Machining center in the process of processing mold, the accuracy and surface processing quality requirements are higher and higher, in order to ensure the quality of mold processing, we should consider the selection of machine tool, tool handle, tool, processing scheme, program generation, operator requirements and other aspects.
- With the improvement of product design requirements and the development of high-speed and high-precision processing technology, the selection of high-precision and high-speed machining center has greatly improved the quality and speed of mold NC processing, reduced the processing procedures, shortened the production cycle and clamping times of mold, and sometimes eliminated the time-consuming fitter repair work. The high-speed and high-precision machining of mold has gradually become one of the important contents of the technological transformation of mold production enterprises. It is inevitable that the high-speed CNC machining center will replace the traditional low-speed machining, and the development of mold manufacturing technology will also bring us more rich product experience.
- The use of high-speed and high-precision machining center with suitable tool handle structure will also drive the update of relevant process equipment. In particular, the influence of cutting tools on NC machining quality and toolholder will become prominent. In the rotary tool processing system, the chuck is closely connected with the machine tool (or its combination) to ensure the realization of tool processing performance. Generally, there are HSK hollow toolholder and BT toolholder in the interface between machine tool and toolholder. The taper of taper shank interface between machine tool spindle and BT toolholder is 24:7, which is suitable for traditional low-speed machining. Because BT toolholder and machine tool spindle are only taper fit, the clearance of taper fit will increase under the action of high-speed centrifugal force, which affects the quality of NC machining. Generally, when the spindle speed exceeds 16000 rpm, we will need to use HSK hollow handle. The positioning structure of HSK arbor is over positioning, which provides a standard connection with the machine tool. Under the pulling force of the machine tool, the short cone and end face of the arbor are closely matched with the machine tool.
- Choosing the right cutting tools, the reasonable use and selection of cutting tools will be an important factor affecting the quality of NC machining. Cemented carbide tools are more and more widely used. In high speed machining, coated cemented carbide will replace most of the front steel tools, including reamer, ball head tool, boring tool and other simple tools. Coated cemented carbide will play an important role in high speed machining tool materials and be applied to most of the conventional processing fields. Generally, we know that in rough machining, we will use large diameter tools for processing. In order to save cost and reduce the difficulty of tool manufacturing, we will use machine clip cemented carbide blade In the semi finish machining, the insert tool with high speed and high feed is used to make the semi finish machining move faster; in the finish machining, the high-precision round head mirror blade is used to ensure the strength of the tool and the tool holder, which can save the expensive cost of selecting the whole alloy tool while maintaining the machining accuracy. In the process of machining, we also need to pay attention to the inner contour fillet radius of the finishing parts must be greater than or equal to the radius of the tool, select the tool whose radius is less than the radius of the corner fillet to process in the way of arc interpolation or diagonal interpolation, so as to avoid the phenomenon of overcutting caused by linear interpolation and ensure the quality of mold finishing.
- The importance of NC process design in high-speed and high-precision machining is raised to a higher position. The whole process of machining must be controlled. Any error will have a serious impact on the mold quality, so the process design will play a decisive role in the machining quality. NC machining process design can be considered as the state control of a system process plan from the part blank to the part forming. A good process plan is difficult in the whole design process, which can be obtained only after continuous practice summary and modification. A large amount of information should be considered in the design process, and the relationship between the information is extremely complex, which must be guaranteed by the actual work experience of the programmer. Therefore, the design quality of process plan mainly depends on the experience and level of technical personnel.
Generally, a complete NC machining process planning includes the following contents:
1) CNC machine tool selection.
2) Processing method selection.
3) Determine the clamping mode of the part and select the fixture.
4) Positioning method.
5) Inspection requirements and methods.
6) Select the tool.
7) Error control and tolerance control in machining.
8) Define NC process.
9) Numerical control process sequencing.
10) Cutting parameter selection.
11) Work out NC process program sheet.
- CAM software a good software can also improve the quality and efficiency of mold processing, such as Unigraphics and cimiamtron , are very good mold processing software, especially the two kinds of software rich practical different processing strategy, in NC milling programming, turning programming, WEDM programming are widely used, complement each other, so that the quality and efficiency of NC machining has been greatly improved. Cimiamtron can add the screw function when clearing the offset area in rough machining, which will make the actual cutting more stable, eliminate the mutation of feed direction between adjacent tool paths, reduce the acceleration and deceleration of cutting feed, maintain a more stable cutting load, prolong the tool life, and also play a good role in protecting the machine tool. Software is just a tool. An excellent programmer has rich experience and theoretical knowledge of on-site machining. At the same time, the NC programmer who is proficient in the software function is the decisive factor in the mold NC machining, which plays a key role in the quality and efficiency of NC machining.
- The operator of machining center is the executor of NC machining, and their control of NC machining quality is also very obvious. In the process of performing processing tasks, they know the real-time status of machine tools, toolholders, cutting tools, processing technology, software and cutting parameters best, and their operations have the most direct impact on NC machining, so the skills and sense of responsibility of machining center operators are also the key factors to improve the quality of NC machining!
