Custom CNC machining applications
Product Description
CNC program staff in process analysis must have the machine manual, manual programming by scale, standard tools, fixture, cutting the manual data, according to the shape of the material, the outline of the processed workpieces, the machining accuracy, and choose the right machine, setting processing scheme, determine the machining sequence of parts, each working procedure used cutting tools, fixture, cutting dosage, etc. In addition, programmers should continue to summarize and accumulate practical experience in process analysis and write high-quality CNC machining programs.
First, the reasonable selection of machine tools
There are generally two situations when using CNC machine tools to process parts. The first case: there are parts drawing and blank, to choose the CNC machine tool suitable for processing the parts. The second case: there is already a CNC machine tool, to choose suitable parts for processing on the machine tool. In either case, the main factors to be considered are the material and type of the blank, the complexity of the outline shape of the parts, the size, the processing accuracy, the number of parts, the heat treatment requirements, etc. To sum up, there are three points: (1) to ensure the technical requirements of processing parts, processing qualified products. ② It is beneficial to improve productivity. ③ As far as possible to reduce production costs (processing expenses).
Two, numerical control machining parts process analysis
Numerical control processing technology analysis involves a wide range, in this only from the possibility of numerical control processing and convenience of two aspects to be analyzed.
(1) The size data on the part drawing shall conform to the principle of convenient programming
1. The dimension marking method on the part drawing should adapt to the characteristics of NC machining. On the part drawing of NC machining, the dimension should be noted with the same datum or the coordinate dimension should be given directly. This marking method is not only convenient for programming, but also for the coordination between dimensions, which brings great convenience in maintaining the consistency of design datum, process datum, testing datum, and programming origin setting. As part designers generally consider assembly and other use characteristics more in dimension marking but have to use the local scattered marking method, which will bring a lot of inconvenience to the process arrangement and NUMERICAL control machining. Due to the high precision of NC machining and repeated positioning, the use characteristics will not be damaged due to large accumulated errors. Therefore, the local scattered labeling method can be changed to the same reference size or directly give a coordinate size labeling method.
2. The conditions of geometric elements forming the contour of parts should be sufficient
Base points or node coordinates are computed during manual programming. In automatic programming, all geometric elements that make up the contour of a part are defined. Therefore, in the analysis of part drawing, it is necessary to analyze whether the given conditions of geometric elements are sufficient. For example, an arc and a straight line, an arc and an arc are tangent to each other on the drawing, but according to the dimensions given on the drawing, when calculating the tangent conditions, they become intersecting or separated from each other. Due to the insufficient condition of the geometrical elements of components, it is impossible to start programming. In such cases, the part designer should be consulted.
(2) The structure of the processing parts should conform to the characteristics of NUMERICAL control processing
1) It is best to adopt uniform geometric type and size for the cavity and shape of parts. This can reduce the number of tool specifications and tool changes so that programming is convenient and production efficiency is improved.
2) The size of the inner groove fillet determines the size of the tool diameter, so the radius of the inner groove fillet should not be too small. The process quality of the parts is related to the height of the processed contour and the radius of the arc.
3) When the parts are milling the bottom plane, the radius r of the groove bottom fillet should not be too large.
4) Unified benchmark positioning should be adopted. In numerical control machining, if there is no unified datum positioning, the reinstallation of the workpiece will lead to the disharmony of the position and size of the contour on the two surfaces after processing. Therefore, in order to avoid the above problems and ensure the accuracy of the relative position after two clamping processing, a unified reference positioning should be adopted.
It is better to have appropriate holes on the parts as positioning reference holes, if not, to set up process holes as positioning reference holes (such as increasing process lugs on the blank or setting process holes on the allowance to be milling out in the subsequent process). If the process hole can not be made, at least the surface after finishing as a unified benchmark, in order to reduce the error caused by two clamping.
In addition, we should also analyze whether the machining accuracy and dimensional tolerance required by the parts can be guaranteed, whether there are redundant dimensions that cause contradictions or closed dimensions that affect the process arrangement.
Three, the selection of processing methods and processing scheme
(1) selection of processing methods
The selection principle of machining method is to ensure the machining accuracy and surface roughness of the machined surface. Since there are many machining methods to obtain the same precision and surface roughness, the shape, size, and heat treatment requirements of parts should be considered comprehensively in the actual selection. For example, for the IT7 level accuracy of the hole is boring, hinged, grinding and other processing methods can meet the accuracy requirements, but the box on the hole is generally boring or hinged, and should not use grinding. Generally, small size box hole selection reaming, when the aperture is larger, should choose boring. In addition, the requirements of productivity and economy should be considered, as well as the actual situation of the factory's production equipment. For the economical machining accuracy and surface roughness of common machining methods, please refer to the relevant process manual.
(2) Principles for determining processing schemes
Parts of the more precise surface processing, often through rough machining, semi-finishing, and finishing gradually achieved. For these surfaces, it is not enough to select the corresponding final processing method according to the quality requirements, but also to determine the correct processing scheme from blank to final forming.
Determine the processing scheme, should first be based on the accuracy of the main surface and surface roughness requirements, preliminary determination to meet the requirements of the processing method. For example, for the aperture of the IT7 precision hole, the final processing method to take fine reaming, fine reaming before usually through drilling, reaming and coarse reaming, and other processing.
Fourth, the division of process and working steps
(I) Division of working procedures
With the use of CNC lathe processing parts, the process can be more centralized, in a clamping as far as possible to complete most or all of the process. First of all, according to the parts drawing, consider whether the processed parts can be in a CNC machine tool to complete the whole parts of the processing work, if not, should decide which part of the CNC machine tool processing, which part of the processing in other machine tools, that is, the parts of the processing process. The general process division has the following ways :(2) the division of the work step mainly from the processing accuracy and efficiency of two aspects. In a process often need to use different tools and cutting amounts, different surface processing. In order to facilitate the analysis and description of the more complex process, the process is subdivided into working steps. The following to the processing center as an example to illustrate the principle of the division of work steps:
1) The same surface shall be roughed, semi-finished, and finished in turn, or all the processed surfaces shall be roughed and finished separately.
2) For both milling surface and boring parts, can be first milling surface after boring. The precision of the hole can be improved by dividing working steps by this method. Because of the large cutting force during milling, the workpiece is prone to deformation. Surface milling after boring, so that it has a period of time to recover, reduce the impact caused by deformation on the accuracy of the hole.
3) Divide working steps according to the tool. The rotary time of some machine workbench is shorter than the tool changing time, so the tool can be divided into different working steps to reduce the number of tool changes and improve the processing efficiency.
In short, the division of process and working step should be considered comprehensively according to the structural characteristics and technical requirements of specific parts.
keyword：cnc machining equipment,custom cnc parts
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