Monday, February 20, 2017

Preparation of Carbide Ball End Mills by 3DP Printing Technology

Tool fixture is an important component of metal cutting machine tools, especially the geometry of the tool slot, cooling methods are greatly affected the product of the machining efficiency and processing quality. In recent years, 3D printing with unique technical characteristics, in the field of fixture applications can be said to be moving in the direction of depth.
3D printing technology in the application of the tool is a large faction is 3DP adhesive jet printing technology, through the heat treatment after the hardness of the tool to meet the application requirements. Another large faction is the SLM metal 3D printing technology, through the powder bed selective laser melting technology to create metal cutting tools or a special tool within the complex cooling channel. These two technologies are increasingly attracted the attention of the tool industry. In this issue, 3D Science Valley and Guyou jointly to enjoy the Harbin University of Technology through 3DP printing technology to prepare micro-texture carbide ball milling cutter technology.
When the titanium alloy is machined, the friction coefficient between the titanium alloy and the tool is large, the friction speed of the titanium alloy chip along the rake face is higher, and the friction caused by the abrupt friction makes the tool wear and the surface quality is poor. Factors, the use of titanium alloy parts and components of the performance depends mainly on the quality of parts processing, such problems have become the most concerned about the aerospace researchers one of the issues.
In recent years, bionic tribology has proposed a concept of surface texture. SurfaceTexturing, also known as surface micro-modeling, is in the friction surface processing with a certain size and arrangement of the pit or tiny groove lattice. High-performance surface texture can achieve a good anti-friction, anti-adhesion and improve wear resistance, which to the tool surface surface friction to bring a new research direction, but also provides a theoretical basis. At present, few scholars at home and abroad have carried out the application of surface texture on cutting tools. Although the research is in the initial stage, the research results show that the surface micro-weaving tool has the effect of improving the cutting performance of the tool.
The research on the application of micro-texture on the surface of the tool and the influence on the tool performance is still in the initial stage, mostly on the turning insert and the indexable face milling cutter. The cutting material is mainly 45 # steel and aluminum alloy. The micro-texture is applied to the study of titanium milling of ball-end milling and the research on micro-texture optimization. Therefore, it changes the current inefficient machining mode of titanium alloy, and makes high-quality and high-quality cutting of titanium alloy for micro-texture tool Helpful exploration.
The existing surface micro-texture preparation methods are: laser surface texture technology (LST), surface laser shot peening (LPT), LIGA technology, reactive ion etching (RIE), engraving technology, electrolyte processing, EDM , Electrical processing and so on. These techniques are based on the surface of the substrate directly to the micro-area processing to achieve weaving, but most of the existing texturing technology or "cutting material" manufacturing technology, mainly in the etching, embossing, etc. in the form of a single concave Pit, or groove, in which the laser surface texture technology is widely used in the surface microstructure of the surface texture of the laser surface texture technology with its manufacturing processing speed, wide application material, high precision, no pollution to the environment and excellent shape and size control ability field. However, the use of this method in the tool surface processing micro-texture is easy in the micro-texture around the heat generated area and micro-cracks, will affect the tool in the processing of the strength and service life.
With the plastic material 3D printing technology is relatively mature, metal 3D printing technology highlights the great potential for development, as the rapid development of today's important areas of development and research hot spots. Most of the metal 3D printing technology uses laser as the input heat source, by melting or sintering metal powder layer by layer stacking parts. But for the hard alloy of the two kinds of different nature of the composite material, which WC is ceramic, high melting point; and Co is metal, low melting point. Although the laser reaches the temperature enough to melt the WC, but to WC melting temperature, Co will evaporate, after solidification of the alloy structure can not meet the requirements as a carbide.
Harbin University of Technology through the 3DP adhesive injection 3D printing technology to solve the existing 3D printing technology can not produce carbide cutting tools and the existing technology in the preparation of micro-texture on the tool there are some problems, and then put forward a 3D print Preparation of Micro - Texture Carbide Ball - end Mills. Specifically, the following steps are included:
- Preparation of YG8 Carbide Ball Milling Cutter Powder Material: YG8 Carbide Ball Milling Cutter Powder Ingredients The main ingredient ratio is 8% cobalt powder and 92% tungsten carbide powder;
