ENGR 2220: Computarized Engineering Graphics Computarized Engineering Graphics – ENGR 2220 Professor: Dr. Omar E. Meza Castillo Department of Mechanical Engineering

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 2 BIENVENIDOS

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Technical Drawing Tools Chapter 2: Instrument for Engineering Graphics 3 "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

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Graphics Communication Part 1 Chapter 3: Sketching, Text, and Visualization 4 "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

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 5 Here’s what we talked about last time: Lines may be defined as……. 1.A series of points in space organized in a rational order 2.The shortest distance between two points 3.The geometry created by the intersection of two planes or surfaces 4.A set of points organized that have length and direction, but no thickness

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 6 The “Alphabet of Lines”… Lines have both style and precedence. Object (visible) lines are the MOST important…then hidden lines… then center lines… etc.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 7 Examples of line use and layout: Note: The center line has many variations. It’s job is to show the theoretically perfect center of arcs, holes, circles, and cylinders.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 8 Applications of lines

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 9 Sketching 1.Sketching is an important method of quickly communicating design ideas. 2.Sketching is a way of thinking as it is a method of recording ideas and communicating to others. 3.Most new designs are first recorded using design sketches.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 10 Methods for creating drawings: Sketches Using T- squares, triangles, etc. CAD produced drawings

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 11 Sketching the idea (ideation sketch) Subsequent document sketch

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 12 Multi-view sketch : Good for someone who understands technical drawings

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 13 NOTE: There are also “technical sketches” used in industry which may include notes, and several versions that show motion. Pictorial view: Good for communicating the design. Suitable for nontechnical people.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 14 Sketching Grids: A.Orthographic grid B.Isometric grid C. Perspective grid

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 15 Sketching lines

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 16 Sketching lines The line is built up from a sequence of 2, 3 or more passes with a pencil.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 17 Sketching Hold your pencil correctly, and have a relaxed grip. Use a strip of paper to draw lines parallel to the edges of the paper.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 18 Sketching Each side of the square is equal to the diameter of the circle. Draw the diagonals and mark the midpoints. On the diagonals mark 2/3 of the distance between the center and each corner. Connect all the points. An alternative method

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 19 Sketching Examples of poorly drawn circles (with flat arcs and sharp corners)

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 20 Sketching techniques: 1- Proportion is important. It is the ratio between any two dimensions of an object.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 21 Sketches use “proportion”, not scale! Proportion allows the designer to use approximate values to create a balanced looking object. Sketches are accurate freehand drawings which use single lines to represent edges and features. Multi-line sketching is NOT used in engineering design. (Scribbling!)

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Draw the bounding box. 1- Consider the correct proportion. 3- Draw the construction lines. These are every light thin lines representing the details of the object. 4- Finish the sketch with darker lines.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 23 You can use construction line to find the center of squares or rectangles

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 24 Sketching identically proportioned squares

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 25 Grid paper is used to scale an object.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 26 1.Stand at a distance, 2.Hold a pencil at arm’s length in front of you, 3.Align the tip of the pencil with one edge of a feature, 4.Mark the length of the feature with your thumb, 5.Translate the same length to your sketch. 6.Repeat this for other lengths. Don’t change your position.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 27 Classification of Sketches: Each classification of sketch has a particular purpose from production use… to technical illustration.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 28 QUESTION! How do you know when a sketch or CAD drawing is complete? ANSWER: When the production people can make the part without having to ask you any questions! Most drawings not only have views of the object, but also it include written notes and dimensions to aid in its production.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 29 Types of Lettering: Simple Gothic is used for engineering design. Notice that it is “san serif” (no hats or shoes!)

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 30 Types of Lettering: Inclined Gothic is often used for architectural drawings, and various types of technical illustrations. (All the lettering used in these presentations is inclined gothic.)

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 31 Projection Drawings use various types of projection (how we view the object), to enhance our ability to visualize what we are being asked to see or understand. Let’s look at the various styles of projection used…

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 32 Most common types of projections: 1.Multiview (Showing 2 dimensions) 2.Pictorial (Showing 3 dimensions) OR Most common types of projections: 1.Parallel 2.Perspective projections

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 33 Pictorial Projection: Here’s how the same object may look using different projection styles.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 34 Projection types: Projection type is defined by the “line of sight” from the observer. Let’s look at some of these…..

