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New Zealand Journal of Forestry (2004) 48(4): 17–22
©New Zealand Institute of Forestry

Research article
Improved sawlog quality through statistical quality control

Brent Gould and John Ellis

Statistical quality control (SQC) has been applied to sawlog production by a New Zealand forest company. Non-conforming quality features (defects) were grouped into five categories: dimensions, straightness, branching, log ends, and appearance. Each of the 23 defects was considered to be of equal importance. Check sheets, control charts and Pareto charts were used to feed back information to harvesting contractors whose target defect ratio was set at 10%.
Over the two and a half-year period that SQC has been used, an initial defect ratio of 37.5% was reduced to about 15%. Not all of the company's 29 harvesting contractors are in control, but for each there has been a change in the distribution of defects. It is concluded that SQC is not a costly exercise and does effect change by providing objective data for regular communication between harvesting contractors and company staff.

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