335 mm long! What is the scale? 1/5 or 1 mm=5 mm

15. Civil scale: • The civil engineer's scale is a decimal scale divided into multiple units of 10 and is called a fully divided scale.

16. 10’ Each Scale represents any quantifiable item in multiples of ten. 10’ 10’ 10’ 10’ 10’

17. Civil scales: There are 6 scales to use. Every inch on the drawing is equal to 60 feet in real life!

18. Regardless of the number you see on the corner (here 10), every division of the scale is always 1 foot in real life (for this course we consider the most common case). Always count the number of divisions and that is the measurement in feet. Below, you see 17 divisions, which are equal to 17 feet and 26 divisions which are equal to 26 feet! This is actually one inch, which is equal to 50 feet in real life! So a civil engineer can use this scale to draw bridges and other long structures.

19. How long is this bridge in real life?

20. The bridge is longer than 120 feet. Remember that each number should be multiplied by 10 to show the actual number in feet. It is 3 divisions more or 3 feet. So the bridge is 123 feet long. What is the scale? 1 " =50’ 20 feet 60 feet 120 feet 40 feet

21. There are other possible scales for each scale ruler that we choose, but for this course we focus on the most common case.

22. How long is the width of this small cottage in real life?

23. The width of the cottage is longer than 20 feet. Remember that each number should be multiplied by 10 to show the actual number in feet. It is 4 divisions more or 4 feet. So the bridge is 24 feet long. What is the scale? 1 " =20’ 10 feet 20 feet 30 feet

24. Architect’s scale: • Architect's scales may be flat, with 4 scales, or have a symmetric 3-lobed cross-section, with 11 scales. • So remember that for metric or civil scales, we have a total of 6 scales, whereas for architect’s scale, there are 11 available scales.

25. Find the 11 scales on this Architect’s scale!

26. Architect’s scales: There are 11 scales to use.

27. Architect’s scales: Divide the number on the corner by 12 to get the actual scale.

28. Determine the scale of your plans. It will be labeled on the plans and should be found in the bottom corner. Turn the ruler to the corresponding scale factor. For instance, if the plans read ¼ inch equals one foot, you will use the ¼ inch scale on the ruler. Measure the desired line starting from zero on the correct scale. In this case, you would need to use the ¼ inch scale. The measurement you calculate equals how many feet the line actually is at full scale dimensions.

29. Full size or scale of 1: This is similar to the normal school box ruler. Every inch has 16 divisions. So each division is 1/16 ". Count the number of divisions and divide by 16. So 8 divisions are equal to 8/16 or 1/2 inches. Watch this video

30. Read this measurement. This is one inch and 9/16 inches. You should write it as 1 9/16 ". Watch this video

31. For the 10 remaining scales, we have a region on the left or a small scale which always represents 1 foot. How long is this line? It is more than 3 feet and less than 3.5 feet. But how do you find out how much it’s length exactly is? Small scale

32. Align the right side of the line with number 3 and check the small section on the left (step 2). You read 4 larger marks in that small section (remember that we have 12 marks in that section representing 12 inches or 1 foot). So the length of the line is 3 feet and 4 inches. You write it as 3’-4 ". Each foot on the scale has 24 divisions. So every 2 divisions is one inch. Every 2 divisions are equal to 1 larger mark that we considered! 1 foot 4 2 1 3

33. Read this measurement. This is equal to 3 feet and something! The smaller scale reads something between 3” and 6” (closer to 3”). The smaller section shows 5/16’ (5/16’)x12 " =15/4=3 ¾ inch. You can find this by saying that each division on the small scale is in fact ¾ " . So the length is 3'-3 ¾" ? 6 3

34. 1" =1" or full size Test yourself! Find all the scales? 3/32 " =1’ or 1/128 3/16 " =1’ or 1/64 3/4 " =1’ or 1/16 3/8 " =1’ or 1/32 3 " =1’ or 1/4 1 ½ " =1’ or 1/8 1/2 " =1’ or 1/24 1 " =1’ or 1/12 1/8 " =1’ or 1/96 1/4 " =1’ or 1/48

35. Read these two measurements. A=? B=? The 3/32 scale numbers are circled by red. The other numbers belong to the scale 3/16 on the left. Length A is 3 feet more than 100 feet. So it is 103’-0”. Length B is longer than A. It is A plus half way in the smaller scale. The small scale is 1 foot or 12 inches and half of it is 6 inches. So B= 103’- 6”

36. Read these measurements. 12 A=? B=? C=? D=? 1 inch= 8 divisions This scale is 3 " =1’ (or ¼ of scale). The section that you see is the small scale section which is 1 foot or 12 inches. So all the measurements here are less than 12 inches! This one foot has 12 divisions. Check the red circles. Remember that each inch has 8 divisions. So each division is 1/8 ".

37. So A=1/8 " , B=1 ½ " , C=8 " and D= 9 ½ " .

38. Homework2  WebPage Due, Thursday, February 02, 2012 Omar E. Meza Castillo Ph.D.