Do you have any books about welding?

1, the concept of mechanical drawing

(1) engineering drawing: an engineering drawing drawn according to the projection method and the provisions of national standards is called engineering drawing.

◆ Engineering drawing can be divided into: mechanical drawing, architectural drawing, hydraulic engineering drawing, etc.

(2) Mechanical drawing: it is the theory and method of drawing mechanical drawing. It is the most basic technical document in production; It is the basis of designing, manufacturing, inspecting and assembling products. It is the engineering language of scientific and technological communication. Its main content is a set of machine parts views drawn by orthogonal projection method, as well as the dimensions and technical requirements needed for processing and manufacturing.

Step 2 infer

Basic concepts of (1) projection

◆ When an object is illuminated by light or sunlight, it will produce shadows on the ground or walls. This phenomenon is called projection.

Orthographic projection: When the projection lines are parallel to each other and perpendicular to the projection plane, the projection of an object on the projection plane is called orthographic projection.

(2) Three views: refers to the front view of an object on the orthographic projection plane, the top view on the horizontal projection plane and the left view on the side projection plane.

◆ Front view: shows the shape, length, height and position in the left, right, up and down directions when looking back from the front of the object.

◆ Top view: shows the shape and length, the dimension in the width direction and the position in the left, right, front and back direction when viewed from above the object.

◆ Left view: shows the shape and width, height dimension and front, back, up and down position of the object when viewed from the left to the right.

3. Drawing perspective

(1) Drawing methods of perspective definition mode: "first perspective" and "third perspective"

According to ◆ISO international standards, the first angle projection method and the third angle projection method are equally effective in expressing the structure of machine parts.

Our country is dominated by the first corner painting (Britain, Germany, etc.). ), while our company focuses on the third-party painting (American, Japanese, Hong Kong-funded and Taiwan-funded enterprises).

◆ Definition of perspective

The first angle of view: it is a method to make the figure obtained by orthographic projection according to the relative position of person (observer), object (machine part) and surface (projection surface).

The third angle of view: it is a method to make the graphics obtained by orthographic projection according to the relative position relationship between people, surfaces and objects.

(2) Examples of angle recognition

◆ The first perspective:

◆ The third perspective:

(3) the third triangle projection view

◆ When each projection plane of the third angle projection method is unfolded, it is the same as that of the first angle projection method, the V plane is fixed, and other projection planes are rotated to the same plane as the V plane.

◆ The expanded top view is located above the front view, and the right view is located on the right side of the front view.

◆ The names of the six basic views obtained by the third triangle projection method are: front view, top view, right view, back view, bottom view and left view.

(4) Names and configurations of the first and third triangle views.

(5) Comparison of two projection methods

◆ Similarities

The views drawn by the two projection methods are obtained by orthogonal projection on three mutually perpendicular projection planes.

-When expanding the projection plane, the V plane is fixed, and the H plane and the W plane are rotated to be the same plane as the V plane, so the projection law of "long alignment, high alignment and equal width" is still maintained between the views in the third triangle projection.

◆ Difference

-The first angle projection is to put the object between the observer and the projection plane, that is, people → objects → maps.

-The third triangle projection is to put the projection plane between the observer and the object, that is, people → pictures → objects. It can also be assumed that the projection plane is transparent and the view is the main content of the observer: reading three views, cross sections and cross sections with common shapes, training common part drawings, reading part drawings and assembly drawings, and basic knowledge of mechanical drawing recognition.

Detailed catalogue of mechanical drawing reading:

Lecture 65438 +0 ~ Lecture 5 Basic knowledge of reading pictures

Mode, three views

Projection characteristics of lines and surfaces, three views of basic geometry

The sixth lecture ~ the first 1 1 talks about three-view reading of common bodies

Projection analysis of three views of cutting body and common intersection body

Three views, complementary views and assembly lines

Lecture 1 1 ~ Lecture 16 How to read views, sectional views and sectional views.

Cross-sectional view and cross-sectional view reading, sketch

Lecture 16 ~ Lecture 20 How to Read Parts Drawings

Overview of part drawings and identification of part drawings

Lecture 265438 +0 ~ Lecture 25 Understanding and Reading of Drawing Methods of Common Parts