미래 산업에서 제조 기술의 우위성을 확보해 가기 위해 단순히 인건비 절감과 에너지 절약 등 제조 과정의 비용 절감을 목적하는 것만으로는 한계가 있다. 제조공정 단계에서 소재의 낭비를 최소화하면서 높은 고부가가치를 달성하는 것이 중요하며, 또한 고부가가치를 창출하기 위해서는 가공 기술의 정밀화와 미세화가 반드시 필요하다. 미래의 고부가가치 제품에는 높은 형상정밀도뿐만 아니라 다양한 미세표면 형상을 가진 부품의 요구가 점점 높아지고 있다.
미세입자 분사가공은 마이크로 단위의 미세입자를 고압의 공기압을 이용해 분사하는 가공방법으로 일반적인 기계가공으로서는 가공이 어려운 경도가 높고 취성이 강한 세라믹 재료 또는 유리 등을 침식시켜 원하는 형태의 구조물을 만들거나 너무 연성이 높아 기존 절삭가공으로 표면형상가공이 어려운 경우 사용 가능한 방법이다. 최근 금속 표면에 코팅, 이온주입 등 표면 개질 기술이 발달함에 따라 금속표면에 폴리머, 세라믹뿐만 아니라 이종금속 혹은 원소에 의한 표면 특성 향상이 더욱 요구되고 있다.
미세 입자 분사 가공의 재료 측면에서 연성재료인 알루미늄에 관하여 다양한 연구들이 진행되고 있으며. 그중 알루미늄 A1050-H14 소재는 알루미늄 성분이 99.5% 함유되고 연신율이 5(A50mm %)인 극연성 재료로서 우수한 내식성, 용접성, 열, 전기전도성이 우수하나 강도가 낮은 것이 단점으로, 알루미늄 합금에 비해 낮은 가공성으로 제한적 용도로 사용된다. 최근 코팅이나 다른 금속원소의 이온주입을 위해 가공된 표면보다 거친 표면이 요구되고, 이는 향후 알루미늄이 다양한 분야에 사용되기 위해 미세 표면 형상 가공 또는 이종 재료와의 접착력 향상에 대한 대책이 요구 되고 있다. 이러한 모재의 미세 표면 형상 가공에 대한 수요가 증가하고 있으나 이에 따른 연구가 미미하고 향후 산업분야에서 다양하게 요구 되어질 알루미늄 재료의 미세 표면 형상과 이종 재료와의 접착력 향상에 대한 대책과 연구가 필요하다.
본 연구에서는 마이크로 입자 분사가공 시 원형, 사각형등 다양한 형상을 표면에 분사하기 위해 시퀀스 제어가 가능한 2축 스테이지 장치를 개발해서 여러 형태의 궤적을 선택하고 그 도형에 해당되는 X축과, Y축 궤적 형태로 전개되면서 분사가공을 진행하여 표면 형상 미세입자 가공 특성을 파악하고자 한다. 실험조건의 수준별 주요인자의 값을 양극화시켜 2수준으로 설정하고 실험계획법 중 직교배열표에 의한 실험을 시퀀스 제어 2축 분사장치로 각 변의 길이가 16mm인 정사각형 궤적으로 구동하여 분사실험을 실시한다. 2축 궤적 분사가공을 통해 가공조건의 주요인자로 미세입자인 탄화규소, 산화알루미나, 그리고 분사입자, 분사압력, 노즐직경, 이송속도, 그리고 분사 사이클횟수 등과 같은 인자별 영향력을 분석하고, 다양한 형상 가공을 위한 적합한 가공 조건을 규명하는 것이다. 실험인자에 의한 실험조건은 직교배열표에 따라 8회 랜덤하게 진행하고 주요인자의 중심선 평균거칠기(Ra)와 분사면 표면깊이(max depth)에 대한 결과값의 관계를 실험계획법의 분산분석기법을 통하여 인자별 기여도와 주효과도를 분석하고자 한다. 실험 결과에 따라 인자별 영향력과 더 주요한 3가지 주요인자가 무엇인지 찾아내는 것을 목적으로 하여 분사압력, 분사입자, 분사노즐이 주요 3인자로 영향력이 높게 나타났다.
