CNC milling machine is generally suitable for various types and small and medium-sized batch production. In order to clamp workpieces of different shapes and sizes, the fixture processed by CNC milling machine should be flexible, and the workpieces of various shapes and sizes can be clamped by proper adjustment. The special fixture of CNC milling machine has four functions: positioning, clamping, guiding and tool setting. The CNC machine tool is usually equipped with touch test head, tool presetting instrument and tool setting parts.
The precise positioning accuracy controlled by the program on the CNC machine tool can complete the tool guiding function in the fixture. Therefore, the fixture in NC machining usually does not need the function of orientation and tool setting, only needs the function of positioning and clamping, which can meet the needs of use.
(1) NC machining fixture should be able to use pneumatic, hydraulic, electric and other active clamping equipment to clamp quickly, so as to shorten the auxiliary time and provide the efficiency of NC machining.
(2) CNC milling machine model is used to NC multi-faceted processing. To prevent the fixture layout including the components on the fixture from interfering with the tool motion track, the fixture layout should not hinder the tool from multi-faceted machining of various parts of the workpiece.
(3) The fixture itself should have enough rigidity to adapt to large cutting parameters. Numerical control machining has the characteristics of process convergence. In one clamping of workpiece, it is necessary to carry out rough machining with large cutting force and finish machining to meet the demand of precision at the end of the workpiece. Therefore, the stiffness and clamping force of the fixture should meet the demand of large cutting force.
(4) The positioning of the fixture should be firm, the positioning elements should have high positioning accuracy, and the positioning position should be convenient for chip removal without chip accumulation. If the positioning surface of the workpiece is too small, the technical boss or auxiliary datum can be added.
(5) For the type of CNC milling machine, the minimum clamping deformation shall be ensured for the workpiece with small stiffness,
For example, make the clamping point close to the supporting point and prevent the clamping force effect on the hollow area of the workpiece. When rough machining and finish machining are finished in the same process, if the above methods can not control the workpiece deformation within the range of machining accuracy requirements, the program shall be suspended before finishing, and the operator shall change the clamping force (properly reduced) before finishing after rough machining, so as to reduce the influence of clamping deformation on machining accuracy.
Numerical control milling machine is a kind of machine tool which integrates digital control system on ordinary milling machine, and can carry out milling more accurately under the control of program code. It has the following features:
- Parts processing has strong adaptability and flexibility, and can process parts with extremely disordered shape or difficult to control scale, such as mold parts, shell parts, etc;
- At present, the pulse equivalent of CNC equipment is usually 0.001mm, and the high-precision CNC system can reach 0.1 μ M. in addition, the CNC machining also avoids the operator’s error;
- It can process the parts which are difficult to machine or cannot be processed by machine tools, such as the disordered curve parts described by mathematical model and the three-dimensional curved surface parts;
- It can process parts that need to be processed in multiple processes after one clamping and positioning;
- With high production efficiency, CNC milling machine usually does not need to use special fixture and other special process equipment. When replacing the workpiece, it only needs to call the processing program stored in the CNC equipment, clamp things and adjust tool data, thus greatly shortening the production cycle. Secondly, CNC milling machine has the functions of milling machine, boring machine and drilling machine, so that the process is highly concentrated and the production power is greatly improved. In addition, the spindle speed and feed speed of CNC milling machine are stepless, so it is helpful to select the best cutting parameters;
What is CNC machine tool
CNC milling machine is the abbreviation of digital control machine tool, which is an automatic machine tool equipped with program control system
The control system can process the program with control code or other symbol instructions logically, decode it, express it with coded number, and input it into CNC device through information carrier. After calculation and processing, the CNC device sends out various control signals to control the action of the machine tool. According to the shape and size required by the drawing, the parts can be processed automatically.
Similarities and differences between machining center and CNC milling machine:
Like CNC milling machine, machining center is also composed of CNC system, servo system, mechanical body, hydraulic system and other parts.
But machining center is not the same as NC milling machine. The biggest difference between machining center and NC milling machine is that machining center has the function of automatic tool exchange. By installing different tools in the tool magazine, they can pass through in one clamping. In addition, the machining range of the two is different. The functions of machining center include milling workpiece, drilling workpiece, setting space, etc The machine can only mill the workpiece. The automatic tool changing device can change the cutting tool on the spindle to realize the functions of drilling, boring, reaming, tapping and grooving.
CNC machine tools, machining centers, is a kind of high precision, high efficiency automatic machine tools. It has a wide range of processing properties, and can process straight line cylinder, oblique line cylinder, circular arc and various threads. It has various compensation functions of linear interpolation and arc interpolation, and has played a good economic effect in the mass production of complex parts.
About the author