Wide belt sander SCM Sandya Uno K Throwing Belts

[Curtis Kimble]

Hey there, my first post here! I recently acquired a SCM Sandya Uno 1k belt sander. I had to buy a couple parts to get it running. Now that it runs, once I put a belt on this machine it only runs for a second or two until it pushes the belt off to one side of the roller until either safety switch is tripped. It hasn't been favoring throwing the belt to just one side, so far it's 50/50 depending on which side it ends up at. I've learned the top roller is supposed to oscillate...is this to keep the belt in line? Is there adjustment I need to do to this function or is there a guide I'm missing that keeps the belt in line? It would seem to me a guide to keep the belt in line would be a no go, since it would actually cause wear on the side of the belt. I apologize, but I'm completely new to a larger, professional belt sander like this machine. Also, another thing I noticed was the machine was missing the bottom sanding belt pressure pad assy. So I bought and installed a new, stiff pad. Interesting thing is there isn't anything obvious to anchor the pad from sliding back out. Is this normal? On one side of the pad a bolt and washer keep it from traveling further to the back side, but on the installation side I find nothing to hold the pad in place! Any advice?
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[David Kumm]

First, are you pushing the tension button to tighten the belt to the roller? If so, pneumatic cylinder in the fifth picture should be oscillating the roller. It has adjustment to speed or slow the oscillation and must be adjusted so the oscillation matches the travel from the cut off switches on either side you can see in pic #4. sometimes they fail, sometimes they need to be freed up and adjusted. Dave

[Robert L Stewart]

My (1975) 25x75 wide belt sander uses air tracking to oscillate the belt. Newer units usually have optical tracking. My sander was out
of service for 8 years. It took quite a bit of fiddling and way to many destroyed belts to get the air tracking to function properly.

Looks like yours is an air tracker.

[Curtis Kimble]

I have put the tension knob in the right position and was able to observe the roller raise up and put tension on the belt. But, now that we're talking about this, I felt like the belt was "snug" but not "tight". Maybe I need to look into adjusting the air pressure on ther tensioning roller...I'll look at adjusting the oscillation, the SCM manual I have is lack-lustre at best. Thanks!

[Curtis Kimble]

I think you're right, it just needs fiddling. Evidently the shop that had it before just left it alone in a corner for awhile...Well, I'll post an update when I figure it out.

[Curtis Kimble]

I found there was a hidden photoelectric sensor that was covered in dust. I cleaned that off. Now, depending on the position of the belt the photoelectric sensor will engage the pneumatic oscillating cylinder. I found a cam that the oscillating cylinder rides on and was able to adjust it to the point the belt NEARLY stays in the same place. But the problem is when the belt is riding perfectly just out of sight and to the right of the sensor, everything is fine. It doesn't even creep too far to the right at all. But if it travels towards the left just a bit and trips the photo sensor and engages the oscillating cylinder - you'd think it would kick it back to the right....but no, it kicks in the wrong direction and pushes it even harder left. I thought, perfect, I just need to swap the air lines and make the cylinder kick back in the other direction, but the cylinder only has one air line connection. I tried adjusting the cam the oscillating cylinder rides on 180 degrees out and that made things worse....

[Richard Coers]

There can be a lot of steps to get a belt tracking. It must constantly move left and right in the machine. It's not meant to idle in the center position because when you put a narrow board on one side, the sanding forces move the belt. So it must constantly oscillate. There may be a spring return for the oscillation. You'll know if it moves by air if the oscillating cylinder has two lines going to it, making it a 2 way cylinder. Too much belt tension and too low of oscillating pressure and it won't move correctly. Lots of tweaking, especially tough for a guy who doesn't know how the machine works. Must be some videos on youtube on thickness sanders, although I've never looked.

[Bobby Robbinett]

The sanding belt should move from left to right constantly. It should never stay in the middle, or to one side contentiously. Download the manual from SCM and go through the belt tracking section of the setup guide. Once you do that if you still can’t correct the issue then give SCM’s technical help department a call. They are great and offer lots of support for these types of things.

[Curtis Kimble]

Very good info...thank you

[Curtis Kimble]

Awesome, thank you!

[Curtis Kimble]

I found out my electricians wired the 3 phase backwards which was making the oscillating roller operate in reverse!

[Curtis Kimble]

I found out my electricians wired the 3 phase backwards which was making the oscillating roller operate in reverse!

[Kevin Jenness]

Congratulations on the fix. Did the belt run backwards too?

I once made a major dust collection system improvement at my employer's shop by realizing that the blower motor was running in reverse.

By the way, don't worry about the platen being secured. Can you adjust it out of the way when calibrating, or do you have to remove it?

[Curtis Kimble]

LOL....Yes, I did. The reason I didn't notice it right away is because I've not worked with these machines other than smaller contractor units.

ROFLOL That's a MAJOR improvement to the dust collection! I needed a good laugh today!

Good info on the platen. I found that I could adjust it on the fly with everything installed and running as I bypassed the door switch temporarily. (One of the perks of being the tech, you can go on "danger drives", then put it back together safely for the crew...lol I'm so happy right now though