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Pneumatic tracking on a wide belt sander.

2/19/18       
Ziobro Member

Having trouble getting the head to oscillate on a RB-25 powermatic sander. Downloaded a user manual to verify it is wired and initial setup is per the book. Need trouble shooting guidance, this model has three air controls on the side with the "U" shaped belt surround not shown in manuals I could find online. All work, air flow control knobs.
Tubing on roller side blows hard. Can oscillate by hand blocking air pressure. Belt can be in position and does not accuate the ossillation cylinder before tripping the limit switch. Have turned opposite side cam to track head straight to allow more time in front of vent without success.
Bought machine out of storage, prior owner not available, long term storage, used for 50-100 hours max so wear is not an issue.

Rob at 270-365-2543
Thank you in advance.

2/19/18       #2: Pneumatic tracking on a wide belt s ...
duster

The double action cylinder that controls the belt oscillation may be stuck. Some moisture in there, or lack of lubricating oil can cause that. Try taking the cylinder apart, clean it and shoot some WD-40 in there.

After reassembly, make sure the automatic oiler on the air regulator is full and working properly.

Hopefully you have a refrigerated air dryer between your compressor and the sander. If not, you will get moisture in the cylinder and it will seize again.

2/20/18       #3: Pneumatic tracking on a wide belt s ...
door shop guy

I have an RB25 also. I use mine everyday and have never had a problem. Let me know if you need me to check anything for you. Like Duster said check the cylinder it is stuck it sounds like.
Mine does not have an automatic oiler and i have never fed oil into the air on my machine.
I bought mine out storage also about 10 years ago. It had hardly been used and had the origional sanding belt that was solid as a rock. lol

2/20/18       #4: Pneumatic tracking on a wide belt s ...
Ziobro Member

Thank you to both of you.
My machine does not have an oiler, a moisture blow out on incoming pressure regulator and a trash trap on the air valve.
Both are clean and dry. My little air compressor has an oiler at it.
The system works when I cover the air orifice, item 6 per page 22 in the manual.
If I cover the opposing orifice, like a vacuum, item 7 same page, it will not work. So it would appear neither is plugged and system should register a belt in front of the blast. It is slow. So the three air valve, item s 4 and (2) item 11 were threaded all the way in. I have backed them out to various amounts, no real effect. Do either of you have a set point reading? Like on a carburetor, thread in all the way and back out "x" turns for a home position. The oscillation adjustment knob, item "A" page 13 is in the middle and hand tight. Have not taken valve "B" apart yet as it works in the hand covering mode.
Thanks again.

2/20/18       #6: Pneumatic tracking on a wide belt s ...
door shop guy

You just have to play with the 3 air adjustment valves. I think one controls how fast the oscillation is and the other two control left and right...cant remember for sure but it is a thing where you have to get the 3 valves and the adjustment knob all to play nice together and it just takes some time. Once you get it dialed in it should be good for years and years. I have not had to play with anything on mine in a long time. Its been a very solid machine for me.
Keep posted and if you cant get it and need me to measure or check anything i will for you.
What belts are you running?

2/26/18       #7: Pneumatic tracking on a wide belt s ...
B.H. Davis Member

My old Timesaver had an electric eye that activated the air cylinder movement. If the eye got too much dust on it tracking would fail.

You haven't talked about what is the tracking generator on your PM but I'd suggest checking into that next.

BH Davis

3/3/18       #8: Pneumatic tracking on a wide belt s ...
karel

Good Day,
I had an older Sandingmaster and have a Taiwan air eye operated sander currently. The air goes across the U shaped sensor and into a tube where it activates a diaphragm that controls the shuttle valve for the oscillation. Sometimes this diaphragm becomes clogged with sawdust or develops a small hole this can slow down the oscillation. you might check that . to trouble shoot the system take off the air bleed valves initially until you have it working then reinstall them and use them to make the action softer. there is no need to beat up your machine with the oscillation. There are usually regulators to adjust the air eye air pressure and a separate one for the oscillation cylinder. adjust the air eye pressure so that it will just actuate your oscillation.

3/7/18       #9: Pneumatic tracking on a wide belt s ...
Ziobro

Karel,
I have adjustable and full flow from the inside of the U, the drum side. I've turned the oscillation valves from zero to full in half turn increments. Not sure where the diaphragm item you are mentioning is located, the oscillation piston on the other end of the machine? Have called powermatics service line three times, no answer or call back.

I have a smaller wide belt with the photo eye system, bought new in 1995. Have to keep it clean but is very easy to reset if a belt goes too far when conditions create excessive dust within the housing that my dust collection system can not remove.

If I can not get it by this weekend it is going up for sale. 10 hp 2011 year made with extremely low hours. Need another?

3/8/18       #10: Pneumatic tracking on a wide belt s ...
karel

Good Day,
follow the air line from your U shaped sensor and it should go through a filter followed by a round item attached to a shuttle air valve this valve controls the air to your oscillation cylinder attached to your top belt roller.. the round item attached to the shuttle air valve has the diaphragm inside. This is the way my old Sandingmaster and my Taiwan machine are set up. maybe attach a photo don't give up they are simple and dependable when you get them working. If I were to buy your sander shipping might be a problem I live in the Philippines.. He He He... Oops I forgot sometimes the air eye can be worn and the air stream does not properly enter the sensor hole on the other side of the U shaped piece check that as it can give you the same symptoms.

