new development in shot blasting machine. - Metalworld.co.in

TechnologyProperly designed shot blasting machine will not only cleanthe castings efficiently, but it will also satisfy the usersquality needs and also assure optimum productivity and thelowest possible operating cost.Abrasive Flow Control Valve (Fig-11)(soundabrator):The abrasive flow to each wheel isregulated to match the mechanicalcapacity of the abrasive reclaimingsystem and must stay within theAmperage capacity of Electric Motor.Enclosed air operated Soundabratorreduces noise level, which is below 85(Fig-11) dB and prevents leaking of shots and itis easy to maintain.Shot Peening : (Fig-12)Shot peening is one of the application for increasing thefatigue life of various components like Coil Springs, LeafSprings, Gears, Rack & Pinion, Torsion Bar, ConnectingRod, Crank Shaft widely used in auto industries. We SeeMany trucks broken down on the Road due to Fatiguefailure of axle Shaft or Spring, Sometime it results inSerious accidents. This Fatigue can be reduced byadoption of Shot Peening Process.Shot & Abrasive : (Fig-13).070”.0110”Effect of Shot Size on Impact & CoverageSHOT SIZEInches in (mm)0.18mm0.30mm.0170” 0.40mm.0230” 0.60mm.0280” 0.70mm.0330” 0.80mm.0390” 1.00mm.0460” 1.20mm.0550” 1.40mm.0660” 1.70mmApprox. ImpactValue14920335590150260440Approx. Nos. ofShots / ID82,00,00021,00,0007,45,0003,24,0001,92,0001,14,00068,00040,00024,00014,000Equiv. Size ofin GritG-80G-50G-40G-25G-18G-16G-14G-12Shot Impact Value varies as the cube of the diameter (2:1 Size = 8.1Impact Value and 1:8 number of Shots / Ib). Considering Impact valueof 70 size shot as 1.Fig. 13(Fig-12)The impact Power and coverage of steel abrasive isgoverned by its mass and velocity in accordance withequation of kinetic energy.Ke = ½ MV2 (Where Ke = Kinetic Energy M=MassV=Velocity).The impact force delivered to the work piece will changeonly if the mass factor (i.e. the abrasive size) is altered.The relationship of abrasive size to both impact power andcoverage is shown in figureThe economy and performance of blast cleaning dependsupon the abrasives used. The proper size and type ofabrasives is most important. The following three factorsshould be considered while selecting the abrasivesa. Area of job surface these can cleanb. Quality of work producedc. Cost of the shotsChilled Iron ShotsThe shots are manufactured by quenching the stream ofmolten gray iron over high pressure water jet. Its hardnessis about 60 Rockwell C.Due to this hardness and quenchedstructure it fractures and disintegrates very quickly onimpact with the work surface. Due to greater amount ofdust produced in fracturing process, the part cleaned bychilled iron shot does not have very good finish. Also themaintenance cost is very high. This led to the introductionof malleable iron-, cast steel-, cut wire-shots and heattreated steel shots.Heat-Treated Steel ShotsThe heat treated steel shots are having hardness of 45Rockwell C (424 Brinell hardness). These are the mostsuitable for the shot blasting machine.Stainless Steel Shot & Cut Wire Shots (Fig. 13)Die casted components manufactured from Aluminium,Zink & Magnesium Alloys required to be blasted forremoving burr and also give asthetic value with aim toobtain even, shiny finish on all sides. Many users preferstainless steel shot as the consumption is one sixth of steelshot, carbon steel shot give dull grey finish, while stainlesssteel imparts matt silver finish pleasing to eye. Many autounits like Honda, Bajaj, Endurance are uses stainless steelshots.Concluding RemarksShot blasting is no more an optional process in a foundry. Itprovides faster and better cleaning. It saves power, labour,space and also saves on cutting tools and permits betterinspection, thus minimizing the rejection of castings. Apartfrom foundry it is also widely used in many otherindustries.Proper understanding about the machine, itsconstruction and use enables us to improve its efficiencyand utility. Before Selecting the equipment it is necessary,to consider above points, spare parts, availability, salesservices offered, and many other points.24June 2009