Sander problem

[Mark Gibney]

I got a used 15" Lobo sander in great condition and installed it. But it sands a groove on the open side,


Screen Shot 2016-07-14 at 7.29.24 AM.jpg

The sander was used for one big job and has sat around for a few years. The insides are very clean, and I cannot find any thing that could be the cause of this.

Screen Shot 2016-07-14 at 7.30.26 AM.jpg

The bed is flat and the rubber conveyer belt is even and uncracked. The rollers are clean with no bulges. The pressure bar and the felt strip feel even without any depressions or bulges. I put a straight edge to anything I could and didn't see any curves.

I put the piece of MDF in the picture thru the machine positioned a little past the range of the belt so it shows the wear. I put it thru twice, no reason, so that accounts for the overlap of the wear pattern at the front of the picture.

Anyone know what could be going on? thank you.

[glenn bradley]

I have a couple of observations. Any single pass of material that extends beyond the head will leave a mark, of course. You are removing material from part of the surface and not from the other.

The picture makes it appear that you are taking a fair amount of material off. If you rotate the piece and send it through again is there a mark at the new exposed end?

Open ended sanders that will be used to sand beyond one-pass capacity have to be adjusted for this. Some sanders, Supermax for one, have a built in system to provide a slight angle between head and table to accommodate this. This comes at the cost of a subtle irregularity in the overall surface that is generally not noticeable or impactive to the part's use.

If reversing the material and re-running it does not eliminate the marks you can offset the table to head alignment to be a bit more "open" at the open end thereby minimizing or eliminating the issue.

[Mark Gibney]

Glenn - the lines I drew on the MDF before putting it thru the sander are only worn away on the left, where the groove is made. To my mind there is something way out of whack here - 95% of the board is untouched, but the grooving at the left is very pronounced.

I didn't see any way to adjust the open end relative to the rest of the sanding area, but I'll for sure have another look.