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Can't seem to find the problem!!

Started by Gipper, May 16, 2004, 12:06:25 PM

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Gipper

After lurking around here for a little over two years, reading the post and learning a great deal about sawmilling, I decided to join in.  I have  solved a great number of problems from the knowledge gained here but this time it appears I can't seem to find the culprit.

Hopefully, I can give enough information, in short enough form,  to get some thoughts from those more experienced sawyers out there.  I have a fully hydraulic Accu Trac 36 by Cook Saw MFG.  I recently moved it back home from a large sawing job - 61,000 bf, and before setting back up to saw, did some fine tuning, servicing and added a couple of factory upgrades.  Due to some unforseen circumstances, I did not get back to sawing as quickly as I wanted to, but now that I'm set up and sawing, cannot saw a good board.  The first log produced boards with waves that would make the ocean look like ripples!  After three days, six logs and a pile of worthless boards, it is a little better, but not acceptable.  Fortunately they were my logs and not a customers, and not top grade logs.  The wavey problem is now better, but not fixed completely, but now I cannot get the cant the same size on both ends.  It's off by 3/16 in. in 16 foot log.  Things I have done to try to fix problem are:  Removed, inspected, cleaned and reinstalled roller guides and set to 3/16 in down pressure.  Installed new blade and made sure it is running approx. 1/8 in from flange on back of guide and 1/16 in from the gullet on the band wheels, and that the blade tension is what it is supposed to be.  Drive belt and hydraulic pump belt are both tight.  Bunks are level from side to side and with a string stretched from end to end, the mill is level that direction.  I have watched the blade carefully and have not notice any obvious dive or rise in the cut.  The band wheels both still have crown.  The mill only has 600 hours on it and these band wheels only have about 200 hours on them.  The wavey board did improve with the new blade, but are not eliminated entirely.  I feel that I'm overlooking something simple, but I cannot find it.  Any thoughts?  I've got over a 1000 bf of red oak for a customer waiting to be sawed but I won't attempt it producing boards like I am now.  I think he is starting to get concerned about his logs.

One other note.  The upgrades could not have anything to do with it.  They were dog slides and a new support arm with  improved slides for the moveable roller guide.  It did not fit well so I now have it back off and the original back on the mill.  It is now as it has been for the past two years in which we have sawed a great deal of quality lumber.  The logs sawed are not extremely hard wood, but have been down a while.  Couple each of maple, birch and poplar.

Appreciate any thought, ideas and help.

Eddie

Frickman

I can't help you much with a band mill Gipper, but I can say welcome to the forum!

If you're not broke down once in a while, you're not working hard enough

I'm not a hillbilly. I'm an "Appalachian American"

Retired  Conventional hand-felling logging operation with cable skidder and forwarder, Frick 01 handset sawmill

Pretend farmer when I have the time

Tom

welcome, Gipper

In order of importance, I've found the following to be the cause of wavy boards.

!. difficult wood.  Loblolly Pine comes to mind.  I have trouble with wide grained boards that have a hard winter ring and a soft summer ring.  Some folks say Early and Late, some Spring and Summer.  I'm not going to argue symantics. :D

2. A dull blade.  Usually this causes the blade to dive one way and stay there but it can also cause it  to wave in the board because it is meeting with varied resistance.

3. Too little set.  If the kerf isn't opened enough, the blade tends to follow the grain and doesn't guide itself through the tough spots very good.  Knots and end-grain will give it trouble too.

4. Too little down pressure on the guide.  The guide needs positive pressure to guide the blade.  If that pressure is lacking then the wood guides the blade by pulling it away from the guide.

5. Lack of tension.   too little tension will cause all manner of blade problems.  If the blade is perfect, the problems will not appear.  As the blade dulls, the problems become evident quickly.  It gives the impression of a blade dulling too quickly when actually it isn't dull at all.  It is just too dull to guide itself.

6 Gummng.  This causes the blade to act as if  its set has diminished.  It also causes it to track on the guides and bandwheels differently than you set it up to do.

7. Distance to the guide flange.  The blade is distorted from the cutting pressure because it has to bend before it is supported by the back of the guide. The blade can waver up and down because of the lack of support. You may also notice stress cracks developing in the "back" of the blade.

8, Drop in blade RPM's.  This can be caused by the engine not maintaining its RPM's or by belts slipping or even the band slipping on the band wheels.  Usually a blade in this situation will go one direction and stay there, either dive or rise and may even lock itself in the cant and stop all together.

Wavy cuts are almost always a blade problem.   I would definitely start with "sharpness" followed by "set".


D._Frederick

gipper,

An 1/8 of an inch is too much distance between the blade back edge and the flange on your roller guide. This distance should be less than 0.020 inches with blade under pressure and turned by hand.