7/1/18       #11: Pneumatic tracking on a wide belt s ...
James Biddle Member

You're just firing up the machine again; make sure your belt is spinning in the right direction. I recently helped someone having the same issue and it turned out that the belt was spinning in the wrong direction, and as unlikely as it was for that to be the cause of the tracking issue, it tracked perfectly once I corrected it.

3/22/22       #12: Pneumatic tracking on a wide belt s ...
Mark Member

I too am just getting an RB-25 back into service after years of sitting idle, because it was broken beyond repair (so they said). After replacing all of the air lines, everything works great. I did have to lube all of the fittings, and get the cylinders moving with a little coaxing. The three flow control valves: Two smallest lines extend/retract the oscillating cylinder. Bigger line provides air for both (I think).

I haven't seen any info on these, just went off of pneumatic prior experience. Bottomed them out, then opened up about 2 full turns. Turned machine on, let it oscillate for a few minutes to work in the cylinder. Then I slowly opened up the two smaller ones, until oscillation speed looked good. Opened the bigger one about a half turn more than the smaller ones.

I am having an issue with the left limit switch not shutting off the belt before it destroys itself. It'll be working fine for a while, then it just overshoots left oscillation, and destroys the belt. I've manually operated the switch, and the switch is fine, it's just not shutting off the belt like it is supposed to.

3/22/22       #13: Pneumatic tracking on a wide belt s ...
door shop guy

Mark, do you have the ceramic part of the limit switch?
These are awesome little sanders! I just looked up a new one..almost $17K!
Bought mine for $3k about 14 years ago.

3/23/22       #14: Pneumatic tracking on a wide belt s ...
Mark Member

I don't know anything about a ceramic part. I've attached a pic of the switch, and the edge of the destroyed belt. Unfortunately, this belt hasn't touched a piece of wood yet.

Like I said earlier, I've got the oscillation working great. Every once in a while, something sticks, it overshoots the switch, and destroys the belt.


View higher quality, full size image (640 X 480)

3/23/22       #15: Pneumatic tracking on a wide belt s ...
door shop guy

Hi Mark

There should be a white ceramic type of material sleeve that goes over your limit switch...it rotates freely so that it wont scuff the edges of your belts.
If you have the owners manual on page 50 it is the LIMIT SWITCH LEVER and is listed as part number 6288612

Sometimes these limit switch levers can vibrate out and fall out over time.
Just looked up that part number on powermatic.com parts and it turned up no results...weird.

Late 2019 i ordered two of these and they listed as "stock number" 6294461 and i just looked that up and it does not come up either ...weird

Maybe look at a newer manual and get the part number off it..

3/23/22       #16: Pneumatic tracking on a wide belt s ...
Ziobro

Website: http://atouchoftradition.biz

The machine originally written about had clear plastic limit switch “arms”.
Acrylic?

They did not rotate.
2001 year of manufacture.

When the oscillation system did not work a belt would track off the closed frame side.
This would sand/grind a groove into the switch arm.
A rotating sleeve would have been nice.
Sold the machine, and many others last year.

3/23/22       #17: Pneumatic tracking on a wide belt s ...
Ziobro

Website: http://atouchoftradition.biz

The machine originally written about had clear plastic limit switch “arms”.
Acrylic?

They did not rotate.
2001 year of manufacture.

When the oscillation system did not work a belt would track off the closed frame side.
This would sand/grind a groove into the switch arm.
A rotating sleeve would have been nice.
Sold the machine, and many others last year.

3/23/22       #18: Pneumatic tracking on a wide belt s ...
door shop guy

https://powermatic.com/wb-43-sanding-belt-and-accessories

scroll down and see LIMIT SWITCH TUBE

But you first need to find out why your belt is running off..

3/24/22       #19: Pneumatic tracking on a wide belt s ...
Mark Member

Here's another problem I have with getting replacement parts. I go to Powermatic website, I can find exploded view drawings with parts list. No order information for most of the parts....No way to add them to the cart. I've tried e-mailing "contact us", and calling, with no response.

Still working on limit switches, going to pull the switches, check with a multimeter, and verify they're working. There's an audible "click" when I trigger them, but who knows.

3/24/22       #20: Pneumatic tracking on a wide belt s ...
Ziobro

Followed the parts link to the limit switch and discontinued switch arm.
My RB-25 did not come with either of these.
The extended wire portion has a cast in place clear plastic 1/2” diameter rod that does not rotate.

I understand machine manufacturers do not make the consumable items like bearing, hardware, belts and switches, have 25 years as an engineer for Ingersoll Rand. Mine must have been assembled with parts available in 2001.

The bladder was torn in the air valve. A $38 part from e replacement parts.

Have upgraded to a Halsty, AEM that uses very readily available switches, bearings and such. Kind of a home made machine by comparison but even the gauges are McMaster Carr off the shelf items. Motion Industries has the bearings and switches. Replaced the bolts with SHCS just because I like to. Oscillates with a photo eye and a dust shield. 2,000 plus hours and perfect.


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