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.

[5quarter]

Peter...if you don't know what you're talking about, then I'm really out in the wilderness.  ;) :D

[Cazzhrdwd]

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.

I don't know if its intentional or not, I will say I spent thousands on a new moulder and knife grinder and they intentionally dropped that line like a rock, its put me in quite a position. I may have to deal directly with the Chinese to get parts, I'm incredibly angry about it.

It seems the grease in the bearings dries out more, was wondering if any of you noticed that?

[4x4American]

What kind of grease are you using?

[Cazzhrdwd]

The newer bearings are sealed bearings and it seems to be some type of synthetic grease. If I can reuse them I'll do like a previous poster suggested, pull the seal out and add grease to them.

[Kbeitz]

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.

The diamond tip carbide turning tool is not good for interrupted cuts.

[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.

The diamond tip carbide turning tool is not good for interrupted cuts.

I guess I don't know better, Have done 30 or 40 of them. :D :D :D

[Al Miles]

I'm replying to this old post as I am going through a similar problem with Woodmizer rollers.

While doing a complete alignment recently, with a blade on , tensioned, properly positioned on the blade wheels, with new guide rollers and engine off, I was turning the blade wheels by hand. Every time the inner blade guide roller did a revolution the flange would contact the blade. That would only happen for about one third of the blade then the blade would move away from the roller. Once the blade did a revolution the flange would once again start hitting the blade back every time it turned.
After further investigation I discovered two problems. The first being the blade was welded out of square. I put a two foot straight edge across the back of the blade, with both ends of the straight edge touching the blade a space was in the middle near the weld. The space was larger the closer to the weld with a 1/16th inch space at two inches on either side of the weld. After rotating the blade half way around I put the straight edge across the back of the blade and the straight edge rocked on the blade, contacting in the center but not the edges.
I checked four of the box of ten they were all not square. Woodmizer sent me a new box of blades, I've checked and used one and it is welded straight.
The other problem is the flange of the blade guide roller was wobbling as it rotated. Quite easy to see the flange move fore and aft every time i spun the roller. Unfortunately I did not measure the flange out of true or the roller barrel itself. Woodmizer sent me a new roller, it was out of true as well. Woodmizer wanted the roller back to evaluate but I haven't heard what the outcome was as of yet. I did measure the second roller, it wasn't as noticeable as the first roller but was out of true 7 thou on the flange and 8 thou on the barrel. That roller made the blade vibrate so bad I thought the drive belt was loose. I tightened the belt but the noise continued. I ordered a new drive belt, not inexpensive. Thinking it may be the roller and not the belt I took off the new roller and installed an old used one. The noise stopped. So far Woodmizer has sent me four rollers and all four run out of true.
It could be the roller are machined untrue or perhaps the bearing bore is not parallel to the sides of the barrel, or maybe the bearing installation.

I do know one cannot cut straight lumber with a defective roller. Maybe that was the cause of your washboard cuts.

[Cazzhrdwd]

Not sure about your rollers Al, they do come with messed up welds sometimes. I just replace my third potentiometer. First one lasted 18 years, second one year, we shall see about the third. Mike Eichenberger at Woodmizer is very knowledgeable.

As far as washboard, Mike was the one who convinced me to use the 7degree turbos after 20'years using 10degree blades. He said the washboard was typical with them. They are certainly much better blades, too bad I'm so late in using them.

[Cazzhrdwd]

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.

It's usually the water side, seems to get in there and foul things up. But the marks are definetly from seizing, Its happened to me several times.

[Magicman]

I am loving 7° turbos, but I have to listen to the engine and push the blades to the limit.  I believe that it is the amount of sawdust that they are bringing out that will cause ripples if/when you slow down.  (Just my thought)  I see no way that they could be effectively used with lower HP engines.

[OffGrid973]

Stupid question but unless you are trying to cut too quickly shouldn't the blade not be actively riding against that vertical part of the wheel?

[Al Miles]

Ripple cuts can be a result of feeding the blade too slowly, worse in some wood than others. I know of one case where just switching from a 10 to a 9 degree hook stopped the ripple.

I measured the barrel diameter of one of the defective rollers, it is round to within five ten thousandths of an inch. This roller has run-out of 7 thou on the flange and 8 thou on the barrel.

