Sawmills also face the challenge of making ideal use of all their resources. In order to achieve maximum added value, existing roundwood must be processed as quickly as possible, with a minimum of waste and into the most profitable products. In addition to production adapted to the market, local dynamic changes such as stock levels and machine conditions must also be taken into account at short notice.
The machining process along a chipper line can be summarized in the following steps as an example: Log infeed, debarking, twisting, chipping, separation of side products, separation of main products and transport by conveyor belt to the sawn timber sorting plant. The valuable main product is extracted from the inside of the round timber. Side products are sawn timber at the edge of the round timber with a defined proportion of forest edges:
Where the forest edge is considered to be the part of the sawn timber with the original (and debarked) surface of the log. The main product is usually cut sharp-edged (without a forest edge) because it is fitted inside the diameter graded log. However, since each log is grown differently and is specially curved, the ideal position and size of the desired side-goods boards per squared log varies, especially if the aim is usually to achieve price-optimized sharp-edged side-goods.
In the cycle time of the conveyor on the chipper line, which is often operated at a feed speed of 2.5 meters per second (and beyond), not only the most profitable sidewall boards for the current log must be found, but also their ideal positions so that the cutters can be positioned appropriately.
In cooperation with Sprecher Automation, RISC Software GmbH has created a high-performance optimization solution for the price-optimized cutting of the sidewalls. Besides the consideration of a large variety of possible side product boards, given by their dimensions in length and width, their price values and their allowed dimensions of the forest edge characteristics, the ambitious goal of the development was mainly the shortest computing time of well below one second per log.
Several well coordinated and interlocked software components harmonize ideally and guarantee the high performance of the optimization solution. A solid multi-core architecture coupled with efficient memory management provide the basis for the fastest calculations. The intelligent search algorithm based on this architecture not only provides reliable optimal solutions with regard to product selection and cutter positions, but also provides information as to whether a global optimum has been found, which usually takes only a few milliseconds.
Since spring 2019, the optimization software has been in use at a first plant, where it supports the optimal log yield. Further applications and targeted further development are planned.