I recently received a call from a friend of mine about one of his customers. I knew the news couldn’t be good. Turns out, this customer had been burning up saws for a long time. The customer’s edger had an untreated problem for many years. When I use the term “burning up,” it may make you imagine some kind of Hollywood movie with special effects and a steel saw blade exploding in flames. I guess this would be a great shot for a movie, but in a sawmill this means that there is a lot of downtime and problems.
When I talk about a saw burning up, I am referring to a saw blade becoming very hot and losing its tension or rigidity and folding over like a wet pasta noodle. It can be a funny sight to see at first, but having this constantly happen is a real concern in a sawmill because it causes downtime and loss of productivity. If you work in a sawmill, you probably know that the cost of downtime per minute is huge. Many mill managers will constantly remind their crews just how much this cost is.
In the case of this particular mill, the saws that were burning up were located in the middle of the stack of edger saws. My friend asked me to call his customer to see what I could do. When I contacted the customer, I asked them to send me both a photo and a physical sample of their sawguide. After receiving both items it was plain to see that there was more than one problem going on in this sawguide stack. When I say ‘more than one’, I mean almost ten unique problems. To go through the entire list would probably result in me writing a novel. Since I’m sure many of you would not find a novel on sawguide problems a pleasant and satisfying evening read, I will just mention the one big thing that was staring me right in the face. We can talk about the other nine problems another time.
The big problem I saw right away was that the coolant nozzle holes were 1/8” (0.125”) in diameter and each sawguide had six of them. Yikes! The hole going along the sawguide stack was 3/4” (0.750”) in diameter. If this large diameter hole fed just one sawguide then it would not be such a problem. In this case, it was feeding twenty-two sawguides. Twenty-two!
My mind instantly jumped to the shower located at the back of my house. Every time I take a shower, one or two of my children suddenly have an urgent need to flush the toilet, get a drink of water, wash their hands or do some other thing involving water. When they do these things, I lose water pressure and the temperature of my shower alternates between boiling hot or freezing cold. Needless to say, I do not find it pleasant and it usually leads to a lot of cursing.
The same kind of plumbing problem was happening in this stack of sawguides. Due to the six 1/8” holes, there wasn’t enough flow getting to the centre of the stack. The first few sawguides were getting plenty of coolant but after the first few, very little was left for the rest. To this sawmill’s credit, they were feeding coolant from two sides of the stack of sawguides. Regardless, with the giant coolant holes – typical coolant holes are 1/16” in diameter – there was just not enough flow to get to the centre of this Tootsie pop.
I don’t know why they decided on 1/8” diameter holes, but part of the reason may be related to the other nine problems with the sawguides and stack. But just the simple fact that they had large 1/8” holes instead of 1/16” holes caused a definite problem. I know that switching to 1/16” diameter holes will start to fix the problem but it will not totally resolve it.
This whole issue sounds really simple when you compare it to a home plumbing problem. The trouble is to recognize a simple sawmill problem when it’s occurring, and not to overthink it when trying to diagnose the issue. So please keep this in mind when you have saws that are burning up, or also if your shower suddenly gets too hot. It’s time to fix the plumbing!
Author: Udo Jahn
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