가공공정 모니터링이 가능한 치과용 크라운 가공기 개발

이종항,허우석 한국산학기술학회 2022 한국산학기술학회논문지 Vol.23 No.5

Dental crowns are shaped by machining with a five-axis machine using the CNC(Computer Numerical Control) program. On the other hand, an operator is required to monitor the machining process consistently when the CNC program is used. Thus, there is a need to monitor the machining process to increase the machining efficiency and achieve smart machines with artificial intelligence functions in the future. This paper proposes a new sensor installation method that can easily produce acquisition machining process information during machining. The continuous monitoring of the machining process using this sensor was assessed. The bearing temperature and rotational speed were monitored using a thermocouple and inverter for the motor controller. In addition, a three-axis load cell was used to monitor the spindle vibration and tool wear. In particular, the load cell was installed between the spindle and the vertical column to avoid interference by signal lines between the tool and the workpiece. Monitoring the temperature, rotational speed, spindle vibration, and tool wear using these sensors allowed the machining process to be assessed while machining the crown without an operator. Moreover, the developed machine tool for dental-crown showed a machining accuracy of less than 30 micrometers. 치과용 크라운의 형상은 5축 가공기의 CNC 프로그램에 의해서 가공된다. 이 CNC 프로그램에 의한 가공은 작업자가 가공공정을 항상 모니터링 할 필요가 있다. 미래에 인공지능 기능을 갖춘 스마트 공작기계를 구현하기 위해서는 가공공정을 모니터링 할 수 있는 능력을 갖추고 가공 효율을 높일 필요가 있다. 본 연구에서는 치과용 크라운 가공 중 가공공정 정보를 용이하게 수집할 수 있는 새로운 센서 설치법을 제안하고, 이 센서를 이용하여 가공공정을 지속적으로 모니터링 할 수 있는 가능성을 확인하였다. 스핀들 베어링에 열전대를 설치하여 베어링의 온도를 모니터링하고, 모터 제어용 인버터로 부터 회전수를 모니터링 한다. 또한, 3축 로드셀을 사용하여 스핀들 진동과 공구마모를 모니터링 한다. 특히 로드셀은 공구와 공작물 사이의 신호선에 의한 간섭을 회피할 수 있도록 스핀들과 상하 이송용 컬럼 사이에 설치된다. 이러한 센서들에 의하여 온도, 회전수, 스핀들 진동, 그리고 공구마모를 모니터링 한 결과, 작업자의 도움 없이도 크라운을 가공하면서 충분히 가공공정을 감시할 수 있었다. 또한, 개발된 치 가공기는 30 micrometer 이하의 가공오차를 갖는다.

Generating Machining Directions for 5-axis NC Machining of Cycling Helmet’s Mold Components

Alan C. Lin,Mohammad Khoirul Effendi 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.9

Mold components for producing a cycling helmet are one of the most complex parts encountered in 5-axis NC machining. One important factor namely machining direction is used not only for checking collision, but also for reducing machine setup and shaping surface with low curvature variations. This paper focuses on how to minimize the total number of machining direction in 5-axis NC machining of cycling helmet’s mold components. In the proposed method, the machining direction candidates are generated using a regular placement method. V-maps are also used to select the machining direction through cascade filter of V-maps. Genetic algorithm is also used in order to identify the initial machining direction. Moreover, blockage solver and agglomeration method are applied in sequence to update the machining direction results. Additionally, to evaluate the performance of the proposed method, a CAD model for the cycling helmet mold components is created and used as a model of implementation. The computational result shows that the CAD model can be machined using the minimum number of machining directions. A 5-axis NC machine is also used to really produce the mold components.

A study on the machining characteristics of specimens with spherical shape using laser-assisted machining

Kim, I.W.,Lee, C.M. Pergamon ; Elsevier Science Ltd 2016 Applied thermal engineering Vol.100 No.-

Materials such as nickel-based alloys have high strength and excellent resistance to many corrosive environments, and are widely used in various industrial fields, but are difficult to machine using conventional machining. To machine difficult-to-cut materials, thermally enhanced machining (TEM) has been developed internationally. One of the currently applied thermally enhanced machining methods, laser assisted machining (LAM), uses laser preheating to locally soften materials ahead of the cutting tool before machining. There have been no research works by LAM for three-dimensionally shaped specimens. Compared to a plate shape, it is more difficult to predict the optimum LAM preheating temperature for a three-dimensional shape, because with a 3D surface, the shape of the preheated spot changes continuously during machining. In this study, LAM was applied to spherical shaped specimens of three different materials, AISI 1045, Inconel 718 and titanium alloy for three dimensional machining. Before the machining experiments, thermal analysis was carried out by finite element analysis (FEA) to determine the optimum preheating temperature. A contouring machining method was used in the experiments. Cutting force and surface roughness were measured to analyze machining characteristics, and were found to be improved by LAM. These results can be applied to similar machining of difficult-to-cut materials.

