[机械模具数控自动化专业毕业设计外文文献及翻译]【期刊】磨粒喷射加工玻璃微槽-外文文献

Journal of Materials Processing Technology 146 (2004) 234240Micro-grooving of glass using micro-abrasive jet machiningDong-Sam Parka, Myeong-Woo Chob, Honghee Leeb, Won-Seung ChocaDepartment of Mechanical Engineering, University of Incheon, 402-749 Incheon, South KoreabDivision of Mechanical Engineering, Inha University, 402-751 Incheon, South KoreacDivision of Material Science, Inha University, 402-751 Incheon, South KoreaReceived 11 February 2002; received in revised form 5 September 2003; accepted 4 November 2003AbstractAbrasive jet machining (AJM) is similar to sand blasting, and effectively removes hard and brittle materials. AJM has been applied torough working such as deburring and rough finishing. With the increase of the needs for machining of ceramics, semiconductors, electronicdevices and LCDs, micro-AJM has become a useful technique for micro-machining. This paper describes the performance of micro-AJMin the micro-grooving of glass. The diameter of the hole-type and the width of the line-type groove are 80H9262m. Experimental results showedgood performance in micro-grooving of glass; however, the size of machined groove increased about 24H9262m. With the fine-tuning of themasking process and the compensation for film wear, micro-AJM could be effectively applied to the micro-machining of semiconductors,electronic devices and LCD. 2003 Elsevier B.V. All rights reserved.Keywords: Micro-abrasive jet machining; Micro-abrasive; Grooving; Masking process1. IntroductionRecent development of special purpose parts, such as theparts for semiconductor processing, the parts and sensors formicro-machine fabrication, etc., has been expanded. Thus,it is essential to develop micro-machining technologies forhard and brittle materials such as glass, ceramics, etc. How-ever, such materials are generally difficult-to-machine dueto the properties of extreme hardness, brittleness, corrosionresistance and melting temperature. Using conventional ma-chining technologies has been difficult since thermal and/orchemical machining methods (such as chemical etching,laser and electron beam machining, EDM, and electrolyticmachining) cause an excessive heat affected zone, while us-ing mechanical machining methods (such as ultrasonic ma-chining, grinding, polishing) have limitations in productivityand accuracy.Thus, abrasive jet machining has been considered oneof the most appropriate micro-machining methods for hardand brittle materials, since the productivity is high and heataffected layers caused by material removal are very thin.Among abrasive jet machining methods, dry machininghas proven to be a suitable micro-machining technologyCorresponding author.E-mail address: dsparkincheon.ac.kr (D.-S. Park).for the production of micro-parts of semiconductors andLCD. Recently, research on micro-abrasive jet machining(MAJM) using micro-particles as abrasives has been ex-tensively tested. Momber dealt with water jet machiningprocess 1. He presented the first comprehensive review ofsuch machining techniques dealing with a broad range ofissues including mixing and acceleration process, materialremoval mechanism, process optimization, etc. McGeoughsummarized the current understandings and practices ofmicro-machining of engineering materials 2, and intro-duced the machining techniques that had been developed todeal with difficult-to-treat materials such as polymers, hardmetals and ceramics 3.Recent studies on MAJM have focused on the follow-ing topics: abrasive jet machining mechanism identification4,5, machining characteristics of MAJM 69, develop-ment of an MAJM machine and alternating micro-machiningprocesses for glass 10,11, technological trend and appli-cation case studies 1115. Much research is being carriedout to define the machining mechanism and to introducecase studies of MAJM based on the results of the abovestudies.The main objective of this study is to perform essen-tial experiments required to machine hole- and line-typemicro-grooves using MAJM. To achieve the goals, optimumconditions for masking, along with the process of abra-sive machining, are obtained while a feasibility analysis to0924-0136/$ see front matter 2003 Elsevier B.V. All rights reserved.doi:10.1016/j.matprotec.2003.11.013D.