Basic knowledge of machining process

According to the above basic requirements, the correct clamping force to determine the three elements (direction, function points, size) is a not to be neglected.

1. Determine the direction of clamping force

(1) the direction of clamping force should not damage the workpiece positioning.

Figure 3-4a is not the correct clamping scheme, the clamping force with upward pitch FW, so that the correct positioning of the workpiece from the original location. Figure b is the correct clamping scheme.

(2) clamping force should point to the main orientation direction of the surface.

2. Determine the point of clamping force

(1) clamping force supporting the role of points should fall within the scope.

Figure 3-5 shows the clamping force acting point fell outside the scope of positioning the supporting element, clamping the correct position will be destroyed, so it is not correct.

(3) clamping force acting point should fall on the better parts of the workpiece rigidity.

Figure 3-6a axial rigidity than the thin-walled sleeve radial rigidity with radial clamping jaws when the large deformation of the workpiece, if the clamping force applied along the axial deformation will be much smaller. As shown in Figure 3-6b clamping thin-walled box, the clamping force should not be acting on the top box, but should function better in the rigid convex edge. Or as shown in Figure 3-6c to three clamping, changing the focus position, in order to reduce clamping deformation.

(3) the role of point of clamping force should be close to the workpiece processing site.

Figure 3-7 shows, the clamping force away from the processing area, processing area should be added in the secondary clamping structure to prevent vibration when machining affect processing quality and safety.

3. Estimation of clamping force size

Process, the workpiece by cutting force, centrifugal force, inertia and gravity, and the role of theoretical clamping force should be used with the force (moment) the role of equilibrium. However, the size and direction of cutting force in the change process is, therefore, the size of the clamping force can only be rough estimates. Estimation method:

(1) identify the instantaneous state of clamping the most negative, to estimate the state of clamping force required.

(2) to simple, only the main factors considered in the force system in the effects of factors omitted in the system of forces in the secondary impact.

(3) According to the state of the workpiece, set out force (moment) of the balance equation, solving for the size of clamping force, should also give due consideration to safety factors.

For clamping force estimates refer to the relevant information.

Fourth, the type and characteristics of mechanical processing

(A) Production Programme

Enterprises in the plan period the number of products as production programs and schedules. Part of the production program can be calculated as follows:

The formula N - program annual production of parts (pieces / year);

Q - the production platform of products (units / year);

n - each the product of the number of parts (parts / unit);

a% - the percentage of spare parts;

b% - the percentage of waste.

The size of the production program of organizational forms and parts production process plays an important role, which determines the required process automation and the degree of specialization, and determines the method to be used in the process and process equipment.

(B) the type and technical characteristics of production

Enterprise (or workshop, steps, team, work) degree of specialization of production as the production type classification. Production types generally can be divided into: single-piece production, mass production, mass production of three types.

1. Single production

Single production of basic characteristics: a wide range of products, each product yield little, and little repetitive. Such as heavy machinery manufacturing and new product testing belong to a single part production.

2. Mass production

Mass production of the basic characteristics are: to produce the same product batches, producing repeated periodically. Such as machine tools, motor manufacturing is mass production. Bulk production batch size can be divided into small groups according to their production, in batch production, mass production of three types. Among them, the small batch production and mass production of the technical characteristics of production and separately with one-piece features a large number of similar production processes; in the batch production process characteristics between a large number of small-batch production and between production.

3. Mass production

Mass production of the basic characteristics: yield, less variety, most of the work to a long term of repeated parts of a working procedure of the processing. For example, cars, tractors, bearings, etc. are all mass production manufacturing.

Types of production and production programs in addition to the division, should consider the size and complexity of the product. Table 3-3 lists the types of production relations and production program, a reference for determining the type of production.

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