Lesson 1 Mechanical Drawing

Big Mouth

Directions: Read the following words. Mark the one whose underlined part has NOT the same pronunciation as the given phonetic symbol.

Big Ears

Vitruvian Man

Directions: Fill in the blanks according to what you have heard.

I’m Steve Ember.

And I’m Shirley Griffith with EXPLORATIONS in VOA Special English. Today, we tell about one of the greatest thinkers in the world, Leonardo da Vinci. He began his (1)as an artist. But his (2)in the world around him drove him to study music, math, science, (3) and building (4). Many of his (5)were centuries ahead of his time.

We start with one of Leonardo da Vinci’s most famous (6), called “Vitruvian Man.”This work is a good example of his ever questioning mind, and his (7)to bring together art, math and science.

“Vitruvian Man” is a detailed (8)of a man’s body, which is drawn at the center of a(9). The man’s stretched arms and legs are in two (10), showing the range of his (11). His arms and legs touch the (12)of the square and circle.

With this drawing Leonardo was considering the (13)of the human body and its relationship to (14)and the writings of the ancient Roman building designer Vitruvius.

Leonardo wrote this about how to develop a complete mind, “Study the science of art. Study the art of science. Develop your senses — especially (15). Realize that everything connects to everything else.”

Small Notebooks

Directions: Choose the best answer according to what you have heard.

1.What did Leonardo da Vinci do to record his thoughts and project ideas?

A.He made drawings and explained them in details in a series of small notebooks.

B.He did experiments with them.

C.He succeeded in having many of them built during his lifetime.

D.He didn’t want people to know his findings.

2.According to the passage, Leonardo designed the following engineering devices except______.

A.weapons

B.engines

C.bridges

D.robots

3.What kind of early versions of modern machines did Leonardo da Vinci design?

A.Boat

B.Tank and helicopter

C.Motor

D.Container and train

4.Which of the following is true statements?

A.He was born before his parents got married.

B.Experts do not know for sure about his father.

C.He lived in a family quite different from that of others.

D.He was greatly interested in drawing, sculpting and observation.

5.How did Leonardo study the human body?

A.He learned from his teacher, Andrea del Verrocchio. B.He took special training programs.

C.He developed extraordinary artistic skills.

D.He took apart and examined dead bodies.

A Great Artist

Directions:Decide whether the following statements are true or false according to what you have heard.

1.His mind was too active to finish his many projects.

2.“Adoration of the Magi” is a famous religious painting he finally finished.

3.He was well known for his knowledge of geometry, volume and depth.

4.In 1482, Leonardo was invited to work as an artist in Milan.

5.In “Virgin of the Rocks”, Leonardo observed the nature carefully to paint many kinds of plants.

Big Mind

Engineering Drawings

A washing machine and a robotic hand can be clearly represented for visual purpose by photographs. However, these products could not be manufactured solely from photographs. Detail drawings must be prepared that note the exact shape, size and material composition of each component; assembly drawings that show how the total product is put together by fastening each part in proper sequence are also needed.

Engineering drawing is the means by which engineers design products and create instructions for manufacturing parts. An engineering drawing can be a hand drawing or computer model showing all the dimensions necessary to manufacture a part, as well as assembly notes, a list of required materials, and other pertinent information. Engineering drawings are legal documents, so they must be formal and precise.

In modern manufacturing industry, several types of drawings are acceptable. However, the standard engineering drawing is the multi-view drawing. An engineering drawing usually contains two or three views ( front, top, and side ). Each view is an orthographic projection of objects. The projection on the frontal plane ( x-z ) is fixed and the image is called front view. With the projected image, the horizontal plane ( x-y ) is rotated 90°clockwise on the x axis; the result is the top view of the object. The profile plane ( y-z ) is rotated 90°clockwise about z axis to obtain the side view.

Line types and conventions

Acceptable quality of a drawing is dependent on the density and uniformity of line work ( and lettering ). Types of lines described here are merely line conventions, but in every case, each type of line shall be opaque and of uniform width.

Scales

Drawings shall be made to full scale unless the parts ( or assembly ) are too large to permit it or so small and complex that drawing to an enlarged scale is essential for clarity. When the main views of large parts are drawn to a reduced scale, the detail views “taken” to clarify detail should be made to full scale whenever possible.

Sketch drawings

A sketch is a quickly executed freehand drawing that is not intended as a finished work. In general, sketching is a quick way to record an idea for later use.

Detail drawings

A detail drawing should be a complete and accurate description of a part, with carefully selected views and well-located dimensions of the part. The detail drawing should include all of the necessary information to enable procurement, manufacture and should identify all of the relevant codes and standards. Finished surfaces should be indicated and all necessary shop operation shown. The item weight/mass should also be included for reference. The title should give the material of which the part is to be made and should state the number of the parts that are required for the production of an assembled unit.

Assembly drawings

A drawing that shows the parts of a machine or machine unit assembled in their working positions is an assembly drawing. A typical assembly drawing may contain the following:

· one or more views, including sections or auxiliaries

· enlarged views to show small details

· overall or specific dimensions needed for assembly

· notes on manufacturing processes required for assembly

· balloons to indicate item number

· parts list or bill of materials ( BOM )

Assembly drawings vary somewhat in character according to their use, such as, design-assemblies, working drawing assemblies, general assemblies, installation assemblies and check assemblies.

Power Speech

Dialogue 1

Mike: Hello. I heard the U.S. Standard for multi-view drawing is different from that of China.

Lisa: Yes. In the United States and Canada, the third-angle projection is the system used. A multi-view drawing usually contains two or three view ( front, top, and right side ). While in China, a multi-view drawing usually contains front view, bottom view, left side view.

Mike: Oh, I see.

Lisa: Each view is an orthographic projection of a plane. In the Figure 1-1, the four quadrants of the x-z plane ( called the I, II, III, and IV angles ) are illustrated. For the third-angle projection, we always place the object in the third quadrant and project the object in three planes. This is done by projecting the object onto the frontal, horizontal and profile planes.

Mike: I see. Thank you very much.

Figure 1-1

Dialogue 2

Judy: What is manufacturing process of parts?

Peter: The process by which the shape, dimensions and performances of raw materials or rough casting are changed directly by mechanical manufacturing into desired parts is called component manufactured part production, or process route.

Judy: Here is the part drawing (Figure 1-2). Could you tell me what process route we should adopt?

Peter: Milling face ( 2 inch face mill ), milling profile ( 1 inch end mill ), center drill ( No.3 center drill ) and chamber, drill hole is ? 0.191 ( No.11 twist drill ). Machine other face: Milling face ( 2 inch face mill ), chamber hole ( No. 3 center drill ). Machine groove and slot: Machine slot ( 6 inch DIA 0.094 inch wide slot saw ), machine groove ( 1 inch groove tool ).

Judy: Thank you very much.

Peter: You are welcome.

Figure 1-2