EngineeringManufacturing

Projection Types And Methods In Technical Drawing

The technical drawing is a common language between engineers, workers, and experts who are dealing with that specific topic. In mechanical engineering technical drawing, there are different illustrations of parts which can be individual or assembly, called projections. Here you can find the general information about the projection types in technical drawings of mechanics. 

Perspective projection(Image Source:Frederic E.Giesecke, Shawna Lockhart, Marla Goodman, Cindy M. Johnson, Technical Drawing With Engineering Graphics, 15th ed, Prentice Hall Pearson, pg 32).

Projections In Technical Drawing

Projections are created in technical drawings according to the observer or reader of the technical drawing. The observer generally is looking at the projection plane, which is generally called technical drawing paper. And the projectors create the projected view of the 3D model on technical drawing paper. Projectors are also rays, which are starting from the observer’s eyes or observer’s itself to part. A view of part can be created on the projection plane between the observer and the part itself. 

Projection Types In Technical Drawing

Three view orthographic projection(Image Source: civilseek.com/orthographic-projection-drawing/).

In general, there are two main projection types in technical drawing. 

  • Perspective Projection: The first one is the perspective projection in which the projectors are starting from a point(observer’s eye) to each point of part. 
  • Parallel Projection: The other projection type is the parallel projection in which the projector lines are parallel to each other. This projection type is more useful in engineering-level technical drawings because the exact sizes of parts can be viewed on the projection plane or technical drawing sheet. Dimensions and tolerances can be illustrated on these types of projected drawings. 
  • Oblique Projection: In parallel projection, the angle between the projection plane and projector lines is 90 degrees. If this angle is not 90 degrees, this projection type is called oblique projection.

In technical drawing, multiview projection type is generally used. In multiview projection, the part is illustrated on a technical drawing sheet with multiple views from different sides. Observer or reader of that technical drawing can illustrate the 3D part from these 2D views. 

Conclusion

The most general and basic explanation of the projection types in technical drawing is like this. 

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2 Comments

  1. What are the differences between orthographic projection and oblique projection.
    What are the major types of projection and where they are mostly use

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