Manufacturing Processes II: Joining Methods & Cost Estimation, Lecture notes of Engineering Dynamics

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MANUFACTURING

PROCESSES II

APPLICATIONS, PROCESSES AND COST

ESTIMATIONS IN JOINING METHODS

APPLICATION PROBLEMS

Problem 2

For the application given in Problem 1 , what is the recommended electrode- to-workpiece distance for preventing arc blowing?

Problem 3

When the thickness of the parts given in Problem 1 decreases to 3 mm, which parameters do you change to obtain the correct seam quality?

Problem 4

Low carbon steel plates will be welded by MIG method. If the welding current is 250 A and the welding voltage is 35 V in the joining process, then calculate the arc heat energy used during welding (arc efficiency ( η ) is 0. 7 )

Problem 5

A low-alloyed steel plate will be joined with the TIG method. The total arc heat energy generated during welding process under current of 120 A is 7440 Watt. Calculate the arc heat energy used during welding if the arc efficiency is ( η ) 0. 3.

REMINDER:

When the welding process is considered as a moveable heat source, the welding speed must also be taken into account when calculating the heat input. The heat input to which the welding speed is taken into account can be expressed as follows: U; voltage - I; current - V; welding speed

𝑸 = 𝑼 ∙ 𝑰 ∙ 𝜼 ∙ 𝟔𝟎 𝑽 (J/mm)

Problem 7

A 2. 5 mm thick 312 austenitic stainless steel plate will be joined by TIG and plasma welding methods. In the TIG welding process, the welding current is measured at 125 A, the welding voltage is 12 V and the welding speed is 260 mm/min. In the plasma welding process, the welding current is measured as 75 A, the welding voltage is 18 V and the welding speed is 340 mm/min. Calculate the source heat input for both methods. Interpret the results. The arc efficiency for the TIG method and the plasma source will be 0. 6. Discuss HAZ.

COST ESTIMATION IN WELDING

COST OF PRODUCT (LADDER OF COSTS)

The components of cost can be grouped as follows;

1. Prime cost = Direct material cost + Direct labor cost + Direct

expenses

2. Factory cost = Prime cost + Factory expenses

3. Production cost = Factory cost + Administrative expenses

4. Total or Ultimate cost = Production cost + Selling and distribution

expenses.

5. Selling price = Ultimate cost + Profit

COST ESTIMATION IN WELDING

Estimation of Cost in Welding

The total cost of welding consists of the following

elements;

1. Direct material cost

2. Direct labor cost

3. Direct other expenses

4. Overheads

COST ESTIMATION IN WELDING

1. Direct Material Cost

The direct material cost in a welded component consists of the

following;

( i ) Cost of base materials to be welded i.e., sheet, plate, rolled

section, casting or forging. This cost is calculated separately.

( ii ) Cost of electrodes/filler material used. The electrode

consumption can be estimated by using the charts supplied by

the suppliers. Another way to find the actual weight of weld

metal deposited is to weigh the component before and after

the welding and making allowance for stub end and other

losses during welding.

Also the weight of weld metal = Volume of weld × Density of weld

material

COST ESTIMATION IN WELDING

3. Direct Other Expenses The direct other expenses include the cost of power consumed, cost of fixtures used for a particular job etc. Cost of power : The cost of power consumed in arc welding can be calculated from the following formula; where; V = Voltage A = Current in Amperes t = Welding time in minutes E = Efficiency of the welding machine (E= 0.6 for welding transformer; E= 0.25 for welding generator) r = Ratio of operating time to connecting time taken by the operator C = Cost of electricity per kWh COST ESTIMATION IN WELDING

4. Overheads

The overheads include the expenses due to office and

supervisory staff, lighting charges of office and plant,

inspection, transport, cost of consumables and other

charges. The cost of equipment is also apportioned to the

individual components in the form of depreciation.

COST ESTIMATION IN WELDING