A Brief Introduction to Engineering Graphics. Will Durfee & Tim Kowalewski Department of Mechanical Engineering University of Minnesota

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1 A Brief Introduction to Engineering Graphics Will Durfee & Tim Kowalewski Department of Mechanical Engineering University of Minnesota

2 Opening comments Engineering graphics is the method for documenting a design Mechanical engineering students must be familiar with standards of engineering graphics as it is expected in industry This set of slides introduces some of the basics, but is not comprehensive For more, see Engineering Graphics section on the Resources page of the course ME2011 website Any engineering graphics textbook

3 Documenting a part requires SHAPE 2. SIZE 3. MATERIAL 4. TOLERANCE 5. FINISH

4 Engineering drawings Universal language Conventions (drawing grammar) simplify communication; your drawing is at risk if you defy CAD packages make formal drawing easy if you follow the conventions The machinist will laugh at you behind your back if you show up with a non-standard drawing

5 Multiview drawings TOP FRONT RIGHT SIDE 3 rd angle projection

6 Multiview drawings TOP Views MUST align FRONT RIGHT SIDE 3 rd angle projection

7 Multiview drawings TOP Views MUST align FRONT RIGHT SIDE You walk around part to the right (US) 3 rd angle projection Rotate the part to the right (Europe)

8 The Glass Box: Bertoline, Engineering Graphics

9 Alignment & Orientation are preserved Bertoline, Engineering Graphics

10 Six Principle views: obey layout

11 Basic lines (the alphabet of lines ) Object line Hidden line Center line Dimension line

12 HIDDEN LINES

13 CENTER LINES

14 Interpreting Center Lines Enough Info? Enough Info?

15 COULD BE THIS...

16 OR THIS Centerlines imply symmetry, NOT revolution per se

17 HERE, ONLY 2 VIEWS NEEDED (Correct drawing)

18 Find The Mistakes!

19 Find The Mistakes!

20 FRONT

21 FRONT FIND THE MISTAKES!

22 CORRECT DRAWING

23 SECTIONS A A YES NO

24 Working with person sitting next to you copy this and draw the TOP VIEW

25 Working with person sitting next to you copy this and draw the TOP VIEW Possible Geometries

26 Working with person sitting next to you, sketch the Section View

27 OK OK Correct Section Views

28 Wrong Wrong Working with person sitting next to you, Find the MISTAKES

29 Working with person sitting next to you, sketch the Section View

30 REVOLVED SECTION Preferred True section

31 DIMENSIONING 1. SHAPE 2. SIZE 3. MATERIAL 4. TOLERANCE AND FINISH

32 Dimensioning Conventions exist for choice and placement Not too many and not too few Never should measure off drawing with a ruler

33 Under/Over Dimensioning

34 Dimensioning rules: find the mistakes

35 Dimensioning guidelines Don t overdefine or underdefine the object. [MOST IMPORTANT] 2. Dimension to the visible contour or shape of the feature / Don t dimension to hidden lines. 4. Don t dimension to object lines (model edges), use extension lines. 5. Don t overlap a dimension and the model. Place dimensions away from the model s surface. 6. Don t cross extension lines if possible. 7. Group dimensions when possible unless it become difficult to read. 8. Place dimensions on the side of the view were adjacent views exist (for easy referencing). 5

36 Design Detail ½ thick aluminum block Which is more expensive: A or B and why? A B

38 Dimensioning Choices & Design Intent If change width of block to 8, what happens to the hole location? A B

39 Placement conventions extension line dimension small gap about 3/8" f rom part about 1/4" between dimensions a little extended letters about 1/8" tall 6.2 arrow touches dimension line

40 1.00 Lettering: 1 or 2 directions only OK OK NO

41 Extension Lines no break in line no gaps

42 All on one side YES NO

44 Dimensioning Rounds R Place dimension on view that shows the circle Show diameter rather than radius

45 TOLERANCES

46 Tolerances Matter because parts cannot be made to an exact dimension Must specify dimension tolerance so that every part A fits every part B Higher tolerance = higher cost A ½ inch hole made on an ordinary drill press gives you a hole in the range to (+/ ). For higher precision, drill undersize and use a reamer but it will cost you more and take longer to fabricate.

