Machining process route development need to pay attention to what aspects?

Development of the process route is the most critical step in the design of the process regulations, the following aspects of the work to be completed in order.

1, select the positioning benchmark

Location benchmarks include coarse and fine benchmarks. Rough datum refers to the unprocessed surface of the blank as a benchmark. Precision datum refers to the surface has been machined as a benchmark.

1, the selection of coarse datum principle:

1) the principle of reasonable distribution of machining allowance

a, should ensure that the machining of the surface have enough machining allowance: such as the outer circle machining to the axis as a benchmark;

b, to the machining of a small and uniformly important surface for the coarse datum to ensure that the surface of the machining of the surface of the even distribution of the allowance, the surface of the high quality; such as the body of the bed Processing, the first leg of the bed and then process the guide surface;

2) to ensure that the machining surface of the part relative to the non-machining surface has a certain positional accuracy principle

Generally should be non-machining surfaces as a coarse datum, so as to ensure that the non-machining surface relative to the machining surface has a more accurate relative position. When there are several non-machining surfaces on the part, should choose the non-machining surface with high relative positional accuracy requirements of the machining surface as a coarse datum.

3) the principle of easy clamping: choose the surface of the plane as a rough reference to ensure accurate positioning, reliable clamping.

4) coarse datum generally shall not be reused principle: in the same size direction coarse datum is usually allowed to use only once, this is because the coarse datum is generally very rough, repeated use of the same coarse datum processed between the two sets of surface position error will be quite large, therefore, the coarse base shall not be reused in general.

2, the choice of surface machining methods

(1) the economic machining accuracy and surface roughness of various machining methods

Different machining methods such as turning, grinding, planing, milling, drilling, boring, etc., the use of its selection of the different, the accuracy and surface roughness can be achieved is also very different. Even the same machining method, in different processing conditions under the precision and surface roughness are very different, this is because in the processing, there will be a variety of factors on the precision and roughness of the impact, such as the technical level of the workers, cutting amount, tool sharpening quality, machine tool adjustment quality and so on.

Economic machining accuracy of a certain machining method: refers to the machining accuracy that can be achieved under normal working conditions (including intact machine tools and equipment, the necessary process equipment, the standard technical level of workers, the standard consumption of time and production costs).

(2) the choice of machining methods and machining programs

based on the technical requirements of the machined surface, to determine the machining methods and machining programs;

This program must be stable and reliable in ensuring that the parts to meet the requirements of the drawings, and in terms of productivity and machining costs are the most economically rational.

To consider the nature of the material to be processed;

For example, hardened steel with the grinding method; and non-ferrous metals are grinding difficulties, generally using diamond boring or high-speed precision turning methods for finishing.

To consider the production program, that is, consider the productivity and economy. Such as: large quantities of production should be selected with high efficiency processing methods, the use of specialized equipment. For example, the plane and the hole can be broached, shaft parts can be semi-automatic hydraulic imitation lathe processing, disk or set of parts can be used in single-energy lathe processing.

Should consider the plant's existing equipment and production conditions: that is, make full use of the plant's existing equipment and process equipment.

In the selection of processing methods, first of all according to the main surface of the parts of the technical requirements and specific conditions of the plant, the first selected its final process method, and then selected one by one the surface of each of the relevant leading process processing methods.

3, machine tools and equipment and process equipment selection

1, the size of the selected machine tools and equipment should be adapted to the size of the workpiece form;

2, the accuracy level should be adapted to the requirements of this process;

3, the motor power should be adapted to the power required for this process;

4, machine tools and equipment, automation and productivity should be adapted to the type of workpiece production. efficiency should be compatible with the type of workpiece production.

The choice of process equipment will directly affect the workpiece machining accuracy, productivity and manufacturing costs, should be appropriate according to different circumstances:

1, in small and medium batch production conditions, should first consider the selection of general-purpose process equipment (including fixtures, cutting tools, gauges and auxiliary equipment);

2, in large quantities of large-scale production, according to the requirements of the processing of the design and manufacture of special process equipment. Equipment.

The selection of machine tools and equipment and process equipment should not only consider the current benefits of investment in equipment, but also consider the possibility of product restructuring and conversion, should be made flexible enough.

4, the division of the processing stage

1) according to the technical requirements of the parts processing stage.

Divided into the following stages:

Rough machining stage:In this stage is mainly to try to remove most of the residual amount, the main consideration of productivity.

Semi-finishing stage:In this stage, the main purpose is to prepare for the finishing of the main surfaces and to complete the final machining of the secondary surfaces (drilling, tapping, milling keyways, etc.).

Finishing stage: in this stage is mainly to ensure that the main surfaces to meet the requirements of the drawings, the main task is to ensure the quality of processing.

Finishing stage:In this stage is mainly to obtain high quality of the main surface and dimensional accuracy.

2) The main purpose of dividing the machining process of parts into machining stages is:

(1) to ensure the quality of parts processing (because the workpiece has internal stress deformation, thermal deformation and deformation of the force, precision, surface quality can only be gradually improved,);

(2) conducive to the early discovery of defects in the blanks and be dealt with in a timely manner;

(3) conducive to the reasonable Utilization of machine tools and equipment.