EZ

All good answers but I do agree with D. Frederick. Your blade should be a little closer. I was sawing Sat. and everything was going great until I started getting a wave. I put a new blade on and check everything, but the flange and the back of the blade I eyeballed it and it look good. After a couple cuts it started to wave again. I check the fange and blade with my gauge and it was off. Bought the blade in and sawed the rest of the day with no wave.
EZ

Larry

I would take a real hard look at your band even if it is brand new.  Check sharpness, tooth angle, and set on both sides.  I once got a box of new bands that were only set on one side.

Suggestion – once you get it cutting right make a few cuts with a band to make sure it is cutting right.  Take the band off and mark it as "test band".  Next time you have a problem put the test band on and you can isolate the problem to the mill or band real quick.  This excellent idea came from another forum member but can't remember who it was.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

Gipper

Hi Guys,

Thanks for welcoming me to the forum, and for your thoughts and ideas.  I finally got to try it again this afternoon, and I do believe the first blade was a set problem.  I haven't got to check it on the setter yet, but it looked like it was weak on one side.  The new blade, for some reason, had come farther forward on the band wheels with the same amount of tension as the re-sharpened blade.  I did not get to check that when I quit Sat. evening due to shutting down in a hurry because of a super "popcorn" thunder storm.  Today, after carefully checking everything, particularly the space from the blade to the flange and adjusting it closer, as some of you mentioned, with the new blade, the waves were gone.  I still have a slight problem with the cant being off size a little on a 16 footer.  I think I have it figured out, but darkness caught me tonight.

One of the confusing things to me was thinking I had everything set exactly as I had for the past two years in which I had sawed a lot of quality lumber.  I guess this old stiff back and failing eyesight won't let me get down there and look at those close tolerance areas any longer.  :D  I did take another look through the manual and it does say 1/8 in. between the blade and flange.  In another section, it indicates it to be closer, but does not specify numerically.

Again, thanks for the information and ideas as to what to look for.  I have learned a great deal reading from this site for the past couple years.  Guess I should have signed up long ago.  I do have some interesting pics if I can figure out how to get them on.

EZ

The only way your cant could be off the way you say it is, is your log bunks are'nt level. My old frame was pretty week. I would get the bunks level, throw a log on and the bunks would be out again. This would happen if the ground was soft. I fix that problem tho.
EZ

KURT_STURZ

Hi Gipper,
I've been reading your post concerning your problem with uneven cutting. When I've experienced uneven cant dimensions from one end or side to another, the problem has been in the bed of the saw. I think that your bed has a twist in it. It is very hard to detect. But if it has a twist, the saw will follow it. When you turn your cant 180 degrees it compounds it on the other side giving you bad cants. If your bed is out by 3/32", when you turn your cant and cut again, it's now out 3/16". The saw follows your rails, and a slight twist in them is hard to see and find. Try to get a long straight edge to check camber or bow in the bed. Your lumber will be as true as your foundation. Hope this helps. Good luck.
Kurt Sturzenbecker

Tom

The blade can cause the cant to be smaller on one end than the other too.   Before you start making a lot of changes to the mill, verify that the blade is cutting straight.

A dulling blade or a misaligned guide can cause the blade ot rise in the cut and stay there. It's fairly easy to verify.  the blade may look like it is cutting straight but when it exits the end of the cant it will drop below the kerf line.  If it does that then the end of the cant will be bigger than the beginning.  Actually the beginning or entry end will only be smaller for six inches to a foot and then the blade will rise and stay there for the continuance of the cut.

You can notice this sometimes if the feed speed is too great or the set is too great.  

Swede

Once I saw the band changed direction (by reflecting light) just when it left the log .
I adjusted the band guides tighter to the band and it did help.
I´ve never had any other problems by droping or rising blade and the plates in my guides isn´t very good.

Swede.
Had a mobile band sawmill, All hydraulics  for logs 30\"x19´, remote control. (sold it 2009-04-13)
Monkey Blades.Sold them too)
Jonsered 535/15\". Just cut firewood now.

Gipper

Thanks to all for the help!  One of the things I found yesterday that I failed to mention in the last post is exactly what EZ said.  I was "losing" a little level each time I rolled a log on due to the set screws slipping on the outriggers at each end.  After discovering that, I re-leveled and added a great deal of torque.  Guess I had gotten weaker during the month away from sawing. :D  After that, the 8 ft. logs were no problem.  The last one was a 16 ft. log that had the exact characteristics Tom described - about 12 to 16 inches into the cant was all the sizing was off.  The last 14 to 15 ft. the cant was uniform. The movable guide is the one I put the upgrade on and had to go back to the original.  As you described, that could very well be the biggest part of my problem now.   Did not get to do anything today with the mill.  Tomorrow will look again at the roller guide alignment.

Hopefully, with the help I've gotten from you folks, by the weekend, I should be able to get to the customers nice red oak logs.  Thanks again.

Eddie

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