Wavy cuts need help please.

[MSTireman]

I've done some searches and checked all the usual stuff so far I think.  We are running a Logmaster LM5 with a 85 hp Cummins and a 2" .055 band.  We got the mill and have had to replace the roller guides. We went with the mega rollers from cooks.  That seemed to help but these bigger logs are giving us problems.  My dad got some big southern yellow pine to cut. After getting squared up it was around 26 inches. We were getting wavy cuts both lengthwise and across the cut. We have a new munks blade installed . We were running ripper 37 and had the same problems just not as pronounced.  It seems that entering the cut we are really close to being straight but across the log into the cut is where problems are happening. I will attach some pics (same place lengthwise just halfway across the log) right now the cant is 22" square. This log was a butt cut and had a big swell 38" to 30" on small end. We've checked blade alignment and adjusted it with no change in how it's cutting. I've changed feed speed, blade tension, and checked tooth set. I have run tension anywhere between 4 and 7k psi. Set is between .020 and . 025 with the bottom side of blade being .020. My roller guides are getting hot to the touch after 4-5 cuts. Never felt them before so really don't know if this is normal. So far no matter what we've tried, no change performance. I know with this mill there is no real tech support so we are just trying to figure out everything our own. Any help and suggestions are welcome. 


 

 

 

 

[DDW_OR]

my thoughts, in no order

speed
pitch build up on blade
dull blade
tooth angle
blade tension

Wood-Mizer can be modified to cut wider.
https://forestryforum.com/board/index.php?topic=84823.msg1297441;topicseen#msg1297441

here are some good links to read


Observations of a New Sawyer in Sawmills and Milling

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this is a really nice looking table
Toddlers cedar picnic table in General Woodworking

[jimbarry]

Are you able to slow the engine speed on the motor? When I have to deal with big flared buts and knotty logs, I slow the engine speed to 2800-3000 rpm. Kinda like driving on driving in slippery conditions, you gotta slow the acceleration in order to control your travel.

20210617 saw milling knotty spruce

[Southside]

Heat says to me you have a friction issue. Big SYP log and the issues you describe say dull band to me. Are you running a debarker? SYP is notorious for trapping sand in the bark. Even if it looks clean it can dull a band quickly, and with big logs everything needs to be right.

Do you have a new band you can try? Myself with SYP as long as you have the HP to pull it I find the Turbo 7 works best overall. I have no experience with the Ripper 7 but sharp it should do fine in clear pine, knots will be the tell. 

[terrifictimbersllc]

Are the blades actually sharp. Hand lens with a 10 X magnification is the most reliable way to check.

Is your drive belt tensioned to what it supposed to be?

The above two items are the most common origin of any wavy cuts that I see on my sawmill. It happens with blades that I thought were sharp, ones I sharpened myself. A quick look with a hand lens and I see rounded outside corners or a glint of light thatI didn't notice in the sharpening/ setting process, That band should have gone around the sharpener again.

Is your blade staying clean? The amount of set that you describe is not a lot for sawing softwood. Any build up and cut quality goes downhill fast, faster with that amount of set.

[jimbarry]

... rounded outside corners or a glint of light thatI didn't notice in the sharpening/ setting process, That band should have gone around the sharpener again.

Is your blade staying clean? The amount of set that you describe is not a lot for sawing softwood. Any build up and cut quality goes downhill fast, faster with that amount of set.

Good point there. That glint is a tell tale sign for sure. 

[Larry]

I have run tension anywhere between 4 and 7k psi.

I assume the 4 to 7k psi is a reading from a gauge on your saw.  That would be something to check right off.  A lot of these gauges are a shot in the dark and the number means nothing.  The tension on your band should be something in the range of 20,000 to 24,000 psi strain.  You can get the exact number from the band manufacture.  To check the tension you need a band tension gauge.  WM and Lenox both sell them as do others.  Once you get the tension correct look at the gauge on the saw and mark it for reference so you don't need to use the band tension gauge except to check calibration.

With the heavy bands your using and your horsepower something has to be terribly bad to get the waves your getting.

[slider]

After what you have done i would look at drive belt tension .