47 ½ inch drill bit: +/ ½ inch reamer: ,

48 LEGOS! You can combine six 8-stud bricks of the same color 102,981,500 different ways 91% of all households with children in Denmark own LEGO products During the period , 110,000,000,000 (110 billion) LEGO elements were molded Bayer Corporation's Polymers Division is the official supplier of ABS plastic to the LEGO group. Exact specifications of the Bayer resin supplied to the LEGO Group are a closely held secret. Dimension tolerance of mold is mm ( inch)! D

49 Representing tolerances ± ±.005

50 Tolerance stack-up What is min and max height of stack?? high stack

51 Tolerance Stacking What s the tolerance (+/-) on dimension x? Ans: +/- 0.3

52 Chain or Baseline Dimensioning? You decide 1.0 ± ± ± ± ± ±.1

53 Chain or Baseline Dimensioning 1.0 ± ± ± ± ± ±.1

54 Holes and shafts 1. Will all shafts fit into all holes? 2. What is maximum clearance? hole shaft

55 ANSI standards for shaft & holes Clearance Interference Transition Shaft smaller than hole for all shafts and holes Shaft larger than hole for all shafts and holes Smallest shaft fits in largest hole Running/Sliding Force/shrink and others Basic hole Basic shaft RC1 (fit together, no play) to RC9 (fit loosely) FN1 (light drive and pressure) to FN5 (high stresses and pressures) Like Locational, etc. Use nominal size of hole as starting point Use nominal size of shaft as starting point

56 Preferred Fit Example

57 Basic Hole Tolerancing Example Drawing shows 1 in. nominal, ANSI RC4 clearance fit Basic Hole means smallest possible hole = nominal, then size shaft for clearance RC4 clearance = [0.0008, ] = [smallest hole-largest shaft, largest hole - smallest shaft]

58 Title block information for tolerance ALL DIMENSIONS IN INCHES HOLD ALL DIMENSIONS TO ± UNLESS SPECIFIED Dimension Tolerance X.X ± 0.1 X.XX ± 0.05 X.XXX ± 0.001

59 Design Detail Bent aluminum sheet, 1/16 thick A or B: Which is more expensive and why? { A B

60 Tolerance vs. Cost 1.00 ±.075 $ 1.00 ±.05 $ ±.005 $$ ± $$$$

61 Manufacturing Tolerances

62 Geometric Dimensioning and Tolerancing (GD&T)

63 Traditional tolerancing is ambiguous ± ±.005??

64 Ambiguity.25 ± ± Square deviation Circular deviation

65 Geometric Dimensioning and Tolerancing.125 +/ Ideal position of hole..25, is marked with box and no +/- notation. Feature control box shows how close hole is to exact; within circular tolerance zone with diameter.01

66 Geometric Dimensioning and Tolerancing.25

GD&T Resources ME2011 website: https://sites.google.com/a/u mn.

67 GD&T Resources ME2011 website: mn.edu/me2011/resources Efunda tutorial: signstandards/gdt

68 Threaded Fasteners What they are and how to indicate on a drawing

69 Threaded Fasteners Holes Threads Threaded fasteners

Holes 19 DRILL 0.75 DEEP or O.166. 75 DEPTH 0.

70 Holes 19 DRILL 0.75 DEEP or O DEPTH 0.75 REF Pix from unless noted

71 Thru holes 19 DRILL THRU or O.166

72 Threads

73 Threaded Fasteners (screws, bolts) Specify diameter, thread, length, head 1/4-20 x 1, RHMS 1/4" DIA 20 THREADS PER INCH 1" LONG ROUND HEAD MACHINE SCREW

74 Common screw thread sizes Unified Thread Standard /4-20 3/8-16 1/2-13 5/8-11 3/4-10 DIA. = (N*.013) (inches)

75 Alternate Thread Callout

76 Head shapes Cap screw Pan Flat Socket head cap screw (SHCS) Round Set screw

77 Driving a fastener Slotted Hex cap Phillips Torx Hex head (Allen head)

78 McMaster-Carr

79 Name the Fastener:

80 Name the Fastener: Socket Head Cap Screw Socket Head Cap Screw with counterbore

82 Socket Head Cap Screw with counterbore Phillips Flat Head Screw with countersink

84 Countersunk, Phillips Flat head Set Screw

85 Convention for screws SCHEMATIC SIMPLIFIED

86 Convention for threaded holes 6-32 THRU TOP FRONT FRONT SECTION

87 Blind threaded holes 1/2 13 x DEEP / THREAD DEPTH DRILL DEPTH

88 Countersunk holes O CSK, x 82 O

89 Counterbored holes 19 DRILL 29 CBORE, 14 DEEP C-BORE DEPTH

91 Other Items for Drawings

92 Leaders & notes FINISH TOP SURFACE SMOOTH NOTE B

93 TITLE BLOCKS Basic Title Name Date Units Optional Company name, sheet number, scale, tolerances, material, finish... Follow your company standards

94 MY PART W. DURFEE 10/2/2014 ALL DIMENSIONS IN INCHES

96 A title block using a company template

97 Production Drawings Many types of drawings can be produced from the CAD database ASSEMBLY SKETCHES SKETCHES SKETCHES MODEL DETAIL DETAIL DETAIL DETAIL DETAIL BOM MANUALS MFG PROCESS

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