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Widebelt Sander Help Needed6/30/19
Don't you think it is past time to retire a 35 year old machine? You aren't saving any money if you have to rework product!
Nope. Not planning to retire this machine. It's still a great machine with plenty of life left in it. It just needs some adjusting. I have plenty of older industrial machines. I prefer the older equipment.
Logic. Just a bit of applied logic.
First, what you are seeing is a snipe. Not like chasing one in the woods, but a snipe - fore or tail. You run moldings, so you have seen snipes before on moldings, usually tail snipes. Planers will also snipe, fore and or tail.
Second - determine for certain what you are seeing on your doors - fore snipe is the first leading edge of the panel. Tail snipe is the last.
Now, for logic. Measure how long the snipe is. Not how wide, but how long. Lets say 5" tail snipe. Now go to the machine and open it up (power off, 100%) and visualize your panel feeding thru the machine. Take a thin stick, mark 5" on it and 'feed' it thru. Where the 5" mark is on the abrasive wheel (the sanding cylinder), you will see the end of the stick coming out from under the holdown roller. This allows the tail of the panel to rise into the abrasive.
Careful observation will tell you what is happening. Careful analysis of these events will help tell you what to do.
It ain't simple, but it is a good exercise in logical thinking. The age of the machine would lead me towards a bearing problem/solution, but that is not a given.
Snipe on a planer comes from the stock moving around until it hits the chip breaker or outfield roller, or both. I'm having trouble visualizing how a pinch roller would work without a pivot and springs. How would the infeed pinch roller work when you have it all set to remove 1/32" and then move the bed to remove 1/64"? Doesn't that mean you now have 1/64" clearance under the roller? Also what happens when you change grit? An 80 grit belt is much thicker than a 120 grit. Are you constantly changing the roller positions? How long have you owned it? Has it always done this?
Thank you, David. I'm going to determine whether it's the leading end of the trailing and of the doors that has the snipe when I run my next batch of doors. And, I will do what you suggest about using logic to determine when and where the snipe is occuring. Apparently, this sander was built before they started putting spring loaded pinch rollers on wide belt sanders. I have wondered if not having spring loaded pinch rollers has been the main problem with the snipe issue. I have thought that the spring loaded pinch rollers would easily let off the tension as the door passes through. Whereas a fixed pinch roller is not going to easily let off the tension. I have wondered if it's possible to convert my fixed pinch rollers to spring loaded rollers. Have you ever heard of anyone doing that? Thanks again for your help.
Rich, it's been a while since I set the pinch rollers. I can't remember if I set them to be inline with the contact drum or not. I will find out soon though. I don't move the pinch rollers once I have them set. The pinch rollers are on a cam. You just loosen a set screw and then you rotate them to make them go up or down. I usually am only using one grit size belt. I typically use a 100 grit belt. I have had a long history with this machine. My first boss bought this machine at the IWF show in Atlanta. I used to use this machine when I worked for him. I ended up buying the machine when my old boss's shop got sold to another fellow. I've owned the machine for the last 22 years or so. My old boss did not do maintenance on it like he should have. I had Black Brothers recover the contact roller and I replaced the conveyor belt. I am thinking of having the pinch rollers recovered too, but I'm trying to decide if I should do that or if I should try to modify it to make the pinch rollers spring loaded (if possible) Thanks for your help too, Rich.
Costa sets the pinch rollers 0.05mm below the shoes from the factory. This causes far more problems than they would ever admit. I've seen multitudes of issues that would easily be fixed by simply using softer rubber and a bit more pressure. I've seen hundreds of sanders with sticks used to push parts through.
I would pull the shoes and set the rollers to 0.3mm below the shoe. I like to mill a step into the middle of a piece of aluminium that I can set across the shoe while it is inverted on a table.
The shoe itself would be set to the same height as the head it follows. The roller will give much better drive this way without causing a snipe from the roller itself.
This will help with drive issues through the machine.
If you would like you can private message me and I can walk you though it or help directly.