Sanding Defects on Doors with a Wide-Belt Sander
From contributor L:
I know just what you are talking about. Our shop used to use a Jet 36" widebelt, and I got the same marks you are talking about. Hard to sand out by hand, if you were lucky enough to see them in the hand sanding phase. I tried everything to get these marks to go away, adjusting the sander, etc. The closest I got to eliminating them was to run the doors bottom rail first through the sander, and not take very much off with each pass (5 thousandths). I still got them every now and then. We recently bought an SCM 43" widebelt and the marks are gone, so it has to be the way the two sanders work. Our Jet had a single head and the SCM has double heads plus a longer infeed and outfeed supports. Good luck trying to figure out your problem. I would vote for the new widebelt.
From contributor Y:
There was just a thread describing this same problem a couple weeks ago. The conclusion was that the problem was the equivalent of snipe on a planer, and was related to the feed roller setup. I'm lucky; my 24" Sunhill (Sheng Shing) is dead flat.
From contributor A:
This post is a little different than the one a couple weeks ago. There, they were getting snipe at the ends, a sign the rollers are not set low enough. This poster is having problems anywhere the rail intersects with the stile, across the entire length of the door. That is a sign that the operators are running the door too tight. Probably trying to take too much off in one pass. As long as it is sanding on a rail, the force is distributed over a longer length, so the contact drum doesn't dig in. Once it gets past the rail, it is sanding a much smaller surface area, but applying the same force, so it digs in. Try taking less off. If you have tried that, but there wasn't enough pressure on the door, then your rollers are too high relative to the bed and need to be lowered. Either way, you are just sanding too hard per pass.
From contributor T:
Yes, too much pressure on those passes. Let up on the contact drum and use the platen. 5 thou is a lot of material resistance across a 3 foot door. It's doing just what contributor A is telling you.
From contributor C:
Right on. If a second pass without adjustment evens some of it out, it's definitely too much for a final pass.
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