Abstract: This paper elucidates the concept of five-axis machining technology. Taking the actual machining of mold parts as an example, it analyzes the feasibility and importance of applying five-axis machining technology in mold processing. After comparison with three-axis machining technology, it is found that five-axis machining technology can improve processing efficiency and part quality, reduce the number of electrodes, and help mold processing enterprises to make fuller use of five-axis machining technology, improve product quality, and shorten product production cycle.
Keywords : Five-axis machining technology; mold processing; advantages and applications
With the improvement of my country's manufacturing technology, higher requirements are being placed on mold parts processing technology, and five-axis machining technology is being recognized and applied by more mold processing companies. However, due to the high technical requirements for five-axis machining operators and the lack of corresponding professional personnel, the five-axis machining equipment and technology of many companies are not being fully utilized.
This article takes the processing of typical mold parts as an example and conducts an in-depth analysis of the advantages of five-axis machining technology in mold manufacturing, so as to promote more enterprises to understand the advanced equipment and processing technology innovation in the manufacturing industry and apply five-axis machining technology.
1. Analysis of Five-Axis Machining Technology
Generally speaking, when a three-axis machining center completes the machining of a deep cavity mold, it can do so using only a long cutting tool and tool holder. However, in the process of machining a five-axis mold, a single clamping is used, and through the movement of the table or the swing axis, a flat-bottomed end mill is used to machine each surface of the mold in a way that keeps the tool axis perpendicular to the machining end face. This can reduce machining costs and machining time.
Meanwhile, the five-axis machining center is also suitable for milling angled sides. The machining process can avoid the rib-like texture caused by ball end mills machining inclined surfaces on three-axis machining centers, so that the surface quality of the mold can easily meet the expected requirements. It also avoids a series of problems such as positioning errors and non-coincidence of reference surfaces when the workpiece is adjusted and clamped during the second positioning of conventional machine tools.
This not only shortens the time for auxiliary debugging and processing of the workpiece, but also reduces the errors that may occur. The cost of tooling fixtures and cutting tools required for workpiece installation is also reduced. However, when machining parts with complex features such as thin walls, corners, and curved groove bottoms, three-axis machining uses ball end mills for finish milling to achieve better surface quality. However, because the linear velocity of the ball end mill approaches zero after the tool center rotates, it will cause tool damage, reduce its service life, and also affect the surface quality.
By utilizing the characteristic that five-axis machining can form a certain angle with the machined surface, shorter tools can be used, tool rigidity can be improved, and the entire part can be machined quickly without the need for a second clamping, and the surface quality of the part is also very good.
2. Analysis of the specific applications of five-axis machining technology
Five-axis machining technology can rapidly enhance machining efficiency in mold manufacturing, generally in the following ways:
(1) Most of the machining can be completed in one clamping of the parts;
(2) The local area has high processing accuracy and short processing time;
(3) As the number of difficult-to-machine parts decreases, the number of electrodes is reduced accordingly, and the mold production cycle is shortened.
The shape of a part determines its machining method. Therefore, before programming, the shape and machining process of each part should be analyzed to ensure the selection of cutting tools and the placement of the part, thereby reducing the need for secondary clamping and machining. The 3D drawing of the air conditioner frame mold part is shown in Figure 1. This is also a typical part processed using five-axis machining technology in mold production.
Figure 1. Two-dimensional drawing of air conditioner frame mold parts
Five-axis machining technology allows for the simultaneous execution of multiple tasks during a single workpiece clamping process by changing cutting tools and altering the tool or workpiece tilt angle. Cutting occurs during the contact between the tool and workpiece, with the tool rotating at high speed, achieving the desired cutting effect.
Different contact angles between the cutting tool and the workpiece surface lead to different cutting principles, resulting in varying cutting qualities. In planar finishing and side-cutting, the workpiece and tool engage in surface contact, which, compared to point contact, offers better machining quality and efficiency, effectively reducing the workload of surface polishing.