-S. Park et al. / Journal of Materials Processing Technology 146 (2004) 234240 235machine micro-grooves using MAJM is carried out by pre-cisely analyzing machined groove shapes.2. Basic principles of MAJMThe basic machining principle of MAJM (micro-abrasivejet machining) is shown in Fig. 1. In the process,micro-abrasives (tens of H9262m), accelerated by highly com-pressed air or gases, are forced through a micro-nozzle,and collide with hard and brittle workpieces at a very highvelocity (80200 m/s) and density. Since the material re-moving process of MAJM is performed by an integrationof brittle mode machining based on micro-crack propaga-tion, there is very little heat, chipping, and crack generationin the workpiece. Thus, this method is very suitable forthe machining of micro-shapes (such as grooves, holes,pockets, etc.) of hard and brittle materials (such as glass,ceramics, silicon, and crystal, etc.). A rebounded mixtureof abrasives and chips from the workpiece is sent to thedistributor, which then separates the mixture into chips andabrasives for recycling.According to the machining model proposed bySlikkerveer et al. 16, when a sharp indenter tip movesdown to the inside of the workpiece, a plastic deformationzone is formed under the indenter tip due to the compres-sive force. The formed plastic zone becomes larger as thecompressive force increases. Eventually, radial/median andlateral cracks are formed along the perpendicular and par-allel direction of the surface, respectively. At this time, itcan be assumed that the lateral cracks have relationshipsFig. 1. Schematic diagram of the MAJM.Fig. 2. Micro-crack propagation in the indentation process.with the workpiece removal process in MAJM, and the ra-dial/median cracks have relationships with the surface crackformation. It plays a key role in accelerating the removalprocess at some level as the machined depth is increased.Fig. 2 shows the micro-crack formation in the indentationprocess.Process parameters to define MAJM are: (1) blasting pres-sure, time and velocity, (2) material properties, size anddensity of the abrasives, (3) velocity and number of nozzlescanning times, and (4) stand-off distance (distance betweenthe nozzle and workpiece). Such parameters should be ap-propriately determined to improve machining accuracy andefficiency.3. Micro-grooving processThe total process flow of micro-grooving using MAJM isillustrated in Fig. 3. As shown in the figure, the total processis composed of the following three steps:(1) Masking process: The masking process is used to pre-pare the specimens having required patterns for MAJM.Dry film is used for the masking process; and film thick-ness influences the resolution and accuracy of machinedshapes. UV hardening polyurethane is used as a filmmaterial to provide wear-resistance property during theMAJM process. The applied masking process in this re-search is as follows: Laminating: A film is adhered to the workpiece. Exposure: A parallel UV beam is irradiated to makerequired patterns. Developing: The specimen is developed using a de-veloping solution, which is composed of distilledwater and a 5% Na2CO3solution. Finally, requiredpatterns can be obtained by removing the masks onthe desired regions.236 D.-S. Park et al. / Journal of Materials Processing Technology 146 (2004) 234240Fig. 3. Micro-pattern making process for the MAJM.(2) Abrasive jet machining process: MAJM is performedon the machine. Here, the regions, where masks are re-moved in the developing process, are selectively ma-chined.(3) Mask removing and cleaning process: After the machin-ing process is finished, any remaining mask adhered tothe workpiece surface is removed, and the workpiece iscleaned using ultrasonic cleaning equipment.4. Experimental works4.1. Masking processIn this experiment, the following laminator and exposingequipment are used: YH-6300TCL and YH-70908K (YoungHwa, Korea), respectively, masking film BF-405 (Ordyl,Japan).To machine the grooves to 80H9262m width and the holes to80H9262m diameter, it is very important to determine appropri-ate parameters for masking, which precedes the machiningprocess. In this study, an attempt is made to obtain optimummasking results based on the following variables: Pre-heating temperature of glass: A specimen of glass ispre-heated to achieve optimum adhesion results to the dryFig. 