Basic knowledge of the hottest machining process (

Basic knowledge of machining process (Continued)

determination of three elements of workpiece clamping force

according to the above basic requirements, correctly determining the three elements of clamping force (direction, action point, size) is a problem that cannot be ignored

1. determination of the direction of the clamping force

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

figure a shows the incorrect clamping scheme. The clamping force has an upward component F W, which makes the workpiece leave the original correct positioning position. Figure B shows the correct clamping scheme

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

2. Determination of the action point of the clamping force

(1) the action point of the clamping force should fall within the support range

(3) the action point of the clamping force should fall on the part with good rigidity of the workpiece

figure a the axial rigidity of the thin-walled sleeve is better than that of the radial one. When pressing the Save button to save the experimental data to the database, the workpiece deforms greatly when clamping radially with the claw. If the clamping force is applied along the axial direction, the deformation will be much smaller. When clamping the thin-walled box shown in Figure B, the clamping force should not act on the top surface of the box, but on the convex edge with good rigidity. Or change to three-point clamping as shown in Figure C, and change the position of the force point to reduce clamping deformation

(3) the action point of clamping force should be close to the processing part of the workpiece

as shown in the figure, the clamping force is far away from the processing part, so an auxiliary clamping mechanism should be added to the processing part to prevent vibration during processing and affect the processing quality and safety

3. Estimation of clamping force

in the process of machining, the workpiece is affected by cutting force, centrifugal force, inertia force and gravity. Theoretically, the action of clamping force should be balanced with the action of the above force (torque). However, the magnitude and direction of the cutting force change during the machining process, so the magnitude of the clamping force can only be roughly estimated. Estimation method:

(1) find out the most unfavorable instantaneous state for clamping, and estimate the clamping force required in this state

(2) for simplicity, only the influence of major factors in the force system is considered, and the influence of minor factors in the force system is omitted. Filter element

(3) according to the workpiece state, list the balance equation of output (torque), solve the size of clamping force, and properly consider the safety factor

if you need to estimate the clamping force, please refer to relevant materials

IV. types and characteristics of machining production

(I) production program

the quantity and schedule of products produced by the enterprise within the planning period is called the production program. The annual production program of parts can be calculated according to the following formula:

where n - annual production program of parts (pieces/year)

q - annual production program of products (set/year)

n - quantity of this part in each product (piece/set)

a% - percentage of spare parts; 1. Accurate testing and control will not be achieved; 2. Yamaha Mounter does not have accurate information (or convert reliable data), undistorted input

b% - percentage of waste products

Jinan new era Gold Testing Instrument Co., Ltd. has more technical materials. The size of the production program plays an important role in the production organization form and parts processing process. It determines the specialization and automation and degree of each process, and determines the process methods and equipment that should be selected

(II) production type and process characteristics

the classification of production specialization of enterprises (or workshops, sections, teams, workplaces) is called production type. Production types can generally be divided into three types: single piece production, batch production and mass production

1. single piece production

the basic characteristics of single piece production are: a wide variety of products are produced, the output of each product is small, and there is little repeated production. For example, the manufacturing of heavy machinery products and the trial production of new products belong to 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. For example, machine tool manufacturing and motor manufacturing belong to batch production. Batch production can be divided into three types according to its batch size: small batch production, medium batch production and mass production. The flexibility is better than pet. Among them, the process characteristics of small batch production and mass production are similar to those of single piece production and mass production respectively; The technological characteristics of medium batch production lie between small batch production and mass production

3. Mass production

the basic characteristics of mass production are: large output, few varieties, and most workplaces repeatedly process a certain process of a certain part for a long time. For example, the manufacturing of automobiles, tractors, bearings, etc. is mass production

in addition to the production program, the division of production types should also consider the size and complexity of products. The relationship between production type and production program is listed in the table, which can be used for reference when determining production type

table relationship between production program and production type

production type

annual production program of parts (pieces)

heavy parts

medium parts

light parts

single piece production

small batch production

medium batch production

mass production

5 ~ 100

100 ~ 300

1000

10 ~ 200

200 ~ 500

.500 ~ 5000

> 5000

100 ~ 500

500 ~ 5000

5000 ~ 50000

> 50000

different production types, The process methods, equipment and process equipment used in product manufacturing and the organizational form of production are different. For mass production, high-efficiency equipment and process methods should be adopted as far as possible to improve productivity; General equipment and process equipment should be used for single piece and small batch production, and advanced numerical control machine tools can also be used to reduce production costs. Refer to the table for the process characteristics of various production types

table process characteristics of various production types

process characteristics

production types

single small quantity

medium batch

interchangeability of a large number of

parts

repair method, fitter repair, lack of interchangeability

most of them are interchangeable. When the assembly accuracy is high, the grouping assembly method is flexibly applied, while retaining some repair methods

which have wide interchangeability. A few of them have high assembly accuracy, and the manufacturing method and machining allowance of group assembly method and adjustment method

blank

wood mold manual manufacturing or free forging are adopted. The blank precision is low, and the machining allowance is large

some parts adopt metal mold casting or die forging. The blank precision and machining allowance are medium

metal mold machine modeling, die forging or other efficient methods are widely used. High blank precision, small machining allowance

machine tool equipment and its layout form

general machine tool. According to the machine tool category, the machine group layout is adopted

some general-purpose machine tools and high-efficiency machine tools. Arrange the equipment in sections according to the workpiece category

efficient special machine tools and automatic machine tools are widely used. Arrange the equipment according to the assembly line and automatic line

process tooling

most of them use general fixtures, standard accessories, general cutting tools and universal measuring tools. Achieve the accuracy requirements by scribing and trial cutting

fixtures are widely used, and some of them are aligned and clamped to meet the accuracy requirements. More special tools and measuring tools are used

special efficient fixtures, composite tools, special measuring tools or automatic inspection devices are widely used. Achieve accuracy requirements by adjustment method

technical requirements for workers

need workers with higher technical level

need workers with a certain technical level

have high technical level requirements for adjusters and lower technical level requirements for operators

process documents

have process cards, key processes need process cards

have process cards, key parts need process cards

have process cards and process cards, Key processes need adjustment cards and inspection cards

cost

high

medium