• Title/Summary/Keyword: 머시너블 세라믹스

Search Result 9, Processing Time 0.018 seconds

Machinability Evaluation of ${Si_3}{N_4}$-hBN Machinable Ceramics Using Experimental Design Method (실험계획법에 의한 ${Si_3}{N_4}$-hBN 머시너블 세라믹스의 절삭성 평가)

  • 장성민;임대일;조명우;조원승
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2002.10a
    • /
    • pp.291-295
    • /
    • 2002
  • Ceramics are very difficult-to-cut materials because of its high strength and hardness. Their machining process can be characterized by cracking and brittle fracture. Generally, ceramics are machined using traditional method such as grinding and polishing. However, such processes are generally costly and have low material removal rate. In this paper, to develop machinable ceramics those have good machinability without losing their material properties, machinability evaluations are performed by applying the experimental design method. In this paper, to evaluate the machinability of the developed ceramics, various workpieces are machined on the CNC machining center, and surface roughness are measured under predefined process parameters obtained using Taguchi method. And the experimental results are investigated to derive optimum cutting parameters for the given materials.

  • PDF

Surface Properties and Tool Wear of Si3n4-hBN Machinable Ceramics in Endmill Machining using Tungsten Carbide Tool (텅스텐 카바이드 공구를 사용한 앤드밀 가공에서 Si3n4-hBN 머시너블 세라믹스의 표면특성과 공구마멸)

  • Jang, Sung-Min;Cho, Myeong-Woo
    • Journal of the Korean Society of Manufacturing Process Engineers
    • /
    • v.3 no.1
    • /
    • pp.15-21
    • /
    • 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.

  • PDF

A Study on the Micro Hole Drilling Characteristics of Machinable Ceramics (머시너블 세라믹스의 마이크로 홀 가공특성에 관한 연구)

  • 김동우;조명우;조원승;이응숙
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
    • /
    • 2002.04a
    • /
    • pp.597-602
    • /
    • 2002
  • Ceramics are very difficult-to-cut materials because of its high strength and hardness. Their machining mechanism is characterized by cracking and brittle fracture. In this paper, to give good machinability to the ceramics, BN powders are added to Si$_3$N$_4$ by volume of 20, 25 and 30%. And the machiniability of the produced ceramics are tested using micro drilling system. Through required experimental works, it is shown that the micro drilling machinability is varied along with the volumetric percentage of BN powders. Also, it is verified that the obtained results can be used to develop new machinable ceramics of good material properties and machinability.

  • PDF

Evaluation of R-curve Behavior Analysis and Machinability of $Si_3N_4-hBN$ Machinable Ceramics ($Si_3N_4-hBN$ 머시너블 세라믹의 R-curve 거동분석과 가공성 평가)

  • 장성민;조명우;조원승;이재형
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.21 no.1
    • /
    • pp.61-70
    • /
    • 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.

Micro-Pattern Machining Characteristics Evaluation of $Si_3N_4$-hBN based Machinable Ceramics Using Powder Blasting Process (파우더 블라스팅에 의한 $Si_3N_4$-hBN계 머시너블 세라믹스의 미세패턴 가공성 평가)

  • 박동삼;조명우;김동우;조원승
    • Transactions of the Korean Society of Machine Tool Engineers
    • /
    • v.13 no.2
    • /
    • pp.33-39
    • /
    • 2004
  • Sandblasting has recently been developed into a powder blasting technique for brittle materials. In this study, the machinability of $Si_3N_4$-hBN based machinable ceramics are evaluated for micro - pattern making processes using powder blasting. Material properties of the developed machinable ceramics according to the variation of h-BN contents give a good machinability to the ceramics. The effect of scanning times, the size of patterns and variation of BN contents on the erosion depth of samples without mask and samples with different mask patterns in powder blasting of $Si_3N_4$-hBN ceramics are investigated. The Parameters are the impact angle of $90^{\circ}$, the scanning times of nozzle up to 40, and the stand-off distances of 100mm The widths of masked pattern are 0.1mm 0.5mm and 1mm. The powder used is Alumina particles, WA#600. and the blasting pressure of powder is 0.2MPa. Through required experiments, the results are investigated and analyzed. As the results, the machinability of the developed ceramics increases as the BN contents in the ceramics.