In three-axis machining processes, the "bevel" machining method is generally selected, as shown in Figures 2(a) and (b). In this method, the ball end mill and the surface of the workpiece have only one contact point, which cannot guarantee machining efficiency, and there is a "bevel" between the two toolpaths.
The presence of "residual height" indicates a significant amount of polishing work to be done in subsequent processes.
Within the same area, five-axis machining is used. After positioning, the surface to be machined and the tool axis remain perpendicular, as shown in Figures 3(a) and (b). Using the cutting method of a planar wide-angle tool, the tool and the workpiece are in surface contact, which not only achieves high machining efficiency but also extends the tool life. Furthermore, there is no "residual height" between toolpaths, resulting in high-quality machined surfaces. Moreover, by changing the tool, the machine tool's own precision can be used to complete some precision boring, grinding, and polishing processes. In subsequent work, only simple polishing is required.
Figure 2 Comparison analysis of three-axis machining and five-axis machining
Figure 3 Comparison analysis of three-axis machining and five-axis machining
As we all know, the level of product design is related to the level of mold designer, which in turn affects the shape of various parts. When designing products, we need to combine customer requirements, pay attention to exquisite details, and ensure ease of use. This places new demands on the machining of mold parts. As shown in Figure 4, the side wall of the part has a small step, which is difficult to machine accurately in three-axis machining. An electrode should be used for electrical discharge machining (EDM) to remove the step. Figure 4(a) shows the machining electrode, whose dimensions are 112mm × 24mm × 174mm, and machining it is very time-consuming. Using five-axis machining, by selecting the optimal angle, as shown in Figure 4(b), the side wall step can be completely milled without the need for EDM.
Figure 4. Small steps on the side wall during three-axis and five-axis machining.
In injection molding, it's common to encounter cavities with rounded corners on molded plastic parts, a process known as "corner clearing." During corner clearing, the cutting tool is selected based on the corner radius. However, due to limitations in the length-to-diameter ratio, the tool length is also restricted. Many deep cavities with rounded corners cannot be machined to the required depth using three-axis machining and must be cleared using electrode machining. Experimental results show that using five-axis machining technology for corner clearing simplifies the machining process, shortens mold production time, and improves tool utilization efficiency.
In general, many unexpected situations arise during tool and workpiece machining, and the relative motion between them is unpredictable. To ensure program stability, five-axis machining programming should be simulated to avoid other problems during machining. Currently, various software such as NX6.0 and VERICUT can perform high-precision simulation of five-axis machining, calling up models of tools, machine tools, and parts, effectively reading program information, ensuring the mutual movement of the workpiece and tool, and simulating the cutting process in 3D animation. Simultaneously, it can also detect overcutting of individual parts.
In simulation, programmers can observe the actual machining process and promptly identify problems that arise, thus ensuring the rationality of five-axis machining programming. Compared to three-axis machining, five-axis machining has two additional degrees of freedom, which significantly increases the performance requirements of the machine tool. In programming, all information related to the application of five-axis machining technology should be carefully considered. Once the workpiece meets the machining requirements, a suitable machine tool should be selected, and the clamping method should be clearly defined based on the machine tool's performance.
3. Conclusion
As can be seen from the above analysis, applying five-axis machining technology to the production process of mold parts can not only improve the machining accuracy of parts, but also reduce the workload of polishing parts and shorten the production cycle of molds. However, in many ways, the machining tools and programming work have put forward new requirements for the relevant personnel, requiring them to have a comprehensive understanding of five-axis machining technology and be able to operate the corresponding software proficiently.
Five-axis machining technology has also developed rapidly with the advancement of mechanical equipment technology. Furthermore, my country is currently placing increasing emphasis on cultivating talent in the manufacturing sector. All of these factors have laid the foundation for the widespread development and application of five-axis machining technology. It is expected that in the near future, five-axis machining technology will be applied to more fields.
