Masahiro Hagino

Cutting Characteristics of CFRP Materials with End Milling

This paper presents the results of groove and end face milling of CFRP materials by high speed steel end mill tools and polycrystalline diamond (PCD) and TiAlN-coated tungsten carbide end mill tools. The experimental results of end-face milling show carbon fibers on the surface of all the tools used in this experiment. However, the carbon fibers do not occur in groove milling when using PCD coated tools. In addition, the distribution of the carbon fibers of CFRP composites changed with the cutting temperature and cutting force. The overall result shows PCD-coated tools have longer tool life compared to high speed steel and TiAlN-coated end mill tools in processing carbon reinforced plastic composites.

Damage of PVD-Coated Cutting Tools Due to Interrupted Cutting of Ni-Based Superalloys

Ni-based superalloys are typically difficult-to-cut materials. During machining, the cutting forces and temperatures of these superalloys are generally higher than those of other materials. Therefore, the tool life of the coated carbide cutting tools used for superalloy machining is shortened. This study evaluates the damage of the coated end mills during interrupted cutting of alloy 718 and finds the coating properties necessary for improved cutting of Ni-based superalloys. Damage of the PVD-TiN-coated cutting tools was observed by scanning electron microscopy and transmission electron microscopy of the surfaces and cross sections. In addition, friction forces were measured during turning for some coatings, and hardness of the coatings was measured after annealing. Plastic deformation of the coating and crack formation was shown to occur at the coating cross section. In addition, we determined that the major factor for the damage was high friction force between the coating surface and work material at high temperatures. In summary, coatings with stability at high temperatures and low friction forces during machining can reduce the damage of coated cutting tools, thus increasing the tool life.

New Machine Tool on Collecting Cutting Chips of CFRP for Working Environment Improvement

In machining to CFRP material has many important problems, about necessary of high-precision machining, improvement of tool life and dispose of cutting chips etc. Especially in case of twist drill almost cant collect under 0.5 μm cutting chip, the fine-cutting chips diffuse into the sliding table and spindle head with the machine. Moreover, the fine-cutting chip is mixed and diffuse into the atmosphere. The possibility to remarkable decline of working efficiency so the dust-collection provision technology is wished. It is important also from the viewpoint of keep safety of a worker and work environment preservation because the CFRP utilizes in market for industrial structure materials, is increasing. As one method of solving this problem which aspirates and ejects cutting chip from a penetration hole through outside in the central part of the drill shank the new tool and cyclone type dust-collection system were developed. These technologies were used for perforate of CFRP material, and investigated about the cutting characteristic of the hollow type drill, and the effect of work environment improvement to dust-collection performance of cutting chips. As the result, our development machine tool and cutting tool can collect approximate 99.5% cutting chip.

The Machinability of CFRP with Cutting Movement of End-Milling

Recently, carbon fiber reinforced plastics (CFRP) are expected to be used more in the aerospace and automotive industries, because of their outstanding lightweight material characteristics and tensile strength [1][2]. Underlying this are problems closely related to improvement of the earth’s environment. However, a mechanical property is influenced by the difference in the distribution state of the carbon fiber, and the adhesion intensity of the binding material. Moreover, they have the characteristic of intense anisotropy, strength wise depending on the orientation of the carbon fibers [3][4]. Therefore, CFRPs are considered difficult-to-machine materials [5], because the surface finish deteriorates according to the carbon fiber orientation. Establishing the optimal cutting conditions to solve such problems also from an economical viewpoint is essential. In our study, end milling operations of different carbon fiber orientation CFRP composite material were investigated with three kinds of different helix angle end mills. Evaluations were based on the surface finish, cutting force and cutting temperature. Moreover, the relationships between the carbon fiber orientation and the machining operations were determined. We earlier evaluated the machinability from the relationship between carbon fiber orientation and tool helix angle by down-cut milling to solve these problems [6]. In this study, machining operations of different carbon fiber orientation CFRP composite material were investigated with three kinds of different helix angle end mills by up-cut milling. Evaluations were based on the surface finish, cutting force and cutting temperature. Moreover, the results of this experiment were compared with the results of down-cut milling.

New-Technique Drilling with Modulated Rotation Spindle Machine

In drilling deep holes with small-diameter tools in particular, chip shape is a major problem along with tool rigidity. In this study, we developed a spindle machine that has regularly repeating acceleration and deceleration regions in each drill rotation (called modulated rotation) as a new drilling spidle machine that can improve chip discharge ability. For an analysis of the cutting mechanism based on the basic principles of this device and its drilling characteristics, holes were drilled in CFRP, and Ti alloy (Ti-6A1-4V) materials using a straight shank drill. The relationship between the torque and thrust of cutting resistance force was obtained to show the relationship between cutting chips shape and cutting force. The characteristics of drilling with the developed spindle device were evaluated in comparison with regular drilling methods. It was found that the torque with this device was reduced by about 10% compared with general drilling. Outstanding chip breakup was seen with Titanium alloys in particular, as a result of which chip discharge could be improved.

