Troubleshooting a belt sander

[Travis Porter]

I was using the belt sander Sunday and screwed up. I didn't realize it, but I was trying to sand 1/4" off of a board in a single pass with the platen in the thing. The belt got hot and it self destructed. The platen had a tear in it, but seemed ok, so I put it back in and a sanding we went.

Sorry, no pics, but I was having a lot of fun sending the stuff through to Doug Robinson and Shamrock. Otherwise, I was a bit tired and wasn't a lot of fun. My apologies to Doug and Mike on that.

Then it hit. The sander quit..... I tinkered around with it and finally got it going again, and a sanding we went.

Then it quit again..... We called it a day.

Of course, my first thoughts are the worst and most extreme. Phase converter is shot. Nope, it works all the other stuff.

Next thought - phase converter isn't big enough. Too much strain. Need a BIGGER PHASE CONVERTER. Reason I was thinking this was that maybe I was putting too much strain with a small converter and that it was causing the thermal overload to trip. The more I thought about it, the more I figured that was wrong. Start up is the biggest load and it had been starting......

I read the manual some. What a bunch of gibberish. For what this machine cost, I would grade the manual as "fair". It is thick, but it has a bunch of stuff about OSHA, laws, etc that really didn't do a lot for me. It did have a mediocre wiring diagram, and a below average parts breakdown. I have never seen pneumatics, electrical, and mechanical drawings laid out separately on a machine before.

After taking the electrical panel off the machine, I believe I have an electrical issue. The red light on a relay is why I believe this. Looking at the relays, there are 3 that are the same. I swap the one with the light on with one that the light isn't on, and the red light stays in the original relay slot.

This relay thingamajig is labeled right below it as RM. No where can I find RM in the electrical drawings. I do notice that the second relay thingamajig lights up when I open the door. Seems like a safety/sensor relay thing to me.

Since I think it is a safety, and looking at the drawings it appears initially to me that this is the belt tension sensor. This sensor/relay prevents the machine from starting if the belt is under tension.

The sensor is on the top and fits between a set of forks. Up it is closed, when it goes down it is tripped. Right below it is a pneumatic piston/cylinder that is really kind of neat. More on that later.

So I check this switch and it works and is triggering properly, so that one is out.

I see if the belts and the motor spin. This motor is HUGE.

I take the front off and try to spin the belt. I can, but it is a bit stiff.

I pull the platen back out, and oops...... The graphite on the platen is destroyed. Not good. I screw around and realize the contactor has a reset. It appears the contactor was tripping due to the platen being screwed up. I remove the platen, reset the contactor, red light goes away, and it runs!! Now I get to replace the graphite on the platen.....:BangHead:


More pics and details to follow.

 

[McRabbet]

I can recall the one time I didn't carefully check the position of the drum on my Woodmaster and just fed a panel in... Tore the sandpaper clear off the drum in a heartbeat and "ruint" [for the uninitiated, that is the partial pluperfect past tense of "ruined", aka "messed up"] the hook and loop layer on the drum. Fortunately, I had more paper to roll on the drum and the H&L wasn't totally ruint and I could continue. But I had to order a new H&L strip to go on the drum (only $26 from Woodmaster) and I must say I "learnt" my lesson [until I forget to check the next time!]. I presume you might have "ruint" the belt on that bad boy too, right?

 

[FredP]

I did that once on my dual drum sander. I was lucky as it kicked the breaker before it chewed up the feed belt.:icon_cheers I did have to replace the paper though.:gar-Cr

 

[Travis Porter]

The belt was destroyed, literally. $44 gone.:cry_smile The graphite I am fortunate enough to have some of and plan to replace tonight. I understand it's cost is $200 to $300 a foot.

 

[Bigdog72]

Gee, I initially thought this thread was about belt sanders. You know, 3"x21", 4"x24".

:banana::banana::banana:

 

[mshel]

Travis,

Taking 1/4" off a pass!!!!!!!!!!!!!:elvis: OMG, mine sometimes trips when taking 1/32" off. Course mine is a performax and I think the 20 amp breaker isn't enough since I have other things on the same line. That thing must be a beast. Concerning the graphite, you might check with Klingspor on it since I know they have it available for smaller belt sanders.

Mike

 

[Travis Porter]

Well, you can take a 1/4 if you have the stars aligned. No platen as it is a heat generator, the right grit of paper say 40, and a low feed rate.

Thing is, I had 120 grit paper, the polishing platen, and a fast feed rate. I didn't plan on taking a 1/4 off so that is what got me in trouble in the first place.

 

[Travis Porter]

The graphite on the platen was torn from me not properly measuring the wood thickness and inadvertently trying to sand 1/4" in a single pass. This messed up the graphite on the platen and in turn caused too much tension and caused the overload to trip on the internal contactor - the red light.

The graphite before it gets a belt spun on it looks like roofing paper, but it is fairly slick. This stuff is super expensive, but I was lucky as I got enough of it when I bought the wide belt to replace it with.

What is really neat and what I didn't know is that the belt oscillates. It is constantly oscillating. I didn't realize it worked that way. Between the pneumatic cylinders, electric eye, and the motor, it is a very neat set up.

http://www.youtube.com/watch?v=r9r9Ad1oIYk

Alan in little Washington, eat your heart out.

 

[Glennbear]

That is indeed a neat setup. I sincerely hope this is the end of your trials and tribulations. :wsmile:

 

[McRabbet]

Glad the repair worked out easily! I loved the video -- that is one sophistocated mechanism and I'll bet it gets a panel super smooth! I'm jealous even though I've got a good drum sander.

 

[cpowell]

Next thought - phase converter isn't big enough. Too much strain. Need a BIGGER PHASE CONVERTER. Reason I was thinking this was that maybe I was putting too much strain with a small converter and that it was causing the thermal overload to trip. The more I thought about it, the more I figured that was wrong. Start up is the biggest load and it had been starting......

Travis - This is usually NOT true on a belt sander. The highest loads are generally the heaviest cuts.

PM if you want additional geek EE info. :gar-La; :slap:
Glad you got it sorted out.

Chuck