The main difference between the CNC machine tool machining center and the ordinary CNC machine tool is that it has the function of automatic tool change. Therefore, the tool change program is a program unique to the machining center. Except for the hate program, the programming method is basically the same as that of the ordinary CNC milling machine.
First of all, it is the content that must be considered before programming the machining center
Since the machining center has the characteristics of process concentration and automatic change, the processing technology of some parts should conform to these characteristics as much as possible, and the multi-process processing such as milling, drilling, boring and tapping should be completed in one clamping as much as possible. However, a single-table machining center cannot include all the processing procedures of a part. It is necessary to give full play to the specialties of the machining center, and reasonably arrange some procedures for processing on other CNC machine tools.
The size of the parts processed by the machining center must be compatible with the machine tool table and each direction stroke. The size of the hole to be machined must be smaller than the allowable size of the automatic changing device, otherwise, it is necessary to use manual tool change or use a rod milling cutter to add arc interpolation to the hole milling method, and the gloomy machining accuracy will be reduced at this time.
Since the machining center has the characteristics of high rigidity and high efficiency, the cutting amount of Lei can be used in the process, so as to save the machining time as much as possible while meeting the machining accuracy. Before the machine is turned on, the cutting tools must be fully prepared to save man-hours. When selecting a machining center as production equipment, a reasonable process plan must be adopted to achieve high-efficiency processing.
When compiling the CNC machining program of the machining center, the process analysis and processing should be carried out according to the workpiece pattern, the CNC machine tool should be selected, the feed route should be formulated, and the tool and cutting amount should be selected before the machining program can be compiled. The following should be considered when programming the CNC machining center. to an aspect;
2. Division of processing steps
Generally, when processing shi parts on the machine tool of the machining center, the process should be arranged according to the principle of process concentration, that is, all the processes can be completed in one clamping as much as possible. At the same time, the rough machining of the workpiece should be arranged on the ordinary machine tool as far as possible, and then clamped to the machining center for processing.
The principle of the division of processing procedures is: according to the rough and rough blue sky sub-process. Taking into account the machining accuracy, stiffness and deformation of the workpiece, the rough and rough machining processes of the workpiece should be carried out separately. That is, rough machining is performed first, then finishing is performed, and then finishing is performed. For box-type workpieces, in order to improve the positional accuracy of the hole, the surface should be machined first, and then the hole should be machined. It is recommended to refer to the following procedures: milling too flat – rough boring – semi-finishing boring – end mill machining – drilling center hole – drilling gadolinium – tapping thread – finishing – whichever and finishing milling, etc. Divide the process according to all the tools, that is, in one clamping, the same tool should be used as much as possible to process the same parts on the finished part, and then another tool should be used to process other parts.
3. Clamping method of workpiece
The positioning and installation of workpieces on the machining center is the same as that of ordinary machine tools, and the positioning datum and clamping scheme should also be selected reasonably. The selected positioning method should have high positioning accuracy, no positioning interference phenomenon and facilitate the installation of the workpiece, and under-positioning is never allowed. At the same time, when selecting the positioning method, the number of clamping should be minimized. When some workpieces need to be clamped twice, the same reference should be used as much as possible to reduce the positioning error. When considering the clamping plan, pay attention to the action point and direction of the clamping force. The clamping force action point should be close to the main support point or within the triangular area formed by the support points.
Combined fixtures should be used as far as possible on the machining center, and special fixtures can be designed if necessary. When choosing a fixture, the characteristics of the CNC machining center should be considered. First, it is necessary to ensure that the coordinate direction of the fixture and the coordinate direction of the machine tool are relatively fixed; the second is to coordinate the dimensional relationship between the workpiece and the machine tool coordinate system.
5. Automatic tool change operation
For automatic tool change, there should be enough space for tool change. Some tools have larger diameter or longer size. When automatic tool change, care should be taken to avoid collision accidents.
The tool change action must be carried out under the condition that the spindle is stopped. In order to save the automatic change time and improve the processing efficiency, the tool selection action and the machining action of the machine tool should be overlapped in time. For example, the tool selection action command can be arranged in the reference point return time before the tool change, and the time used for returning to the reference point is less than the travel action time, then the tool selection action should be arranged in the longer processing block before the tool change. After the tool change is completed, the command to start the spindle needs to be arranged. This arrangement is convenient for the independent height program for each process, and it is also convenient for readjustment due to the unreasonable processing sequence. For the sequence that needs to be called multiple times, G91 incremental programming method can be used to process the key blocks, so that it can be called by M98P method in the main program, which can simplify the program amount.
6. simplify the procedure as much as possible
Use the functions of mirroring, rotation, canned cycle and macro instruction programming provided by the CNC system of the machine tool as much as possible to simplify the program quantity.
7. Determination of the amount of knife to eat
8. When the rigidity of the system allows, try to choose the amount of cutting back to be equal to the machining allowance, so as to reduce the number of machining times and improve the efficiency of adding power. For workpieces with high requirements on machining accuracy and surface quality, a little machining allowance should be left, and finishing is performed at the end.
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- CNC machining can create very similar parts to series parts. It is often more efficient and faster than other rapid prototyping technologies for the manufacture of a quantity of prototypes between 1 and 10 parts . We also recommend CNC machining for parts with large sizes (greater than 600 mm).
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