TITLE OF PROJECT”Optimization of process parameters inPhotochemical Machining of Phosphor Bronze with spray etching.
” RELEVANCEØ Photo chemical machining is an engineering productiontechnique for the manufacture of burr free and stress free flat metalcomponents by selective chemical etching through a photographically producedmask.Ø For complex parts Ø Characteristicsof metal material not alteredØ Variable edge profileØ Multilevel depth etchingØ Lowcost toolingØ Lead-timesin hours/days not weeks/monthsØ Anymaterial temperØ Virtuallyevery metal typeØ Stressand burr free manufactureØ Noadditional costs for complex shapesØ Interfaceseasily with other manufacturing techniquesØ Economic manufacturingcost PRESENTTHEORY & PRACTICES The development of knowledge ofacid attack upon metals is not new; its origins lie in antiquity. Legend tellsthat the ancient Greeks had discovered a fluid, which is referred to as liquidfire that attacked both inorganic and organic materials. However as this wasthe Bronze age it is unlikely that they possessed the technology to manufacturesuch an acidic chemical. The ancient Egyptians etched copper jewellery with citricacid as long ago as 2500BC. The earliest reference to this process describes anetchant made from common salt, vinegar and charcoal acting through a handscribed mask of linseed oil paint.
These techniques were adapted and improved byetchers operating in close co-operation with armourers until, by theseventeenth century. Thesixteenth century saw the use of etching techniques to produce printing platesof a superior quality to those previously engraved. The main advantage beingthe lack of burrs. By 1925 the huge daily newspaper industry made large-scaleuse of printing plates etched in nitric acid solution. By 1927 the use ofchemical milling through a rubberised paint mask, which was hand cut around atemplate, was being used as an engineering production tool.
John Snellman may have been thefirst to produce flat metal components by photo chemical machining of shimstock that was too hard for punching. He innovated the use of cutting lines, oroutlines, in the photoresist mask. This ensured even simultaneous etching ofevery component detail and also his use of tabs secured the parts into theparent metal sheet. He patented the process in 1944 where after it was increasinglyused to manufacture shims, springs, stencils, screens and virtually any complexshape which for technical reasons could not be punched. The technique is relativelymodern and became established as a manufacturing process about fifty five yearsago. The processing technology has been kept a closely guarded secret within asmall number of industrial companies but despite this, the sales of parts madeby pcm at the end of the twentieth century was approximately US $ 6billion. PROPOSEDWORKØ PLANOF PROJECT Year 2011-2012 Activity Month July Aug Sept Oct Nov Dec Jan Feb Mar Statement of problem Literature survey Purchase of material D.
O.E. Experimentation set up Preliminary Test D.O.E. Test Analysis &Con.
Report writing Ø Selectionof material§ Type:Phosphor bronze§ Dimensions:flat rectangular sheet thickness 0.013mm to 2mm§ Properties:Alloy of copper with 3.5% to 10% of tin and phosphor content 1%.These alloys are notable for their roughness,strength, low coefficient of friction and fine grain. Ø Selectionof chemicals § Dipcoating: photoresist (1020),Photo resist developer, photoresist dye, lith film§ Etchant: Ferric chloride solution. Ø Equipmentsused§ Dipcoater§ Airdryer § UVexposer§ Sprayetching setup Ø Experimentaldesign In dip etching process some removed materialparticles during chemical reactions deposited on workpiece which affect thefurther material removal rate (MRR).
In spray etching process this problem isover come by carried away the deposited burrs by pressurized etchant to achieveMRR. Designa spray model with titanium heating element inside the cpvc pipe to achievedesire temperature for effective etching. In which pump is used to pressurizethe etchant.
The nozzles are used to spray the hot etchant on workpiece.EXPERIMENTAL VARIABLESØ Controlparameters § Temperature(oC)§ Time(Min)§ Concentrationof etchant. Ø Fixedparameters There are other factors, which can beexpected to have an effect on the measures of performance. In order to minimizetheir effects, other factors were held constant. The other fixed parameters are§ Etchant– Ferric chloride§ Workpiece material § Workpiece thickness§ Workpiece area§ Workpiece size DESIGN OF EXPERIMENT A well planned set of experiments, in which allparameters of interest are varied over a specified range, is a much betterapproach to obtain systematic data. Mathematically speaking, such a completeset of experiment ought to give desired results.
Usually the no of experimentsand resource (Materials, time and money) required are prohibitively large.Often the experimenter decides to perform a subset of the complete set ofexperiments to save time and money. However, it does not easily lend itself tounderstanding of science behind the phenomena. The analysis is not easy.(Though it may be easy for the mathematician / statistician) and thus, effectof various parameters on the observed data are not readily apparent. In many case, particularly those in which someoptimization is required, the method does not point out the best setting ofparameter. Any experiment that has flexibility to make desired changes in theinput variables of process to observe output response is known as experimentaldesign.
Good experiment must be efficient. It is not an isolated test but wellplanned investigation that point the way towards understanding the process.Experimental design is a systematic manipulation of set of variables in whichthe effect of these manipulation is determined, conclusions are made and theresult are implemented.