A Monte Carlo simulation to estimate fatigue allowance for female order pickers in high traffic manual picking systems

The paper presents a Monte Carlo simulation model to estimate the average rate of energy expenditure (Kcal/min) and, consequently, fatigue allowance in manual order picking systems with high demand rates. The study is limited to picking a low number of low weight items per order in a compact warehouse system with traditional layout configuration of parallel racks with equal size storage cubicles. Replicates of 10,000 orders with random order sizes and random locations of items per order are used to estimate the average rate of energy expenditure for female pickers with various combinations of body mass and walking speeds. Design for the average and design for percentile are investigated to estimate a maintainable work standard to maximise productivity while maintaining energy expenditure within acceptable limits. Results illustrate the significant impacts of body mass and walking speed on the productivity and rate of energy expenditure, especially for the above average weight picker. Moreover, results reveal the difficulty of adopting recommendations on limitations on energy input and degrade in aerobic capacity with age and health conditions when setting productivity limits for pickers with a wide range of weights.