Drum sander problems creating cupping

I have a performax and the manual says to raise the end of the drum (like a couple thou) if sanding boards wider than the actual drum to prevent this very thing from happening.

I also don’t recommend sanding the edge grain before cutting and re-gluing. I personally don’t believe it leaves a good enough glue joint surface. I’m sure others think it’s ok but I don’t. The board really needs to go through the planer before crosscutting and gluing.

-- Childress Woodworks

I’m not having problems like the manual shows. I’m only feeding a 16” wide piece but, that 16” piece is coming out cupped instead of flat.

I’d use a planer but my planer is 12.5” wide, not big enough for my 16” wide board.

Check the platten for distortion. You may be taking off too much
material in a pass. Drum sanding to accurate thickness takes several
passes in my experience with a cantilever drum.

Loose paper in the center of the drum could possibly cause some problems.

You might want to correct the problem with a handplane for now
and try sanding to thickness again working from a flatter panel.

It sounds to me like you are either trying to remove too much material in a single pass, or your pressure rollers need adjustment.

On my drum sander, the two drums and the feed belt are a softer composite material. With enough pressure, I could imagine they would deflect just enough to produce cup or non flat surface.

-- http://www.niceashplanes.com/ http://www.efcabineture.com/

You may want to check both sides for flat. If the whole panel has a bow in it, the rollers will flatten the panel through the equipment and the bow returns on the other side. If this happens, put the panel on another board, put spacers under to bow so the panel cannot flatten and then run it assembly through the sander. I have a board with a whole bunch of machine screws that I adjust to “mold” to one side, run the board a couple of times to make it flat, turn the board over and run that without the “leveling” board.

If you don’t want to go through this trouble, I have run a board about 4 times without changing the hieght, this puts less pressure on the board and tends to flatten things out.

-- David in Damascus, MD

Thanks for the replys. Let me clarify a little. When the board comes out it comes out cupped but thats not really the problem. The problem the thickness isn’t even acrossthe panel. The middle is not only cupped but thinner in thickness than the the outsides.

What grit sandpaper are you using. You can start with 60 to 80 grit. Then proceed to finer grit up to about 150. Any more and it will start burning. Finish with a ROS .

-- Oldworld, Fair Oaks, Ca

I would call the manufacturer.

-- David in Damascus, MD

i do my wide panels and boards
in multi-passes
just a little at a time
flipping over and over
and end for end
and cleaning the table of sawdust in between
takes longer
but helps with this problem

-- david - only thru kindness can this world be whole . If we don't succeed we run the risk of failure. Dan Quayle