4. SEM photograph of WA#800 abrasive (2000).film. Pre-heated temperatures used for laminating are 85,90, 95, 100 and 105C. Exposure amount: Exposure amounts are 150 and 160 mJ.When using masking film (BF-405), the above conditionsare followed based on the manufacturers (Ordyl) recom-mendation.4.2. Process parameters for MAJMFor micro-grooving using MAJM, process parameters,such as distance between nozzle and work piece, inner di-ameter of the nozzle, blasting air pressure, and flow rate ofmicro-abrasives, are maintained at constant through the pro-cess. WA type abrasive (Fig. 4) is used for machining. WAmeans white alundum, and its main ingredient is Al2O3. Ap-plied process parameters for the experiments are listed inTable 1.4.3. Shape measurementAn optical microscope is used to investigate masking re-sults and analyze machined shapes of the groove. Necessaryimages are captured and processed using a CCD camera andimage processing board (DT3153, Data translation) installedin the PC. Also, for the measurement of the groove shapesin micro-scale, a non-contact type three-dimensional mea-surement equipment (WYKO NT-2000) and image analysisprogram (WYKO Vision 32) are used.Table 1Process parameters for MAJMStand-off distance 110 mmAir pressure 0.25 MPaAbrasive WA#800Nozzle diameter 8 mmFlow rate 80 g/minY Pitch feed 5 mm/sD.-S. Park et al. / Journal of Materials Processing Technology 146 (2004) 234240 237Table 2Masking results85C90C95C 100C 105C150 mJLine Good Good Good Good GoodHole Good Good Fair Poor Poor160 mJLine Good Good Good Good GoodHole Good Good Good Good Fair5. Results and analysis5.1. Masking resultsMasking results of the workpieces, according to the vari-ance of masking process conditions, are listed in Table 2.Itcan be observed from the table that masking results are gen-erally good when the exposure amount is 160 mJ; however,when the exposure amount is 150 mJ and the heating tem-perature is above 150C, the masking results of hole-typegrooves are poor.Fig. 5 shows the masking results according to the temper-ature variation (when the exposure amount is 150 mJ). Asshown in the figure, the hole-type patterns in figure (c) and(d) look darker than (a) and (b) due to insufficient exposure.On the other hand, when the exposure amount is 160 mJ, allof the masking results are good.5.2. Grooving resultsFig. 6 shows the machined results of micro-grooves ac-cording to temperature variation, when the exposure amountis 150 mJ. As noted above, it was shown that hole-typegrooves are not well generated when the temperature isabove 100C(Fig. 6(c) and (d). When the exposure amountis 160 mJ, machined grooves generally show good condi-tions, regardless of the heating temperature variation.Fig. 5. Masking patterns with laminating temperature variation (150 mJ).Fig. 6. Groove patterns with laminating temperature variation (150 mJ).Fig. 7. Hole-type groove.By analyzing the measurement results of machine shapesusing an optical microscope, it can be shown that the diam-eter of the micro-groove is larger than that of the maskedhole (80H9262m) by 24H9262m. Such results are due to the wearof the mask film boundaries during the MAJM process.A three-dimensional image of a micro-hole-type groove,captured for precise analysis of the groove, is shown inFig. 7. The X-directional cross-section of the groove asshown in Fig. 8, has a U-type shape. The diameter and depthof the machined hole-type groove is 82.9 and 14.6H9262m, re-spectively. From the measured results, it can be observedthat there are some fluctuations of the machined depth atFig. 8. Cross-section of a hole-type groove.238 D.-S. Park et al. / Journal of Materials Processing Technology 146 (2004) 234240Fig. 9. Spreaded hole-type groove.Fig. 10. Cross-section of expanded hole.the central region of the groove. Such results seem to becaused by (1) the difficulty increase of chip discharge, and(2) the velocity and pressure decrease of micro-abrasives asthe machined depth increased.Fig. 9 shows an internal groove shape, which is trans-formed to a plane to calculate actual surface roughness.Fig. 10 represents the cross-section of the groove alongcenterline, with a calculated surface roughness of Ra=0.59H9262m. From experimental results, it can be shown that itis possible to achieve good surface quality for micro-patternsusing micro-abrasive jet machining (MAJM) technology.A three-dimensional image of the machined line-typegrooves is illustrated in Fig. 11, and the cross-sectionalprofiles along X- and Y-direction are illustrated in Fig. 12.From the figure, it can be seen that the profile has a U-typeshape, as is the case of the hole-type groove, making itvery difficult to generate an accurate square-shaped groovedue to the basic characteristics of MAJM. The measuredmaximum width and depth of the machined grooves areFig. 