본 실험으로 진행된 2차 실험에서는, 다구찌 실험계획법을 통해 1차 실험에서 도출된 주요 인자 3가지를 4수준으로 설정하고 나머지 인자에 대해선 1수준의 고정인자로 하여 32번의 실험을 실시한다. 총 실험의 횟수는 실험의 재현성을 위해 동일한 조건의 반복실험을 통해 2번 반복 총 64번의 정사각형 구동궤적 분사실험을 진행한다. 중심선 평균거칠기와 분사면 표면깊이, 분사면 코너 반경(corner radius)측정값을 통해 주요인자와 결과값의 관계를 실험계획법의 분산분석 기법으로 인자별 기여도와 주효과도를 분석하였다.
결과에 따라 인자별 영향력을 분석한 결과 표면거칠기(Ra)와 분사면 표면 깊이(max depth)에 미치는 기여도는 분사압력, 분사입자, 노즐직경 순으로 나타났고, 인자별 주효과도에 따라 분사입자는 탄화규소(SiC)의 영향력이 크고, 분사 노즐은 3수준(Ø1.16)이 4수준(Ø1.5)보다 영향력이 크게 나타났다. 이는 노즐직경이 Ø1.16 까지는 압력의 증가에 따른 분사력이 유지되나 노즐직경이 ?1.5로 커질 때 압력이 분산되는 것으로 판단되었으며 1차, 2차 실험에서 동일한 경향을 나타내었다. 분사압력은 높을수록 증가하고 4수준(650kPa)에서 영향력이 높았다. 분사면 코너부 반경 데이터 값을 분석을 한 결과 분사입자에 관계없이 노즐직경 ?0.7에서 코너 반경값이 적게 나타나 안정적인 분사가 이루어지고 탄화규소보다 산화알루미나로 분사가공 시 동일한 노즐 내 분류량이 작은 것으로 나타났다.

A cost reduction objective in manufacturing process such as labour cost reduction and energy saving has a limitation in securing manufacturing technology’s dominance in future industry. It is important to achieve a high added value while minimizing waste materials in manufacturing process phase. In addition, precision and refinement of processing technology are essential for creating high added values. For the high added value products in future, demand for not only a high form accuracy, but also for parts having various shapes of micro surfaces is increasing.
Micro particle blasting is a processing method of blasting micro-unit fine particles using high pneumatic pressure. This method can be used to erode ceramic material or glass, etc. having a high hardness and fragility, which are difficult to process using a general machining, to create a desired structure, or in a case where the existing cutting machining is difficult to perform surface shape machining due to the material’s high ductility. Due to the recent development in surface reforming technologies such as coating and ion injection, etc. on metal surfaces, demand for not only improving surface characteristics of metals by polymer and ceramics, but also by dissimilar metals or elements is emphasized
In material aspect of micro particle blasting, various studies are being conducted on aluminium, which is a ductile material. Among those, aluminium A1050-H14 material is an extremely ductile material with elongation percentage of 5% which contains 99.5% aluminium component. Although it has excellent corrosion resistance, weldability, heat and electrical conductivity, one of its cons is the low strength. Thus, it is being used for limited purposes as it has lower processability than aluminium alloy. Recently, surfaces that are rougher than the processed surfaces is required for ion implantation of coating or other metal elements. This requires solutions for micro surface shape machining or improvement of adhesive strength by dissimilar materials to allow aluminium to be used in various fields. Despite the increasing demand on micro surface shape machining of the basic materials, there are only few studies conducted on this topic. Therefore, solutions and studies shall be provided for aluminium material, which will be required by industry fields in future, regarding its micro surface shape and improvement of its adhesive strength with dissimilar materials.
In this study, in order to blast various shapes such as circle and square, etc. on surfaces when performing micro particle blasting, a biaxial stage equipment that could perform sequence control was developed. The study aimed to identify characteristics of surface shape micro particle machining by using the equipment that selects various shapes of trajectories, follows the trajectory in X-axis and Y-axis that correspond to the figure, and proceeds blasting. The major factor value of each level of experimental condition was polarized and set to level 2. In addition, for the experiment based on orthogonal array among experimental plan methods, a blasting experiment was performed by driving a sequence-
controlling biaxial blasting equipment to a trajectory of a square with the length of each size as 16 mm. Through the biaxial trajectory blasting, analysis was performed on major factors of processing condition such as silicon carbide, alumina, as well as influence of each factor such as particle, blasting pressure, nozzle diameter, feed speed and number of blasting cycles, etc. to investigate a suitable machining condition for machining of various shapes. For the experimental condition based on the experiment factors, the experiment was performed 8 times randomly according to orthogonal array, and relation between result values on center line average height (Ra) and maximum depth of blasting surface was used to analyse level of contribution and main effects by each factor through analysis of variance of the experimental plan method. The purpose was to find effects by each factor and 3 major factors based on experimental result, and blasting pressure, particle and blasting nozzle were indicated as the 3 major factors having high effects.
