Exercise: Projection Drawing

Projection drawing is means of generating two-dimensional drawings of three-dimensional objects by flattening them. One view is drawn, and lines are projected from it to generate the other views. By using projection lines, you can save time in drawing, eliminate measuring errors and increase consistency.

In this exercise you will be drawing a physical object using projection methods. You will need to find an actual object to draw. NO DRAWINGS FROM IMAGES THAT YOU FIND ON THE WEB.  The object must look different from three sides. A bottle is not a good choice because it is the same in two directions (front and side). The example in this tutorial is a coffee mug, but your subject can be other types of objects. The idea is to choose something that allows you to explore curvilinear shapes.

From the plan view (top view) you will generate elevation and section drawings. The drawings will be drawn at their full size, but scaled in the viewport to a smaller size.

Objectives/Outcomes and Assessment Criteria

Students will acquire and demonstrate: 1.) technical competency in working with projection drawing and scaled viewports, 2.) sense of craft through precision and care in the presentation of the work, 3.) design aptitude in the ability to solve an organization problem and explore possible solutions, 4.) judgment in the composition of objects within a field. 5.) consideration of limitations and constraints in the problem solving process.

Steps

PD.1. Make a new file by making a copy of your titleblock. Name the file with your last name followed by your first name followed by ProjectionDrawings (YourName_ProjectionDrawings). Open the renamed file.

PD.2. Create new layers as described below

Layer name, Beyond; color 6

Layer name, Cut; color, color 4

Layer name, Fill; color, 253

Layer name, Behind; color, 8; linetype, hidden2

If lines needed a special linetype (dashed, center, hidden, phantom, etc.), the best way is to assign the linetype to the layer. All objects drawn on that layer will have the linetype that is assigned.  Follow the steps below to load a linetype.

Here is a link to a slideshow with examples.

Here is an article that shows building plans and sections.

PD.3.  Measure and draw the object that you found from the top. The images below are an example. Your drawings will look different.  You will be asked to take photos of the object and load them into the Google Drive folder along with your work.

Set your layer to Beyond. In model space begin by drawing the top view of your object. Be as precise as possible. Be sure to use show rounded corners and joints. The FILLET command will be helpful for this.

PD.4. Use projection lines (black) to construct the elevation directly below the top view. You could make a new layer for these lines or use the current layer. They are normally erased once you have completed the drawing. The Quadrant object snap has been turned on to increase precision. You can use lines as projection lines or try Xlines (command: XL) which extend a line infinitely in two directions. The projection lines get erased later.

PD.5. Draw another elevation. Choose the elevation that shows the most information. You may find it helpful to make a copy of top view, rotate it and place it above the second elevation. Use projection lines as necessary.

PD.6. So far all of the views you have created are from outside the object. The next set of drawings will be slices through your object.

What is the difference between an elevation view and a cut view? Anything that is cut is shown with a heavy line. The cut pepper below is a good example of this. A profile line has been drawn in the place where the pepper was cut. The cyan colored profile line has been drawn on the Cut layer. Note: you do NOT need to draw the pepper. It is just provided as an illustration.

PD.7. Next the cut areas are filled with poché (pronounced poh-shay). The term is a french term and it is used to represent to the areas of a section that are cut.

PD.8. Next the objects that are visible beyond are drawn. In our pepper example there are seeds and portions of the skin that protrude into the hollow space of the pepper. Those objects are drawn with a lighter line. They have been drawn on the Beyond layer in the image below.

Note that sometimes the section is left without fill, but the lines representing the cut profile are always shown with a heavy line. The thickness of the cut line will depend upon the scale of your drawing. For this exercise show your cut areas with fill (poché). There should be no lines within the cut profile (where there is fill) for presentation drawings. In construction drawings more detail is shown inside the cut profile lines.

PD.9.  Construct two sections of your object. One section should be a horizontal cut. The other should be a vertical cut. In the example below red lines indicate the locations for the section cuts. The location of the vertical cut is shown in the top view. The location of the horizontal cut is shown in the bottom view. In the image below black projection lines project from the red lines. The gray hidden (dashed) lines indicate the edges of objects above the cut. They are put on the layer called Behind. 

Steps: 1. Make copies of your top view and one of your elevations. 2. Choose a place to cut the horizontal section and a place to cut the vertical section. 3. Draw a line to represent those locations. 4. Draw the cut profiles or change the layers for lines that are cuts instead of lines beyond. On the Behind layer draw the lines in the plan that are edges behind the cut lines or change existing layers. 

From layout view the sections would appear as shown below. 

PD.10. Create two layout views. In one layout include the Top View, Front View and Side View. In the other layout include the Horizontal Section and Vertical Section.  Maintain the alignments used in projecting the images. 

PD.11. Set the viewport scale to a preset scale. The drawings should be as large as possible, but should fit within the viewport and should use a preset scale. Double click in the viewport. You know that you are inside a viewport when the viewport perimeter is a bolded line. Once inside the viewport, approximately center the group of views. and change the viewport scale. You will find the Viewport Scale options by clicking on the arrow shown below which can be found near the bottom right corner of the screen. 

Try a scale of 1:1 first, then 1:2, etc. until you find one that will fit. Repeat for both sheets.

PD.12. Add titles for your drawings in layout view (paper space). Name the views Front View, Side View, Top View, Horizontal Cross Section, and Vertical Cross Section. Use the style you created for your titleblock. Center justify the text below each view or align the text with the left of the view. The text height should be 1/8". The image below illustrates how the sections of the object would look when printed using wright.ctb to control the lineweights. The lines that surround the fill should be heavy. Lines below or beyond would be light. 

PD.13. Take a few digital photographs of your object. Look for a place where you have a neutral background. I can help you set this up in class. 

PD.14. Retrieve ccc.ctb, print to pdf, save your drawing file, close your drawing file, and upload the drawing file and two pdf files (or one if they all fit on one sheet) to your Google Drive folder. Also, upload the images of the object. 

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