This chapter focuses on producing orthographic drawings of components, a critical skill for biomedical engineers involved in designing, manufacturing, and maintaining medical devices and equipment. Orthographic drawings provide precise, multi-view representations of components, enabling clear communication between design teams, manufacturers, and quality control personnel. Mastery of pictorial drawing techniques, which complement orthographic projections, enhances visualization and interpretation of complex biomedical parts, such as prosthetic joints, surgical instruments, and diagnostic equipment components.

2.1 Drawing and interpretation of orthographic elevations

Orthographic projection represents a three-dimensional component on a flat sheet by a set of separate two-dimensional views, called elevations and plans, each looking straight at one face of the component. Unlike a pictorial drawing, each view shows true shapes and true lengths of the faces parallel to it, so dimensions can be taken directly from it. Orthographic drawings are the standard working drawings used to manufacture, inspect and repair biomedical device parts.

Example: the biomedical engineering workshop of a county referral hospital in Embu draws the front elevation, end elevation and plan of a worn infusion stand clamp so that a local machine shop can make a replacement in aluminium.

Principal views

• Front elevation: the view looking at the front of the component; it is chosen to show the most characteristic shape and the most detail.
• End (side) elevation: the view from the left or right side, showing depth and height.
• Plan: the view from above, showing width and depth.
• Auxiliary view: a view taken square to an inclined face, showing its true shape.
• Sectional view: a view of the component imagined cut through, used to show internal features.

First angle and third angle projection

The projection symbol is drawn in the title block so the reader knows which method is used.

Procedure for drawing orthographic elevations

1. Study the component: identify its overall length, width and height and choose the front view.
2. Choose scale and layout: select a standard scale (1:1, 1:2, 2:1) and space the views evenly on the sheet, leaving room for dimensions.
3. Draw the front elevation: start with construction lines for overall sizes, then add detail.
4. Project the other views: project horizontally to the end elevation and vertically to the plan, using a 45° mitre line to transfer depth between plan and end view.
5. Add hidden and centre lines: show hidden edges with dashed lines and axes of holes and cylinders with chain lines.
6. Line in: darken visible outlines with thick continuous lines and check that every feature appears correctly in all views.
7. Complete the title block: title, scale, projection symbol, material, drawing number and draughtsman's name.

Line types (BS 8888 and ISO 128)

Interpretation of orthographic elevations

Reading an orthographic drawing means building a mental picture of the component from its views.

• Read the title block first: note the projection method, scale, units and material.
• Relate the views: a point or edge in one view lines up with the same point in the adjacent view.
• Identify each surface: a line in one view may be an edge, the edge view of a surface, or the outline of a curved surface; check it in the other views.
• Interpret hidden lines: dashed lines show holes, slots and internal steps not visible from that side.
• Use the centre lines: they show cylindrical features such as holes, bosses and shafts.
• Sketch it: a quick pictorial sketch confirms the shape before manufacture.

Sectional views

A section shows a component as if cut by a cutting plane, with the cut surfaces hatched with thin lines at 45°. Full sections, half sections and local (part) sections show internal features of parts such as pump housings and valve bodies more clearly than hidden lines.

Chapter Summary

This chapter explored the concept of pictorial drawings, emphasizing their role in representing three-dimensional objects on two-dimensional media for better visualization. It detailed the different types of pictorial drawings used for components, starting with isometric drawings that depict objects with equal foreshortening along three axes. The chapter then explained oblique drawings, highlighting how the front face is drawn true to scale while the other faces are projected at an angle. Cabinet oblique drawings were also covered, showing how the depth dimension is scaled to half to reduce distortion. Additionally, the chapter clarified the importance of symbols and abbreviations in technical drawings as standardized shorthand to convey information efficiently and unambiguously. Overall, the chapter provided foundational knowledge for producing clear and accurate orthographic representations of components using pictorial techniques and standard conventions.