What's the cause of board slipping on sand paper belt?

[TurtleCove]

I've been carving some cedar boards that are 41" long, and 3.5" wide.
All of a sudden, when it measures the board in the beginning, part way thru the measurement, I see the sand paper belt moving, but the board not. I've tried a couple of boards, and it's happening with both. Boards are nice and flat.

What's the typical cause of such behavior ?

[bergerud]

Does it happen when the ends of the board are trying to push up the rollers? Head pressure or non level head? Tape on the bottom of the board for traction?

[fwharris]

Adding to Bergerud's comments,

Dust between the belts and the tray.

Belts are stretched on one end (keyboard side) from doing lots of narrow board carvings.

[TurtleCove]

Does it happen when the ends of the board are trying to push up the rollers? Head pressure or non level head? Tape on the bottom of the board for traction?

No, it's happening about 1/2 way thru the board.
ok, I'll add masking tape to the board bottom, for traction.

[TurtleCove]

Adding to Bergerud's comments,

Dust between the belts and the tray.

Belts are stretched on one end (keyboard side) from doing lots of narrow board carvings.

Are you suggesting I remove the best, and clean underneath it?
Or are you suggesting I replace my belt?
This belt has less then 15 carvings on it.

[bergerud]

No, it's happening about 1/2 way thru the board.
ok, I'll add masking tape to the board bottom, for traction.

There must be something causing drag. Something jammed above the rollers? Check the rollers. (It is not that the out feed tables are too high is it?)

[fwharris]

Are you suggesting I remove the best, and clean underneath it?
Or are you suggesting I replace my belt?
This belt has less then 15 carvings on it.

I was just tossing out possible causes. If the belts are basically new I would not think they are stretched. You might be able to blow air under them with out taking the belt tray out.

Can you manually push on the belts and move the them with out them slipping on the belt tray?

Also make sure they are not rolled over on the ends.

[TurtleCove]

The rollers turn freely, when I try to turn them by hand. So, nothing is jammed.
The outfeed tables are not too high....maybe a bit low, but they are not the cause.
Maybe the cedar is just too smooth on the bottom...and masking tape will help.

You suggest "too much drag". Like too much head pressure? I would think not enuf head pressure would cause slippage.....

[bergerud]

I did not mean head pressure when I said drag. I meant something else like a piece of wood jammed in above a roller. Try pushing the board by hand. Can you make it slip? If so, head pressure or head not level could be it.

[bergerud]

Could the gear on one belt be slipping (so that belt is not driven). Watch to see if both belts are slipping together on the board. If one belt slips and the other is stationary, it would be a drive problem. Did you adjust those end gears when you changed the belts? Just another thought.

[badbert]

check to make sure the movable fence is not wedging. The board could be tapered.

[TurtleCove]

check to make sure the movable fence is not wedging. The board could be tapered.

The fence is not wedging.

When it's slipping, here's what happening....
When facing the keypad, there's a left belt, and a right belt.
Part way thru the carve, the left belt was turning, trying to advance the board, but the board was not advancing. The left belt was moving...but the board wasn't. The right belt was not moving.

Does that mean I have a drive issue? Should both belts be turning?
If so, I should probably remove that cover over the gears, and see if I misaligned something, when I changed the right belt a few weeks ago.

[badbert]

yes they are both driven, they should both turn.

[bergerud]

Take off the x gear cover and find out what is miss aligned or slipping.

[TurtleCove]

The left edge of the right belt had curled under.
For some reason the belt had tracked itself to the left (towards the keypad), hit the edge, and then started to curl under.
I replaced the sand paper belt, and all seems well for now.

[lynnfrwd]

The left edge of the right belt had curled under.
For some reason the belt had tracked itself to the left (towards the keypad), hit the edge, and then started to curl under.
I replaced the sand paper belt, and all seems well for now.

Symptom your head pressure is off.

[fwharris]

The left edge of the right belt had curled under.
For some reason the belt had tracked itself to the left (towards the keypad), hit the edge, and then started to curl under.
I replaced the sand paper belt, and all seems well for now.

Bingo - Also make sure they are not rolled over on the ends.
:D

[bergerud]

That is the first time I have heard of a belt stopping on its rollers from a roll up. Must have been quite a jam. You should check head level and pressure. There must be a reason for such a jam. (I thought for sure a gear was slipping.)

[TurtleCove]

Several of you are mentioning my head pressure is out of wack.
Are you suggesting it's too high, or too low?

And, why would improper head pressure, cause a sand paper belt, to not track straight?

[bergerud]

I am not sure. Years ago when drifting belts and roll ups seemed to be more of a problem, LHR always blamed it on head pressure. I suppose if the head pleasure is large enough, the belts cannot move sideways. The board will not let it.

Your problem must be something else. Maybe the squaring plate is not square and the board forces the belt sideways.

[badbert]

I always try to use 14.5" wide boards or my 14.5 sleds. I have never had the roll under problem since I started this practice. Always thought an auto centering bar would solve that problem. Make sure the wood is always applying pressure to the center of the belts. The belts last a lot longer too!

[bergerud]

If you do notice that your belt has drifted sideways, you need not take it all apart to move the belt back.

http://forum.carvewright.com/showthread.php?20113-Roller-compression&p=171537#post171537

[TurtleCove]

I am not sure. Years ago when drifting belts and roll ups seemed to be more of a problem, LHR always blamed it on head pressure. I suppose if the head pleasure is large enough, the belts cannot move sideways. The board will not let it.

Your problem must be something else. Maybe the squaring plate is not square and the board forces the belt sideways.


Hmm, that could be. I have had head pressure issues. Too high. But, I don't understnad how that could cause belt drifting.
Non-square squaring plate makes more sense.
I'll check it out.