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30120140504012

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  • 1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 96-102 © IAEME 96 AN OVERVIEW OF PROCESS PARAMETERS OF MICRO GRAVURE COATER TO IMPROVE THE QUALITY OF WET COATING Pradip S Asodekar1 , Prof. Jeevan Salunke2 1 (M.E.Mechanical, IInd Year, Deogiri Institute of Engineering and Management Studies, Aurangabad(MS), India) 2 (Associate professor in .Mechanical Engineering, Deogiri Institute of Engineering and Management Studies/ Aurangabad(MS). India) ABSTRACT Lamination is the process of applying the wet adhesive on the substrate. Later it is dried in oven or by means of u .v. lamp. The process is accomplished with the help of a roll which revolves in opposite direction to the web travel in an adhesive pan. The roll is engraved or the helical grooves are cut on it with great precision. This roll is also called as gravure roll. In conventional gravure roll the diameter of the engraved rolls are typically in the range of 125 to 250mm, but in micro-gravure the rolls diameters is in the range of 20 to 50 mm. The main objective of any lamination processes is to achieve the uniform & even coating thickness & coating pattern. In this investigation an effective approach is based on experiments & analysis of various process parameters, (e.g. viscosity, web speed, micro-gravure r.p.m.). These experiments were conducted in the film mfg. company. The process parameters were analyzed to find their effects on coating thickness, coating quality. From these experiments it concludes that the quality of lamination, i.e. adhesive deposition(g.s.m.) is directly proportional to viscosity, micro- gravure speed (r.p.m.) & inversely proportional to web speed (m.p.m.) Keywords: Coating, Deposition (gsm), Lamination, Micro Gravure, Substrate, U.V. Lamp, Viscosity. 1. INTRODUCTION This research paper is aimed at improving our understanding of gravure roll coating process, which is an important & widely used value adding process. In this process, a thin liquid film is deposited on to a moving substrate in order to change its surface properties. A comprehensive INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 5, Issue 4, April (2014), pp. 96-102 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2014): 7.5377 (Calculated by GISI) www.jifactor.com IJMET © I A E M E
  • 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 96-102 © IAEME 97 understanding of the process has proved elusive. The development of the detailed model will have significant benefit by analyzing the complex gravure roll coating process. The roll is not smooth the helical pattern allowing faster operating speed & thinner liquid film to be deposited. 1.1 Types of Coating Process Coating or the lamination is the process of applying the adhesive or a coat on the film surface. The purpose is to improve the qualities of the film surfaces, to impart additional optical qualities in the film surfaces. e.g.- to improve optical density, heat resistant properties, visual light transmission, haze & clarity etc. There are many coating process available, direct or reverse gravure, reverse roll, die coaters, wire bars, blade or doctor blade coaters, kiss gravure method 1) Standard gravure coating method - in this process a cylindrical gravure roll with diameters 125 to 250 mm used, which revolves in the adhesive pan in reverse direction. It is called reverse gravure coating. When the roll rotates in the same direction as web travel it is called direct coating, 2) Die coater - This is also a coating method in which adhesive passes on to the substrate through very thin slot made, an adhesive pump is provided for adhesive circulation. Adhesive deposition on the film surface is possible due to the vacuum provided. The thickness of wet deposition can be varied with varying the speed of adhesive circulation pump 3) Mayor bar - It is a bar on which a thin stainless steel wire is wound on it. The extra adhesive from the film surface is removed by the mayor bar & gives the uniform coating. The mayor bar lines & orange peel are the prominent defect observed in this coating method. 4) Doctor blade - In this process a doctor blade is used to remove the excess adhesive from the film surfaces. 5) Micro gravure - the method is same like the conventional standard gravure, the only difference is its small diameter roll. It gives the excellent quality of coating & less variation of coating thickness. 1.2 Micro Gravure Coating Process Micro gravure is the reverse, kiss gravure coating method, the gravure roll (engraved cylinder) roll rotates in the small adhesive pan with partially submerged conditions. It picks the wet adhesive & transfers on to the film surface. A blade or knife is used to remove excess coating solution. Without this, the cell volume could not be the major factor in determining the thickness or the of weight of wet coating on the film. However the blade used is quite different from the blades used in most of the gravure process. The major departure relates to stiffness & the angle of attack of the blade to the roll surface. Micro gravure blades are quite thin and flexible in comparison to those typically used gravure process. The pressure of the blade against the roll is rather light or even zero. The angle of attack of standard gravure roll is steep. The line of the blade extensions typically passes close to the roll center. The thin flexible Micro gravure blade lays on the roll, nearly tangent to the surface. The comparison here is scraping action versus smoothing or metering action. In standard metering causes, considerable wearing of blade & the roll surfaces occur. Thus the life of the blade & roll is extended because of the more gentle action in micro gravure process.
