10.1. Engineering Drawing and Its Concept

10.1.Engineering drawings and its concepts:

 

FUNDAMENTAL OF STANDARD DRAWING SHEET

 

The standard drawing sheet, also known as the engineering drawing sheet, is a standardized format used for creating technical drawings in engineering and design fields. It provides a consistent layout and organization for communicating design information. Here are the fundamental aspects of a standard drawing sheet:

 

Title Block:

The title block is located in the lower-right corner of the drawing sheet and contains essential information about the drawing. It typically includes details such as the title of the drawing, drawing number, revision number, date, scale, and the name of the drafter or designer.

 

Border and Frame:

The drawing sheet is surrounded by a border and frame, which provide a clear boundary for the drawing and help maintain its integrity. The border may include reference lines, grid lines, and tick marks for measurement.

 

Drawing Views:

The main portion of the drawing sheet is occupied by drawing views, which depict the object or component being represented. The drawing views may include orthographic projections (such as front view, top view, and side view), isometric views, section views, and detailed views as needed to communicate the design intent.

 

Dimensions and Annotations:

Dimensions and annotations are placed directly on the drawing views to provide measurements and additional information about the object being drawn. This includes linear dimensions, angular dimensions, tolerances, surface finish symbols, notes, and other annotations that aid in the interpretation and manufacturing of the design.

 

Bill of Materials (BOM):

For assembly drawings, a Bill of Materials (BOM) is often included. It lists the individual parts or components required for the assembly, along with their quantities, part numbers, and other relevant information.

 

Revision History:

In the title block or adjacent to it, a revision history table may be included to document any changes made to the drawing over time. It helps track revisions, dates of revisions, and the individuals responsible for the changes.

 

Scale:

The drawing sheet usually includes a scale reference to indicate the ratio between the drawing dimensions and the actual size of the object. The scale may be expressed as a fraction, a ratio, or a graphical representation.

 

Notes and Symbols:

Additional notes, symbols, and graphical representations are often used to convey specific information or requirements related to the design. This may include surface finish symbols, weld symbols, geometric dimensioning and tolerancing (GD&T) symbols, material specifications, and other relevant symbols and annotations.

 

These fundamental aspects of a standard drawing sheet ensure clarity, consistency, and uniformity in the presentation of technical drawings. They facilitate effective communication among designers, manufacturers, and other stakeholders involved in the engineering and design process.

 

DIMENSIONS SCALE IN DRAWING

 

The scale in a drawing refers to the ratio between the dimensions of the drawn object on the paper and the actual size of the object in real life. It allows engineers, architects, and designers to accurately represent the object's proportions and dimensions on a reduced or enlarged scale.

 

The scale is typically indicated in the title block or adjacent to the drawing. It is expressed in different formats, such as:

 

Ratio Scale:

The ratio scale represents the relationship between the dimensions on the drawing and the actual size of the object. For example, a ratio scale of 1:50 means that every unit on the drawing represents 50 units in real life. If a line on the drawing measures 50mm, its actual length is 50mm x 50 = 2500mm (or 2.5 meters).

 

Fractional Scale:

The fractional scale is represented as a fraction, such as 1/4" = 1 foot. This means that every inch on the drawing represents four feet in real life. If a line on the drawing measures 4 inches, its actual length is 4 inches x 4 feet = 16 feet.

 

Graphic Scale:

A graphic scale is a graphical representation of the scale, usually depicted as a ruler or a series of lines with labeled distances. It allows the reader to visually compare the dimensions on the drawing to the real-life measurements.

 

Choosing the appropriate scale depends on various factors, including the size of the object, the level of detail required, and the available space on the drawing sheet. Smaller objects or complex designs may require a larger scale, while larger objects or simpler designs may use a smaller scale.

 

It is important to note that the scale should be clearly communicated and understood by anyone reading or using the drawing. It ensures that accurate measurements and proportions are maintained during the interpretation and implementation of the design.

 

LINE DIAGRAM

 

In engineering drawing, a line diagram is a type of technical drawing that uses lines and symbols to represent various components, connections, and relationships within a system. It is typically used to convey information about electrical, mechanical, or hydraulic systems. Here's a step-by-step guide on how to create a line diagram in engineering drawing:

 

Identify the system or object you want to represent in the line diagram. It could be a mechanical assembly, an electrical circuit, or a hydraulic system.

 

Gather all the necessary information about the components, connections, and specifications of the system. This may include measurements, part numbers, symbols, and any relevant technical data.

