Puodžiūnas, M. and Fjeld, D. 2008. Roundwood Handling at a Lithuanian Sawmill – Discrete-event Simulation of Sourcing and Delivery Scheduling.  Baltic Forestry 14(2): 163-175

Roundwood receival and sorting are the first in a long series of operations which require coordination to ensure high capacity utilization for sawmill. Variation in these operations can also cause queuing and reduced capacity utilization for wood transporting companies and delays in measurement and payment for suppliers. Two factors – sourcing and delivery scheduling have potential for reducing variation in roundwood receival.
The aim of this study is to estimate the effects of roundwood sourcing and delivery scheduling alternatives on roundwood handling at a Lithuanian sawmill. The study was done with discrete-event simulation and focuses on the unloading and sorting operations. The model was built in the ARENA simulation package.
Based on the modeling of present delivery volumes (21,000 m³/month), better roundwood sorting and handling operations can be achieved by replacing some unfavorable import sources (giving an increase of sorter productivity from 620 to 678 m³/day) and by improved scheduling of wood arrivals (reduction of extra log handling from 34% to 21% of loads).
Based on the modeling of planned delivery volumes (30,000 m³/month), replacing unfavorable import sources with domestic supply gave an increase of sorter productivity from 697 to 901 m³/day. Improved scheduling of truck arrivals reduced the percent of loads requiring extra handling from 49% to 36% with present sourcing and from 38 % to 18 % with increase domestic sourcing. In most cases improved scheduling reduced truck waiting time by 50 %. Both additional loader capacity, improved sourcing and improved scheduling are necessary to reach the planned production volumes of the future.

Key words: sourcing, delivery scheduling, discrete-event, queuing time, intermediate storage, sorter production