[MSTireman]

Thanks for all the replies. To answer a few questions, I can control engine speed but the mill is all hydraulic including the blade drive.  The mill behaves better at wide open as far as control of carriage etc.  I think my blade speed is way too high but according to ed@ Logmaster I can't change it unless I change the gears in the hydraulic motor.  Maybe someone can weigh in on this point also.  According to the formula from cooks, my blade speed is around 9420 sfpm. (2x3.14x15=\12)x1200rpm at wheels .  Maybe someone can tell me if I'm doing that wrong.  We did make some progress in readjusting the roller guides as far as downward tension and pitch of blade. We have the guides 1/4 inch down and have the blade pitched up 1/16 right now in the front. Gonna readjust and try for 1/8 to 3/16 up this weekend. It looked like when we are coming out of the cut the rear of the blade is higher than the tooth side so that's why we are adjusting the front side up. The heat factor on the roller guides is still there but they seem to be close to the same. The blade is cool to the touch.  We are not having a pitch problem since we switched to diesel/trans fluid for the lube.  Our mill does not have a debarker so I may have some dulling issues with sand/dirt but it has been constant with several blades so far.  Guys I appreciate all the replies and hope to some day be able to repay the forum members back with some knowledge myself. 

[JoshNZ]

If your wheel radius is 15" at 1200rpm then yep 9425fpm, that's awfully quick alright.

[Southside]

FWIW my Super 70 band speed is 5400 FPM.  

[customsawyer]

If you have .025 set on the top teeth and .020 set on the bottom teeth then the blade is going to do what it is doing in the picture. Check if the flange on the blade guides are to close to the back of the blade.

[Peter Drouin]

The blade is not level with the bed front to back.

[duffdav]

We have the guides 1/4 inch down and have the blade pitched up 1/16 right now in the front

From my experience this may be your problem.

I had a homemade resaw with a 24 inch belt. For years I ran 1 ½ wide blades with no problem as long as I kept a sharp blade with good set. I thought I would give some 2 inch wide/one inch spacing .055 Munksforsagers a try. Sawed about 18 inches..  the blade was shooting for the sky...nearly an inch rise. Tried two more new ones same thing. Put my normal 1 ½ back on and sawed fine.

Months later I go the 2 inchers back out again. I put a six foot level across the top of the band. Way out of parallel with the belt. About  six inches difference between the height at the ends of the level. I adjusted things until the height was the same at both ends then they sawed fine.

It is logical considering the geometry of things that the wider the blade the less forgiving they are. The wider the blade the more pronounced the back end will be when out of parallel kicking the back end up or down more than a narrower blade not being able to clear the gap the set creates.

The back end takes control and acts like a rudder guiding the path causing friction and overheating things.

I sharpen blades for others with BMS500/8 inch CBN wheel.

Have a guy with a big mill using two inch blades. I sharpened a round and they cut fine. The next batch he complained did very poorly. I said bring them back for a redo. The blades had a heavy ridge on the backside from running too tight against the guide. The back of the blade too wide to clear the kerf gap and took control. Expensive blades to the junkpile.

[KenMac]

Thanks for all the replies. To answer a few questions, I can control engine speed but the mill is all hydraulic including the blade drive.  The mill behaves better at wide open as far as control of carriage etc.  I think my blade speed is way too high but according to ed@ Logmaster I can't change it unless I change the gears in the hydraulic motor.  Maybe someone can weigh in on this point also.  According to the formula from cooks, my blade speed is around 9420 sfpm. (2x3.14x15=\12)x1200rpm at wheels .  Maybe someone can tell me if I'm doing that wrong.  We did make some progress in readjusting the roller guides as far as downward tension and pitch of blade. We have the guides 1/4 inch down and have the blade pitched up 1/16 right now in the front. Gonna readjust and try for 1/8 to 3/16 up this weekend. It looked like when we are coming out of the cut the rear of the blade is higher than the tooth side so that's why we are adjusting the front side up. The heat factor on the roller guides is still there but they seem to be close to the same. The blade is cool to the touch.  We are not having a pitch problem since we switched to diesel/trans fluid for the lube.  Our mill does not have a debarker so I may have some dulling issues with sand/dirt but it has been constant with several blades so far.  Guys I appreciate all the replies and hope to some day be able to repay the forum members back with some knowledge myself.

