ESTIMATION OF WELDING COST:

Welding procedure specification provide important data needed to calculate the cost of weld. Typical variables that includes 1)Cycle time, 2)Electrode or filler wire Size, 3)Type Electrode, 4)Deposition efficiency, 5)Type of joint, 6)Type of weld, 7)Weld size, 8)Type of shielding, 9) Shielding gas, 10)Flow rate, 11)Flux consumption ratio, 12)Welding current Arc, voltage,13) Power source efficiency, 14)Welding time, 15)Operator factor, 16) Labor rates, 17) Overhead rate, 18) Filler metal cost,  19) Shielding gas cost , 20) Setup costs Inspection  all these cost determines the cost of welding.

Material estimate:

Amount of filler material deposited can be basis of all the material cost apart from filler material other cost like process specific variables.

Labour hours can be calculated from accurate list of materials and summary of operation required for production.

Bill of materials

When the material estimate is prepared welding procedure and joint geometry are assigned  to each weld , weight of metal deposited is calculated from that cost of welding can be calculated.

Arc time = Deposited metal(Kg)/ Deposition rate (Kg/hr)

Labour cost

 Labour cost includes arc time, non-arc time also referred as handling time and miscellaneous time like joint preparation, testing, inspection, documentation and quality control.

Arc time influenced by 1) Process 2) Power source 3)Weld metal volume 4) Current, voltage 5)Travel speed 6) Material dimension.

*Non-arc time can be estimated with reasonable accuracy for those operation which are repetitive

Labour time = Arc time / K

*where K is operation factor depends on process.

Overhead cost :

1)      Salary

2)      Employee benefits

3)      Rent and depreciation

4)      Ground, tax , safety

5)      Maintenance cost

Significance of cost summary:

1.       Validation of cost accounting of welded items

2.       Preparation of accurate cost estimate and submiss of appropriate quotations

3.       Justification of purchases of welding or cutting equipment

4.       Building company’s historical database and developing confidence in use

5.       Contributing to the personal involved at all levels

6.       Improving communication

Methods of controlling welding cost

1.       Joint design : The joints should be made in such a way that decrease the deposited weld metal without compromising quality and strength requirements

2.       Weldment design : A source of cost reduction lies in the redesign of weldments to take full advantage of the accuracy of computer-controlled thermal machining centres and their ability to produce complex geometry in-expensively. Improved design eliminates the need for layout, improves quality, and makes operations mistake-proof.

3.       Mistake proofing : Self-inspecting workpieces can eliminate steps in the inspection process, thus reducing costs.

4.       Process selection : The optimum process is that which fabricates weldments at the lowest cost while producing accept[1]able quality at high deposition rates and with high operator factors. It is selected based on a compromise between welding speed (deposition rate), versatility (all-position), and portability (operator factor).

5.       Welding procedures : The procedures should be thoroughly tested to verify that weldments of the desired quality are produced when the procedures are followed.

6.       Field welding :  Considering the many complex conditions and unknown variables encountered in field welding, the number of rejected welds and rework may be greatly reduced by performing the appropriate welds in the shop.

7.       Unforeseen cost: like quality factors and over welding

 

Reference : AWS HANDBOOK VOL 1