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A Brief Introduction to Engineering Graphics

A Brief Introduction to Engineering Graphics. Engineering graphics is the method for documenting a design. Documenting a part requires. 1. SHAPE 2. SIZE 3. MATERIAL 4. TOLERANCE 5. FINISH. Engineering drawings. Universal language

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A Brief Introduction to Engineering Graphics

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  1. A Brief Introduction toEngineering Graphics Engineering graphics is the method for documenting a design

  2. Documenting a part requires... 1. SHAPE 2. SIZE 3. MATERIAL 4. TOLERANCE 5. FINISH

  3. Engineering drawings • Universal language • Conventions (drawing grammar) simplify communication; your drawing is at risk if you defy • CAD packages make formal drawing easy…but you must still follow the conventions

  4. Top Right Front Multiview drawings TOP RIGHT SIDE FRONT “3rd angle projection”

  5. The Glass Box:

  6. Alignment & Orientation are preserved…

  7. Six Principle views

  8. Basic lines Object line Hidden line Center line Dimension line

  9. HIDDEN LINES

  10. CENTER LINES

  11. Interpreting Center Lines Working with person sitting next to you, sketch the top view and side view

  12. CAN BE THIS...

  13. OR THIS

  14. HERE, ONLY 2 VIEWS NEEDED

  15. Working with person sitting next to you, sketch the bottom view

  16. FRONT

  17. FRONT FIND THE MISTAKES!

  18. CORRECT DRAWING

  19. A A SECTION YES NO

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

  21. REVOLVED SECTION Preferred “True” section

  22. DIMENSIONING 1. SHAPE2. SIZE3. MATERIAL4. TOLERANCE AND FINISH

  23. 3 5 Dimensioning 5 3

  24. 5 5 3 3 3 2 5 5 Under/Over Dimensioning

  25. 5 5 3 3 2 3 5 5 Dimensioning rules: …find the mistakes.

  26. 5 5 3 3 2 3 5 5 Dimensioning rules:…more like guidelines. 1. 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).

  27. 6.0 6.0 Design Detail½” thick aluminum block Which is more expensive: A or B and why? A B 4.0 4.1

  28. www.mcmaster.com

  29. 6 6 2 4 2 2 6 6 Dimensioning Choices& Design Intent B A

  30. Placement conventions

  31. Lettering: 1 or 2 directions only OK OK NO

  32. Extension Lines

  33. All on one side YES NO

  34. f 0.75 R 0.125 f 0.25 Dimensioning Rounds Place dimension on view that shows the circle Show diameter rather than radius

  35. NOTE B Leaders & notes

  36. TOLERANCES www.efunda.com/processes/machining/drill.cfm www.efunda.com/processes/machining/drill_press.cfm

  37. ½ inch drill bit: +/- .0040 ½ inch reamer: +.0003, -.0000

  38. D 5 8 1.7 9.6 ABS plastic 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 1949-1990, 110,000,000,000 (110 billion) LEGO elements were molded • Dimension tolerance of mold: 0.005 mm (0.0002 inch)!

  39. Representing tolerances

  40. Tolerance stack-up What is min and max height of stack? 14.7515.25 ? 3.0 ± .05 5 high stack

  41. Tolerance Stacking Issues? ?

  42. Tolerance Stacking

  43. Chain or Baseline Dimensioning

  44. .626 .623 .625 .622 Holes and shafts • Will all shafts fit into all holes? • What is maximum clearance? hole shaft .623 .622 .626 .625

  45. ANSI standards for shaft & holes

  46. Preferred Fit Example…

  47. + .0012 - .0008 1.0000 1.0000 - .0000 - .0016 “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, 0.0028]

  48. Title block information for tolerance ALL DIMENSIONS IN INCHES HOLD ALL DIMENSIONS TO ± 0.010 UNLESS SPECIFIED Dimension Tolerance X.X ± 0.1 X.XX ± 0.05 X.XXX ± 0.001

  49. { A 0.030 + B 0.003 4.0 - Design Detail Bent aluminum sheet, 1/16” thick A or B: Which is more expensive and why?

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