11. Line-type groove.Fig. 12. Cross-section of line-type grooves.about 84 and 15H9262m, respectively. The required depth of thegroove can be obtained by selecting an appropriate numberof nozzle scanning times. Fig. 12(b) shows the Y-directionalprofile (measured along bottom line) of the groove, whichcan be regarded as surface roughness. Measured surfaceroughness of the line-type groove is about Ra= 0.8 and0.5H9262m, which is very similar to the hole-type grooves.From the above experimental results, it can be seen thatit is possible to machine micro-patterns on the glass usingMAJM. Thus, such machining technology can be effectivelyused for the production of micro-machine and electronicparts including LCD.5.3. Influence of the number of nozzle scanning timesThe influence of the number of nozzle scanning times tothe depth and width of the line-type hole is exhibited inFig. 13. Fig. 13(a) shows the experimental results of thespecimen that has line-type patterns of 60H9262m width afterexposure. The results are calculated from the X-profile inFig. 12(b). From the figure, it can be observed that the depthand width increase as the number of scanning times in-creases. Machined depth increases in near proportion to thenumber of scanning times; however, the width of the ma-chined grooves increases as a second-degree function. Thesame tendency can be observed in all of the machined spec-imens using MAJM (Fig. 13(b) and (c).D.-S. Park et al. / Journal of Materials Processing Technology 146 (2004) 234240 239Fig. 13. Effect of the number of nozzle scanning times on groove shape.In the case of the number of scanning times is fixed, theincreasing rate of the machined depth decreases as the widthof the masked pattern. This is because of the “blast lageffect” 10, caused by the decrease of particle impact an-gle to sidewall as masked line width decrease. On the otherhand, the increasing rate of the machined width increases asthe width of the masked pattern decreases. This tendency issupposed that masking film wear is prompted by the inac-curate exposure for smaller patterns.As the performed experiments show, a deeper machineddepth can be achieved by increasing the number of scanningtimes; however, the machined width also greatly increases.Increase of width is basically due to masking film wear.Thus, to obtain a deep groove along with desired width; (1)the masking film should have a high wear resistant property,and (2) the width of the masked pattern should be smallerconsidering the increasing effect of the machined groovewidth.6. ConclusionThe results of this study, on the micro-grooving of glassusing MAJM, can be summarized as follows:(1) When the exposure amount is 160 mJ, good maskingresults can be obtained independent of the heatingtemperature. Also, good machining results can beobtained.(2) Machined profiles of the grooves show U-type shapes.Thus, it is very difficult to machine accurate square typegrooves due to the basic characteristics of MAJM.(3) Due to the wear of the mask film and “blast lag effect” atthe boundaries, measured dimensions of the machinedspecimens are slightly larger than the masking patterns.(4) Measured surface roughness is about Ra= 0.8 and0.6H9262m for the hole-type and line-type grooves.(5) Machined depth increase is near proportional to thenumber of scanning times; however, the width increasesas a second-degree function.AcknowledgementsThis work was supported by Grant No. R01-2001-000-00257-0 from the Basic Research Program of the KoreaScience and Engineering Foundation.References1 A.W. Momber, Principles of Abrasive Water Jet Machining, SpringerVerlag, Berlin, 1998.2 J.A. McGeough (Ed.), Micromachining of Engineering Materials,Marcel Dekker, New York, 2001.3 J.A. McGeough, Advanced Methods of Machining, Kluwer, Dor-drecht, 1988.4 A. Evans, M. Gulden, M. Rosenblatt, Impact damage in brittlematerials in the elasticplastic response regime, Proc. R. Soc. LondonA 361 (1978) 343365.240 D.-S. Park et al.