Numerical control programming:
The programming methods of NC machining can be divided into manual programming and automatic programming. Manual programming, all the contents of the program are written by hand according to the instruction format stipulated by the numerical control system. Automatic programming is computer programming, which is divided into language-based automatic programming method and drawing-based automatic programming method. However, no matter what automatic programming method is adopted, corresponding hardware and software are needed.
It can be seen that the realization of NC machining programming is the key. But just programming is not enough. NC machining also includes a series of preparatory work that must be done before and after programming. Generally speaking, CNC machining technology mainly includes the following contents:
(1) Select and determine the parts and contents of NC machining;
⑵ Process analysis of NC machining of part drawing;
⑶ Process design of NC machining;
(4) Mathematical processing of part drawings;
5] write processing program sheet;
[6] making control media according to the program list;
Once the verification and modification of the program;
Being preliminary examination and on-site problem handling;
Levies finalize the design and filing of NC machining process documents.
In order to improve production automation, shorten programming time and reduce the cost of NC machining, a series of advanced NC machining technologies have been developed and applied to aerospace industry. For example, computer numerical control is to replace the controller in the numerical control system with a small or microcomputer, and the software stored in the computer performs the calculation and control functions. This soft-connected computer numerical control system is gradually replacing the original numerical control system. Direct numerical control is to directly control multiple CNC machine tools with one computer, which is very suitable for small batch and short cycle production of aircraft. The ideal control system is an adaptive control system that can continuously change the machining parameters. Although the system itself is complex and expensive, it can improve the processing efficiency and quality. The development of numerical control not only improves the numerical control system and machine tools in hardware, but also is the development of software. Computer-aided programming (also called automatic programming) means that programmers write programs in numerical control language, then input them into the computer for translation, and finally the computer automatically outputs punched tape or magnetic tape. APT is a widely used numerical control language. Generally, it is divided into main processing program and post-processing program. The former translates programs written by programmers and calculates tool paths; The latter compiles the tool path into the machining program of NC machine tools. Numerical control machining is to write programs on the computer in advance before machining the workpiece, and then input these programs into the machine tool controlled by the computer program for compulsory machining, or directly write instructions on the control panel of the machine tool controlled by the computer program for machining. The machining process includes: feed, tool change, speed change, reversing, stopping, etc. These are all done automatically. NC machining is an advanced means of modern mold manufacturing. Of course, numerical control machining means must also be used not only for mold parts processing, but also for a wide range of purposes.
Mechanical products refer to finished products or accessories provided by machinery manufacturers to users or markets, such as automobiles, engines and machine tools. , are called mechanical products. According to the traditional custom, any mechanical product can be regarded as a component composed of several parts, and can be divided into different levels of sub-components (also known as sub-components or assemblies) to the most basic parts unit.
The production process of products refers to the whole process in which raw materials become finished products. The production process of mechanical products generally includes:
(1) Production and technical preparation, such as process design, design and manufacture of special process equipment, preparation of production plan, preparation of production materials, etc.
(2) blank manufacturing such as casting, forging, stamping, etc. ;
(3) Processing, cutting, heat treatment and surface treatment of parts;
(4) product assembly, such as assembly, assembly, debugging, inspection and painting;
5] Production services such as supply, transportation and storage of raw materials, purchased parts and tools.
The processing of parts includes the production of blanks, and the process of machining, special processing and heat treatment of blanks to make them qualified parts. Few parts are processed by chip-free processing methods such as precision casting or precision forging. Usually, the production of blank includes casting, forging, welding and so on. Commonly used machining methods include: locksmith machining, turning machining, drilling machining, planing machining, milling machining, boring machining, grinding machining, CNC machine tool machining, broaching machining, grinding machining, honing machining and so on. Common heat treatment methods include normalizing, annealing, tempering, aging, tempering and quenching. Special machining includes: EDM, WEDM, electrolytic machining, laser machining, ultrasonic machining and so on. Only according to the material, structure, shape, size and service performance of the parts, the appropriate processing method can be selected to ensure the product quality and produce qualified parts.
The drafting of process route is the overall layout of the process, and the main task is to select the processing mode of each surface, determine the processing order of each surface and the work order number in the whole process. The formulation of process route must follow certain principles.
