Band saw blade goes crazy. Wavey cut

[Dan R]

Cutting a Douglas fir today and opened the first two faces with a blade that was on the mil( lt 15 with power feed )for a bit. On the  third face replaced blade with one I had just sharpened and set. Was cutting 2 inch boards for stair treads, cut width was about 14 inches wide. Cut the can't down from 12 inches to 2 inches. Blade cut very good. Flipped up those 6 boards and went to edge them to 12 inch and that is when blade sounded terrible and was cutting wavey and I noticed it moving forward and backwards at the blade guide rollers. I stopped the mill about 3 feet into the 9 foot log and tried to see if anything stood out to cause this. One thing I noticed was that the band was riding a bit forward on the wheels. The B 57 belts are fairly new could this be causing the band to be forward?
I didn't have anything else to cut and need to pick up some more belts otherwise I would have tried that to see if that was the issue. In the 5 years I've been sawing I've never had a cutting issue. Douglas fir and Western red cedar are very easy species to mill. 
Any thoughts are appreciated 
Dan. 

[rusticretreater]

Sounds like you lost the tracking on your wheels.  You could just open the cover and manually spin the wheels to see if there is anything obvious.

I would remove the blade and check everything from bearings out.  Reset everything, relube everything, re-tension everything.
  

[uler3161]

Might want to check for cracks in the blade as well.

[barbender]

 If it is pushing forward and back it just isn't cutting. Either dull, maybe you hit something, or the set is off on one side.

[YellowHammer]

If the band was cutting, then stopped cutting relatively abruptly, then it's most likely the band.

Of course, check the other stuff described in my First Five test video, but in all probability, I would put on another band and anther log, and get back to it.  

[DanielW]

In addition to what others have said: In my experience, the most common cause of band wander is blades not running up to speed, and that's usually caused with too little belt tension. You say the B57's are recently replaced? It could be initial stretch of new belts, or possibly the tension mechanism has backed off (the drive belt tension mechanisms on Woodland Mills are especially bad for this - easily fixed with a coupling nut welded such that the head of a square-head set-screw can thread in and push against the tensioner, keeping it in-place). If you think the band is good, my next step would be to check and adjust drive belt tension before looking at tracking.

[booman]

Isn't this a Woodmizer LT15?

[jpassardi]

Yes an LT15, tension can't really back off on them. They have a rubber spring that maintains tension/cushions. The B57's will wear/compress slightly but not enough in one blade use.
I'd lean to an issue with the band itself as noted by others. Check for anything obvious, if nothing, throw another known good blade on and give it a rip before diving in too deep.

[Dan R]

Thanks Guys for the replys as always a weath of information here on the FF. I've put this blade aside and will have a closer look at it.I ended up with 34 2x6 stair treads 42 inches long that I sanded and relieved the edges and didn't see anything that looked like blade strike. I'm heading away for a couple of weeks and will get back to cutting on my return. 
Thanks all again
Dan

[esteadle]

You might have nicked a dog or a post then. When a blade goes from good to bad in a cut or two, something damaged the working edge of the teeth. If it wasn't metal in the wood then it might have been metal on the mill, or a rock in the bark maybe, or mud on the entry side.

[Dan R]

Barbender
It was a fresh blade that I had just ran though the sharpener and setter. The sharpener is a BMS 250 but the Setter might not be the best but does have a dial indicator and I try to aim for about 25 thou
Per side. 
Troubling that it cut the boards great then the edging went to heck. Couldn't have been mill metal strike as I was cutting 12 inch off the deck 
Dan.