In this study, in order to blast various shapes such as circle and square, etc. on surfaces when performing micro particle blasting, a biaxial stage equipment that could perform sequence control was developed. The study aimed to identify characteristics of surface shape micro particle machining by using the equipment that selects various shapes of trajectories, follows the trajectory in X-axis and Y-axis that correspond to the figure, and proceeds blasting. The major factor value of each level of experimental condition was polarized and set to level 2. In addition, for the experiment based on orthogonal array among experimental plan methods, a blasting experiment was performed by driving a sequence-controlling biaxial blasting equipment to a trajectory of a square with the length of each size as 16 mm. Through the biaxial trajectory blasting, analysis was performed on major factors of processing condition such as silicon carbide, alumina, as well as influence of each factor such as particle, blasting pressure, nozzle diameter, feed speed and number of blasting cycles, etc. to investigate a suitable machining condition for machining of various shapes. For the experimental condition based on the experiment factors, the experiment was performed 8 times randomly according to orthogonal array, and relation between result values on center line average height (Ra) and maximum depth of blasting surface was used to analyse level of contribution and main effects by each factor through analysis of variance of the experimental plan method. The purpose was to find effects by each factor and 3 major factors based on experimental result, and blasting pressure, particle and blasting nozzle were indicated as the 3 major factors having high effects.
In this study, in order to blast various shapes such as circle and square, etc. on surfaces when performing micro particle blasting, a biaxial stage equipment that could perform sequence control was developed. The study aimed to identify characteristics of surface shape micro particle machining by using the equipment that selects various shapes of trajectories, follows the trajectory in X-axis and Y-axis that correspond to the figure, and proceeds blasting. The major factor value of each level of experimental condition was polarized and set to level 2. In addition, for the experiment based on orthogonal array among experimental plan methods, a blasting experiment was performed by driving a sequence-controlling biaxial blasting equipment to a trajectory of a square with the length of each size as 16 mm. Through the biaxial trajectory blasting, analysis was performed on major factors of processing condition such as silicon carbide, alumina, as well as influence of each factor such as particle, blasting pressure, nozzle diameter, feed speed and number of blasting cycles, etc. to investigate a suitable machining condition for machining of various shapes. For the experimental condition based on the experiment factors, the experiment was performed 8 times randomly according to orthogonal array, and relation between result values on center line average height (Ra) and maximum depth of blasting surface was used to analyse level of contribution and main effects by each factor through analysis of variance of the experimental plan method. The purpose was to find effects by each factor and 3 major factors based on experimental result, and blasting pressure, particle and blasting nozzle were indicated as the 3 major factors having high effects.
In the 2nd experiment which was proceeded as the main experiment, the 3 major factors derived from the 1st experiment through Taguchi Experimental Method were set to level 4, and the other factors to level 1. These were used as fixed factors, and the experiment was conducted 32 times. For the reproducibility of the experiment, it was repeated twice under the same condition, which is total of 64 square-driving trajectory blasting experiments. Through measured values of center line average height, maximum depth of blasting surface and blasting surface corner radius, the relationship between main factors and result values was used in analysis of variance of the experimental plan method, to analyse the level of contribution and main effects by each factor.
The result of analysing effects by each factor indicated that the blasting pressure had the highest level of contribution to center line average height (Ra) and maximum depth of blasting surface, followed by particle and nozzle diameter. Based on main effects by each factor, it was indicated that particle had a high effect of silicon carbide (SiC), and the blasting nozzle of level 3 (Ø 1.16) had a higher effect than that of level 4 (Ø 1.5). The reason behind it was because the pressure was dispersed when the nozzle diameter increased to ?1.5, although the nozzle with the diameter up to Ø 1.16 maintained its blasting power. The 1st and 2nd experiments showed the same tendency. The effect increased as the blasting pressure increased, and it was especially high in level 4 (650 kPa). The result of analysing data values of blasting surface corner radius indicated a smaller corner radius value at nozzle diameter of ?0.7, which led to stable blasting. It was revealed that when the same nozzle was used, blasting with alumina (A12O3) had a less minimum flow rate inside the nozzle compared to using silicon carbide.