Can the hottest hard milling solve all the problem

2022-08-19
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Can hard milling solve all the problems in mold processing

in the next few years, the proportion of high-speed machining, more specifically hard machining, in the processing technology of tool and mold manufacturing will increase by 20%. This assessment does not come from some interested machine tool manufacturers, but from the exciting conclusion drawn by the Fraunhofer production technology research institute after investigating 600 mold manufacturing enterprises in Germany in 2004

at present, hard milling has been applied in a large range of tool and mold manufacturing industry. Facing the increasing competitive pressure, tool and mold manufacturing enterprises should adopt a rapid and flexible process to process the direction of tearing cut should be different from the rolling direction. In most cases, this competitive pressure is not the processing time itself. Because the processing time can be shortened by using modern machine tools and milling cutter technology. The problem is that the process arranged in the front and middle, such as quenching, takes a lot of time, and will increase the logistics of materials, which will prolong the production time during mold manufacturing. Through various experiments, it is shown that the hard milled workpiece surface can greatly reduce manual grinding, that is, it can reduce operations such as polishing. This effect mainly lies in that hard milling can obtain a more uniform micro geometric surface than grinding. In addition, there will be no thermal effect of the surface layer during hard milling, which is called "white surface layer" in EDM, and this white surface layer must be removed by manual grinding

Figure 1 hard milling: when hard machining tool steel made by powder metallurgy, there are special requirements for machine tools and milling cutters.

this figure is hard finish milling of mold (57hrc)

these examples show that hard milling has great application potential compared with the traditional production process in mold manufacturing industry. Therefore, it is entirely possible to increase the application of hard milling by 20% as described at the beginning of this article. However, hard milling is not feasible or effective in all cases. Because all processing has the problem of economy. If processing high-strength special materials, processing patterns and tiny parts or parts with particularly complex geometry. Even today, there is still a certain scope of application for the processing technology that can be used. Therefore, based on some current examples, this paper summarizes the feasibility of hard milling at present, the focus of development today and its future development prospects

smaller and smaller Molds - the development trend of continuous miniaturization

nowadays, the number of narrow and tiny mold cavities on die castings is obviously increasing. If combined with the technical products of the entire micro system, this small mold processing is a strong growth field. In addition, because the mold requires high precision and surface quality, it is a precision niche product. If effective processing technology is adopted to process such products, it will provide a large potential market for German and European enterprises in the future. Based on some basic considerations, hard milling technology has great advantages for manufacturing micro structure molds. Only one fact is that the components can be machined in one clamping, which significantly improves the machining accuracy. According to this processing method, the additional machining allowance required for workpiece clamping can be significantly reduced. Due to the new development in the field of machine tools, the tolerance less than ± 0.01mm can be reliably maintained even when machining large die cavities. For special applications, the machine tool can also better ensure 1 μ M accuracy. Today, carbide milling cutters with a diameter of 0.1mm have been listed in the product catalogue, and some products with smaller diameters are also available. For the processing of hardened materials, of course, coated tools are used, which has been confirmed by many experiments

a small difference in Figure 2: cemented carbide milling cutters with diameters of 0.3mm and 4mm

if machining deep grooves, small diameter cutters need to be used. In this way, milling and EDM suddenly compete. In this case, in typical mold manufacturing, enterprises will decide to adopt milling instead of EDM because of favorable factors in most cases. However, the first advantage of small cavity milling is that it can obtain better surface quality and simplify the production process. This is obviously very beneficial for the processing of small molds

high hardness tool steel - processing of powder metallurgy tool steel

the recycled film can be made into other useful products. Tool steel made by powder metallurgy can significantly improve its thermal hardness, wear resistance and toughness due to its good properties. These are important properties used as tool steel. However, these characteristics often lead to a rapid reduction in tool durability and poor machining results. Fraunhofer production technology research institute has used coated tools made of fine grained cemented carbide for cutting experiments. The fine structure of powder metallurgy is the reason for a series of changes in hard milling. The advantage of fine distribution of carbides is that when milling, it will not suddenly increase the load on the cutting edge like processing the coarse and strip carbides in traditional materials. When cutting traditional smelting cold work tool steel, coarse and strip carbides often lead to serious edge collapse, which makes the tool prematurely damaged. When processing powder metallurgy materials, due to a large number of carbides, abrasive wear and strong bonding occur, which speeds up tool wear. This is also the reason why the durability of milling cutters (especially in finishing) decreases rapidly