Eco-Friendly Face Milling of Titanium Alloy

Park, Kyung-Hee,Yang, Gi-Dong,Lee, Myung-Gyu,Jeong, Hoon,Lee, Seok-Woo,Lee, Dong Yoon 한국정밀공학회 2014 International Journal of Precision Engineering and Vol.15 No.6

Recently, a use of difficult to cut materials including titanium alloy has been substantially increasing in aerospace and automotive industries. Eco-friendly machining technology, which eliminates or minimizes cutting fluids in machining fields, has been emerged in compliance with green manufacturing trend. In this regard, machining technologies, such as hard milling, laser assisted machining (LAM), and enhanced lubrication/cooling method, have been adapted by the industries. Among the technologies, cryogenic machining has been considered for a viable solution for the materials without any environmental problems. LAM and minimum quantity lubrication (MQL) can be useful method to cut these materials with an appropriate use. In this study, machining performance of eco-friendly machining techniques was compared experimentally for the titanium alloy (Ti-6Al-4V). The machining performance was evaluated in terms of tool wear and cutting force. From experimental results, coated cutting tool with flood cooling condition was not recommended in titanium machining. The cryogenic, MQL, LAM showed outstanding machining performance than dry and flood cooling. Especially MQL machining was superior with relatively simple system setup. In addition, lubrication and cooling mechanism by combination of MQL and cryogenic reduced cutting force and tool wear. For energy consumption, MQL and cryogenic methods can be a sustainable solution.

A Study on the Machining of Compressor Rotors Using Formed Tools

박상윤,Hi-Koan Lee,양균의,문상돈 한국정밀공학회 2010 International Journal of Precision Engineering and Vol. No.

In this paper it was suggested the machining method that can improve machining accuracy and reduce the machining time applying the formed tools based on the rotor shape feature to finishing machining for efficient machining of asymmetric rotors. For machining the complicated asymmetric rotor profile, machining area is divided and formed tools are manufactured based on the rotor feature., and the efficient machining method of screw motor was proposed using the formed tools and four axis machining devices. With the suggested machining method, machining time could be reduced compared to the general end mill machining method, and the machining errors of the proposed method could be within the allowable tolerance of the product so as to carry out the precise machining.

Development of Electric Rust Preventive Machining Method System - Safe Water Using for Machining Fluid: Complete Removal of Bacteria (Enterobacter aerogenes) -

Naohiro Nishikawa,Katsuhiko Omoe,Kenji Murakami,Yusuke Sato,Takekazu Sawa,Yoshihiro Hagihara,Nobuhito Yoshihara,Hiroaki Okawai,Toshirou Iyama,Masahiro Mizuno,Shinya Tsukamoto 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.

It is great concern that is environmental load in manufacturing. In machining site, metal working fluid (coolant) such as cutting oil,grinding fluid is used. It contains several chemicals that are oil, surface active agent, extreme pressure additive, antirust agent,antifoaming agent, preservative, biocide etc.. It is thought that it is not good for environment and human body. Machining fluid mist and splash contained several chemicals that are cause of danger for worker’s health while machining. Furthermore, time elapses, fluid is rotten by bacteria. Bad smell and degradation of machining performance occurs. Therefore, after using machining fluid, waste fluid is disposed. Incineration or coagulative precipitation and landfill etc. are necessary. It arise great disposal cost and environmental load as discharging of huge amount green house gas (CO2 etc.). Then, machining fluid decreasing or non-using is demanded in industry. So, in this investigation, new environmental machining method: the electric rust preventive machining method system that uses only water as machining fluid has been developed. In this paper, water purification recycle system in water machining system development is mentioned. Therefore, complete removal of bacteria (Enterobacter aerogenes) without using chemicals such as biocide is examined for corruption, malodor prevention and safe machining water.

