Wash board ripple effect, and needing some guidance

[hunz]

Today while sawing some EWP, I began to notice a slight ripple/washboard effect on some of my wider cuts. As a little bit of back history, I bought the mill used a couple of months back, and sawed some white pine with zero issue right when I got it home. Since then I have wondered why after "aligning" my mill, I have been having some minor problems with cut quality.


 

I ran into an issue a week or 2 back, with some wide(20") cuts in black walnut, being ever so slightly wavy. By wavy, I mean 1/16" of variance at most. None the less, i'm a picky guy when it comes to my equipment, especially when sawing for customers. This issue had me a little stumped when it occurred after a full alignment.   I was running 7* 1-1/4" .055 blades(brand new) today, when I started seeing my issue. I called Wood-Mizer and got Mike on the line, who led me in the right direction with trouble shooting. He suggested an oscillation could be occurring due to an egged out blade guide roller, or incorrect feed rate. He suggested trying different feed rates and observe what happened. Well that didn't yield a fix, just a different washboard effect, so I tried the next thing.

I swapped the outer blade guide arm roller with the inner, and bam!, no more washboard. I pulled the rollers off after I finished sawing, and pulled out the dial calipers to see if I could figure out why swapping the rollers cured my problem. Both rollers were exactly same in every way....every diameter measurement taken read 1.975" on both rollers. Turns out after mulling over why my issue disappeared when swapping the rollers if they are the same, I noticed this..
 



 


So my problem disappeared when the above roller was thrown on the outer guide, and this roller was on the inner guide position.


 
At this point I was stumped, and honestly still am, but I did come up with my conclusion unless someone else can steer me in the right direction. My gut said that the outer guide roller on the blade guide arm is more apt to be causing unwanted vibrations in the blade, if something in the roller was worn vs an issue with the inside roller. That hypothesis didn't get proven right, when my problem disappeared after installing the back scuffed roller in the outer guide position. So here's where i'm at now:

The back face of the inner guide roller is only supposed to be 1/16" from the back of the blade edge, while the outer guide roller is supposed to be 1/8" away. I'm assuming that means the inner guide roller will come in contact with the back of the blade first, if pressure is applied to the blade in tougher sawing conditions. Could the back scuffed roller pictured above, in the inner guide position, cause the blade to make this washboard pattern because of it hitting the back of the roller and oscillating the blade? Other than that I am at a loss. I may be looking into this way more than it needs to be, that's why I'm calling all Sherlock Holmes's of the bandmilling world.

[Jeff]

Maybe it was the log. Looks like it was worse coming into and leaving that one set of knots.  Some logs just don't want to be boards.

[hunz]

Well I wish that were it, here is a picture of another log that it did it on :-\:


 

[hunz]

Related thread https://forestryforum.com/board/index.php/topic,74787.0.html

with no answer........

[Magicman]

There are so many variables in sawing.  Different oscillations set up by different blade sharpness/set, log hardness, log species, etc.  Your blade dampener may not be close enough to smooth out oscillations, a belt could be slipping, and the list goes on.  Your blade guide horizontal tilt could be out of specs.

[shakebone]

Mama said sawmilling is like a box of chocolates never know what your gonna get !   :

[ozarkgem]

Mass horizontal harmonic imbalance properties with the possibilities of gyroscopic stress induction.

[WDH]

From the marks on the back of the guide roller in the first pic, the blade was definitely riding on the back of the guide roller. 

[Peter Drouin]

The cut in the back of the roller is from sawdust stopping the thing from turning. And the blade cutting into it. If you cut a piece of 5 gl bucket and put a hole in it and let it rub to fit on the blade it will help to keep the sawdust out. In this pic the blade is loose.


 


When I get a bunch of wheels with cuts in them, I have them turn like new. By the 3 time there none.


 
old one


 
Fix one


If the blade waves, It's dull even new out of the box.
There's a lot of things some say with the log wash board. But I think it's in the way the blade was made.



