Papers by Author: Koichi Kitajima

Abstract: The results of an investigation on the effects of surface roughness on adhesion to the coating using the assumed tungsten carbide end mill tip with various degrees of rake surface roughness are reported here. The grindstones with varying in grit between #230 and #1500 were used to grind tungsten carbide tips and then coated the tips with TiAlN film, CrSiN film, and TiSiN film. The state of adhesion on the films on the rake surface as well as the surface roughness and cutting resistance were measured in the continuous lathe turning. The results show that, in generating the cutting cutoff, the optimum grinding roughness differs between the near vicinity of the cutting-edge ridgeline and the part of the rake surface that is further away from the cutting-edge ridgeline. From that fact, it can be understood that the cutting characteristics of the work material and the surface area of the rake surface that is in contact with the cutting cutoff exert their respective influences during the cutting.

Abstract: This study investigated adhesion of coatings on a grinding surface. This was carried out using scratch testing as a function of surface roughness. Three types of coatings were explored: TiAlN, CrSiN and TiSiN. With smaller surface roughness, the coating adhesion showed a tendency to become stronger. In particular, in the case of surface roughness under 2 micrometers for a coating, the coating adhesion was good. Specifically, the CrSiN coating yielded a very smooth surface.

Abstract: For the improvement of the performance in centrifugal disc finishing, the flow-through system for supplying the compound solution is tried and its influences on finishing characteristics are experimentally investigated. Workpieces (22 mm in diameter and 15 mm in thickness) of plain carbon steel (S45C in JIS), aluminum alloy (A2017) and copper alloy (C3604) are finished with ceramic media (Equilateral triangular prism 6 mm in side and 5 mm in thickness). The conclusions are summarized as follows; The compound solution has more influences on finishing characteristics than plain water. It makes the relative stock removal larger and the surface roughness smaller than the water. The relative stock removal and the media weight loss on the flow-through system are larger than those on the batch system.

Abstract: Conventional coating tools have a high affinity for ductile materials, like aluminum alloy, so cutting chips tend to adhere to cutting edge and work material surface. Therefore, chipping is caused, and surface texture is degraded. In order to solve these problems, recently, DLC (Diamond-Like-Carbon) has been applied to coating material. In this research, it is curried out cutting of Aluminum alloy by the use of DLC coating tool, and examined influence of DLC coating conditions on cutting characteristics. So far we have been concerned with the effect of type of hydrocarbon gas (acethylene:C2H2, methane:CH4) on cutting. As a result, it is revealed that cohesion of chips decreases, and surface roughness of work material improves in the case of acethylene-DLC. On the other hand, internal stress is produced by deference in hardness between tool surface and DLC film, and which is considered cause of film peeling [1]. Therefore, we examined interlayer between DLC film and tool surface in order to relax of internal stress. As a result, it was cleared that Titanium interlayer excels in adhesion.

Abstract: The machining of metal dies involves a variety of processes that include grinding, polishing and electrical discharge machining in addition to various cutting processes such as turning, boring, and milling. The precise machining of complex dies, particularly in deep machining, has largely been done by electrical discharge machining in the past, because the use of end mills and other cutting tools for such work has been difficult. In recent years, however, problems such as low machining efficiency and the creation of an affected layer have made the use of end mill cutting tools the general approach to this task. In the research reported here, our objective was to establish guidelines for the optimum design of small radius ball end mills for the deep machining of dies by systematic investigation of the cutting tool characteristics, which is to say the rotational behavior, cutting resistance, actual rate of depth of cut and machining accuracy of small radius ball end mills. Here, the guidelines obtained for ultra-deep, highly-accurate machining that is applicable to machining programs and is based on quantitative results for amounts of tool wear and tool deflection that obtained using the optimum tool shape reported earlier are presented.

Abstract: Recently, wet blasting is generally used such as liquid honing and water jet machining in surface before plating of stainless steel. The outstanding feature of wet blasting is to prevent generation of static electric charge, to use micro abrasive grain, and to have cushioning for workpiece. On the other hand, the disadvantage of wet blasting is to generate corrosion of equipment and liquid waste under processing. Moreover, the using abrasive grain is available on a limited basis. In particular, improvement disposal of liquid waste under processing is crucial in the near future. This paper makes proposal for improvement of surface texture by utilizing dry blasting, and it conducts improvement of surface texture about martensite stainless steel (SUS420J2 In JIS), which is used in material for scale. In the previous report, it has been cleared that relationship between surface texture and wettability. In this report, adhesion of plating was measured by scratch test. As a result, it was cleared that availability of adhesion evaluation by utilizing wettability.

Abstract: The speed-up of the disc rotation in dry centrifugal barrel finishing is done and its influence on finishing characteristics is experimentally examined. The workpiece is a sliced cold rolled bar of plain carbon steel (S45C in JIS, HB221). It is 32mm in diameter and finished to10mm in thickness by belt grinding. The equilateral triangular prism nylon media (
1010mm, A#320) is used at 20vol% in media charging ratio. The disc rotation speed is increased up to 500min-1. By speeding up the disc rotation, the finishing speed improves, but the total efficiency decreases.

Abstract: This paper investigates how to use shape memory alloy (SMA, Ni-Ti alloy) as a method of chucking parts. It is because tool holder can be simplified and miniaturized. SMA cannot be utilized as chucking tool because it is one-way direction, but it is possible to shrink and release a tool by changing temperature in case SMA is made of combing cylinder with alloy tool steel (SKD61 in JIS). In this report, prototype shrinking tool holder that used combing cylinder with SMA was developed and tried milling processes. As a result, it is clear that combing cylinder with SMA can endure cutting force.

Abstract: Recently, wet blasting is generally used such as liquid honing and water jet machining in surface before plating of stainless steel. The outstanding feature of wet blasting is to prevent generation of static electric charge, to use micro abrasive grain, and to have cushioning for workpiece. On the other hand, the disadvantage of wet blasting is to generate corrosion of equipment and liquid waste under processing. Moreover, the using abrasive grain is available on a limited basis. In particular, improvement disposal of liquid waste under processing is crucial in the near future. This paper makes proposal for improvement of surface texture by utilizing dry blasting, and it conducts improvement of surface texture about martensite stainless steel (SUS420J2 In JIS), which is used in material for scale applications. As a result, it is cleared that relationship between surface texture and blasting conditions. Furthermore, based on these results, it reports relationship between surface texture and wettability.

Abstract: Machining of complex shape and deep micro cavity in die and mold is mostly carried out by electrical discharge machining process. However, it may not be able to sufficiently meet delivery deadline minimization and cost reduction of die and mold. Therefore, precision machining method using small radius ball end mill capable of machining deep cavities in miniature die and mold is proposed as a substitute for electrical discharge machining. This report presents such a result supported by experiment in which it has been proved that long tool life of ball end mill can be maintained by changing coating material and edge profile of small radius ball end mill experiencing form accuracy and get needed surface finish in workpiece. Therefore, for precision machining of die and mold as substitute for electrical discharge machining, it is proposed to perform deep precision machining using small radius ball end mill. This paper shows effect proved by experiment how cutting characteristics which occur by changing of coating material and edge profile of small radius ball end mill influence form accuracy and finishing surface of workpiece.