Mechanical Properties and End-milling Characteristic of AIN-hBN Based Machinable Ceramics (AIN-hBN계 머시너블 세라믹스의 기계적 특성 및 엔드밀링 가공성 평가)

  • Beck, Si-Young;Cho, Myeong-Woo;Cho, Won-Seung
    • Journal of the Korean Ceramic Society
    • /
    • v.45 no.1
    • /
    • pp.75-81
    • /
    • 2008
  • In this study, machining characteristics of AIN-hBN composites were evaluated in end-milling process. As a first step, AIN-hBN composite specimens with various hBN contents were prepared using hot press method. Material properties of the composites, such as relative density, Young's modulus and fracture toughness, were measured and compared. Then, a series of end-milling experinients were performed under various cutting conditions by changing cutting speed, depth-of-cut and feed rate. Cutting force variations were measured using a tool dynamometer during the cutting experiments. Machined surfaces of the specimens were observed using SEM and a surface pro filer to investigate the surface integrity changes. The cutting force decreased with an increases of hBN content. The cutting process was almost impossible for monolithic AIN, owing to severe chipping. In contrast, at high content of hBN, surface damage and chipping decreased, and better surface roughness can be obtained.

Experimental Investigations on Micro End-milling Cutting Characteristics Comparison and Tool Wear Behavior of AlN-hBN Composites Sintered by Hot-pressing (열간가압소결에 의해 제조된 AlN-hBN 복합재료의 마이크로 엔드밀링 절삭특성 비교와 공구마모에 관한 실험적 연구)

  • Beck, Si-Young;Shin, Bong-Cheol;Cho, Myeong-Woo;Cho, Won-Seung
    • Transactions of the Korean Society of Machine Tool Engineers
    • /
    • v.17 no.4
    • /
    • pp.104-111
    • /
    • 2008
  • The objective of this study is to evaluate micro end-milling characteristics and tool wear behavior of AlN-hBN composites. First, AlN based composites with hBN contents in the range of 10 to 20vol% were prepared by hot-pressing. Vickers hardness and flexural strength of the prepared composite specimens were measured and compared according to the vol% of hBN variations. Then, cutting force variations were measured and analyzed using a tool dynamometer during the micro end-milling experiments; and machined surface shapes and roughness were investigated using a 3D non-contact type surface profiler. After micro end-milling, worn tools were investigated using a tool microscope and SEM images. From the experimental results, it can be observed that the cutting forces decreased, and surface qualities were improved with increasing hBN contents. At low content of hBN, tool chipping was observed; and tool wear rate decreased with increasing hBN contents. The results of this study insist that proper machining conditions, including tool wear behavior investigation, should be determined for the micro end-milling of AlN-hBN composites for its further application.

Effect of h-BN Content on Microstructure and Mechanical Properties of AIN Ceramics (AIN 세라믹스의 미세조직과 기계적 성질에 미치는 h-BN 첨가의 영향)

  • 이영환;김준규;조원승;조명우;이은상;이재형
    • Journal of the Korean Ceramic Society
    • /
    • v.40 no.9
    • /
    • pp.874-880
    • /
    • 2003
  • The effect of h-BN content on microstructure, mechanical properties, and machinability of AlN-BN based machinable ceramics were investigated. The relative density of sintered compact decreased with increasing h-BN content. The four-point flexural strength also decreased from 238 MPa of monolith up to 182 MPa by the addition of 30 vol% h-BN. Both low Young's modulus and residual tensile stress, formed by the thermal expansion coefficient difference between AIN and h-BN, might cause the strength drop in AlN-BN composite. The crack deflection, and pull-out phenomena increased by the plate-like h-BN. However, the fracture toughness decreased with h-BN content. The second phases, consisted of YAG and ${\gamma}$-Al$_2$O$_3$, were formed by the reaction between Al$_2$O$_3$ and Y$_2$O$_3$. During end-milling process, feed and thrust forces measured for AlN-(10~30) vol% BN composites decreased with increasing h-BN particles, showing excellent machinability. Also, irrespective of h-BN content, relatively good surfaces with roughness less than 0.5 m (Ra) could be achieved within short lapping time.