Assignments

In the manufacturing industry it is important to have a working drawing of the object being produced. If a toy company wants to produce a new mindteaser called Chang’s Cubes; the company will require a complete set of drawings to mass-produce the blocks.

An isometric drawing may be required (Fig. 1). An isometric drawing is a three-dimensional view of an object, a true-scale model of that object.

An orthographic drawing may be required (Fig. 2). An orthographic drawing has three views, showing the top, front, and right side views. It may have dimensions (measurements) of each part. An orthographic drawing is to be drawn in a standard engineering format. All engineers draw orthographic the same way.

A full-size flat pattern layout may be required (Fig. 3). A flat pattern is a full-size drawing of the object to be made. It can be copied, traced, or punched directly into the material the object is being made from. By folding on dotted lines, the pattern folds into a three-dimensional shape.

In modern manufacturing practices, many different manufacturers, in different locations around the world make many component parts. The components are sent to an assembly plant where they are joined with other components to make the finished product. Airplanes, automobiles, radios, computers, and video game system are made this way.

One manufacturer could make Chang’s Cubes. The block contains five smaller blocks that, when fitted together, make one big block. In the manufacturing process, each block is made on a different production line by a different team of workers. Each team is responsible for its block per the working drawing. If one team makes a mistake in building its block, its component will affect the finished product – in a bad way.

Think of orthographic drawings as “blowing up” the house. Start with a “typical” house shown in three dimensions.

Now start “unfolding” the planes of the house keeping the sides, top, and bottom connected.

As you unfold the house to form a flat pattern you can easily see the direct relationship the top, front, and right side views align.

How to Draw a Front View

To draw a front view of an object, first imagine you are holding your paper in front of the object and looking at it as shown in Figure 1. If you do this you will only be able to see the darkened surfaces of the object. Drawing the outlines of these surfaces only, exactly as they look, is called drawing a front view. Figure 1 shows how the front view drawing of Figure t2 will appear when finished.

The examples that are given show various front view drawings of the object. Please note that you are drawing the general outlines of the major features of the object, not any of the details.

How to Draw a Top View

To draw the top view of an object, imagine you are holding your paper directly above the object and looking down on it (Fig. 2). If you did this then you would only be able to see the shaded surfaces of the object. Draw only the outlines of the shaded surfaces. Do not make any observations about angles or shapes of any of the surface areas. If you drew the outline of the block, you would get a top view drawing looking like Figure 1.

Examples of top view drawings are shown below. Please remember that you are drawing the general outlines of the major features of the object, not any details.

How to Draw a Right Side View

To draw a right side view of an object, imagine that you are holding your paper to the right side of the object and looking at it as shown in figure 2 below. If you do this you will only see the darken surfaces of the object. Drawing the outlines of these surfaces only, exactly as they look, is called a right side view. Figure 1 shows how the right side view will appear when finished.

Examples of right side view drawings are shown on the next two pages. Please note that you are drawing the general outlines of the major features of the object, not any details.

Dimensions and Lines

It would be difficult to make something from a drawing that did not indicate the sizes and features of parts. Dimensions tell the size of the object. They are its measurements. Dimensions also show feature locations. For example, if a hole is to be drilled in an object, a dimension will show the distance between the hole and the edge of the object.

Lines

Dimensions are usually placed on the outside the object. Dimension lines on each side of the number run parallel to the object and shows the area to which the number refers. Look at the figure below. Arrowheads at the end of each dimension line touch extension lines projecting from the object. Extension lines indicate the beginning and end of the distance being measured.

Leader lines are used when dimensioning features such as circles, cylinders, and arcs. They are drawn at an angle to the feature, usually at 45 degrees. The arrows at the end of a leader line points to the center of the feature, although it touches only the feature’s edge. Leader lines also have a short “tail” at the top that extends from the dimension.

General Dimensioning Rules

• Dimensions are never written on the object unless there is no other space available.

• Objects are dimensioned in the view that shows the various dimensions in the clearest way.

• Dimensions for the smallest areas are placed the closest to the object. Other dimensions follow in order of their size. The largest dimension is placed farther away.

• The size for a hole is its diameter.

• The drawing should be drawn so that it is clear as to which part the dimensions refer.

• Dimensions given on the drawing are always the object’s actual size.

Hidden Lines

A “hidden” line represents an edge, hole, or corner that can not be seen when drawing a front, top, or a right side view. Using a series of small dashes as shown in the front view drawing (Figure1) shows where a hidden line is.

Examples of drawings using hidden lines are shown on the next two pages. Please note that you are drawing the general outlines of the major features of the object, not any details.