I’m hearing a lot of people talk about reducing the amount of coolant they use to cool their saws, it’s a real concern since the wetter the wood, the longer it takes to dry. These days it’s all about how quickly you ship the wood to the market. To get it there faster you need to be able to process quickly because the quicker you process the wood the more money your sawmill will make.
In my recent blog “Gap Control Revisited” I spoke about many sawmills running a larger than standard gap because of sawguides that had a high variation in thickness due to their poor condition. Believe it or not this is happening more often than you would think because the sawguides are preventing the sawmill edger motors from turning the saws. The gap between the sawguide and the sawblade is too tight because of the gap variance. To overcome this, many sawmills run a bigger gap to get the motors to turn the saws on the edger. As I mentioned, this larger gap can lead to higher (within board) variation.
The coolant pocket that is on the babbitt pad is supposed to cool down the saw. If it doesn’t fill up properly because of the increased gap between the sawblade and babbit pad allows the coolant to flow out faster than with a narrower gap. If the coolant pocket isn’t functioning properly the saws can heat up and fold over. This causes downtime.
In order to get the saw to cool properly there needs to be an increase in flow to fill the pocket. When the flow is increased, the amount of coolant increases and so does the cost of consumption. The increase in flow also means that the wood is subject to more coolant, and therefore the sawdust has significantly higher moisture content.
The trend in the industry is to use the sawdust to fuel the kilns for drying, especially with continuous dry kilns. With higher moisture content more energy will go to drying the sawdust instead of drying the wood, which decreases the efficiency of the kiln and its productivity.
When you combine the increased cost of coolant, the decreased efficiency of the dry kiln, and the tremendous cost, you can see that the increased gap between the sawguide and sawblade is a significant problem to the overall cost efficiency and productivity of a sawmill. The major contributor to this increase in gap is sawguides that are in poor shape or not accurately made.
Many mills wait too long to replace their worn sawguides and therefore their ability to control the gap is a problem. As well many mills look at the cost of a sawguide and not the accuracy. Inaccurate sawguides lead to major issues with gap control. The lack of gap control leads to poor productivity and increased costs.
Author: Udo Jahn
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