SCANNING & OPTIMISATION – On the frontline
Delta motion controllers enable high productivity
Delta Computer Systems out of Canada is providing a range of motion controllers crucial to Finnish sawline supplier, Veisto, in its delivery of precise, high speed sawlines to operations worldwide
environment. They need to generate profits from available logs, which are often of lower quality than in years past. Mill operators are looking for machinery that automates the process of optimising log yields, and the manufacturers of the machines are looking to make them smarter and more flexible than ever before. The Veisto Group of Mantyharju, Finland, is a private, family-owned company whose roots lie deep down in the Finnish forests. The experience of many generations has taught the company how forests can be used economically, ecologically and profitably. This sawmill machinery manufacturer is committed to leading the way in automating the log breakdown process and serves sawmillers globally.
F The company’s compact sawing
lines are designed to perform all of the processing steps, from handling of raw logs through
orest products manufacturers are faced with tough challenges in today’s
The log rotator at the input to HewSaw SL250 DUO saw line
HewSaw curve saw showing motion axes. For each axis, transducers provide position information to the motion controller, which sends a proportional output signal to a servo-quality valve
production of made-to-measure finished lumber, in a single processing pass. The lines typically consist of two or more sawing units, conveyers, and log positioners. They have integrated edging capabilities to square-up log surfaces, so separate edging
devices are not required. In addition to finished lumber, Veisto’s HewSaw product lines simultaneously produce top quality pulp chips.
There are four processing stages to the typical HewSaw line: • Log infeed/scanning and optimisation/orientation
• Four-side chipping and controlled curve sawing
• Sideboard optimisation and edging
• Double arbor rip sawing and optimised edging.
In the optimisation stage, an optimising computer performs three-dimensional modelling of each log, selecting the best cuts by trying thousands of
A HewSaw SL250 DUO saw line takes in raw logs at one end and produces finished lumber
28 International Forest Industries | FEBRUARY/MARCH 2012
combinations of log orientations and cutting patterns to achieve the best value from each log. Based on a new set of computations that are made for each 50 mm along the log, the
optimiser produces target positions for all of the hydraulic actuators, which guide each log as it moves through the machine. The motion of the actuators that dynamically steer the logs through the chippers and saws, and the actuators that dynamically position the saw blades themselves, need to be geared to the speed of the feed chain that transports the logs. Usually the maximum recovery results if the log can be cut along the grain, which may have a curve. Cutting curved logs along their curves is an improvement over the old practice of always making straight cuts, which resulted in losing wood at the ends of curved logs, producing shorter boards. A tightly integrated processing line such as the HewSaw system requires a lot of coordination between the sequential process stages. As described above, many motion steps need to be
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