According to the above basic requirements, the correct determination of the three elements of the clamping force (direction, point of action, and size) is a problem that cannot be ignored.
1 . Determination of clamping force direction
(1) The direction of the clamping force should not destroy the positioning of the workpiece.
Figure 3-4a is an incorrect clamping scheme. The clamping force has an upward component force FW, which leaves the workpiece away from its original correct positioning position. Figure b shows the correct clamping scheme.
(2) The direction of the clamping force should point to the main positioning surface.
2 . Determination of the point of action of the clamping force
(1) The point of application of the clamping force should fall within the support range.
The point of action of the clamping force shown in FIGS. 3-5 falls outside the support range of the positioning element, and the correct position is destroyed when clamped, and thus is incorrect.
(3) The point of application of the clamping force should fall on the part where the rigidity of the workpiece is better.
Figure 3-6a The axial rigidity of thin-walled sleeves is better than that of radial ones. When the jaws are clamped radially, the workpiece deforms greatly. If the clamping force is applied axially, the deformation will be much smaller. When clamping the thin-walled box shown in Fig. 3-6b, the clamping force should not act on the top surface of the box, but should act on the stiffer rim. Or, as shown in Figure 3-6c, change to three-point clamping to change the position of the force point to reduce the clamping deformation.
(3) The point of application of the clamping force should be close to the processing area of ​​the workpiece.
As shown in Fig. 3-7, the clamping force is away from the machining area. Therefore, an auxiliary clamping mechanism should be added to the machining area to prevent vibration during machining and affect the processing quality and safety.
3 . Estimation of clamping force size
During the machining process, the workpiece is subjected to cutting force, centrifugal force, inertial force and gravity. In theory, the effect of the clamping force should be balanced with the above-mentioned force (moment). However, the size and direction of the cutting force are changed during the machining process, so the size of the clamping force can only be roughly estimated. Estimated method:
(1) Find the most unfavorable momentary state of clamping and estimate the clamping force required in this state.
(2) For the sake of simplicity, only the influence of the main factors in the force system is considered, and the influence of the minor factors in the force system is omitted.
(3) According to the status of the workpiece, the balance equation of force (torque) is listed, and the magnitude of the clamping force is solved, and the safety factor should also be properly considered.
If you need to estimate the clamping force, please refer to the relevant information.
Fourth, mechanical processing production types and characteristics
(I) Production Plan
The quantity and schedule of products produced by a company during the planning period are called production plans. The annual production schedule of parts can be calculated as follows: 
N in the formula - the annual production plan of the parts (items/year);
Q - annual production plan for products (Taiwan / year);
n - the number of parts in each product (piece/table);
a% - the percentage of spare parts;
b% - Percentage of scrap.
The size of the production program plays an important role in the organization of the production and the processing of the parts. It determines the specialization and degree of automation required for each process, and determines the process method and equipment to be selected.
(II) Production Types and Process Characteristics
The classification of production specialization degree of an enterprise (or workshop, section, team, and workplace) is called a production type. Production types can be generally divided into three types: single-piece production, mass production, and mass production.
1 . Single production
The basic characteristics of single-piece production are: a wide variety of products are produced, and the output of each product is small, and production is rarely repeated. For example, the manufacture of heavy machinery products and the trial production of new products are all single-piece production.
2 . Batch production
The basic characteristics of batch production are: the same products are produced in batches, and the production is repeated periodically. Such as machine tool manufacturing, motor manufacturing and other batch production. Batch production can be divided into small batch production, medium batch production and large batch production according to the batch size. Among them, the process characteristics of small batch production and large batch production are similar to those of single production and mass production, respectively; the characteristics of medium batch production are between small batch production and large batch production.
3 . Mass production
The basic characteristics of mass production are: large output, few varieties, and long-term repetition of the processing of a certain part of a part in most work places. For example, the manufacture of automobiles, tractors, bearings, etc. is all mass production.
Apart from the production program, the division of production types should also consider the size and complexity of the product. Table 3-3 shows the relationship between the type of production and the production plan, which can be used for reference when determining the type of production.
Table 3-3 Relationship between Production Programs and Production Types
Production type
Annual production schedule of parts (pieces)
Heavy parts
Medium-sized parts
Light parts
Single production
Small batch production
Batch production
Mass production
Mass production
<5
5 to 100
100 to 300
300 to 1000
> 1000
<10
10 to 200
200 to 500
500 to 5000
>5000
<100
100 to 500
500 to 5000
5000 to 50000
>50000
Different types of production, product manufacturing process methods, equipment and process equipment used, and the organization of production are different. Large quantities of mass production should use high-efficiency equipment and process methods as much as possible to increase productivity; single-piece small batch production should use general equipment and process equipment, and advanced CNC machine tools can also be used to reduce production costs. The process characteristics of various types of production can refer to Table 3-4.
Table 3-4 Process Characteristics of Various Production Types
Process characteristics
Production type
Single piece
Batch
Large quantities
The interchangeability of parts is interchangeable with the fitting method, fitter repair, and lack of interchangeability. When the assembly precision is high, the group assembly method can be flexibly applied, and at the same time, some repair methods are retained to have a wide range of interchangeability. In a few places where the assembly accuracy is high, the manufacturing method of the blank assembly method and the adjusting method blank and the machining surplus wood mold are hand-made or free-forging. The precision of the blank is low, and most of the machining allowance is cast or die forged. Blanking precision and machining allowance are widely used in metal mold machine modeling, die forging or other efficient methods. High precision of blanks, small machining allowances, machine tools and their layouts, general machine tools. According to the machine tool category, it adopts a cluster arrangement of some general-purpose machine tools and high-efficiency machine tools. According to the classification of work-pieces, the equipment is widely used in high-efficiency special machine tools and automatic machine tools. Arrangement of equipment and process equipment by assembly lines and automatic lines mostly use universal fixtures, standard accessories, general-purpose tools, and universal energy tools. Relying on the scribe line and the trial cutting method to achieve the accuracy requires extensive use of fixtures, and some rely on correcting fixtures to achieve accuracy. More specialized tools and gauges are widely used for specialized high-efficiency fixtures, compound tools, special gauges, or automatic inspection devices. The adjustment method to achieve the accuracy requirements for the technical requirements of workers requires a higher level of technology, the workers need a certain level of technology, the adjustment of the workers' technical level requires high, the operator's technical level requires a lower process documentation, process cards, key processes The process card must have a process card, the key parts must have process cards and process cards, and the key processes need to adjust the card and test card at a higher cost and lowerTrailer Fifth Wheel King Pin,Trailer King Pin Plate,Welding Type Trailer King Pin,Forging Semi-Trailer King Pin
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