Roundwood handling at a Lithuanian sawmill - discrete-event simulation of sourcing and delivery scheduling.

摘要

Roundwood receiving 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 receiving. 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 modelling of present delivery volumes (21,000 m3/month), better roundwood sorting and handling operations can be achieved by replacing some unfavourable import sources (giving an increase in 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 modelling of planned delivery volumes (30,000 m3/month), replacing unfavourable import sources with domestic supply gave an increase in 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 in 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.