• Design & Manufacturing
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• 제17권1호
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• pp.33-39
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• 2023

The ball end mill is a type of cutting tool that is widely used to process complex mold shapes including aspheric surfaces. Unlike the flat end mill in which the cutting edge is formed on the cylindrical handle, the cutting edge is formed from the cylindrical handle to the hemispherical shape, which is advantageous for processing curved shapes. However, since the cutting speed continuously changes during machining due to the helix angle of the cutting edge or the machining inclination angle, it is difficult to obtain a precise machined surface. Therefore, in this paper, machining was performed while changing the helix angle of the ball end mill and the angle of the machining slope under the same cutting conditions for STD 11 material, which is widely used as a mold material. Through this, the effect of the two variables on the roughness of the machined surface was analyzed. As a result, if the helix angle was 0 degrees, it showed the best surface roughness of Ra. 0.16 ㎛. When the helix angle was 20 degrees, the best surface roughness of Ra. 0.18 ㎛ was occurred.

• 한국정밀공학회지
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• 제21권1호
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• pp.61-70
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• 2004

Generally, ceramics are very difficult-to-cut materials because of its high strength and hardness. The machining process of ceramics can be characterized by cracking and brittle fracture. In the machining of ceramics, edge chipping and crack propagation are the principal reasons to cause surface integrity deterioration. Such phenomenon can cause not only poor dimensional and geometric accuracy, but also possible failure of the ceramic parts. Ceramics can be machined with traditional method such as grinding and polishing. However, such processes are generally cost-expensive and have low material removal rate. Thus, in this paper, to overcome these problems. BN powder, which gives good cutting property, is added for the fabrication of machinable ceramics by volume of 5,10,15,20,25 and 30%. And, mechanical properties, R-curve behavior and machining tests are carried out to evaluate the machining properties of the manufactured machinable ceramics.

• 한국기계가공학회지
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• 제16권6호
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• pp.41-46
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• 2017

Productivity improvement and cost reduction in the aircraft industry have become major industrial objectives, and improving productivity by reducing machining time has become a key focus. When numerical cutting code is created by CAM software, such as CATIA or UG-NX, it is impossible to control machining feed speed using cutting force changes depending on the machining tool path. However, machining an aircraft engine part from difficult material, such as Inconel 718, takes a long time, and tool chipping or breakage often occurs from forcing the machining path too quickly. This study investigated and verified the reliability of the AdvantEdge production module (PM)using cutting power tests. In particular, diffuser and diffuser case parts were considered, comparing cutting power and machining time using AdvantEdge PM and CATIA.

• 대한금속재료학회지
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• 제48권7호
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• pp.651-659
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• 2010

When high-speed interrupted cutting is carried out for die and mold steels with high hardness, CBN tools manifested a significantly longer wear life than carbide, ceramic, or cermet tools in an experiment of face milling characteristics. In addition, it was also found that they secured a stable surface roughness within a range of 1.6 S~6.3 S, an acceptable range for precision machining for polished machining parts. And it makes them acceptable in the precision machining field, except in industries where very high machining accuracy is required. In the high hardness interrupted cutting, it was advantageous to perform a negaland treatment and a honning treatment on the tools' cutting edge to extend tool life and surface roughness. Also, severe crater development was found on the sloped face in CBN tools following high-speed machining. This caused the cutting edge to be weakened and damaged, and ultimately resulted in a shorter tool life. Finally, as a result of EDX mapping inspection, Cr component was detected evenly on the entire crater wear area, which can be included only in STD 11.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.928-933
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• 2004

A new approach for modelling and simulation of the cutting forces in end milling processes is presented. In this approach, the cutting forces in end milling are modelled based on a predictive machining theory, in which the machining characteristic factors are predicted from input data of fundamental workpiece material properties, tool geometry and cutting conditions. In the model, each tooth of a end milling cutter is divided into a number of slices along the cutter axis. The cutting action of each of the slices is modelled as an oblique cutting process. For the first slice of each tooth, it is modelled as oblique cutting with end cutting edge effect, whereas the cutting actions of other slices are modelled as oblique cutting without end cutting edge effect. The cutting forces in the oblique cutting processes are predicted using a predictive machining theory. The total cutting forces acting on the cutter is obtained as the sum of the forces at all the cutting slices of all the teeth. A Windows-based simulation system for the cutting forces in end milling is developed using the model. Experimental milling tests have been conducted to verify the simulation system.

• 한국기계가공학회지
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• 제3권1호
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• pp.15-21
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• 2004

The machining process of ceramics can be characterized by cracking and brittle fracture. In the machining of ceramics, edge chipping and crack propagation are the principal reasons to cause surface integrity deterioration. Such phenomenon can cause not only poor dimensional and geometric accuracy, but also possible failure of the ceramic parts. Thus, traditional ceramics are very difficult-to-cut materials. To overcome such problems, in this paper, h-BN powder, which gives good cutting property, is added for the fabrication of machinable ceramics by volume of 5, 10, 15, 20, 25 and 30%. The objectives of this paper is to evaluate the fracture phenomenon of the tungsten carbide tool and the variation of surface integrity of the manufactured machinable ceramics under various cutting conditions during end mill machining With CNC machining center.

• 한국기계가공학회지
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• 제14권5호
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• pp.22-27
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• 2015

Processing of low toughness graphite material requires high-speed machine tools and DLC coating. In this study, results of investigation of the tool wear and machining properties of the DLC coating according to the thickness, and the machining time of the tool used for the machining of graphite electrodes, were as follows. 1. DLC coating thickness shows a larger wear amount of the tool center in accordance with thickness; the wear amount of the tool increases in proportion to the machining time. 2. The difference between the amount of wear depending on the processing time shows edge portions larger than the tool wear amount in the center. This amount of wear of the tool edge is formed since the rotating torque is in contact with the graphite material surface significantly more than the central portion. 3. The thicker the DLC coating, the more the coating tool eliminated of the coating area by the interface between the cemented carbide tool being coated with an increased friction of the graphite material and the DLC coating area.

• 한국정밀공학회지
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• 제23권12호
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• pp.111-116
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• 2006

Micro machining of tungsten carbide by electrochemical machining was studied. In ECM, machining conditions and electrolyte should be chosen carefully according to the property of workpiece materials. In this paper, sulfuric acid and nitric acid were used for tungsten carbide machining and machining characteristics were investigated according to machining conditions such as electrolyte, workpiece potential and applied pulse voltage. By using mixture of sulfuric acid and nitric acid, micro structures with sharp edge and good surface quality were obtained. Micro electrochemical turning was also introduced to fabricate micro shafts.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1795-1798
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• 2003

This paper presents a method for impeller modeling by the reverse engineering and the 5-axis machining. The impeller is composed of pressure surface, suction surface and leading edge, and so on. The impeller is modeled by using the characteristic curves of impeller such as hub curves, shroud curves and leading edge. The characteristic curves are extracted from the scanned data. The hub curves and shroud curves are generated by intersection between blade surface and hub boundary and shroud boundary. respectively. A sample impeller machining is performed by tool path plan and post-processing with inverse kinematic solution.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.485-491
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• 1999

A burr is formed in every corner of parts as a result of machining, which produces undesirable edge geometry and influence deeply to surface quality of workpiece. Therefore these burrs must be removed certainly. The cost of removing these burrs is directly proportional to their size. Burrs have been among the most troublesome obstruction to high productivity and automation of machining processes. The proper selection of cutting condition and tool geometry will be helpful to reduce the occurrence of burrs. In paper will observe burr formation along helix angle in end milling and certificate experimentally mechanics relation of helix angle and burr formation.