16.3 Views
Cameron Kjeldgaard
Base and Projected Views
A view on a drawing is an illustration of an object from a certain perspective. Sometimes a view may be pictorial, showing a sort of three dimensional view of an object from a corner perspective.
Most of the time drawings are shown on a print using a method called orthographic projection. This is a way of representing a three dimensional object using two dimensional drawings. There can be up to six views in a drawing like this, and they are always arranged in the same pattern, like an unfolded cube. The front view sometimes called the base view is the primary view and the one from which the others project. Note that what is shown in the front view may not be show the actual front of the object being shown, what the detailer or drafter chooses to show in the front view is often the perspective that can display the greatest amount of relevant information and dimensions for fabricating the object.
A drawing will not always include all these views, three views are often sufficient to display enough information to fabricate something, for example a front, top, and right side view may be all that is needed. The front view, or base view, is always included and the other views must be seen as projecting off of it. When one view projects to another, you must imagine it rotating a certain way. If we use the L shaped piece from the pictorial view in Figure 16.4 below, and look at the orientation of that same object in the orthographic views it is easy to demonstrate this. Remember, the heavy solid lines are object lines representing visible edges, the dashed lines are hidden lines representing edges hidden from view; this is the clue to understanding how one view translates to another.
To look at it another way, take the example of a drawing with just two views, a front view and right side view. The right side view is, and always will be, located to the right hand of the front view. The object lines, which represent the edges of the object, to the rightmost side of the front view represent the surfaces which face the viewer in the right side view. This same logic can be applied when the object rotates from the right side view back to the front view; or from the front view to any other.
Section Views
A section view is a special type of view that makes use of the cutting plane lines mentioned in the previous section. The cutting plane lines indicate where the section view originates and which direction the perspective of the view is facing.
It is often the case for multiple section views to be used. In some cases it is more common for a print to use a single base view with multiple sections, rather than projected views. To keep track of multiple views the cutting plane lines will have reference letters which appear below the resulting section view, as shown below.
Detail views
Detail views are used when a particular feature requires a lot of information to be properly fabricated. Hence the name, detail views are used to provide particularly detailed information. These views are usually shown at an enlarged scale as compared to the rest of the drawing. A small complex feature on a large assembly cannot be properly detailed unless it is blown up. Much like section views, detail views use letters to reference the reader to the resulting view. Rather than using cutting plane lines, detail views use a circular reference line with a single letter to direct the reader to the resulting view, as shown below.
Views With Break Lines
Break lines are used in base and projected views to save space on prints. On large fabrication projects, involving many individual assemblies each with their own print, paper space and printer ink quickly become commodities. If part of an assembly doesn’t have many features which need to be dimensioned rather than illustrating the entire assembly part of it will be omitted to save space. This is where break lines come in, depending on the length of the assembly omitted by the break either short or long break lines will be used. Dimensions can be shown across the break and will remain the same as they would in a view with no break, as shown below.
Attributions
- Figure 16.3: 6 principal views by Snebtor is released under CC BY-NC 2.0
- Figure 16.4: Typical Arrangement of Projected Views by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 16.5: Explanation on Orthographic Projection by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 16.6: Cutting Plane Line and Section View by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 16.7: Cutting Plane Line and Section View by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 16.8: Detail Views by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 16.9: Views With and Without Breaks by Cameron Kjeldgaard, for WA Open ProfTech, © SBCTC, CC BY 4.0
a way of representing a three dimensional object using two dimensional drawings