 

Start with a blank sheet of paper or open a computer-aided design (CAD) software for precise and professional drawings.

 

Begin by drawing the overall outline of the system or object using straight lines. Use a ruler or CAD tools to ensure accuracy.

 

Use standard symbols and conventions to represent different components. For example, electrical components such as resistors, capacitors, and switches have specific symbols. Mechanical components like gears, pulleys, and bearings also have standardized representations. Refer to relevant engineering standards or guidelines for the correct symbols.

 

Draw lines to represent connections between components. Use straight lines to indicate direct connections and arrows to show the flow of energy or signal. Label the lines and arrows with relevant information, such as voltages, currents, or fluid flow direction.

 

Add any additional annotations or dimensions as necessary to provide further clarity or information about the system.

 

Review and double-check your line diagram for accuracy, ensuring that all components and connections are properly represented and labeled.

 

If using CAD software, you can enhance the diagram by adjusting line weights, adding colors, or creating layers for different components.

 

ORTHOGRAPHIC PROJECTION

 

Orthographic projection is a technique used in engineering drawing to represent a three-dimensional object on a two-dimensional surface. It provides multiple views of the object from different angles to accurately depict its shape, size, and features. The views are typically drawn as front, top, and side views.

 

Here's a step-by-step guide on how to create an orthographic projection in engineering drawing:

 

Start with a clear understanding of the object you want to represent. Gather all necessary information about its dimensions, features, and orientation.

 

Choose an appropriate scale for your drawing, considering the size of the object and the available drawing space.

 

Decide on the number of views you want to include in your orthographic projection. The most common views are the front, top, and right-side views, but additional views may be required for complex objects.

 

Begin with the front view. Draw a horizontal line for the ground or reference line. Place the object's front view above this line. Start by drawing the main features of the object, such as its outer shape and any visible details, using straight lines and arcs. Ensure that the dimensions and proportions are accurate.

 

Once the front view is complete, draw the top view directly above it. Align the top view so that it is directly above the front view and parallel to the ground or reference line. Draw the top view by projecting the features and dimensions of the object onto the top plane.

 

Draw the right-side view to the right of the front view. Align it with the front view so that it shares the same ground or reference line. Project the features and dimensions of the object onto the right-side plane.

 

Add any additional views as necessary to fully represent the object, such as a bottom view or sectional views.

 

Use construction lines and projection lines to aid in the accurate representation of the object's features and dimensions. These lines help project points from one view to another.

 

Label each view with appropriate letters or symbols, such as "F" for front, "T" for top, and "R" for right-side view. Label the dimensions and features of the object using numerical values or technical annotations.

 

Review your orthographic projection to ensure accuracy and clarity. Verify that all dimensions and features are correctly represented, and make any necessary adjustments or refinements.

 

Orthographic projection is an essential technique in engineering drawing as it provides a comprehensive representation of the object, facilitating manufacturing, assembly, and communication among engineers, designers, and stakeholders.

 

ISOMETRIC PROJECTION

 

Isometric projection is a technique used in engineering drawing to represent a three-dimensional object on a two-dimensional surface. It provides a realistic and three-dimensional representation of the object by showing all three principal axes—x, y, and z—equally foreshortened at angles of 120 degrees.

 

Here's a step-by-step guide on how to create an isometric projection/view in engineering drawing:

 

Start with a clear understanding of the object you want to represent. Gather all necessary information about its dimensions, features, and orientation.

 

Choose an appropriate scale for your drawing, considering the size of the object and the available drawing space.

 

Begin by drawing a horizontal line to serve as the ground or reference line.

 

Decide on the orientation of your isometric projection. Traditionally, the isometric projection is drawn with the horizontal axis (x-axis) at a 30-degree angle from the ground line.

 

Determine the isometric axes by drawing two lines at 120 degrees from the horizontal line. These lines represent the x and y axes of the isometric projection.

 

Select the scale and dimensions to be used in your drawing. For isometric projections, the scale along each axis is the same.

 

Begin drawing the object by projecting its features onto the isometric axes. Start with the front face of the object, drawing its outer shape and any visible details using straight lines and arcs. Maintain the proper foreshortening of the object's features along each axis.

 

Continue projecting the features and dimensions of the object onto the isometric axes. Use construction lines to aid in the accurate representation of the object's features.

 

Add any additional details, such as internal features or hidden lines, to provide a more comprehensive representation of the object.

 

Label the dimensions and features of the object using numerical values or technical annotations. Pay attention to the orientation of the dimensions and ensure they are placed correctly in relation to the isometric axes.