Al-Li 합금 윙립의 고속가공 변형특성에 관한 연구

이인수(In-Su Lee),김해지(Hae-Ji Kim) 한국기계가공학회 2014 한국기계가공학회지 Vol.13 No.6

Aluminum lithium alloys are new materials developed for lightweight aircraft parts. However, as compared with conventional aluminum alloys in high-speed machining, problems such as tool wear, machining distortion, and cutting ability arise. This study presents the machining distortion characteristics of an Al-Li alloy wing tip in relation to the cutting heat in high-speed machining. A machining experiment was conducted with high-speed machining equipment for an evaluation of the machining distortion characteristics, with each machining stage temperature change of the workpiece machining surface, and the inside and outside temperature changes of the equipment measured. By measuring the amount of distortion of the workpiece before and after machining, the cutting heat was analyzed with regard to its effect on machining distortion in the product.

Five-axis machining time estimation algorithm based on machine characteristics

So, B.S.,Jung, Y.H.,Park, J.W.,Lee, D.W. Elsevier 2007 Journal of materials processing technology Vol. No.

<P><B>Abstract</B></P><P>In this paper, we present a machining time estimation algorithm for five-axis high-speed machining. Estimation of machining time plays an important role in process planning and production scheduling of a shop. In contrast to the rapid evolution of machine tools and controllers, machining time calculation is still based on simple algorithms of tool path length divided by input feedrates of NC data, with some additional factors from experience. We propose an algorithm based on five-axis machine behavior in order to predict machining time more exactly. For this purpose, we first investigated the operational characteristics of five-axis machines. Then, we defined some dominant factors, including feed angle that is an independent variable for machining speed. With these factors, we have developed a machining time calculation algorithm that has a good accuracy not only in three-axis machining, but also in five-axis high-speed machining.</P>

Simulation-based machining condition optimization for machine tool energy consumption reduction

Lee, Wonkyun,Kim, Seong Hyeon,Park, Jaesang,Min, Byung-Kwon Elsevier 2017 JOURNAL OF CLEANER PRODUCTION Vol.150 No.-

<P><B>Abstract</B></P> <P>Optimizing the machining condition is one of the effective ways for reducing the energy consumption of machine tools at a unit process level. Based on statistical approaches with design of experiments, various methods have been developed to reduce the energy consumption by optimizing the machining condition. However, the methods cannot be easily utilized when the optimization target or machine tool design is modified because the optimal solution is determined based on the experimentally measured data. In this study, a simulation-based method that utilizes a virtual machine tool (VMT) to optimize the machining condition is proposed. The VMT model is designed to focus on estimating the energy consumption during machining and is developed by replicating real machine tools. Based on the VMT model, a genetic algorithm is used to optimize the machining condition to reduce the energy consumption. The changes in the optimization target or machine tool design are easily considered by modifying the cost function or component model, respectively. The proposed method is applied to reduce the energy consumption of a three-axis milling machine. The optimal feed rate and spindle speed are obtained for each line of the part program when the thrust force is limited. An experimental setup of the machine tool with an energy consumption monitoring system is constructed to demonstrate the effectiveness of the proposed method. The results show that the total energy consumption of the machine tool reduces by 13% owing to the optimization.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Simulation-based method to reduce the energy consumption of machine tool is proposed. </LI> <LI> Virtual machine tool to estimate the energy consumption during machining is built. </LI> <LI> Optimal machining conditions to minimize the energy consumption is obtained. </LI> <LI> Energy consumption reduction using proposed method is demonstrated experimentally. </LI> </UL> </P>

STD11 금형강의 고속가공에서 가공정밀도 향상에 관한 연구

이춘만,최치혁,정원지,정종윤,고태조,김태형 한국공작기계학회 2002 한국공작기계학회 추계학술대회논문집 Vol.2002 No.-

High-speed machining is one of the most effective technology to improve productivity. Because of the high speed and high feed rate, high-speed machining can give great advantages for the machining of dies and molds. This paper describes on the improvement of machining accuracy in high-speed machining. Depth of cut, feed rate, spindle revolution and cutting force are control factors. The effect of the control factors on machining accuracy is discussed for the results of surface roughness and machining error in Z-direction for the high speed machining of STD11.