In the process from blank to finished product, the total thickness of the metal layer cut off on a machined surface is called the total machining allowance of the surface. The thickness of the metal layer removed in each process is called the machining allowance between processes. For revolving surfaces such as excircles and holes, the machining allowance is considered from the diameter, so it is called symmetrical allowance (that is, bilateral allowance), that is, the thickness of the actually cut metal layer is half of the machining allowance in diameter. The machining allowance of the plane is a unilateral allowance, which is equal to the thickness of the metal layer actually removed. The purpose of leaving machining allowance on the workpiece is to remove machining errors and surface defects left by the previous procedure, such as chilled layer, porosity and sand inclusion layer on the surface of the casting, oxide scale, decarburization layer and surface cracks on the surface of the forging, internal stress layer and surface roughness after cutting. So as to improve the accuracy and surface roughness of the workpiece. The size of machining allowance has great influence on machining quality and production efficiency. Excessive machining allowance not only increases the processing labor and reduces the productivity, but also increases the consumption of materials, tools and electricity, and increases the processing cost. If the machining allowance is too small, it can neither eliminate all kinds of defects and errors in the previous process, nor compensate the clamping error in this process, resulting in waste products. The selection principle is to make the margin as small as possible on the premise of ensuring quality. Generally speaking, the more finishing, the smaller the process allowance.
The machines needed for processing include digital display milling machine, digital display forming grinder, digital display lathe, spark machine, universal grinder, machining center, laser welding, middle wire cutting, rapid wire cutting, wire cutting, cylindrical grinder, internal grinder and precision lathe. , can be used for turning, milling, planing and grinding precision parts. These machines are good at turning, milling, planing and grinding precision parts.
Check:
Inspection is to detect the dimensional accuracy, shape accuracy and position accuracy of blanks, parts, finished products and raw materials with measuring instruments, and to identify the product quality through appearance inspection, nondestructive testing, mechanical performance test and metallographic examination.
Measuring instruments include measuring tools and gauges. Commonly used quantities are steel ruler, tape measure, vernier caliper, caliper gauge, plug gauge, micrometer, angle gauge, dial gauge, etc. Used to detect the length, thickness, angle, cylinder diameter and aperture of parts. In addition, thread can be measured by thread micrometer, three-needle method, thread template, thread ring gauge, thread plug gauge and so on.
Commonly used measuring instruments include buoy pneumatic measuring instrument, electronic measuring instrument, electric measuring instrument, optical measuring instrument and coordinate measuring instrument. , not only can measure the length, thickness, cylinder diameter, aperture and other dimensions of parts, but also can measure the shape error and position error of parts.
Special inspection mainly refers to the detection of internal and external defects of parts. Among them, nondestructive testing is a modern testing technology to detect internal and external defects of parts without damaging the inspected object. Non-destructive testing methods include direct visual inspection, radiographic inspection, ultrasonic inspection and magnetic inspection. Appropriate methods and testing specifications should be selected according to the purpose of nondestructive testing.
Assembly and commissioning:
Any mechanical product is composed of several parts, assemblies and components. According to the specified technical requirements, the process of matching and connecting parts to make them into semi-finished or finished products is called assembly. The process of assembling parts into components is called component assembly; The process of assembling parts, assemblies and components into final products is called final assembly. Assembly is the last production stage in the process of mechanical manufacturing, including adjustment, testing, inspection, painting and packaging.
Common assembly work includes: cleaning, connection, calibration and matching, balancing, acceptance and testing.
Warehousing:
Finished products, semi-finished products and various materials produced by enterprises are put into warehouses for safekeeping to prevent loss or damage, which is warehousing.
Warehousing inspection should be carried out when warehousing, and inspection records and related original records should be filled in; Do a good job in the maintenance and custody of measuring tools, instruments and tools; Relevant technical standards, drawings, files and other information should be properly kept; Keep the workplace and indoor and outdoor clean, pay attention to fire prevention and moisture prevention, and do a good job in safety.
Production type:
The classification of production specialization degree of enterprises (or workshops, sections, teams and groups, workplaces) is called production type. Production types can generally be divided into three types: single production, mass production and mass production.
One-piece production:
The basic characteristics of one-piece production are: there are many kinds of products, the output of each product is very small, and there are few repeated production. For example, the manufacture of heavy machinery products and the trial production of new products all belong to one-piece production.
Mass production:
The basic characteristics of mass production are: mass production of the same product and periodic repeated production. Such as machine tool manufacturing and motor manufacturing, belong to mass production. Mass production can be divided into three types according to its batch size: small batch production, medium batch production and large batch production. Among them, the technological characteristics of small batch production and large batch production are similar to those of single piece production and large batch production respectively; The technological characteristics of medium batch production are between small batch production and large batch production.
Mass production:
The basic characteristics of large-scale 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 manufacture of automobiles, tractors, bearings, etc. It belongs to mass production.