Manual Spot Welding and Robotic Spot Welding

Spot Welding Operation Cycle Time

Cycle time for the weld operation is the time it takes to create the weld represented by the current GCD.

Weld Time = Arc Time + Gun Manipulation Time

For each Weld GCD, weld time is the sum of the following:

  • Arc time (see formula)

  • Gun manipulation time (see formula)

  • Gun clean time (see formula)

Arc Time = Number of Weld Segments * Spot Weld Time

Arc time is the time for the arcing phase of welding. It is the product of the following:

  • Number of weld segments (extracted from the CAD model or specified by the user in the Welding dialog)

  • Spot weld time (specified by the machine property Spot Weld Time)

Gun Manipulation Time = Number of Weld Segments *
Gun Placement Time per Segment

Gun manipulation time includes all tasks between welds such as lifting the hood or visor, moving to the next location, repositioning the torch, readying to strike, and so forth. It is the product of the following:

  • Number of weld segments (specified by the user or geometry extraction)

  • Gun placement time per segment (specified by the machine property Gun Placement Time)

Spot Welding Weld Weight

Weld Weight = GCD Volume * Weld Density

The weight of each weld GCD is used to calculate the total assembly weight, which affects expendable tooling costs for Welding, as well as Pick and Place costs. The weight in kilograms of each weld GCD is the product of the following:

  • GCD Volume (based on geometry extraction or user-specified weld dimensions and weld type; see Weld Volume)

  • Weld density: specified in kg/m3 by the machine property Weld Density. aPriori converts this value to kg/mm3.

Spot Welding Accounting Calculations

Amortized Batch Setup = (Setup Time *
(Labor Rate + Direct Overhead Rate)) / Batch Size

This is the per-part cost of setting up one production batch of parts, that is, the batch setup cost amortized over all the parts in the batch. It depends on the following:

  • Setup time (specified as the machine property Setup Time)

  • Labor rate: this is the product of the following:

    • Machine property Labor Rate
    • Cost model variable laborRateAdjustmentFactor (1 in starting point Digital Factories)
    • Machine property Work Center Labor Rate Factor (1 in starting point Digital Factories)

  • Direct overhead rate (see Direct and Indirect Overhead)

  • Batch size (specified in the Production Scenario screen of the Cost Guide)

Labor Cost = Labor Time * Labor Rate / Final Yield

Labor cost depends on the following:

  • Labor time (see formula)

  • Labor rate: this is the product of the following:

    • Machine property Labor Rate
    • Cost model variable laborRateAdjustmentFactor (1 in starting point Digital Factories)
    • Machine property Work Center Labor Rate Factor (1 in starting point Digital Factories)

  • Final yield (see Yields)

Robotic Spot Welding Labor Time = (Operation Weld Times /
Number of Weld Heads) * Number of Operators * Labor Time Standard

Labor time is the product of the following:

  • Operation weld times: sum of the weld times of all child operations; see Spot Welding Operation Cycle Time.

  • Number of weld heads: specified by the machine property Number of Weld Heads.

  • Number of operators: specified by the machine property Number of Operators or by the PSO Number of operators tending to this machine.

  • Labor time standard: specified as the machine property Labor Time Standard. This multiplier is used to account for otherwise unaccounted for factors that affect labor time, such as operator fatigue or time spent by the operator for cleaning or maintenance.

Manual Spot Welding Labor Time =
(Operation Weld Times + Reorientation Time) * Labor Time Standard

Labor time is the product of the following:

  • Operation weld times: sum of the weld times of all child operations; see Spot Welding Operation Cycle Time.

  • Reorientation time: product of the following:

    • Number of reorientations

    • Time per reorientation:this is looked up by assembly weight and largest dimension in the lookup table componentLoadTime.

  • Labor time standard: specified as the machine property Labor Time Standard. This multiplier is used to account for otherwise unaccounted for factors that affect labor time, such as operator fatigue or time spent by the operator for cleaning or maintenance.

Note: For Manual Spot Welding, labor time is independent of the number of operators, and cycle time is assumed to be inversely proportional to the number of operators (see Manual Spot Welding Process Cycle Time).

Robotic Spot Welding Process Cycle Time

Cycle Time = (Operation Weld Times /
Number of Weld Heads) * Cycle Time Adjustment Factor

Cycle time depends on the following:

  • Operation weld times: sum of the weld times of all child operations; see Spot Welding Operation Cycle Time.

  • Number of weld heads: specified by the machine property Number of Weld Heads.

  • Cycle time adjustment factor: specified by the cost model variable cycleTimeAdjustmentFactor; 1 in aPriori starting point Digital Factories. If you want to model an unbalanced, push assembly line, set cycleTimeAdjustmentFactor to a value greater than 1 in order to account for the cost of extra buffer capacity.

Note: Indirect overhead depends on cycle time, while direct overhead depends on labor time. Cycle time contributes to part cost only via indirect overhead.

Manual Spot Welding Process Cycle Time

Cycle Time = (Labor Time / Number of Operators) *
Cycle Time Adjustment Factor

Cycle time depends on the following:

  • Labor time (see Manual Spot Welding Labor Time in Spot Welding Accounting Calculations).

  • Number of operators: specified by the machine property Number of Operators. Note that cycle time is inversely proportional to the number of operators.

  • Cycle time adjustment factor: specified by the cost model variable cycleTimeAdjustmentFactor; 1 in aPriori starting point Digital Factories. If you want to model an unbalanced, push assembly line, set cycleTimeAdjustmentFactor to a value greater than 1 in order to account for the cost of extra buffer capacity.

Note: Indirect overhead depends on cycle time, while direct overhead depends on labor time. Cycle time contributes to part cost only via indirect overhead.

Spot Welding Expendable Tooling Calculation

Expendable Tooling Cost = Weld Weight *
Wire Cost per Unit / Final Yield

Expendable tooling cost accounts for the cost of the welding wire for assembly. It depends on the following:

Programming Cost for Robotic Spot Welding

Programming cost is the product of the machine Labor Rate and the total programming time. Programming time per weld is specified by the machine property Programming Time per Weld (300 seconds in starting point Digital Factories).