Troubleshooting Widebelt Ripples

Experts suggest possible reasons for imperfect performance by a widebelt sander. February 1, 2015

Question (WOODWEB Member) :
We have a Powermatic widebelt in our shop. We can get rippling right off the bat with some belts and when I find one that doesn't, it seems to only last a couple weeks. We have tried many different brands and Iím having a hard time believing itís the belts that are causing the problem. One thing Iím suspecting is one of the workers always uses the emergency stop to change belts thinking he is saving time, what kind of damage is he doing to this machine? Where would I start looking for obvious places for rippling?

Forum Responses
(Solid Wood Machining Forum)
From Contributor U:
Can you describe your ripples better? Are they going with the feed direction of the conveyor belt? Or are they going side to side? Are they spaced evenly apart? Or are they spaced inconsistently? Are they always on the same spot on the panel?

From the original questioner:
Yes side to side evenly almost like a belt joint. It looks like a washboard effect.

From Contributor U:
Based upon what you are telling me I don't think it is the seam with them already changing out paper, etc. I think you are getting chatter from them trying to remove too much material in one pass. Either your conveyor belt is running faster and needs to slow down or you need to take off less material. Each grit of sand paper can only take off so much material so fast. With it being evenly spaced I don't think there is a mechanical problem. I would just take a look and make sure your drum spins smoothly by hand without any paper on there. I would also check the top idler roller for the same to see if you see or feel any vibrations.

From contributor L:
Do you have a platen? All widebelts will leave ripples if you don't have a platen.

From Contributor W:
If the ripples are very tight together and the ripples and the space between them are nearly identical, then you most likely have a drum that is not perfectly round. Not the most uncommon thing in this industry. If the marks are separated by a space bigger than the mark, then the culprit is most likely a crappy splice. The most likely cause of the fact that it is intermittent and only shows up after wear has to do with the position of your platen. If your platen has just barely enough pressure to remove the marks when the belt is new, the back pressure of the slightly worn belt will soon over power the platen and the marks will start to get through again. Try taking the platen all the way out and running a part. If you see the ripples really well, then you can further diagnose the issue. The drum will always show more of these types of marks than the platen. The platen with this wide surface area really covers up a lot of sins, so to speak. It will sand out some chatter from drum run out and it will hide the marks from a crappy belt splice. As you now know, not always for long. A little more platen pressure might help, but don't put up with crappy belt splices.