 
That's why it's called ruff cut. :D

[pineywoods]

I've seen the same thing. check the horizontal(left-right) tilt on the outboard guide roller. The flange on the back of the guide roller should not be parallel with the back of the blade. Should be tilted slightly toward the tooth side of the blade. That roller is trash, a new one will soon be in the same condition if the alignment is off.

[Alyeska Pete]

Looks like you're holding the answer in your hand in the second picture, the one with the scuffed roller guide. If the trailing  edge of roller guide flange contacts The back of the blade first, the blade will have a tendency to ride the flange up on the scuff marks you see. After it's scuffed in that fashion a few thousandths of an inch, it will cause a flutter in the blade as soon as it has contact with that flange. Kind of like strumming a guitar string.  Would seem the blade made a few revolutions while the roller was not turning but in hard contact with the back of the blade.
Changing them out was definitely the cure, short term. the other guide will soon do the same thing if you don't check the lead on the guides and make sure they are turning freely.
As previously mentioned above, there are many variables that together will set up the wave pattern you see. Usually they are a gradual additive effect. Take one out the mix and it will go away.
Good luck

[4x4American]

Well seems to me that if switching your guide rollers stopped it, it's a guide roller problem.  Not sure why switching it would stop it.  With the guides mounted, is there any play in any direction?  I wonder if it could be a bad bearing.  How many hours have you got on the mill?  Are you sharpening your blades?

[fishpharmer]

On a few Eastern Red Cedar logs I experienced the same sort of washboard effect.  The cedar was especially "pitchy."  Slowing down my milling speed, lessened the effect.  An experienced sawyer told me it was caused by some sort of harmonic oscillation caused by the conditions being just right.  And I think the moon was full ;).

[Peter Drouin]

I've seen the same thing. check the horizontal(left-right) tilt on the outboard guide roller. The flange on the back of the guide roller should not be parallel with the back of the blade. Should be tilted slightly toward the tooth side of the blade. That roller is trash, a new one will soon be in the same condition if the alignment is off.

Do you think my alignment is off With the cuts I have?

[hunz]

Well it seems that it could truly be a whole host of variables. I have checked my drive belt tension...on there. I also have checked the side tilt of the blade guide rollers, to make sure they are pointing slightly rightward if behind the mill. So far it looks like that one guide roller is the cause of my issues. I sawed 3 logs after the switch, one of which was the butt log of the tree I was sawing. You'd think the problem would have reared its head in it, if it was still there.

Peter, have you noticed negative effects to sawing when your guides get grooved like that? Now that you mentioned sawdust causing the roller to stop, it makes perfect sense. The fella who owned my mill before me put 3000 hrs on her. All of which was EWP in New Hampshire; it seems pine has a tendency to gum everything up. Where do you get the rollers turned? I'm assuming its cost effective over a new $50 roller.

I'll be retrofitting the plastic piece to that guide shortly if possible. My mill has the HP blade guides.

[hunz]

Well seems to me that if switching your guide rollers stopped it, it's a guide roller problem.  Not sure why switching it would stop it.  With the guides mounted, is there any play in any direction?  I wonder if it could be a bad bearing.  How many hours have you got on the mill?  Are you sharpening your blades?

I'm guessing the problem occurred when the jacked up guide roller was in the innermost spot, because of the spacing behind the roller to blade. WM manual states that the inner guide roller is to only have 1/16" gap in between the back of the blade and the back of the marred surface you see in the pic. The outer roller is supposed to have 1/8". In this case, the blade contacts the inner guide roller first when pushed hard. I'm guessing when the bad roller is in the inner position, it is contacting those groves and getting "plucked like a guitar string" like others have mentioned. Both bearings spin equally freely.

WM does all of my resharpening, although this was a brand hammer new blade today. I think it's just a matter of needing a new roller bearing or getting the beat up one turned. It was most likely like that when I bought the mill. I've only put 15 hours on it since I bought it!

