Brief Introduction to Engineering Graphics The use of drawings to convey information. Sketching freehand straight edge

Transcription

1 Brief Introduction to Engineering Graphics The use of drawings to convey information. Sketching freehand straight edge CAD drawings 2D drafting 3D model to 2D drawings 1 Different Graphical Representation of objects. On pg 27: See Fig. 3 and Table 1 Orthographics Multiviews Pictorials Isometric - a special type of axonometric which uses 120 degree angles for axis. Obliques-front faces similar to orthographic: 90 axis 120 Isometric 90 Oblique Perspectives Used in architecture, more realistic but hard to use for measuring. 2 Brief Introduction Lecture:F16 Handout Page 1

2 Information that is hard to read is even harder to understand use GOOD ENGINEERING LETTERING Class standard is VERTICAL and UPPERCASE (except in the case of *metric units) as shown on pg. 39 Fig. 21of graphics text Usually height of text is about 1/8 (3 mm) but don t measure it use guidelines if provided. Example of lettering expected for all class assignments. *Note: 25.4 mm = 1 INCH mm is millimeters, leave lowercase 10 mm = 1 centimeter mm IS THE STANDARD METRIC UNIT See pg. 30 Sec. 3 I inch Fractions can vary from standard don t make too small Engineering Lettering 3 Examples of Lettering Decent Lettering spaced a bit too close together Good Form plus correct way to do millimeters (case-sensitive) Same here needs to keep letters VERTICAL!!! FLOATING letters needs to use the guidelines Incorrect fraction (too small). POOR form (one shouldn t have top or bottom plus NON-UNIFORM height. 4 Brief Introduction Lecture:F16 Handout Page 2

3 Expectations of Lettering Good spacing of letterings could be improved upon Fair to Poor form is fine but not uniform height FLOATING letters. Poor to Fail Not vertical, not uniform height, poor spacing. 5 The type or appearance of a line depends on what it is trying to represent. Be familiar with the different types of lines found in Fig. 7 on pg. 29. Solid/Continuous indicates a visible surface/edge Dashed indicates a hidden surface/edge Centerline indicates symmetry Each linetype has its own lineweight too. - Linetypes - Centermark indicates center of circular feature. Extends past actual diameter Ø of circle of or radius of arc. Radius of: 22 mm Started at 10 mm mark - due to manufacture of ruler 6 Brief Introduction Lecture:F16 Handout Page 3

4 Use of straight edge is allowed. Lettering templates, circle templates, compasses and other drafting equipment is not allowed. NEATNESS and ACCURACY do count! Even Lineweight (LWT) Sharp corners Gaps (or no gaps) in important areas Examples will be given showing both good and poor work. - RULES and EXPECTATIONS - 7 GOOD (A work) FAIR (B work) Uneven LW Visible Lines need to be darker Poor dashes POOR (D work) overall neatness used straightedge (sort of) I suggest using a SHARP No. 2 pencil or a 0.7 mm HB lead mechanical pencil. Don t forget the straight edge. Fig. 24 on page 70 shows examples of good totally freehand lines. You are allowed and expected to use a straight edge. - SKETCHING EXAMPLES - 8 Brief Introduction Lecture:F16 Handout Page 4

5 Examples See Methods for sketching circles on page 73 for good circle sketching technique. FAIR circle sketch a bit too flatten bottom Circle form good uneven lineweight (LWT) Uneven LWT Didn t use straight edge 9 Hidden Lines should not be scaled Watch for where gaps should be Uneven linewt This is a better hidden line form. Poor hidden line form, this is a stitch. Circle is poor -More Examples- 10 Follow directions. Gaps should be included only when needed. Uneven linewt Brief Introduction Lecture:F16 Handout Page 5

6 Metric is millimeters 10 mm per centimeter 2.54 centimeter per inch Decimal Inch smallest unit is.02 inch 50 divisions within each inch 12 inches per foot - Decimal Inch and Metric Scale- 11 ABBREVIATIONS USED IN GRADING FOR REFERENCE LWT or LW for lineweight GEL for good engineering lettering ^ for gap needed (or not needed) NEAT for neatness ACC for accuracy WSS for where shape shows FFS from finished surface Brief Introduction Lecture:F16 Handout Page 6

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