Introduction to Engineering Design

Transcription

1 Introduction to Engineering Design Final Examination Spring 2005 Answer Key Parts A, B & C For Teacher Use ONLY

2 Part A Scoring Conversion Chart Raw Converted Raw Converted Raw Converted Raw Converted Part A Multiple Choice Questions A C C 4... A 5... D 6... A 7... B 8... A 9... C D D A C B B C B D C C A A B B D A D A B A or B D B C D D A A D A B Page 2 of 9

3 Part B High School Credit 1. ORTHOGRAPHIC DRAWING Page 3 of 9

4 ORTHOGRAPHIC DRAWING Grading Scale: 10 points: All 3 views are complete, have correct view alignment, and have accurate size; all features are included and correct. 8 points: All 3 views are included, minor orthographic misalignment or some missing/misplaced features, accurate size; remaining features are correct. 6 points: All 3 views are included; views are not properly aligned orthographically but accurate size; some missing/misplaced features (OR) At least 2 views are completed, orthographically aligned and completely accurate. 4 points: At least 2 views are complete, have some orthographic misalignment or missing/misplaced features. 2 points: At least 2 views are partially complete; what has been completed is accurate so far. 2. MISSING DIMENSIONS (any order) 2pts each 1. Radius of filleted corners 2. Location of hole pattern 3. Location of center rib 4. Radius of top arc 3. PART MODELING PROCESS a) The advantage to using a midplane extrude is that it allows for the easiest centering when creating the tab with another midplane extrusion. b) The rounds should all be done in one command because they all have the same dimension and will update simultaneously if a change in size is necessary. c) The advantage of using a linear pattern feature to create the six holes is that it guarantees uniform spacing and easy revision. It also allows the use of the pattern component feature if inserting fasteners in an assembly mode. d) The advantage to using the hole feature rather than extruding a cylinder is that the hole feature contains appropriate parameters for standard sizes and types of holes to work with standard fasteners. In addition, the hole note feature can be used when dimensioning the hole in the drawing view, which will give all of the specifications of the hole. Example: Page 4 of 9

5 4. ASSEMBLY CONSTRAINTS a) Mate the edge of the ruler to the inside bottom edge of the cup. b) Mate the edge face of the ruler to inside left side face of the cup with an offset distance or Flush the edge face of the ruler to the outside left side face of the cup with an offset distance. c) Mate inside right edge of cup to face of ruler. 5. IDENTIFY DISCREPENCIES a) The front view is missing the rear rib. b) The base of the part has five holes in the top view and only four holes in the isometric view. c) The hole in the upright section is shown passing all the way through the part in the top view, but has a finite depth in the front and side views. d) The base has a quarter-circle cutout in the top view, but is rectangular in the isometric view. 6. LINE TYPES a) Section line b) Cutting plane line c) Extension line d) Dimension line e) Center line f) Hidden line Page 5 of 9

6 Part C College Credit 1. ORTHOGRAPHIC DRAWING w/dimensions R Page 6 of 9

7 ORTHOGRAPHIC DRAWING Grading Scale: 10 points: All 3 views are complete, have correct view alignment, and have accurate size; all features are included and correct; all dimensions included and correct. 8 points: All 3 views are included, minor orthographic misalignment or some missing/misplaced features, accurate size; remaining features are correct, and all dimensions are included and correct. 6 points: All 3 views are included, views are not properly aligned orthographically but accurate size; some missing/misplaced features; most dimensioning included/correct (OR) At least 2 views are completed, orthographically aligned & completely accurate; all dimensions are included and correct. 4 points: At least 2 views are complete, have some orthographic misalignment or missing/misplaced features; some dimensions are included. 2 points: At least 2 views are partially complete; what has been completed is accurate so far. 2. PART MODELING PROCESS A. Since the object is symmetrical normal to its length, it would be best to create the base feature using a midplane extrude because then it would be easier to center the slot and spherical cuts. B. The cross-sectional shape would be a semicircle, and the procedure would be a revolve cut about an axis on the midplane. C. The hole feature should be used to create the tapped holes because of its ability to bring in standard fastener parameters for the holes, and because the hole note feature can then be used in the drawing view to fully dimension the holes. D. The advantage to creating the two fillets as one feature is that they are the same size and as revisions are made to the part the part will update more reliably. 3. DEGREES OF FREEDOM a) Base (1) and Jaw (5): Base DOF: Grounded part (1pt) Jaw DOF: translation in Z direction (1pt) Page 7 of 9

8 b) Jaw Insert (6) and Machine Screw (7): Jaw Insert DOF: none (1pt) Machine Screw DOF: rotation about Z axis (1pt) c) Ball Washer (2) and Cap Screw (4) : Ball Washer DOF: _rotation about its own axis, slight rotation about x axis (1pt) Cap Screw DOF: rotation about its own axis (1pt). 4. DESIGN BRIEF [4 points] Answer: The purpose of a design brief is to describe the constraints and requirements imposed on the design. All design concepts need to be evaluated against these constraints to determine viability. 5. PARAMETRIC DIMENSIONING [4 points] D0 is inner diameter D1 is outer diameter D1=D0+2*5 or D1=D DIMENSIONING [4 points] ± pt for the dimension (3 decimal places are required.) 1 pt for each of the three tolerance values Page 8 of 9

9 7. VIEW SELECTION a. front b. right side c. top d. auxiliary order doesn t matter [1 pt each] 8. MASS PROPERTY/INTERFERENCE DETECTION Mass property [2 points] Mass property analysis considers an object s physical properties such as mass/weight, volume, surface area and center of gravity. It is useful to assign physical properties to components to calculate assembly weight and volume, to locate a center of gravity (for placement of a handle that is critical for balance, for example), or to calculate the amount of material needed to cover an object (such as painting or anodizing.) Interference detection [2 points] Interference detection is used in an assembly to determine if any parts will collide or interfere throughout the range of motion. Interference detection is useful for finding problems before parts are actually manufactured. 9. TECHNICAL DRAWING INTERPRETATION [6 points] a. Of what material is the part made? SAE 1030 Cast steel (1 pt) b. What is the nominal dimension A in the front view?.68 inches (1 pt) c. What is the nominal length D of the part? inches (1 pt) d. What type of section view is shown in the front view? broken (1 pt) e. What is the depth of the part? inches (1 pt) f. How many surfaces require finishing? 2 (1 pt) Page 9 of 9