Sawsets vary between fixed-blade and movable she assembly sawing machines.
Fixed-blade sawing machine
The traditional fixed-blade sawing machine allows for the efficient sawing of sorted logs using blade positioning planned and set in advance.
The blade positioning can be changed:
- When starting to saw logs with a particular top diameter.
- Depending on the blades used, they must be replaced due to dulling after a certain period or number of operating hours even if the blade positioning is not changed.
The blade positioning can be changed by changing the blade assembly (circular saw) or the position of the sawing machine and re-adjusting the blade guides (bandsaw). This sawing method requires logs to be sorted before sawing in order to obtain a good yield.
Infeed is optimised based on the log’s dimension data, such as pith, warp and taper, so that the centre yield is as fully edged as possible and the side yield can be used as well as possible.
Optimisation data are also used for the side yield so that the position of a side board with particular dimensions is determined by the scanning. Side boards are then removed in a way that maximises volume or value yield, and the optimal position is chosen around the sides of the log or cant.
Movable saw assembly sawing machine
In movable saw assembly machines, the blade position can be adjusted for each log in order to obtain the highest yield.
- The log or cant is scanned
- The most productive sawing pattern is determined for the individual log or cant based on scanning data.
The blade positions can be freely adjusted using hydraulic or electrical servos.
Logs can be sawn without sorting. However, adjusting blades to suit each log requires that there is a certain gap between each log. This is not necessary when working with fixed-blade sawing machines.
Changing blades in a movable saw assembly machine is faster than in a fixed-blade machine.
When using a movable saw assembly resawing machine for a two-phase sawing method, the movable saw assembly can be used so that the changes are implemented only by re-positioning the blades. This requires that the positioning is set in advance for the upcoming sawing.
One application of movable saw assembly sawing is to steplessly adjust a fixed blade assembly so that the set blade assembly is moved as a whole in relation to the sawing centre line creating a kind of “movable fixed assembly”.
This method is widely used in North America when sawing unsorted small diameter logs. With this type of log, the number of required sawing patterns is limited, which makes this method sufficient.
