An investigation of the measurement accuracy and productivity of a Waratah HTH 625c Processor Head

Log processor heads have become increasingly used in New Zealand (NZ) forest harvesting operations to increase productivity and improve worker safety. Information regarding the measurement accuracy and productivity of new model processor heads is limited. As a result, log quality control (QC) is carried out on logs that have been merchandised by a processor head. This task can have a high risk for injury from man – machine interaction. A trend between studies was that older model Waratah’s did not have sufficient measurement accuracy to alleviate the requirement for log QC. In this study, a Waratah HTH 625c processor head operating in NZ was analysed for measurement accuracy and productivity. Measurement accuracy was considered by measuring logs for length, diameter and branch size. A comparison of two methods of processing was also considered to determine measurement accuracy, productivity and production efficiency for the way logs are delimbed and merchandised. Once gathered, the data was then analysed to identify significant effects, trends and relationships between variables. Length measurements were highly accurate but diameter measurements were under- estimated. It was also evident that although there was absolute accuracy, there was a high variability in measurements with underestimating and overestimating. Branch size was also found to have a significant impact in reducing length measurement accuracy and productivity. Single pass processing has significantly higher production efficiency than two pass processing, although single pass processing had a higher length error associated with it. The Waratah HTH 625c processor head has better measurement accuracy than older model Waratah’s. However, logs are still cut out-of-spec which will require a log QC to identify. As measurement technology is further improved in processor heads, and improvements to NZ’s plantation resource (improved form and smaller branching) are realised at harvest age, measurement accuracy and productivity of log processor heads will further improve