Machining process planning refers to the entire process and cannot be judged by the nature of a particular process or the machining of a particular surface. For example, some positioning datums need to be machined accurately in the semi-finishing stage or even in the roughing stage. Sometimes, in order to avoid dimensional chain conversions, semi-finishing of certain secondary surfaces can also be arranged in the finishing stage.
When the processing method and processing stage of the part surface are determined, the processing of each surface in the same processing stage can be combined into a number of work steps.
The method of CNC Machining process division
In the CNC machine tool processing parts, generally according to the principle of process concentration division process, divided into the following methods.
(1) according to the use of tools divided
To the same tool to complete the process as a process, this division method is suitable for the workpiece to be machined surface more situations. Machining centres often use this method.
(2) Divided by the number of times the workpiece is mounted
The process that can be completed with one clamping of the part is used as a process. This method is suitable for parts with little machining content, where the entire machining content is completed in one clamping under the premise of ensuring the machining quality of the part.
(3) By roughing and finishing
The part of the process completed in rough machining as a process, the part of the process completed in finishing as another process. This division method is suitable for parts with strength and hardness requirements, the need for heat treatment or parts with high accuracy requirements, the need for effective removal of internal stress, as well as parts after processing deformation is large, the need to divide the parts processing by rough and finish machining stages.
(4) by processing part of the part of the process to complete the same surface as a process.
For processing surface and more complex parts, should be reasonable arrangements for CNC machining, heat treatment and auxiliary processes in the order, and solve the problem of the interface between processes.
The Principles for the division of the machining process
The part is composed of several surfaces, which have their own accuracy requirements, and there are corresponding accuracy requirements between the surfaces. In order to achieve the design accuracy requirements of the part, the processing sequence should follow certain principles.
1) The principle of roughing first and then finishing
The processing order of each surface in accordance with the roughing, semi-finishing, finishing and finishing order, the purpose is to gradually improve the precision and surface quality of the parts processing surface. If all the surfaces of the parts are processed by CNC machine tools, the process is generally arranged in accordance with the order of roughing, semi-finishing and finishing, i.e. roughing is completed and then semi-finishing and finishing is carried out. Rough machining can quickly remove most of the machining allowance, and then finish machining each surface in turn, so as to improve production efficiency, but also to ensure the machining accuracy of the parts and surface roughness. The method is suitable for machining surfaces with high positional accuracy requirements. This is not absolute, such as for some size accuracy requirements of the processing surface, taking into account the stiffness of the part, deformation and size accuracy requirements, can also consider these processing surface respectively according to roughing, semi-finishing, finishing the order to complete. For high accuracy requirements of the processing surface, in roughing, finishing processes, the parts are best set aside for a period of time, so that the roughing of the parts after the surface stress is completely released, reduce the degree of stress deformation of the surface of the parts, which is conducive to improving the machining accuracy of the parts.
(2) reference surface first processing principle
Processing a start, always used as a finishing benchmark surface processing out, because the positioning of the benchmark surface precision, clamping error is small, so any parts of the processing, always first positioning benchmark surface for roughing and semi-finishing, if necessary, but also finishing, for example, shaft parts are always positioning benchmark surface for roughing and semi-finishing, and then finishing. For example, shaft parts are always machined with a central bore, then the bore system and other surfaces are machined with the central bore face and locating hole as the finishing datum. If there is more than one fine reference surface, it should be in accordance with the order of reference conversion and gradually improve the processing accuracy of the principle to arrange the processing of the reference surface.
3）First face and then hole principle
For the box class, bracket class, body class and other parts, plane contour size is larger, with plane positioning is more stable and reliable, so should be processed first plane, after processing holes. In this way, not only to make the subsequent processing has a stable and reliable plane as a positioning reference surface, and in the flat surface processing holes, processing becomes easier, but also conducive to improving the hole processing accuracy. Usually, you can divide the process according to the processing parts of the parts, generally first processing simple geometry, after processing complex geometry; first processing lower precision parts, after processing higher precision parts; first processing plane, after processing holes.
(4) First inside, then outside principle
For precision sleeve, the coaxiality of its outer circle and hole requirements are high, generally use the principle of first hole and then outer circle, that is, the outer circle as a positioning reference for processing the hole, and then a higher accuracy hole as a positioning reference for processing the outer circle, so as to ensure that the outer circle and hole has a high coaxiality requirements, and the use of fixture structure is also very simple.
(5) the principle of reducing the number of tool changes
In CNC machining, the processing sequence should be arranged as far as possible according to the order in which the tool enters the processing position.
Machining trades
A trade is a classification term for an object of work, also known as a type of work, such as electrician, clerk, etc. Machining trades are generally divided into three categories: cold machining, hot machining and other trades.
Mechanical processing cold processing category includes.
- 1. clampers: clampers are mostly a manual method of operation of a type of work.
- 2. Turner: Turner refers to the operation of the lathe, the workpiece rotating surface for cutting and processing of the type of work.
- 3. Millwright: A millwright is a trade that operates various milling machines to mill and process work.
- 4. Planer: Planer refers to the operation of a variety of planer equipment, the work of planing processing of the workpiece of the type of work.
- 5. Grinder: A grinder operates various grinding machines to grind workpieces.
In addition to the above-mentioned types of work, the common types of cold processing work: sheet metal workers, borers, stamping workers, combined machine tool operators, etc.. The hot working category of mechanical processing includes
- 1. Casting workers: casting workers refer to the operation of casting equipment, casting processing jobs.
- 2. Forging worker: forging worker refers to the operation of forging machinery and equipment and auxiliary tools, metal workpiece blank preparation, heating, upsetting, punching, forming and other forging processing of the work.
- 3. Heat Treatment Worker: Heat Treatment Worker refers to the operation of heat treatment equipment, heat treatment processing of metal materials.
Other types of work include
- 1. Machinery and equipment maintenance worker: refers to the type of work engaged in the installation, maintenance and processing of equipment.
- 2. Maintenance Electrician: refers to the type of work engaged in the installation, commissioning and maintenance and repair of electrical systems of factory equipment.
- 3. Welder: A welder is a trade that operates welding and gas cutting equipment to weld or cut and shape metal workpieces.
- 4. Electrical processing equipment operator: in machinery manufacturing, in order to process a variety of difficult to process materials and a variety of complex surfaces, often directly using electrical energy, chemical energy, heat, light energy, sound energy and other parts processing, this processing method is generally known as special processing. Among them, the operation of electrical processing equipment for parts processing, known as electrical processing equipment operator.