What do you think of mechanical drawing? How many kinds of mechanical drawings are there?

Drawings are the language of communication between engineers and technicians. It is difficult for non-professionals to read mechanical drawings. At first glance, it seems that you can understand why. On closer inspection, it seems that this is not the case. Simple and able to understand mechanical drawings. Machinery is a rigorous and practical subject. As far as drawings are concerned, there is an unclear place that cannot be used to guide practical application.

1. Determine the type of drawing. There are many kinds of mechanical drawings, including assembly drawings, schematic diagrams, schematic diagrams and parts drawings. You must first determine what kind of drawings you have, and then you will know what objects the drawings express, what aspects they express and to what extent.

2. Read the object information. Although the drawings of each person and company will be different, they all follow the national drawing standards. Paintings are for people to see. There are too many special places, and others will lose their meaning if they can't see them. First look at the information such as the name, number, quantity, material (if any), proportion and unit of the object in the title bar (lower right corner). Please refer to the relevant section of the manual for the location of this information.

3. Determine the view. If it is a non-standard diagram such as a schematic diagram, there is no strict concept of view. A standard drawing has at least one view. The concept of view comes from the projection of descriptive geometry. This knowledge can also be seen in the relevant contents of the manual. In short, according to China's drawing standards, an object is called a front view, a left view is called a left view (placed on the right side of the front view), a top view is called a top view (placed below the front view), and there are many views such as sectional views. Reflected in the figure, the view is a "thing", and there will be no size, text, lines and other contents between blocks, but the middle is blank. People who have the ability to look at architecture are familiar with these concepts, and they are all universal.

4. Distinguish between topics and notes. I have determined how many views there are, and then I have to distinguish the subject (this word was invented by me for the time being). The main body is a line that describes a mechanical part (in the two-dimensional world of the actual part, it is a line), which can be divided according to the thickness of the line (thin lines are all marked lines). The main line has only thick solid lines (the thickness can be judged relatively, and the thickness in the standard is also standard), thick dashed lines and section lines.

5. Restore the actual appearance of the part by the main body. This is the point of view, and everything else can be done by reading books and flipping through manuals. Only this kind of thing that needs accumulation and space imagination can't restore the actual part, and there will be jokes about digging wells but building chimneys. If it is difficult to restore, you can carefully determine what each view is (including cross-sectional views and other expressions) and auxiliary dimensions (for example, R stands for radius, and that line is an arc (surface). These notes can be found in the manual and are relatively simple.

6. Determine the size of the parts. You can have a general look at this, just have a general idea. If it is a manufacturer, you can look at it when you need it.

7. The dividing line between domestic and foreign banks. At this point, as long as you have read the drawings and studied the contents expressed in the mechanical design manual, you can be regarded as a layman who can read the drawings, just like after you read the drawings of a house, you know the structure and size of the house, so you can stop here without going into details. However, mechanical drawing information is far more than that.

8. Enter the machine to read the map. Mechanical drawings (standard drawings, schematic diagrams, etc.). Not introduced here) expresses all the design data used in the mechanical industry, such as the structure, size, material and accuracy of a part or component or a machine. Before getting into the topic, we have seen the material and structure, and then we will talk about other information. Because almost all the mechanical data are in the drawings, there are thousands of pages in the mechanical design manual alone, so we can't share all the experience here, only the experience in the industry.

9. accuracy The size of a machine (such as the diameter of a cylinder) is not just the size. Whether the dimension is marked with tolerance (such as 0. Xx) or not, it is a range. This is the precision of machinery, and this concept should always exist. Because mechanical parts are generally produced in batches, it is necessary to accurately control the size of each part (it can't be the same size, with errors) within a certain range. Similarly, parts and assemblies also have shape and position tolerances (that is, whether they are marked or not). Unmarked precision (tolerance) is stipulated in national standards, and the technical requirements of some drawings will state that precision is the soul of mechanical parts and needs to be accumulated to some extent. You can know the accuracy information on each drawing by referring to the manual.

10. Technology. Simply put, the process is how to make (assemble) this part. Although there is no direct information expression of process, mechanical drawing contains the basic process. Once a part is designed, it doesn't make any sense if it can't be processed. How to deal with it is considered by the designer and will be expressed in the drawings.

Roughness: Roughness determines the use requirements and also limits the requirements of processing methods.

Accuracy: For example, the size, position, shape tolerance and roughness requirements of a component (bearing inner hole) will imply its machining process requirements (grinding).

Heat treatment: heat treatment makes the processing feasible and the performance meets the use requirements.

Surface treatment: Surface treatment is generally put forward in technical requirements.