Conventional Drill Bit Processing
従来の ドリルビット ステンレス鋼や耐熱合金を加工する場合、多くの場合、大きな問題に直面します。加工中に鋭い笛のような音が鳴り、工具の刃先の摩耗や欠けが急速に増加します。典型的な現象は、ガイドエッジとも呼ばれる二次刃先の欠けです。合金の穴あけ時にこの現象が発生すると、工具寿命が短くなったり、工具が廃棄されたりする可能性が高くなります。
超硬工具の再研磨
Regrinding high-quality hard metal tools is often not economical or even impossible.
Chipping of the guide edge on hard metal drill bits is a typical phenomenon when cutting stainless steel and heat-resistant alloy materials.
The main reason for the above phenomenon is the oscillation of the drilling tool, and there are many reasons for the oscillation phenomenon. One reason is that the tool rebounds due to the action of the cut material. When the oscillation occurs, the head of the tool moves along an elliptical trajectory, while the blade or the tip of the tool moves along a polygonal (in most cases a triangle) trajectory. This movement has an adverse effect on the cutting distance of the tool. Whether a drilling tool oscillates and the magnitude of its oscillation mainly depends on the grinding form of the tool head, the type of guide edge, the grinding accuracy and the precision of the grinding work.
For the grinding of hard metal tools, 4-sided and conical surface grinding processes are usually used. Compared with conventional grinding processes, this unique process requires deep drilling into the center of the drill bit when grinding the cutting edge. The tool head form will ensure higher accuracy and be ground as much as possible according to the latest research results of cutting technology. If the centering accuracy at the beginning of drilling is not high, the tool may therefore produce a larger amplitude of oscillation, which may also lead to a decrease in accuracy during processing.
Grinding errors such as low concentricity or low tool symmetry can exacerbate the above phenomenon. Errors in peripheral links can further affect the machining accuracy. Therefore, it is necessary to first merge the deviations and tolerances of the clamping system and the machine tool spindle, for example, concentricity deviation and inclination. Finally, torsional and axial vibrations and low-frequency bending vibrations (oscillating motion) generated between the drill bit and the machine tool can lead to angular or out-of-round apertures.
Tool Intensifies Oscillating Motion
Stainless steels and heat-resistant alloys place high demands on drilling tools. Due to the high hardness of the tool material, high cutting forces are required. The machinability of the steel is adversely affected by the high tendency to cold hardening, the low thermal conductivity and the low toughness. The ductility of the material means that the drilled hole diameter is usually smaller than the nominal diameter due to material rebound. Deviations in diameter and roundness increase the pressure on the guide edge, leading to increased contact between the drill bit and the hole wall and even possible drill breakage. The increased pressure on the guide edge is mainly related to friction and local temperature increase and can also cause damage to the material edge. The load on the tool tip caused by squeezing or oscillation can be determined, which can indicate in advance which areas will break before the standard service life.
切断パラメータ
The cutting parameters also have an impact on the drilling quality, including not only the cutting speed, but also the feed rate, which is also a decisive factor. At present, the maximum cutting speed of quenched and tempered steel is about 200 meters per minute, and the feed rate can generally be much higher than 0.1 mm per turn. For example, a drill with a diameter of 8.5 mm can withstand a feed rate of 0.25 mm per turn or even higher. A higher feed rate can stabilize the drill bit and slightly eliminate the tendency to swing. Therefore, the quality of the drilling process can be appropriately improved.
However, stainless steel and nickel-based alloys cannot use such high cutting speeds and feed rates due to the limitations of the material properties themselves, otherwise the drill bit will be overloaded or even damaged. The feed rate under normal circumstances needs to be kept at a low level, far below the feed rate of 0.1 mm per turn. Since the lateral cutting edge of the drill bit not only cuts the workpiece when cutting in, but also squeezes the workpiece, using such parameters is conducive to avoiding swinging motion. The drill bit will squeeze the surface of the workpiece. If the workpiece interferes with the guide edge of the drill bit, then a drill bit with better symmetry can basically maintain a stable cutting process, and the swinging motion will also follow the spiral line.
The chips generated during the chip cutting process need to be quickly discharged from the chip flute. In addition, the chip generation rate needs to be controlled so that they can be discharged more smoothly to avoid damaging the inner wall of the aperture. The adjusted chip flute profile and optimized chip shape can make the chips curl as much as possible. The chips need to be curled together as much as possible according to different materials. In addition, it is necessary to avoid uncontrolled short chips from entering the chip flute as much as possible, causing damage to the inner wall of the aperture. Using a Y-type drill can achieve better surface quality while ensuring the same service life, while ensuring that the chips are quickly and smoothly discharged into the chip flute.
円錐カッターヘッド
The conical head shape is more conducive to centering. The first impression of the Y-type drill is that the angles between the different chip flutes are not consistent. The three guide edges are arranged in the form of the letter Y, although this drill only has two cutting edges. The Y-type drill has a conical head structure and is precision ground to ensure accurate centering. The TiAlN coating brings high wear resistance and production efficiency, and has a very wide range of applications. Drill bits around the world can be reground and re-coated in a very short time.
The different parts of the chip groove on the Y-type drill can generate a component force aligned with the guide edge, which is beneficial to the cutting process.
Unevenly Arranged Chip Flutes
With the aid of unevenly arranged chip grooves, a directional cutting force can be obtained. Along the direction of the force, there is a guide edge (2) on the cutting edge and another guide edge (3) at the end of the drill back. The Y-shaped structure supports this additional guide edge. The load on the edge (1) arranged opposite to the above two edges is reduced accordingly. During the cutting process, the three guide edges play different roles. The guide edge (1) is responsible for cutting, the guide edge (2) is responsible for cutting and supporting, and the guide edge or sliding edge (3) is responsible for supporting.
With this structural arrangement, the swing of the tool can be basically eliminated, especially when drilling, the roundness tolerance and cylindricity tolerance of the processing can be guaranteed. If the cutting edge is further optimized, the wear can be minimized. The high quality requirements of the drilling process and the “pressure” exerted on the drill, especially the cutting edge and the guide edge, are reduced.
The above technology can appropriately extend the cutting distance of the tool. There is a certain regularity between the hole and the drilling depth, such as the finished hole diameter being slightly larger than the nominal diameter of the drill. That is, the drill is no longer stuck in the hole. Under good conditions, a hole quality of IT8 can be achieved. The first and last hole diameters drilled by the same drill can be kept continuous and stable. The tool life of subsequent processes such as reamers and taps can also be improved.
Y-Drill bits have been successfully used in many occasions. For example, good results can be achieved even when machining stainless steels such as 1.3916, 1.4350 or 1.4542 that have not yet rusted. During the service life, the efficiency improvement can often reach more than 100%. Even when machining heat-stable and even hardened steels with a hardness of 55HRC, Y-drills can still give satisfactory results.