Deep Hole Machining with a Small Diameter Drill and Ultrasonic Vibration

The method of imparting ultrasonic vibration to the cutting tool is known to improve the shape accuracy and finished surface roughness. However, a uniform evaluation of this function in drilling has not been achieved, and the cutting process cannot be checked from the outside. The aim of this study is to investigate the cutting characteristics in deep hole drilling when an ultrasonic vibrator on the table of a machining center provides vibration with a frequency of 20 kHz to the work piece. The ultrasonic vibrations in this system reach the maximum amplitude in the center of the work material. We evaluated the change in finished surface roughness between the section where drilling starts to the point of maximum amplitude with ultrasonic vibration. The main cutting conditions are as follows: cutting speed (V) 12.6 (mm/min); feed rate (s) 30, 60 (mm/rev); depth of cut (t) = 32 (mm); work material, tool steel; cutting tool material, HSS; point angle (σ) 118 (°); and drill diameter (φ) 4 (mm). Lubricant powder was also added to clarify the cutting effect, and compared the condition in which there was no ultrasonic vibration. The results showed that surface roughness at the point of maximum amplitude was better than that with no vibration.

Effects of Tool-Edge Form during the Drilling of CFRP

The drilling of carbon fiber reinforced plastics (CFRP) involves many problems such as an extremely short tool life or CFRP delamination occurring at the exit surface of drill. In an effort to solve these problems, this experiment observed the form of the drill’s tool edge. Then, an investigated the form of the tool edge with regard to low-cost, high-precision, and high-efficiency machining processes. The thrust direction of the cutting force is decreased as the CFRP delamination at the exit surface of drill is decreased. It is considered suppressing the delamination on the exit surface of drill by reducing the thrust force during drilling. In this experiment, the CFRP materials had a thickness of 4 mm. This experiment used sintered carbide, straight shank drill tooling with a diameter of 6 mm. Ten different types of straight shank drills with different point angles and coating treatment were tested. Additionally, this experiment an evaluated the cutting force, the cutting temperature, and the CFRP delamination at the exit surface of drill through the drilling and processing of 100 holes. Moreover, this experiment an evaluated the effects of chamfering of honing the tool edge with regard to the drilling and machinability of CFRP. This experiment used CFRP material with a thickness of 8 mm and four types of sintered carbide drills. As a result, the CFRP delamination distance of the exit surface of drill became smaller at point angles 130° and 140°. No differences in the cutting force or the cutting temperature were observed due to the different point angles. The results of the evaluation indicated that for the case without honing, the thrust force becomes 1/3 less than that for the case with honing of the drill tool. Additionally, in the case of without honing, CFRP delamination was suppressed at the exit surface of drill.

Study on Analysis of Cutting Mechanism of Ball End Mill for Concave and Convex Spherical Surface Using 3D-CAD

In this paper, cutting mechanism and cutting performance of ball end mill for spherical surface with contour path method is investigated. Ball end mills are used to produce molds, dies and so on. However, the edge shape is complex, so cutting process is not clear. Then, it is not clear effectively using method of the tool based on good cutting performance. Therefore, in this study, the purpose is proposal of high efficient and high accurate cutting method is using 5-axis control machine tool. At first, cutting model assembled by a ball end mill (R8 mm) and a workpiece with convex or concave spherical surface (Workpiece radius 20 mm) is carried out using 3D-CAD (SolidWorks). The pick feed direction which is from bottom to top is defined “Stepped up”, the one which is inverse direction is defined “Stepped down”. In addition, both cutting methods include up milling and down milling, then there are four cutting modes. The radius of tool path for contour path are varied from 14.0 mm to 19.4 mm for convex spherical surface, from 6.5 to 9.2 mm for concave spherical surface. The lead angle of the tool is defined the plus sign when the tool is inclined to the tool feed direction and varied from-45° to 45°. Secondly, the cutting cross-sectional area is calculated by the interference of a rake surface of the tool and an uncut chip volume which can be removed by one cutting operation. Thirdly, cutting experiments are done in order to measure cutting force. Finally, analytical and experimental results are discussed, and then the cutting conditions which are expected good cutting performance are considered.

High Aspect Ratio Thin Rib Shape Processing of Carbon Material for Electrical Discharge Machining Molds

Aluminum alloy die casting products are used for automotive LED lamp installation parts. The high aspect ratio shape used for large-volume heat problems needs thin rib parts. In the present study, we obtained basic data for the development of long axis type end mill tools for electrical discharge machining carbon material processing. At the same time, to evaluate the prototype development work, a special tool that enables high aspect ratio thin rib geometry processing was used. Longitudinal direction traverse cutting was done with a small diameter ball end mill tool in the carbon material for electrical discharge machining mold. The transfer accuracy and pick feed shape in the finished surface, the cutting resistance force, and the cutting edge shapes were examined to clarify the relationship between the cutting conditions set. Prototype development of the small-diameter end mill tool with a high rigidity, long axis was done using FEM numerical analysis method. The results showed that the small-diameter ball end mill tool with a tapered length axis in the prototype development had transfer accuracy of the cutting edge shape, and it was possible to reduce the finished surface roughness. Factors such as differences in tool shape are considered to greatly affect the tool rigidity.

Cutting Characteristics of Duplex Stainless Cast Steel X2CrNiMoN25-7-3

X2CrNiMoN25-7-3 duplex stainless steel is suitable for chloride-containing environments such as seawater because it has excellent pitting corrosion resistance. Duplex stainless cast steel is often used to accommodate the complexity of part geometry at joints. However, machining after casting is indispensable. This study evaluated the cutting characteristics of stainless cast steel. Adhesion of the cutting edge was weak at high cutting speeds, but tool wear was large. Diffusion and reactions between the work-pieces and the tool edge were investigated. Slight inter-diffusion and a reaction phase were observed, but the bond-ability was low.