David Larson GTT STI 2010 ENGT 507 Teaching Math and Science in Engineering through PLTW GTT

Orthographic Drawing – Nine Line Technique

Essential Questions:  What are the three views you see in both an isometric drawing and an orthographic drawing?  What are the two axis you see on a coordinate grid?  Which axis runs horizontally through a grid?  Which axis runs vertically through a grid?  Where should a base line be in relation to the x-axis?  How do you know where to put the vertical line?  Where does the width line go?  Where does the height line go?  How far from the height and width lines do the spacing lines go?  At what angle is the diagonal line running?  Where does the diagonal line originate?  When looking at an isometric view, which side is the object is the front?  When looking at an isometric view, which side is the object is the side?  When looking at an isometric view, which side is the object is the top?  What is the purpose of the diagonal line?  How do the dotted depth lines help the person drawing?  What is the purpose of the different views?  Why is the alignment of the different views important?  How are orthographic and isometric drawings similar? …different?

Vocabulary:  Orthographic – Two-dimensional isometric or oblique views of a three-dimensional object on a drawing surface at right angles to the views and the lines of sight (projection). In these views the lines of the object parallel to the drawing surface are of true length and thus can be drawn to scale. Elevations, floor plans, and sections of a building are orthographic projections.  Isometric – A pictorial representation of an object in which all three dimensions are drawn at full scale rather than foreshortening them to the true projection. An isometric drawing looks like an isometric projection but its all lines are parallel to the three major axes are measurable.  Front View – the view of an object at a right angle from the front of the object  Side View – the view of an object at a right angle from the side of the object  Top View – the view of an object at a right angle from the top of the object  Base Line – the horizontal line that runs ¼ inch above the x-axis  Height Line – the horizontal line that is located above the base line at a distance equal to the highest part of the shape.  Width Line – the vertical line that is located ¼ inch to the right of the y-axis  Vertical Line – the vertical line that is located to the right of the width line at a distance equal to the widest part of the front of the shape.  Spacing Lines – lines that run are ¼ above the height line and ¼ inch to the right of the vertical line, originating at the x-axis moving upward and at the y-axis moving right until they intersect.  Diagonal Lines – line that originates at the intersection of the height and vertical lines and moves up and to the right at a 45° angle.  Dotted Depth Lines – the dotted lines that originate at any angle in the side view and move upwards to the diagonal line, then moving horizontally to the left. These lines are used to check the alignment of the side and top views.  X-axis – the horizontal line that runs along the bottom of a grid, intersecting with the perpendicular y- axis at 0.  Y-axis - the vertical line that runs along the left side of a grid, intersecting with the perpendicular x- axis at 0.

Classroom Activity  Teacher will review the basic elements and features of an isometric drawing, asking students for their input and checking for understanding as an informal assessment. This discussion may also involve 2- and 1-point perspective drawings and thumbnails depending on what has already been taught.  As the teacher presents the PowerPoint/SMART Notebook demonstration on the Nine Line Technique for orthographic drawings, students will use rulers, graph paper, and pencils to draw and label each of the 9 lines in their Engineer’s Notebook.  The demonstration, as in the presentation, will focus on a specific object with a basic level of difficulty, and can further progress to different and more difficult objects.  Once students begin to feel comfortable with the process of Nine Lines, they should be encouraged to test their knowledge independently, asking the teacher for feed back as frequently as possible.  A modification to this activity could be to have partners work together to draw through the Nine Line process, collaborating and feeding off of each others’ understanding.

Assessment of Learning  Students must show proficiency on the Nine Line Technique Quiz. Each individual teacher can establish the level of proficiency they expect.  Nine Line Technique Quiz

Instructor’s Guide  This process is an exercise in memorization for most students, making it very difficult for many. It is helpful to have the nine lines and a brief description of each displayed prominently in the classroom.  Create a collection of 15-20 simple isometric objects for students to practice this technique. These should include edges that do not require much length calculation, angles that are 90, and no hidden edges. For students who excel, create a collection of more difficult isometric drawings (i.e. hidden lines, 45 angles, holes, etc).  While a good portion of your students will likely pick up this skill within a short amount of time, it will be important to continue to offer small group assistance. Be sure to NOT do any of the orthographic drawings that you require for the class for them in their Engineering Notebook or on any other student papers, as you want the students to display their knowledge.  When first beginning orthographic drawing with the Nine Line process, spend some time doing fun games for all the students to get them to become familiar with which line is which. This will be helpful right away for students have a hard time with remembering each line.