I can only think  the bearing bore is on a tilted axis, not parallel with the barrel sides, defective bearings or incorrect bearing installation that would cause a round bearing to wobble when it turns.

[bandmiller2]

Maybe its time for manufactures to try different materials for rollers carbide, ceramic, or even Teflon or brass. when I ran the LT-70 WM we had I believe little ceramic pads that were glued in holders. They seemed to work OK but the pads would break bond with their holders but still work because they were in a pocket, no rollers I don't remember any wash board. Frank C.

[Al Miles]

Those ceramic pads are in addition to the rollers, supposed to help prevent the blade from taking a dive or rising, they don't. If a blade is going to dive it will it just bend down from the pads. I took all that off my mill as every once in a while some sawdust or chunk of wood would get caught between the blade and the pad which would cause the outer blade guide arm to slam against the log/cant and cutting would come to an abrupt stop.

As for Cazzhrwd's question about cheap roller bearings, the last couple of rollers I got from Woodmizer has China written right on the bearings.

[Cazzhrdwd]

As for Cazzhrwd's question about cheap roller bearings, the last couple of rollers I got from Woodmizer has China written right on the bearings.

Yep, that's been my experience. I didn't replace my first set for years after my mill was new, now it's just about every other year. Funny how people think they would never do that, they do have a reputation to keep up.   :

I don't blame them though they do have to compete with all the other mill companies out there. I'm just wondering when there is going to be enough mills around me. I'm glad my business is established after 20 years. Helps me to charge confiscatory rates that I wouldn't be able to do if I was begging people to let me Saw for them. Sorry for the rant.

[drobertson]

I've seen it happen with new blades, alignments correct.  Logs, SOG ect...can cause funny things, this said, oscillations can cause it, set screw on top between the wheels.  Discussions on the rollers totally different ball game.  I've trued mine up in the past. Precision grinding, they had wear, smaller on the outside, bigger towards the flange.  I also had the marks on the flange till the day I sold the mill. It showed no signs of wavy marks or signs of oscillations, a good feed rate should be bumping the flange, not riding on it. I would be close to betting a dollar to a dime its the band blades.   

[Al Miles]

You are not the only one ranting. Woodmizer makes a good product but then cheaps out on things that make you shake your head. I talked to a rep about that a couple of days ago and even he is amazed at that tendency. Another rep I knew a couple of years back told me Woodmizer makes a Cadillac of a mill then puts mickey mouse parts on. With the volume of bearings they buy they must be able to buy North American made for a good price. Or buy local and add the extra $0.50 to the price of the part.
There are about 20 sawmilles on the Island I live on, five of them are woodmizers, I have heard from three of the other four owners complain about Woodmizer lowering their standards once a product gets accepted in the industry.

[esteadle]

What I think is happening is that your feed speed is high enough and your blade dull enough that you are pushing the band back into the roller bearing edge and when the mutilated bearing rolls around, it forces the back of the blade up and down, and that creates a blade flutter which creates the ripples. When it was on the "entry" side of the wood, it was probably worse, but you switched it and it probably moved to the other side of the cant.

You probably changed blades too, and changed the sharpness so may have not had as much pushback on the blade, thus masking the problem which was still there, but not evident when you weren't getting blade pushback. But as the blade dulls in the cuts you make, it starts to get pushback and then you get ripples.

Sound about right?

I think you need a pair of brand new roller bearings and your problem goes away. Bite the bullet and get new, vs. trying to figure out if the machining skills you apply to cutting the old bearings are good enough to solve the problem.

In the meantime, you can try to adjust the spacing and give yourself a little more room before you hit the back edge. On my mill (Timber Harvester), I set both guides to 1/8" spacing off the back of the roller. (I get why yours might be 1/16" on the entry side, and 1/8" on the exit side. If the exit roller side is moveable, then it's on a cantilevered arm of some type and that will move a bit no matter how tight the attachment bolts are. They entry side is typically fixed, so it wont' move that way).

You can also try slowing the feed speed down, especially in wide cuts, and as your blade gets duller. That will prevent the blade from pushing back into the edge of the roller.

Good luck to you!

P.S. I just went to Cooks Saw and see that they are selling roller bearings 10% off. http://store.cookssaw.com/