 

Review your isometric projection to ensure accuracy and clarity. Verify that all dimensions and features are correctly represented, and make any necessary adjustments or refinements.

 

Isometric projections are commonly used in engineering and design fields as they provide a clear representation of an object's form and can be easily understood by stakeholders, manufacturers, and assemblers.

 

PICTORIAL VIEW

 

In engineering drawing, a pictorial view is a representation of a three-dimensional object on a two-dimensional surface that aims to provide a realistic and visually appealing depiction. Pictorial views are created using various techniques, such as perspective projection or axonometric projection. These views give a sense of depth and dimensionality to the object being represented.

 

Here are three common types of pictorial views in engineering drawing:

 

Perspective Projection: Perspective projection is a technique that mimics how the human eye perceives objects in three dimensions. It involves drawing the object with converging lines that meet at a vanishing point. This creates a sense of depth and realism. Perspective projections are often used in architectural and artistic drawings.

 

One-Point Perspective: One-point perspective is a specific type of perspective projection where all parallel lines in the object converge to a single vanishing point on the horizon line. It is commonly used for drawings that show a frontal view of an object or a scene.

 

Axonometric Projection: Axonometric projection is a type of parallel projection that maintains accurate measurements along all three axes. It is often used in technical drawings to show objects in a 3D representation without any distortion. Common types of axonometric projections include isometric projection, dimetric projection, and trimetric projection.

 

To create a pictorial view in engineering drawing:

 

Start with a clear understanding of the object you want to represent. Gather all necessary information about its dimensions, features, and orientation.

 

Choose an appropriate scale for your drawing, considering the size of the object and the available drawing space.

 

Select the desired technique for the pictorial view, such as perspective projection, one-point perspective, or axonometric projection.

 

Begin by drawing the main features of the object, such as its outer shape and any visible details, using straight lines and curves. Pay attention to the proper proportions and dimensions.

 

Use the selected technique to create a sense of depth and dimensionality. For perspective projection, ensure that parallel lines converge to vanishing points. For axonometric projection, maintain accurate measurements along each axis.

 

Add shading, shadows, and highlights to enhance the visual realism of the drawing, especially in perspective projections.

 

Label the dimensions and features of the object using numerical values or technical annotations. Place the labels appropriately within the pictorial view, ensuring readability and clarity.

 

Review your pictorial view to ensure accuracy, clarity, and visual appeal. Make any necessary adjustments or refinements to improve the representation of the object.

 

SECTIONAL DIAGRAM

 

A sectional diagram, also known as a cross-sectional view or simply a section, is a type of engineering drawing that shows the internal structure of an object by cutting it along a plane and exposing the internal details. It is used to provide a clear understanding of how the object is constructed and how its internal components are arranged.

 

Here's a step-by-step guide on how to create a sectional diagram in engineering drawing:

 

Determine the object you want to represent and identify the section plane. The section plane is the imaginary cutting plane that will reveal the internal structure of the object.

 

Choose an appropriate scale for your drawing, considering the size of the object and the level of detail you want to show.

 

Begin by drawing the outline or external shape of the object using straight lines and curves. Ensure that the outline is accurate and matches the shape of the object.

 

Indicate the section plane by drawing a dashed line across the object. Label the line with a symbol indicating the direction of the section (e.g., an arrowhead).

 

Select the type of section view you want to create. There are various types, such as full sections, half sections, offset sections, and revolved sections. Choose the type that best suits your purpose.

 

Determine the cutting line or lines that represent the section view. These lines are drawn along the section plane and intersect the object's outer shape. Typically, they are drawn as solid lines and extend beyond the object's outer boundaries.

 

Draw the internal features and components that are revealed by the section view. Show details such as walls, cavities, ribs, holes, and any other significant internal features. Use straight lines, arcs, and other appropriate symbols to represent these features.

 

Add dimension lines and labels to indicate the size and distances of the internal features. Use numerical values or technical annotations to label the dimensions.

 

If necessary, include additional notes or annotations to provide further information or clarify specific details in the sectional diagram.

 

Review your sectional diagram to ensure accuracy and clarity. Verify that the section view accurately represents the internal structure of the object and that all dimensions and features are correctly labeled.

 

Sectional diagrams are widely used in engineering and manufacturing industries to convey detailed information about the internal arrangement of objects. They help engineers, designers, and manufacturers understand how components fit together and assist in troubleshooting, maintenance, and assembly processes.