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 35 Perspective: The line of sight is cone-shaped - which makes objects far away appear smaller to our view. Objects are not “true shape and size”.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 36 Parallel: The line of sight is always parallel regardless of how far away the object is from our view. This allows surfaces to be drawn “true shape and size.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 37 Orthographic: Ortho means “at 90 degrees”, and is a form of parallel projection. Orthographic projections are used to show several views of the same object in one drawing set.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 38 Orthographic: The “principle views“ should be chosen to show the most detail of the object with the least number of hidden lines. Here, the TOP, FRONT, and RIGHT SIDE were chosen.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Isometric: A type of parallel projection that represents all 3 dimensions in one image. 39

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 40 Isometric sketch

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Isometric representations of circles 41

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MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Isometric sketches of common objects. 45

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Use a piece of scrap paper and mark one half of the major axis (AC) and one half of the minor axis (AB). Place A on the center and mark two points representing C and two points representing B (draw major and minor axes). Place C on the minor axis and hold B on the minor axis at any time, then place a mark at point A. Repeat this and connect all the points. ½ Major Axis ½ Minor Axis 46

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 47 Understanding what Center Lines do… Center lines show the theoretical perfect center of arcs, holes, and cylinders. They can be used to show symmetry, or used to aid in dimensioning an object. Center lines NEVER start or stop on another line!

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 48 Steps in creating a 3-view sketch… Step 1: Layout the 3 principle views you have chosen with even margins between views and the outside border of your drawing area. Step 2: Rough out the general shape of each view.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 49 Steps in creating a 3-view sketch… Step 3: Transfer any data from one view to its neighbor using “reverse construction”. This can be done by using a “miter line”. Step 4: Add hidden and center lines to the necessary views.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 50 Steps in creating a 3-view sketch… Step 5: Erase all unnecessary lines and “snap” the lines on your views. “Snapping” adds weight to the lines in each view and makes the drawing easier to read. Step 6: Add notes and/or dimensions to complete your drawing.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 51 Here’s some tips on creating a multi- view drawing: 1. Lightly sketch all the information that you know first. 2. Use reverse construction to locate lines that may be unknown such as compound angles. unknown such as compound angles. 3. Add all circles and other arcs to your drawing. 4. Snap all arcs and circles first, and then straight lines.

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics  Week 3: Multiview Drawings 1 We have already seen how views are aligned with the surface of an object. Using the “glass box” method of visualization helps us understand the relationship views have with one another, i. e. the front view is next to the top and right side views, etc. 52

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Here we can see all the principle views of an object as the glass box is unfolded. It is easy to see that some of the principle views have more detail through the use of object (visible) lines than others. Always choose views that have the least amount of hidden lines in them and show the most detail. 53

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Using miter and projection lines, we can easily transfer “space dimensions” between views. 54

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Projection methods: 3 RD Angle (US Standard) ISO (1 ST Angle Metric Standard) NOTE: Reverse construction methods work just as well in 1 ST Angle projection. 55

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Here, we can see that surface C is shown as both as object and hidden lines depending on the view we are looking at. Remember: One definition of a “line” is that it is the geometry on the edge of a surface. (Surface C appears in its edge view in the front and top views.) 56

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics When choosing which of the principle views to draw, remember these rules: 1.Choose as many views as it takes to show ALL the details of the object. The front view usually shows the most detail, or best view of the general shape of the object in its natural position. 2.Choose views that shows a majority of object (visible) lines, and a minimum of hidden lines. 3.Choose views that show features as surfaces first, and as lines second. 57

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Always try to draw views in their most natural position. This is obviously more difficult to visualize! 58

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Why is the left side view not required? ANSWER: It doesn’t add any new information! 59

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Why is the left side view not required? ANSWER: It has too many hidden lines! 60

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Surfaces will appear as edges at times. Edges may be foreshortened (shorter than normal), or “True Length” (TL). 61

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Oblique edge lines are created by oblique surfaces. These are surfaces that are neither true shape or true size in any principle view. 62

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Even simple, primitive shapes often need several views to fully describe their topology. 63

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics “Limiting Elements” are lines that show the outer boundaries of cylindrical or conical objects. How many views of such objects are usually needed to show its shape? 64

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Remember:In multiview drawings, tangency is shown between to surfaces by the absence of any line. Here, the arched and planar surfaces are tangent. Arched and planar surfaces which are NOT tangent. 65

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Holes and cylinders may appear “True Shape and Size” (TSS), or foreshortened depending on the view in which they appear. (Foreshortened circles will appear as ellipses.) 66

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MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics Homework3  bayamon.inter.edu/omeza/ bayamon.inter.edu/omeza/ Omar E. Meza Castillo Ph.D. 75

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 76 ¿Preguntas? Comentarios

MSP21 Universidad Interamericana - Bayamón ENGR 2220: Computarized Engineering Graphics 77 GRACIAS