Biomedical engineering professionals in Kenya rely heavily on precise technical drawings to design, maintain, and troubleshoot biomedical devices and systems. The quality of these drawings depends not only on the skill of the drafter but also on the proper preparation and maintenance of drawing equipment and materials. This chapter introduces the essential drawing tools, their specifications, and care practices necessary to produce accurate and professional biomedical engineering drawings in a Kenyan context.

1.1 Identification and care of drawing equipment materials

Effective preparation and maintenance of drawing equipment ensure accuracy and durability of technical drawings used in biomedical engineering projects, such as medical device schematics or hospital equipment layouts. Kenyan biomedical engineers must understand the characteristics and handling of various drawing tools to maintain industry standards and comply with Kenya Bureau of Standards (KEBS) and ISO requirements.

1.1.1 Drawing boards

Drawing boards form the foundational surface for all manual technical drawings in biomedical engineering. Their stability, flatness, and size directly influence drawing accuracy and ease of use.

Usage of Drawing Boards

• Surface Preparation: Ensure the board surface is clean and free from dust or debris to avoid damage to drawing sheets.
• Sheet Fixation: Use clips or adjustable clamps to hold drawing paper firmly, preventing movement during drafting.
• Positioning: Place the board on a stable table or drafting stand at an ergonomic angle for ease of drawing.
• Parallel Motion Ruler: Utilize built-in rulers or parallel motion devices for drawing straight, parallel lines accurately.
• Portability: Select lightweight boards for ease of transport between hospital departments or engineering workshops.

Maintenance of Drawing Boards

• Cleaning: Wipe the surface regularly with a soft, damp cloth to remove graphite or ink residue without scratching.
• Storage: Store boards flat or hung vertically in a dry environment to prevent warping or bending.
• Damage Inspection: Check for dents or cracks that could distort the drawing surface and replace the board if necessary.
• Avoid Exposure: Keep boards away from direct sunlight or moisture to extend lifespan.
• Accessory Care: Maintain attached rulers or clamps by lubricating moving parts to ensure smooth operation.

1.1.2 T and set squares

T-squares and set squares are fundamental tools used for drawing accurate horizontal, vertical, and angled lines essential in biomedical engineering diagrams, such as anatomical schematics or equipment layouts.

Usage of T-squares

• Alignment: Place the head of the T-square firmly against the drawing board edge to ensure stable positioning.
• Drawing Horizontal Lines: Glide the blade along the board edge to draw consistent horizontal lines.
• Guiding Other Tools: Use the T-square as a guide for set squares or triangles to create perpendicular or angled lines.
• Paper Orientation: Align drawing sheets with the T-square to maintain consistent margins and orientation.
• Checking Parallelism: Use the T-square to verify parallel lines in biomedical device schematics.

Usage of Set Squares

• Drawing Vertical Lines: Position the set square against the T-square blade to draw perfect vertical lines.
• Angled Lines: Use the 30°-60°-90° set square to draw common engineering angles required in biomedical component designs.
• Line Verification: Confirm angles on existing drawings for accuracy and conformity to standards.
• Layering: Employ transparent set squares to avoid obscuring underlying drawing details.
• Combining with T-square: Use both tools together to produce orthogonal and isometric projections in device blueprints.

Maintenance of T-squares and Set Squares

• Cleaning: Remove graphite and ink marks gently using a soft cloth and mild detergent if necessary.
• Storage: Keep tools flat in a protective case or drawer to prevent warping or chipping.
• Edge Care: Avoid dropping or bending to maintain straight, sharp edges critical for accuracy.
• Transparency Preservation: Store away from direct sunlight to prevent yellowing or brittleness of plastic tools.
• Inspection: Regularly check for cracks or warping and replace tools that compromise drawing accuracy.

1.1.3 Drawing set

A comprehensive drawing set includes instruments such as compasses, dividers, French curves, and pencils, each vital for creating detailed biomedical engineering drawings ranging from circuit layouts to prosthetic designs.

Usage of Compass and Dividers

• Compass Setup: Adjust legs to desired radius using measurement scales for precision in arcs and circles.
• Drawing Circles: Anchor one leg firmly on the paper and rotate the other leg holding the pencil smoothly to create accurate circles.
• Divider Application: Use dividers to transfer distances from scales to drawings without error.
• Measurement Checking: Compare dimensions on drawings by opening and closing divider legs to match lengths.
• Careful Handling: Avoid applying excessive force that could break the pencil lead or bend the legs.

Usage of French Curves

• Curve Tracing: Select appropriate curve from the set that matches the desired shape in the biomedical drawing.
• Positioning: Place the French curve firmly on the drawing and trace along its edge with a pencil.
• Smooth Transitions: Use multiple curves to connect complex shapes seamlessly, such as ergonomic contours of medical devices.
• Verification: Check curves against design specifications for conformity.
• Storage: Keep curves in a flat container to prevent warping.

Usage and Maintenance of Pencils

• Selection by Hardness: Use harder pencils (H to 2H) for fine, light lines and softer pencils (B to 2B) for shading or bold outlines.
• Sharpening: Regularly sharpen pencils with a mechanical or manual sharpener to maintain fine points.
• Handling: Hold pencils at appropriate angles to control line thickness and avoid smudging.
• Storage: Keep pencils in a box or case to prevent breakage.
• Replacement: Replace worn or broken leads promptly to maintain drawing quality.

Chapter Summary

This chapter covered the identification and proper care of essential drawing equipment such as drawing boards, T and set squares, and drawing sets, emphasizing their correct handling to ensure longevity and accuracy. It also addressed the identification and maintenance of drawing materials including various types of drawing papers, pencils, erasers, and masking tapes, highlighting the importance of selecting appropriate materials for different drawing tasks. Reference to manufacturer’s instructions and workplace procedures was discussed to guide the correct use and upkeep of equipment and materials, reducing wear and ensuring safety. The chapter included an overview of relevant environmental legislations that impact the handling and disposal of drawing materials, promoting responsible and sustainable practices. Finally, it outlined proper methods for disposing of waste materials generated during technical drawing activities to minimize environmental harm and comply with regulatory requirements. This comprehensive approach ensures that students develop good habits in preparing and maintaining drawing tools while adhering to legal and environmental standards.