  • 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 96-102 © IAEME 98 2. COATING PARAMETERS & CONDITIONS To achieve the good quality of coating, uniform coating thickness & change in coating thickness, following are the parameters which affects mainly- 1) Viscosity - It is the flow ability of the liquid adhesive. It is measured in standard viscosity ford cup, B2. The unit is in second, i. e. the amount of the time required in second for the adhesive in emptying the ford cup. More the viscosity more will be the deposition (GSM). As the viscosity decreases the deposition (GSM) also decreases. 2) Varying gravure speed (RPM) - By keeping the line speed (MPM) uniform, the gravure speed (RPM) may be varied. The deposition increases by changing the speed ratio. 3) Using various types of gravure sizes (changing mesh, e.g. H04, H06, H09, H10, H11, etc). According to the deposition requirement we may use the various gravure rolls for the specific range. The gravure numbers in ascending orders shows coarse sizes of the gravures which increases the depositions as the cell volumes in respective gravures increases. 4) Changing blade positions / Swivel positions - This is the fine tune to vary the deposition, the blade position towards the gravure roll increases the deposition & the blade position away from the gravure roll decreases the deposition. Besides this the deposition (GSM), also depends on coating thickness of the web (micron), as the thickness increases deposition decreases. Deposition also depends on film surface the rough /corona treated, coated surfaces gives higher deposition than the smooth surface.
  • 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 96-102 © IAEME 99 3. EXPERIMENTAL DETAILS 3.1 Design of Experiments Various trials were conducted to set the required deposition on the micro gravure coater. Following parameters were varied. 1) Adhesive batch viscosity - by keeping all the parameters constant batch viscosity varied from 90 sec to 120 sec the deposition (GSM) increases. 2) Varying gravure speed (RPM) - By keeping the line speed (MPM) constant, the gravure speed (RPM) may be varied. The deposition increases by changing the speed ratio. 3) Changing blade positions / Swivel positions - This is the fine tune to vary the deposition, the blade position towards the gravure roll increases the deposition & the blade position away from the gravure roll decreases the deposition. PARAMETERS RANGE TARGET VISCOSITY (SECOND) 80- 120 SECOND 100 SEC. LINE (WEB) SPEED (MPM) 10- 18 MPM 14 MPM GRAVURE SPEED (RPM) 101-163 RPM TO ACHIEVE THE SPEED RATIO 120-130% KISS COATING ROLL POSITION FRONT-35MM ,BACK- 25MM ROLLS PERFECTLY ALIGN 3.2 Selection of Control Factors From the discussion with company people & with the help of research papers it is strongly felt that the speed ratio – the ratio between line speed to gravure rpm is very important in micro coater deposition (GSM) setting. So deposition is set as response parameters, as coating quality depends on the even deposition. 3.3 Experimental Set Up The essential equipment required for any gravure coating process is a micro gravure head, coating pan, micro gravure roll having different meshes (e.g. – H04, H06, H09, H10, H11, H22, etc), a servo motor to rotate the gravure roll, doctor knife & the circulation system which operates on pneumatic pump.
