Uneven feed rate Supermax 19-38 sander

I've got a whole house full of cherry trim to install and so bought a Supermax drum sander to help ease the endless hours of sanding. It is giving me conniptions because the boards slip on the belt, producing divots in the boards. This is not snipe, it can happen anywhere along the board. Here's what I know:

-- The transit belt is new
-- The belt is not slipping, the board stops and the belt keeps moving.
-- sanding depth is ~1/64th inch with 60 grit bit. (I can turn the drum by hand against the wood)
-- less depth (less down pressure) gives more frequent, but less severe slipping and divots
-- have adjusted feed rollers, per instructions
-- drum is parallel to the deck, sanding is even across the width
-- feed roller pressure adjustment has no apparent effect
-- in and outfeed tables appear to be adjusted correctly

Apparently people use these things successfully all the time, so I must be missing something obvious in terms either of adjustment or technique. Any clues will be most welcome.

Thanks!

I think these are very similar to the Jet sanders. Anyhow, 60 grit paper is very heavy and thick, I think. Readjust the pressure rollers so they're a little bit lower. Then make sure they don't run into the drum when the paper's on it. That would be my initial plan of attack.

BTW, if you ever noticing slipping for some reason, instead of ruining the piece, you can always just put a little pressure by hand on the infeed side, and when it's coming out the other end, you can switch to adding some pressure to the outfeed side. Just a couple of fingers pushing the piece down on the conveyor is usually enough. Get through that piece, and then shut down and figure it out. Sometimes, a piece is just ornery and needs a little encouragement :)

The only time I can remember a problem with mine was when the out feed table was just slightly too high. I run mine to where the out feed table is slightly below the belt until the board reaches the end where it just touches the board. I do not run 60 grit, usually 80 grit and only take off about 0.010 on a pass or less depending on the wood. There customer support is good. Warren even called me one time to make sure the problem was solved.

I have this sander and this is from my experience so, take it with two cents :-). The infeed and outfeed tables should be dead flat to the bed. 60 grit is nearly coarse enough for thicknessing as opposed to sanding. Is the material really that rough or are you trying to dimension it before sanding?

Like any fixed feed-path machine (jointer, planer, etc.) the material needs to be supported all the way through the operation to avoid problems. That is; if the pieces are 8 feet long and you are just starting them into the machine and walking away, there will be issues. As trouble free as the 19-38 is, it is not "George Jetson" woodworking where you just push a button and everything is automatic; you need to control your stock. A little (very little) pressure on the stock pushing it down onto the belt as John mentions will help the feed belt grab.

However, you really want to cure why the feed belt is having to work hard enough to the point that it will fail to move the stock. Do short boards ever fail to feed? Is the material that is longer than the infeed and outfeed being supported or left to pull towards mother earth under the force of gravity? On long pieces if you support the infeed side so that it is level with the infeed table, does the stopping still occur? Is the material dirty or gummy?

If your stock is well supported and you still have issues, when is the last time you waxed the tables and bed? I do mine about once a month unless I am really working the machine hard. Dust build-up on the feed belt due to inadequate dust collection will cause the feed belt to fail to grip reliably. The feed belt should pretty much always look clean; if not, up your DC power.

I hope some or all of this helps.

+1 to upping dust collection and cleaning the belt. Also 60 grit is going to leave serious scratches - I have a dual drum model that I run with 80/100 grits. When I first used a drum sander I tried to take too much off in a pass - try lighter passes.

Some good things to try here, thanks. The boards I'm working on are 8-10 ft long and due to too much wood piled around the shop it's hard to get around from the infeed to the outfeed side quickly so I've probably set the roller stand on the outfeed side a little low to catch the end of the board even if it's sagging. I can see now where that may well cause a problem. Sounds like I should a) clean up my shop and make enough room to work and b) try adding another outfeed support closer in to keep the board dead level (or get someone to help me.) I do try to keep constant pressure on the board. I get the same problem with the finer grits as well.

I have not waxed the table, I will do that.

I haven't tried short boards on it more than once or twice.

I got a deal on a substantial pile of S3S cherry which is very nice, but does have significant chatter from the planer they used. It's almost, but not quite enough to want to run it through my planer again, so I was starting with a fairly rough cut to avoid having to run a couple thousand feet of boards through 2-3 times to get to a flat and smooth starting point.

Knowing that it should work well is half the battle, I appreciate your responses.

I have learned that a couple light passes through the planer saves time in the long run. A light planer pass say 1/16" is equal to 4 to 5 passes through the sander. At this stage I would rip and end trim and then sand. If you get good results with the planer you can jump to 100 grit on the sander. You can also stand the ripped pieces on edge and run several at once for clean edges.

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Originally Posted by roger wiegand

I should a) clean up my shop and make enough room to work and b) try adding another outfeed support closer in to keep the board dead level (or get someone to help me.) I do try to keep constant pressure on the board. I get the same problem with the finer grits as well.

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a) ought to do it. I don't have any supports or tables. I just feed the board in half way and run around to catch it. Never had a problem.
Though I have even put a 10' board through it; never made anything 10' long!

Back in the planning stage a four piece built up baseboard seemed like a good idea-- and I'm sure it will again in a few years after the tedium of cutting and sanding all that wood has passed, but for now there are piles of moulding everywhere!

Following up on this-- it turns out I must have bumped the infeed table as it was high by ~3-4 mm, lifting the boards off the front of the feed belt by just a bit. Dropping the table down to flat and taking light cuts the machine is now working like a champ for me. Made about 600 ft of moulding over the weekend!

I have been having the same problem today, running a 7ft. Long 18inch wide walnut bar top, i adjusted the spring loaded rollers and it didn't seem to help much so I am going to check my infeed and outfeed tables and make sure that they aren't too high.

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Originally Posted by Wayman covey

I have been having the same problem today, running a 7ft. Long 18inch wide walnut bar top, i adjusted the spring loaded rollers and it didn't seem to help much so I am going to check my infeed and outfeed tables and make sure that they aren't too high.

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Do you also have infeed and outfeed support so that the weight of the material is not leveraging on the feed mechanism of the machine? See post #4.