Widebelt Sander Kickback

Cabinetmakers discuss why a widebelt sander kicked some boards out against the feeder belt. October 11, 2012

I have a 42 inch, two headed widebelt sander. Have had the machine for about ten years with no problems. Yesterday two boards shot out of the machine towards the operator side. I didn't see this happen, I just heard about it. To my knowledge this has never happened before.

They were sanding maple boards about 4 inches wide X 20 inches long. On a few occasions they apparently neglected to run the dust collector. There was a fair amount of sanding dust built up in the machine. When you ran your hand over the conveyor, it felt slippery like talc.

The machine has a feature to select its own initial starting position. You stick your material in and raise the bed with a lever. The bed will raise until it hits a desired pressure, then stop raising. At this point you hit an elevation button once that raises the head .2mm. Apparently the operator interpreted this to mean hit the button twice, so the cut was at .4mm.

The conveyor bed is in pretty good shape. The rubber feels a little smooth but the tread is almost 3/16 deep throughout.

What would cause this kind of kickback? My thinking is that the pressure was too great and the conveyor belt too slick. There was some slipping in the machine prior to this. Parts would get stuck in the middle and not continue to pass through. Does the rubber need to be freshened up somehow?

Forum Responses
(Cabinetmaking Forum)
From contributor D:
That happens to us occasionally too. Usually just blowing the excess dust off the feed belt takes care of it. Forgetting to turn on the dust collector will clog the feed belt real quick and make it slick.

From contributor K:
I would think it was caused by too slick a belt, exacerbated by dust buildup, and/or insufficient rather than excessive holddown pressure. On our single head machine, a Sandingmaster, the contact roller height can be adjusted relative to the hold-down rollers, and if set too low can reduce pressure, thus inviting kickback. The belt will get slick over time, so we periodically dress it by raising it carefully up into the abrasive.

From contributor T:
Did they load the right grit papers on the right heads? I would check the owner's manual and/or call the manufacturer. Nothing ever happens to only you.

From contributor M:
I'm with contributor K on the hold down rollers. They could have vibrated loose over ten years, or broken pressure spring; it's something to look at, at least. The rest is just folks not paying attention to what they are doing.

From contributor S:
My old widebelt sander kicked stuff out and it turned out that the down pressure on the rollers was out of adjustment.