Costing of Joining Methods -Arc Welding Costsver. 1ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20091OverviewOverview• Cost components•Estimation of costsEstimation of costs• ExamplesME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20092Cost ComponentsCost Components• Materials•LaborLabor• OverheadME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20093Materials CostsMaterials Costs•ElectrodesElectrodes– Some electrode sticks contain flux–Amount of electrode times electrode costAmount of electrode times electrode cost per unit weight gives electrode cost•Fluxes / Shielding gasesFluxes / Shielding gases– Quantity of flux and/or shielding gas required times unit costs gives flux/gasrequired times unit costs gives flux/gas costME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20094Material CostsMaterial Costs• Other consumables–may include cost of electricity, if not inmay include cost of electricity, if not in overhead–rags, files, blades, chisels….g, , ,ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20095LaborLaborDi t ti f ldi•Direct time of welding– time to produce a length of weld–labor rate– multiplication gives labor cost per length• Set-up time, etc.•Personal timePersonal timeME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20096Overhead RateOverhead Rate• Usually a percentage of direct labor rate•Ranges from 50-400%Ranges from 50 400%ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20097Deposition EfficiencyDeposition EfficiencyN t ll l t d i d it d ld•Not all electrode is deposited as weld– lost as splatter, vaporization–“stub ends” left• Stick-electrode welding - 65%• Self-shielded, flux-cored welding - 82%•Arc welding with shielding gas-92%Arc welding with shielding gas 92%• Submerged arc welding - 100%ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20098Operator EfficiencyOperator Efficiency• Welding time• Personal time• Set-up time• Electrode changing timegg• Slag chipping time (for subsequent passes)–poor weld quality increases timepqy• Time to beat weld to remove residual stressesME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20099Manual Operator EfficiencyManual Operator Efficiency• 10 - 45%– 65% is extreme of human achievement• Personal breaks•Set-up• Change position• Change electrodesg• De-slagging•Removing residual stressesME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200910Removing residual stressesSemiautomatic EfficiencySemi-automatic Efficiency• 25 - 60%•no need to change electrodesno need to change electrodes– wire used•higher currents speeds•higher currents, speeds• some processes require no de-slaggingME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200911Automatic EfficiencyAutomatic Efficiency• Over 90%–if small set-up time, de-slagging timeif small setup time, deslagging timeME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200912Cost ComponentsCost Components• Cost of electrode/length of weld=(WE)(CE)(WE)(CE)• Cost of flux/length of weld=(WF)(CF)=(WF)(CF)• Cost of gas/length of weld(VG)(CG)=(VG)(CG)ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200913Materials Cost/ Length (CM)Materials Cost/ Length (CM)•CM=(WE)(CE)+(WF)(CF)+(VG)(CG)CM (WE)(CE) (WF)(CF) (VG)(CG)•WE = weight of electrode•WE = weight of electrode• CE = cost of electrode ($/wt)WF weight of flux•WF = weight of flux• CF = cost of flux ($/wt)VG l f•VG = volume of gas• CG = cost of gas ($/vol)ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200914Labor Cost (CL)Labor Cost (CL)• CL = (t) (CR) / (OF)• t = time / length of weldCR t f l b h d ($/ti )•CR = cost of labor + overhead ($/time)• OF = operating factor (efficiency)ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200915Labor Cost (CL)Labor Cost (CL)•AlternativelyAlternatively,•t = 1/SSdfld–S = speed of weld• CL = (CR) / S (OF)111• note...1121++=SSnSnSSSt1...1121+++=ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 20091621SSMetal Deposition vs Labor CostMetal Deposition vs. Labor Cost11ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200917Labor cost $/ ft of weldEstimated Cost of ConsumablesEstimated Cost of Consumablesgas = 25-45 ft3/hr, solid flux = wt of deposited metal, 1973 pricesProcess Type ofElectrodeElectrodeCost ($/lb)DepositionEfficiencyCost ofDeposited(%) Metal$/lb $/ftShieldedmetal arcE7024 0.191 65 0.29 0.045metal arcSelf-shielded,flux-coredE70T-G 0.315 82 0.38 0.059SubmergedEL120.199 + flux1000.340.053Sub e gedarc0. 99 u000.30.053Gas metal-arc E70S-3 0.243 + flux 92 0.31 0.048ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200918Estimated CostsEstimated Costs• All about 5¢/ft.ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200919Trade-off Examplep• 1/4” fillet weld, 3/32” E7024 electrode, 85 ft/hr, operating factor 30%, labor + overhead $7/hr• CL = (CR)/S(OF)•CL=(7)/85(0 3) = $0 275/ft•CL=(7)/85(0.3) = $0.275/ft• Can you increase efficiency somehow?– 40% -> $0.206/ftME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200920Comparative CostsComparative CostsFactor E8018 Electrode andManual Welding9000C-1 Wire andSemi-automaticWldiWeldingLabor and overhead rate (CL) $20/hr $20/hrDeposition rate (D) 3.11 lb/hr 5 lb/hrOperating factor (OF)0.3 0.45pg ()Cost of labor and overhead todeposit weld$21.43/lb of weld $8.88/lb of weldElectrode cost (CE) $0.667/lb $1.019/lbDeposition efficiency (DE)068078Deposition efficiency (DE)0.680.78Cost of deposited metal $0.98/lb $1.31/lbShielding gas flow rate (VG) none 40 ft3/hrCost of shielding gas (CG)$0.72/lb dep. metalgg ( )pCost of welding $22.41/lb dep. metal $10.91/lb dep. metal• Labor cost seriously offsets cheap stick costME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 200921Costs of Various Processes(relative for guidance)PAdOtiLb dWldC tProcessArc speed(ft/hr)OperatingFactorLabor andOverhead ($/hr)Weld Cost($/ft)Shielded metal-arc85 0.3 7 0.274Shielded metal-arc85 0.4 7 0.206Gas metal-arcit ti80 0.5 7 0.175semi-automaticSelf-shieldedflux-cored,