Occasionally we have orders for window blinds made of white oak. We make a 2" window blind meaning all the components are 2" in width. Length of parts is determined by the width of the blind. I say this, to better present what may be creating our problem. When running these long narrow parts through our Timesaver, sometimes, but not always, we see what looks like burning on the surface of the wood. Starting gradually a few feet into the pieces as it travels under the sandpaper, and worsening the rest of the way. Obviously the paper is loading up. But with what? Oils or resin of some type? We barely kiss the surface, mostly just clean up passes. In our current order, the pieces are all 2" x 64", so that's a long narrow area generating heat. Funny thing is, the thicker rails are the problem. The thinner 1/8" x 2" slats don't do this.
I'm running 150x Klingspor belts at 1/2 speed. Even brand new belts do this.

As you I suspect it is heat buildup.

Are you using an incorporated platen pressing the belt down to the wood? If so look at the condition of the graphite strips.

Have you tried running the slats through at a slight angle.......say about 15°? The slight cross grain sanding marks a 150 grit belt probably won't be an issue on white oak. This will spread the pressure across a wide area of the belt instead of just at one spot.

What is the condition of your rubber feed belt? If that has some high spots running across the width of the belt from uneven wear or sanding belt hits that might initiate the buildup condition on the belt.

Finally have you tried coarser belts to see if it's a factor of the 150 grit as vs perhaps 80 or 100 grit. If it still happens with 80 or 100 grit then likely something else more sinister is taking place.

BH

Thank you BH, I appreciate your thoughts on this. We are using the platen. The graphite strips and the drum are in good condition, we recently inspected these a few days ago. Also, we haven't been seeing any of these issues when sanding basswood or sugar pine during the last few times we used the time saver. I did try sanding at an angle, but it was more extreme than 15 degrees. It worked but the sanding marks were obvious, I'll try the less angled approach. I think this will definitely spread the heat out.
We had this same experience some months ago, the last time we did white oak blinds. So I think the problem is the procedure we are using, not the sander itself.
We will try other grits this morning. I wanted to ask here, to avoid burning through some expensive belts if possible. Maybe a faster conveyor speed too.
Also I will add, after entering our caliper setting into the Timesaver, we adjust to remove the majority of a pencil line. Then we make a quick adjustment to completely sand the line from the surface. And that is usually sufficient for our purposes and we stop there. Our quick adjust setting is .010 so I'm surprised we are having this happen. It's not like we are trying to remove a large amount of material from the thickness.
I will update our results later.

Are you using the proper sandpaper. I would use at least a 30 pct. open coat and run at a slight angle to give the belt a chance to cool off. hope this helps.

Cris the belts we are running are 311 open coat. Not sure what the percentage is.

Are you taking .01 off with a 150 grit belt? Is this a single head sander? I believe that the max removal for a 150 grit belt is .006 with less being better. I have a chart showing the max removals but got it from online. From what you are saying, I believe you are taking too much off and its way more obvious on white oak than the softer woods you normally do. Thus creating heat and burning and killing the belts. My suggestion is to put a new belt on and remove .005 on white oak and see if you have the same issue.

The adjustments we made this morning have worked. We started with new belt. Switched from 150x to 180x. That was simply because we didn't have any new 150s. We bumped the conveyor feed from 35 fps to 45 fps. And we ran the remaining parts slightly angled to the sanding head. We saw zero burning today.
Thank you for the responses and suggestions. It's a real blessing to have a resource available like Woodweb and the knowledgeable contributors who post here.

Hey there! Sounds like a tricky situation. 🔥

The burning on those thicker rails is likely due to heat buildup from friction, especially given the long, narrow 2" width and the density of white oak. White oak can have more resin and oils, which might be getting worked into the surface and causing that burn-like finish as the sandpaper loads up. The thicker rails likely generate more heat because they're less flexible and create more friction compared to the thinner slats.

A few things you might try:

Adjust Speed/Pressure: Slowing the belt speed or reducing pressure could lessen the heat.
Coolant or Air Blast: Introducing a coolant mist or air blast might help keep things cooler and clear dust.
Different Grit or Belt Material: Experimenting with a different abrasive grit or belt type might reduce the loading and heat buildup.
Frequent Belt Cleaning/Replacement: Regularly checking and cleaning the belts to avoid buildup can help.
Hope this points you in the right direction! 👍