(4) to facilitate the interspersed heat treatment process: interspersed heat treatment process must be divided into several stages of processing, otherwise it is difficult to give full play to the effect of heat treatment.

In addition, the workpiece processing is divided into several stages, but also helps to protect the surface of the finishing process is less bump damage.

5, the division of the process

In the development of the process, in order to facilitate the organization of production, scheduling and balancing of the load of the machine tool, the process is often divided into a number of processes. Dividing the process has two different principles: that is, the concentration of the process and the process of decentralization.

Process concentration principle

Process concentration principle of organizing the process, that is, each process includes as much as possible, the content of the processing of many processes to form a centralized process.

Maximum process concentration, that is, in a process to complete the processing of all surfaces of the workpiece. The use of CNC machine tools, machining centers according to the principle of process concentration organization process, production adaptability, but good, relatively easy to change production, although the one-time investment in equipment is higher, but because of sufficient flexibility, is still receiving more and more attention.

The principle of process dispersion

The principle of process dispersion according to the organization of the process, that is, to make each process includes as little as possible.

Maximum process dispersion is that each process includes only a simple step. :The traditional assembly line, automatic line production is basically according to the principle of process dispersion of the organization of the process, this organization can achieve high productivity production, but the adaptability of the product modification is poor, the transfer of production is more difficult.

6, process order arrangement

1) machining process arrangement principle

1, the first datum surface after the other surfaces: the datum surface is processed first, and then the datum surface positioning to process the other surfaces, in order to ensure the quality of processing.

2, first roughing after finishing: that is, roughing in the front, finishing in the back, roughing and finishing separately.

3, the main surface after the secondary surface: such as the main surface refers to the assembly surface, the working surface, the secondary surface refers to the key bad, coupling with the light hole.

4, the first processing plane after processing holes: the plane contour size is large, the plane positioning installation stability, usually to the plane positioning to process holes.

2) heat treatment process and surface treatment process arrangement: according to the purpose of heat treatment, the arrangement of heat treatment in the processing of the location.

1, annealing: the steel is heated to a certain temperature, held for a period of time, followed by a slow cooling from the furnace of a heat treatment process. Its role is to: eliminate internal stresses, improve strength and toughness, reduce hardness, improve cutting and machinability. Application: high-carbon steel using annealing to reduce hardness; placed before rough machining, after the blank is manufactured.

2, normalizing: the steel is heated to a certain temperature, held for a period of time from the furnace, cooled in the air in a heat treatment process. Note: heated to a certain temperature, which is related to the amount of steel containing C, generally below the solid phase line of about 200 degrees. Its role is: to improve the strength and hardness of steel, so that the workpiece has the appropriate hardness, improve cutting and machinability. Application: Low carbon steel is normalized to improve hardness. Put before rough machining, after the blank is manufactured.

3, tempering: the quenched steel heated to a certain temperature, held for a period of time, and then placed in the air or water cooling a method of heat treatment. :Its role is: to stabilize the organization, eliminate internal stresses, reduce brittleness.

4, tempering treatment (quenching and then high-temperature tempering): its role: is to obtain a detailed and uniform organization, improve the overall mechanical properties of parts. :Application: arranged after roughing, before semi-finishing. Commonly used in medium carbon steel and alloy steel.

5, aging treatment: its role: is to eliminate the blank manufacturing and machining of internal stress. :Application: generally arranged in the blank manufacturing out and rough machining. Commonly used in large and complex castings.

6, quenching: the steel is heated to a certain temperature, held for a period of time, and then rapidly cooled in the cooling medium to obtain a high hardness organization of a heat treatment process. :Its role is: to improve the hardness of the parts. Application: generally arranged before grinding.

7, carburizing treatment: improve the hardness and wear resistance of the surface of the workpiece, can be arranged before or after semi-finishing.

8, in order to improve the wear resistance of the surface of the workpiece, corrosion resistance arrangements for the heat treatment process as well as for decorative purposes and arrangements for the heat treatment process, such as chromium plating, zinc plating, hair of the orchid, etc., generally arranged in the final stage of the process.

3) the arrangement of the inspection process, in order to ensure the quality of parts manufacturing, to prevent the production of scrap, need to be arranged in the following occasions inspection process:

1, roughing all the end of the end;

2, sent to the outside of the workshop before and after the processing;

3, long working hours and the important process before and after the process;

4, after the final processing.

In addition to arranging the geometric inspection process, some parts have to arrange the inspection process of flaw detection, sealing, weighing, balancing and so on.

4) the arrangement of other processes

1, parts of the surface or the inner cavity of the burr on the quality of the machine assembly has a great impact on the cutting process, should be arranged to deburr the process.

2, parts before entering the assembly, generally should be arranged to clean the process. Workpiece bore, box cavity easy to retain chips, grinding, honing and other finishing processes, tiny abrasive particles are easy to adhere to the surface of the workpiece, pay attention to cleaning.

3, after the process of magnetic clamping workpiece, to arrange the demagnetization process, do not let the workpiece with residual magnetism into the assembly line.