Energy-efficient hydraulics for a sawmill

Energy-efficient hydraulics for a sawmill
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July 2015

 

No matter how the Idaho Forest Group turns and moves the wood it processes – the Sytronix family by Rexroth lets the mill operator increase productivity and save a lot of energy.

The aroma of freshly sawn wood pervades the air inside the huge mill operated by the Idaho Forest Group (IFG). Here, one log after the other races through the largest sawmill in North America, located in the small town of Lewiston, Idaho. Depending on current needs, it can cut more than 180 meters of wood per minute, fully automatic and exactly to specifications. Incidentally, and in the same pass, wood chips are created. Situated in Lewiston is one of the five sawmills owned by the company and considered to be among the largest wood producers in the USA. Used here is a line manufactured by a Finnish company, HewSaw. The machine was designed by HewSaw and Bosch Rexroth in Canada provided components and the HPU. The concept was developed with the goal to boost both productivity and energy efficiency.

Saving up to 80 percent of energy consumption

The starting point is the Sytronix series of pump drives built by Rexroth. These variable-speed drives merge the functions and advantages of hydraulics and electronics and making it possible to achieve energy savings of between 30 and 80 percent, depending on the particulars of the application. This was a major advantage especially for the sawing lines. Since no two trees are identical, the fully automated systems have to be flexible enough to accommodate the differing sizes. If the process requires less power at any given moment, then the controls will lower the speed of the pump drives. This not only saves a great deal of energy but also significantly reduces the noise level. To create this customer-specific solution, Bosch Rexroth in Canada formed a project team made up of its industry specialists, the regional sales office, and the engineering and service departments in the hydraulics and controls sectors. The result of this team’s output is the largest HewSaw line installed to date in the North America.

Two families joined

What’s new in this application is that the engineers from Bosch Rexroth for the first time made use of two different Sytronix families: three Sytronix DFEn 5000 units and a Sytronix SvP 7000. The variable-displacement pumps in the DFE system, used in open circuits, are responsible for regulating both pressure and flow. The DFEn regulation electronics for the axial piston pumps, calculate the perfect working points for the pumps and for the variable-speed electrical drives, to best suit immediate pressure and flow demand. In the sawing line at IFG, these three pumps serve a total of 100 hydraulic axes. The SvP system, on the other hand, is used for the log turner in-feed. This is because it is also suitable for closed loop rotational axis control tasks and is characterized by its high dynamics and adjustment accuracy. All these bring about great energy savings. The log rotator moves the logs into the perfect position for sawing. It does this so efficiently that the IFG was able to increase its sawing production considerably. Working together, the two Sytronix families get the most out of the system – in terms of both productivity and energy efficiency.

And there is one more thing that persuaded HewSaw and their customer IFG. The concept is not only highly precise and energy efficient but the Rexroth components can also be monitored with remote diagnosis capabilities.