in addition, the toughness of the material will cause the adhesion of chips to the cutting edge of the tool, and this adhesion will also significantly increase the cutting vibration through periodic chip sliding. In addition, if the geometric angle of the tool is not appropriate, it will aggravate the forming burr. Especially when machining grooves with very small cutters, this has proved to be a great obstacle to reliable machining

in general, in rough machining, powder metallurgy tool steel has good cutting performance compared with traditional smelting tool steel. If a smaller cutting thickness is adopted, it may be the cutting amount used in finishing machining or machining with a tool with a very small diameter, which will aggravate abrasive wear during machining. Obviously, this will offset the advantages of good cutting performance of materials

5 axis machining or just "3+2"

many advantages of using 5-axis linkage control machine tool to process mold cavity have been introduced and recognized as early as the early 1990s. 5-axis machining first requires a milling cutter with wide line spacing, short overhang length and high rigidity, which can process molds with almost any geometry, and has a significantly stable process. But looking around today's many mold enterprises, we found that only in individual cases can we see the real 5-axis linkage processing. Is it true that in many cases, most of the machine tools and equipment that can be used are 3-axis or at most the 4th or 5th axis is added for machining

Fig. 3 great application potential: the investigation of enterprises on the future application potential of milling technology shows that

the use of high-speed milling and hard milling is the development trend

in fact, because the programming of 5-axis linkage machining is more cumbersome, and in many cases there is not enough technical know-how, in the overall consideration, it will be limited to its economy, so that 3-axis machining still seems to be relatively appropriate. In addition, there is no mature cam strategy so far, which makes 5-axis linkage hard milling a reasonable choice for enterprises. This 5-axis linkage hard milling is especially suitable for rough machining and semi precision machining. It is of great significance to keep the cutting conditions and load conditions of the tool constant during machining

however, when investigating some enterprises, we found an interesting prospect: at present, turbine blades (especially the so-called integral blade blank, that is, an integral impeller) are developed for similar edge conditions. Therefore, in the near future, we must start to research and develop the mold processing technology to further reduce the programming cost. Even if we only process a mold cavity, we should also improve its processing economy

the content described here is also one of the goals of the two-year "hard precision" project promoted by the European Commission. The project was officially launched at the Fraunhofer Institute of production technology in December 2005. In order to carry out this project, a temporary joint organization was formed by research institutes, machine tool manufacturers and CAM software companies from all over Europe, tool manufacturers and coating companies, measuring equipment and fixture manufacturers, and end users in different industries of tools and molds for extensive cooperation. The goal is to successfully use 5-axis hard milling to process hardened tools and dies economically and accurately. To achieve this goal, in addition to the use of novel full hydrostatic bearing machine tools, we should also pay attention to the study of the whole processing process of hard milling. Only in this way can we achieve the determined goal

Figure 4 protective measures: in order to reduce wear, the very small milling cutter used for hard milling should be coated

(picture source: Fraunhofer Institute of production technology)

hard milling as a part of the processing process

by adopting new machine tools, new control systems and improved process technology, a single processing process such as hard milling is more comprehensive. Through appropriate production planning, NC programming and integrated milling in the production process of the enterprise, So that enterprises can gain a stronger competitive advantage, and the mechanical property testing of steel wire and wire rope

in production, there are not only many kinds of workpiece materials, but also many kinds of tools and molds, which leads to the process knowledge of process optimization design becoming more and more complex. Nowadays, cam system can help this decision through the database that stores parameters and tool data. Choosing the milling strategy of NC programming correctly has a great impact on the quality and economy of machining. Therefore, the solution: we should regularly check and maintain the electronic universal tension machine. When hard milling is used in the process design, we must pay special attention to it - considering that the required component characteristics are the same as the load borne by the cutter and machine tool. If these edge conditions are taken into account, the application of hard milling will have the possibility of further growth. Even for machining slots, hard milling technology will also be popularized and applied

this abstract is from German form+werkzeug magazine

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