If, in fact, the blade is that much overspeed, that would account for some extra heat in the guide roller bearings. I think on my AC36 they run about 13k rpm already at normal factory speed. Good luck with finding the solution.

[BtoVin83]

Methinks your formula is off, I come up with ~4700 fpm

[btulloh]

You're right.  4700 +/-  

The mistake is in the formula, which as written shows c=2piD. It should be c=2piR or c=piD, which makes the computed fpm shown above twice the actual speed. 

Wavy cut causes are pretty much covered in the previous posts, so it's a matter of checking all the possibilities. I always suspect a dull blade first. 

[MSTireman]

Sorry I thought I put in previous post that I have 30" band wheels.  That's where I got the 15 from.  Sorry for the missing info.

[JoshNZ]

You're right.  4700 +/-  

The mistake is in the formula, which as written shows c=2piD. It should be c=2piR or c=piD, which makes the computed fpm shown above twice the actual speed.

Wavy cut causes are pretty much covered in the previous posts, so it's a matter of checking all the possibilities. I always suspect a dull blade first.

How are you arriving at 4700, with 30" wheels doing 1200rpm?

[btulloh]

I thought the diameter was 15", although that would be mighty small. I picked that up from someone else's post though, which appears to be inaccurate. So the original figure is correct. 

[bannerd]

I'm going to second the issue is with the blade.  Not sharp/ set right, not well lubricated and either moving too fast or not tension enough.  The one picture where there is a dip but level at both ends happen to me once, blade stretched.

[jrsloan1]

A lot of good information has been provided. 

Did you get it corrected? 

I like to run my blades dead flat with my deck/bunks.  My mill seems to saw better.  I find it almost impossible to check the blade flatness without something attached to the blade then a 4' level and a good tape.  It will surprise you what the difference will show up. 

I find loose drive belts cause chatter marks on the lumber.  I did not see any in the pics.

[Chuck White]

Thanks for all the replies. To answer a few questions, I can control engine speed but the mill is all hydraulic including the blade drive.  The mill behaves better at wide open as far as control of carriage etc.  I think my blade speed is way too high but according to ed@ Logmaster I can't change it unless I change the gears in the hydraulic motor.  Maybe someone can weigh in on this point also.  According to the formula from cooks, my blade speed is around 9420 sfpm. (2x3.14x15=\12)x1200rpm at wheels .  Maybe someone can tell me if I'm doing that wrong.  We did make some progress in readjusting the roller guides as far as downward tension and pitch of blade. We have the guides 1/4 inch down and have the blade pitched up 1/16 right now in the front. Gonna readjust and try for 1/8 to 3/16 up this weekend. It looked like when we are coming out of the cut the rear of the blade is higher than the tooth side so that's why we are adjusting the front side up. The heat factor on the roller guides is still there but they seem to be close to the same. The blade is cool to the touch.  We are not having a pitch problem since we switched to diesel/trans fluid for the lube.  Our mill does not have a debarker so I may have some dulling issues with sand/dirt but it has been constant with several blades so far.  Guys I appreciate all the replies and hope to some day be able to repay the forum members back with some knowledge myself.

In most cases the teeth on your blade are NOT supposed to be tipped up, or down!
Your blade "in most cases" should be LEVEL with the deck, bunk, etc, whatever your manual calls the part(s) your log sits on while sawing!

[DDW_OR]

Thanks for all the replies. To answer a few questions, I can control engine speed but the mill is all hydraulic including the blade drive.  The mill behaves better at wide open as far as control of carriage etc.  I think my blade speed is way too high but according to ed@ Logmaster I can't change it unless I change the gears in the hydraulic motor.

my fully hydraulic timberking 2000 has a variable valve that i rotate to change carriage rate.
you should have something like that

more photos of your mill please.




 

[ladylake]

 If your running 30" wheels at 1200 rpm that is 9420 fpm. You need to get that down to at least 5000 fpm or less what ever it takes.  That high speed wont saw straight, break bands way sooner, wear out bearings.  I run my mill quite a bit less fpm than factory and it saws straighter.   Steve