welding cost estimation

Costing of Joining Methods -

Arc Welding Costs

ver. 1

ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton GIT 2009

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OverviewOverview

Cost components Estimation of costsEstimation of costs Examples


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Cost ComponentsCost Components

Materials LaborLabor Overhead


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Materials 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 cost


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Material 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 , , ,


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LaborLabor

Di 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 time


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Overhead RateOverhead Rate

Usually a percentage of direct labor rate Ranges from 50 - 400%Ranges from 50 400%


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Deposition EfficiencyDeposition Efficiency

N 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%


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Operator EfficiencyOperator Efficiency

Welding time Personal time Set-up time Electrode changing timeg g Slag chipping time (for subsequent passes)

poor weld quality increases timep q y Time to beat weld to remove residual

stresses


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Manual Operator EfficiencyManual Operator Efficiency

10 - 45% 65% is extreme of human achievement

Personal breaks Set-up Change position Change electrodesg De-slagging Removing residual stresses


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Removing residual stresses

Semi automatic 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-slagging


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Automatic EfficiencyAutomatic Efficiency

Over 90% if small set-up time, de-slagging timeif small set up time, de slagging time


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Cost 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)


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Materials 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)


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Labor 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)


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Labor Cost (CL)Labor Cost (CL)

AlternativelyAlternatively, t = 1/S

S d f ld S = speed of weld

CL = (CR) / S (OF)

111 note

...1121

++=

SS

nSnSSS

t 1...1121

+++=


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21 SS

Metal Deposition vs Labor CostMetal Deposition vs. Labor Cost

1 1


17Labor cost $/ ft of weld

Estimated Cost of ConsumablesEstimated Cost of Consumablesgas = 25-45 ft3/hr, solid flux = wt of deposited metal, 1973 prices

Process Type ofElectrode

ElectrodeCost ($/lb)

DepositionEfficiency

Cost ofDeposited

(%) Metal$/lb $/ft

Shieldedmetal arc

E7024 0.191 65 0.29 0.045metal arcSelf-shielded,flux-cored

E70T-G 0.315 82 0.38 0.059

Submerged EL12 0.199 + flux 100 0.34 0.053Sub e gedarc

0. 99 u 00 0.3 0.053

Gas metal-arc E70S-3 0.243 + flux 92 0.31 0.048


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Estimated CostsEstimated Costs

All about 5/ft.


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Trade-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/ft


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Comparative CostsComparative CostsFactor E8018 Electrode and

Manual Welding9000C-1 Wire and

Semi-automaticW ldiWelding

Labor and overhead rate (CL) $20/hr $20/hrDeposition rate (D) 3.11 lb/hr 5 lb/hrOperating factor (OF) 0.3 0.45p g ( )Cost of labor and overhead todeposit weld

$21.43/lb of weld $8.88/lb of weld

Electrode cost (CE) $0.667/lb $1.019/lbDeposition efficiency (DE) 0 68 0 78Deposition efficiency (DE) 0.68 0.78Cost 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. metalg g ( ) pCost of welding $22.41/lb dep. metal $10.91/lb dep. metal

Labor cost seriously offsets cheap stick cost


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Costs of Various Processes(relative for guidance)

P A d O ti L b d W ld C tProcess Arc speed(ft/hr)

OperatingFactor

Labor andOverhead ($/hr)

Weld Cost($/ft)

Shielded metal-arc

85 0.3 7 0.274

Shielded metal-arc

85 0.4 7 0.206

Gas metal-arci t ti

80 0.5 7 0.175semi-automaticSelf-shieldedflux-cored, semi-auto

100 0.5 7 0.140

Submerged arcsemi-auto

110 0.5 7 0.127


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Weld Comparison for Mild Steel

b ca

d

f e


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Weld Comparison Examplep p 1/4 diameter, manual metal-arc electrode

with solid flux attached 320 A (a)with solid flux attached, 320 A (a) Deposition rate 6.25 lb/arc-hr (b) Weld required 0.6 lb of weld metal/ft (c) Welding speed 2 in/min (5.75 arc-

minutes/ft) (d) Operating factor 20% (e)Operating factor 20% (e) Time is 28.75 minutes/ft, labor cost at

$8/hr is $3 83/ft of weld (f)ME 6222: Manufacturing Processes and Systems

Prof. J.S. Colton GIT 200924

$8/hr is $3.83/ft of weld (f)

Other IssuesOther Issues

Calculations show what can happen, if you have the correct equipment.y q p

Other costs depreciation taxes etc depreciation, taxes, etc.


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SummarySummary

Costs of arc welding can be calculated Calculations give you guidance on:Calculations give you guidance on:

process selectionoperating condition targets operating condition targets


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welding cost estimation

Documents

manufacturing processes

colton git

time electrode

electrode cost fluxes

labor cost

cost of electricity

electrode sticks

left stickelectrode