  • 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 96-102 © IAEME 100 Table- Specification & Description of the Machine Specification Description Web material PET FILMS Web thickness 15-250 micron Web width 1042mm to 1900mm Machine speed Max 50m/min – Min. 3.0m/min Coating thickness 0.6 GSM to 10.0 GSM Dry zone type Air floating type ,UV Cure Type Unwind Diameter Max 800 mm Rewind Diameter Max 800 mm Drive type Servo 3.4 Experimental Condition By keeping all parameter / condition constant for monitoring the deposition the speed ratios changed. Line speed 14 MPM kept constant & gravure speed in (RPM) changed. The relation between line speed & corresponding gravure speed may be as – Line speed (MPM) = Gravure Speed (RPM) = π *D/1000* N Where, D = Diameter of gravure roll. (50mm) N = Gravure speed (RPM) Following tables shows the results of coating quality & deposition increments with increase in speed ratios when 38 to 42% solid solution is used Deposition (GSM) 0 0 2.5 3.15 3.6 3.85 3.8 3.9 4.0 4.2 4.3 4.2 3.9 Speed Ratio 0% 20% 40% 60% 80% 100% 120% 140% 160% 180% 200% 220% 240% Gravure Speed (RPM) 0 18 36 53 71 89 107 125 142 160 178 196 214 0 1 2 3 4 5 Speed Ratio Deposition(GSM) Deposition (GSM) Speed Ratio From this experiment it is observed that the deposition increases as the speed ratio increases. At speed ratio 200% the deposition goes on decreasing the graph shows the decreasing trend
  • 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 96-102 © IAEME 101 TABLE – The relation between line speed & corresponding Gravure Speed ratio 1: 1 Line speed (MPM) 0 2 4 6 8 10 12 14 16 18 20 Gravure speed (RPM) 0 13 25 38 51 64 76 89 101 115 127 4. RESULT & DISCUSSION The various trials conducted to see the effect of the deposition (GSM) & Coating quality At Line Speed 14 MPM. It is observed that as the speed ratio increases the corresponding gravure rpm also increases & corresponding deposition also increases.1 to 1 ratio is good starting point for examination of few new coating. Some 100% solids formulations have been seen to exhibit rather strange behavior relative to “typical coating” with 1 to 1 ratio although it is not surprising, to see a departure from a typical 30-40% solid solution chemistry. On occasion the ratio of 2 to 1 or 3 to 1has produced good coating with 100% solids UV or radiation curable. At speed ratio 100 to 130% the variation in deposition in TD (Transverse Direction) is less compared to speed ratio 200 & above this can be seen by observation & experiments. 5. CONCLUSION The main objective of any laminating process is to achieve the uniform & even coating thickness. To improve the quality of wet coating in laminating the window film production various trials conducted using different parameters for example change in viscosity, line speed, coating thickness of the film etc. From all these experiments it is concluded that micro gravure speed (RPM) is important. The ratio of web speed to circumferential speed of the engraved roll is critical in establishing the coating thickness (as per graph shown). At given web speed cylinder stationary, no coating is transferred to the web, as rotational speed is increased, coating will start. Additional rotational speed increases the coating weight until flooding or instability, and a decrease in weight occurs. Coating weight (GSM) plotted against the speed ratio will generally show a bell-shaped curve. The behavior of ‘typical’ coating will follow the pattern: at 50% to 60% of speed ratio the coating starts, a smooth & uniform coating starts at 100 to 130%- weight increase, 200% or more weight decrease & instability observes. 6. ACKNOWLEDGEMENT The authors wish to acknowledge the support rendered by Mr. G.D. Joshi (Manager-Utility) & Mr. Navin Saw (Production Officer) of Cosmo Films Ltd, Mr.P.G.Taur (HOD) Mech. Engineering Dept. of Deogiri Institute of Engineering and Management Studies. Also acknowledge support of Dr. Ulhas Shiurkar (Director) of Deogiri Institute of Engineering and Management Studies. To conduct the study of the experiments. Who have encouraged and inspired for the success of this research paper.
  • 7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 4, April (2014), pp. 96-102 © IAEME 102 REFERENCES [1] Coating materials & surface coating defects - By Tracton, CRP Press, By Taylor & Francis. [2] A Hand book of Deposition technology for film & coating –By Peter M Martin ISBN978-0-8155-2031-3. [3] Analysis of Gravure roll Coating Process – by faculty of engineering. www.engineering leeds.ac.uk. [4] Microgravur by Yasui Seiki Co. US4. [5] Electrophoretic Deposition of Nano materials –By James H Dickerson, Springer Publication. [6] Dalip Kumar, Antariksha Verma and Sankalp Kulshrestha, “An Experimental Study of Wear Resistance of Al – Sic Coatings on Steel Substrate”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 4, Issue 6, 2013, pp. 222 - 228, ISSN Print: 0976-6480, ISSN Online: 0976-6499.

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