Production speed effects on log-making error rates and value recovery for a mechanized processing operation in radiata pine in New Zealand

Abstract

Mechanized processing operations are complex “man-machine” systems. The impacts of changes to work practices are, therefore, dependent on the effects the changes have on both the machine and the man. A mechanized processor, delimbing and cutting tree length stems into logs on a landing, was studied in two Pinus radiata plantation forest stands in New Zealand in early 2004 to determine the effect that production speed had on operator decision making and on the machine measurement accuracy and precision. The processor operator was experienced and had a reputation for high value recovery performance. The operator was asked on four occasions to process stems at different production speeds; slow, normal, fast and very fast. Over 150 stems were processed into 849 logs during the four trials. Value recovery, log-making error rates and productivity were assessed during each of the trials. It was found that production speeds ranging from 430 to 610 m³ per day had no impact on gross value recovery, the types of logs cut, or log-making error rates. It was also found that, while length measurement accuracy was not affected by production speed, length measurement precision decreased with higher speeds. Diameter measurement accuracy and precision were both affected by production speed, but there was no obvious trend. Net value recovery increased at higher production speeds as a result of lower production costs.

Keywords: accuracy, productivity, tradeoff, harvesting, plantations, value recovery

Southern African Forestry Journal No. 204 2005: 23-35