- Preparation of organic binder: organic binder of the main components include paraffin and polyethylene glycol, polyethylene, polypropylene, polyvinyl alcohol in one;
- Set the knife-and-chip contact surface of the ball-end milling cutter: The tool-chip contact area of ​​the rake face during the machining of the ball-end milling cutter under the given cutting conditions is calculated and experimentally and on the rake face position;
- Establishment of a three-dimensional model of a micro-textured carbide ball-end mill: The knife-chip contact area model established in the previous step was then implanted in the area of ​​the area with a certain microstructure size, depth and spacing Texture model, which can achieve the best anti-friction effect;
- print the micro-texture tool entity through a three-dimensional model;
- post-treatment process: First, the micro-texture carbide cutting tools into the hydrogen environment for thermal degreasing treatment, remove the adhesive; Finally, the vacuum sintering process of cemented carbide micro-texture ball milling cutter body sintering Processing, sintering temperature of 1400 ° ~ 1420 ° or so, the sintering process duration of 3 to 6 hours; the final micro-texture carbide ball milling cutter to achieve 100% density and sufficient strength.
3DP is a kind of adhesive jet printing technology, Harbin University of Technology through 3DP technology and post-processing technology prepared micro-texture carbide ball milling cutter can make the tool to reach 100% density, and after the post-treatment of tight Degree and strength can be consistent with the traditional processing methods to get the carbide cutter.
Based on the complex shape of a carbide ball cutter, it is cumbersome to use conventional processing methods, and it can also cause material waste. The micro-texture carbide ball milling cutter prepared by the preparation method of Harbin University of Science and Technology can obtain the higher dimensional accuracy, and also establish a unique knife-chip contact model on the rake face, which can realize the contact area Prints a tiny microstructure array with diameters from 50 microns to 200 microns, and the dimensional accuracy is very high.
Compared with the current method of preparing micro-texture on the carbide ball cutter, Harbin University of Science and Technology, in addition to being able to produce complex shape ball-end milling cutter, can also be used in the ball nose cutter The contact area produces a more accurate pits and micro-texture array, which can reduce the contact area of ​​the knife-chip in the cutting process, reduce the friction coefficient of the knife-chip contact area and reduce the wear of the tool.
Harbin University of Technology has also overcome some of the shortcomings of the use of traditional technology in the preparation of micro-texture on a carbide ball cutter. For example, the use of laser technology in the carbide ball milling cutter prepared on the micro-texture size accuracy is very low; carbide surface in the high-temperature melting process may also react with oxygen in the air, resulting in changes in the composition of the tool; In the micro-texture around the heat will produce a zone, may produce micro-cracks and so will affect the tool life. Therefore, Harbin University of Technology in improving the strength of carbide ball milling cutter structure at the same time also further improve the micro-texture tool anti-friction and anti-wear properties, thereby enhancing its service life.
According to the 3D Science Valley market research, the use of 3DP adhesive jet three-dimensional printing technology to produce carbide cutting tools has been abroad. Researchers at the Fraunhofer Institute in Germany have succeeded in producing cemented carbide tools using 3DP adhesive jetting three-dimensional printing technology. Through 3DP print carbide powder, the Institute can easily create complex designs. In this process, the ceramic particles of the ceramic hard material, including the tungsten carbide particles, are printed and bonded by layers of a binder material containing cobalt, nickel or iron. This adhesive material is not only an adhesive between the powder layers, but also allows the product to have good mechanical properties and can produce completely dense parts, and even can selectively adjust the bending strength, toughness and hardness. Subsequent treatments include sintering treatments, resulting in compactness of cemented carbide molds consistent with conventional processing methods.
Not only the 3DP technology used by Harbin Polytechnic University and the Fraunhofer Institute, Gaumet also used SLM metal 3D printing technology and machining technology to manufacture milling cutters. The cutter body with the dense flute is a customized non-standard product made by metal 3D printing technology, and the shank part is the standard product produced by the mechanical processing technology.
In addition, the company also created the QTD series of complex spiral cooling channels through 3D printing technology, which improves the heat transfer capacity of the coolant to the top of the drill. Mappa's drill has a longer life and faster operation than the previous drill.
Whether it is 3DP technology for the manufacture of carbide cutting tools or SLM technology for the manufacture of metal bits and handles, 3D printing technology in the field of manufacturing tool occupies an increasingly important position.

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