[Brucer]

Your explanation sounds exactly right to me. Contact with the flange will also cause waves (but not that close together) if the roller is cocked sideways in the wrong direction.

I have seen similar marks caused by the blade resonating -- just the wrong combination of blade tension, cutting speed, width of cut, and species of wood. The fact that swapping the rollers fixed it suggests that resonance isn't the problem in your case.

[Peter Drouin]

You do have to have the rollers set to one side. The groove in the wheel will happen when the thing stops turning, Just cleen around it and keep cutting. Just keep an eye on it. The more lube you use the more times you have to stop and cleen it,
Mine get real bad before I have them turned by a machine shop. One with cuts in it will not bother anything.  I cut dry 99.9% of the time. If i'm cutting WPine sometimes I have to turn on the Water only on for one cut to cleen the blade. If the blade gets gummed up all the time you're cutting to slow.
I'm on my 3 # Wood Mizer LT 40 and been cutting wood cince before 1987 . But I have no Idea what i'm talking about.   :P

[pineywoods]

I have a lathe and tried turnin my rollers. A carbide bit won't even scratch them. Had to use a tool post grinder. Those rollers are case hardened, which makes them a bit expensive...

[Remle]

hunz
Maybe just the lighting in the picture, but in the first picture of the inside roller, it appears that the outer edge 1/4" edge of the roller is not shinny like the next 3 raised portions are. To me this would indicate that the end is out of round and would allow the front of the blade to deflect slightly every time it rolled over the blade before it entered the cant. Moving it to the outer position it would still make the blade flutter but it would not show up as it would at the inner position. Of course the cuts on the back surface are suspect to but you might want to check to see if the roller is truly round on the front surface or just maybe the mounting bolt is not perfectly square to the roller surface. Again it could be a matter of lighting.

[Peter Drouin]

I have a lathe and tried turnin my rollers. A carbide bit won't even scratch them. Had to use a tool post grinder. Those rollers are case hardened, which makes them a bit expensive...

The tool post grinder does not have the accuracy to do a good job on the shoulder of the wheel. [ the grinder where's down, then you have to redress it] What you use is diamond tip carbide turning tool on your lathe. They're only about $400.00 a tip. But if your good with a lathe you can do a lot of wheels.
Be sure to use a water base coolant and keep it on the hair fileing. They will get hot and catch fire.
Easy.

[hunz]

hunz
Maybe just the lighting in the picture, but in the first picture of the inside roller, it appears that the outer edge 1/4" edge of the roller is not shinny like the next 3 raised portions are. To me this would indicate that the end is out of round and would allow the front of the blade to deflect slightly every time it rolled over the blade before it entered the cant. Moving it to the outer position it would still make the blade flutter but it would not show up as it would at the inner position. Of course the cuts on the back surface are suspect to but you might want to check to see if the roller is truly round on the front surface or just maybe the mounting bolt is not perfectly square to the roller surface. Again it could be a matter of lighting.

Ya, it's the light in that picture. I think your seeing the dark reflection of my black cell phone. I made sure when using digital dial calipers, I checked the diameter of those wheels from every possible direction. Those bad boys are definitely not egged that I can tell.

[Cazzhrdwd]

I get the washboard effect sawing poplar, seems to be some type of blade slap, it only happens on wide boards, a little more tension may help. The guide roller Hunz has definitely has seized up a few times. Has anyone noticed the bearings for the guide rollers seem to fail more? I'm replacing them more, I keep a few in stock. I wonder if Woodmizer is using something cheaper.

[Magicman]

I do not think that any sawmill manufacturer would intentionally use a lower quality item.  They want us up and running sawing all of the time.

[Dave Shepard]

I don't think those marks are from seizing. If the roller is still perfectly concentric, then it is unlikely it ever seized. I don't think any mill manufacturer would knowingly use a low quality part. That is really bad for ones reputation.