- Joined
- Feb 8, 2014
- Messages
- 11,144
I have an old HF blast cabinet and am sandblasting a couple hundred UHMW parts to finish them.
On the far right is the part after machining, center is after sandblasting, and on the left is the finished part after treating with Trim & Shine. (an Armor All like product, but a lot less expensive) This process gives a very nice black matt finish on the part, and covers the machining marks and minor scratches.
It was not going real well, the sand delivery was not very consistent and it was slowing me down.
So a couple quick mods. I had previously shortened the suction hose and ran it over the top, the original configuration enters the bottom of the gun, this seems to work better.
I added a Tee to the inlet air and stuffed the end of that run up the end of the suction tube. It works like a suction dredge.
The other end
That helped immensely with the sand delivery, but........It uses a lot of air. I was controlling the air with a ball valve and the gun trigger. But when I made this mod, the air was always on to the siphon tube. Well that didn't work well, used too much air and was draining the tank too quickly because it was always on.
So...... Time for a foot valve, but no foot valve on the shelf. But I did find an old Parker 3/8'', 5 port solenoid valve on the shelf. OK, that'll work.....
Look around for a foot switch, nope, no foot switches....So off to Harbor Freight. The valve only draws 17 Watts so the HF switch foot switch will probably live.
After about a hundred valve cycles, it quit working. I had removed this valve from a machine about 30 years ago because it wasn't reliable. Well today it failed completely. This is really a new valve, I replaced it during testing of a new machine. These valves are not rocket science, and I found there was no pressure to the pilot port. But it was working, now it's not????????? WTH?????
What I found was that the factory assembled the valve with the wrong size check ball in the pilot pressure port, and it dropped into the port and jammed, thus blocking the port. I punched this one out, and dropped in a 3mm ball and end of problem. (The little ball is sitting on a dime).
So now I'm back to work But........Still using too much air.
About a year ago my air 5 HP compressor motor finally failed after about 25 years. So I replaced the motor with a new one, but I made a slight mistake, the original motor was a 3450 RPM motor and I ordered a 1725 RPM motor. OOPS So I effectively turned my 5 HP compressor into a 2.5 HP compressor, but it runs at half speed and will probably last forever this way. It keeps up with everything but sandblasting.
I traded about 20 minutes of labor for this compressor, but it has a bad motor so I can't just hook it up and go. It says 7 HP on it, it ain't, but it is a true 5 HP. I think they rate these at start load, not running load.
So the next question is what do I do to fix my air problems? I have a few options. The motor on the other compressor would run both of these pumps at half speed and double the current airflow and get me back to a full 5 HP.
So I could build a dual pump system with parts I have.
Or, I could just buy a replacement motor for the black compressor, and switch it on when needed.
Or, I found a 5 HP, 3 phase, 3450 RPM motor on Craigslist for $125, a pretty good deal. I have a 15 HP VFD that is currently running the 3 HP vacuum pump on my router. So I could pull the 3 HP VFD off of my mill and run the vacuum pump with that. Then replace the mill VFD with a new sensor-less vector VFD to facilitate my direct drive conversion later. Then I can use the 15 HP VFD to run the black compressor. I've always wanted to try running a compressor with a VFD and vary the speed based on air use to maintain a constant pressure.
Decisions, Decisions
On the far right is the part after machining, center is after sandblasting, and on the left is the finished part after treating with Trim & Shine. (an Armor All like product, but a lot less expensive) This process gives a very nice black matt finish on the part, and covers the machining marks and minor scratches.
It was not going real well, the sand delivery was not very consistent and it was slowing me down.
So a couple quick mods. I had previously shortened the suction hose and ran it over the top, the original configuration enters the bottom of the gun, this seems to work better.
I added a Tee to the inlet air and stuffed the end of that run up the end of the suction tube. It works like a suction dredge.
The other end
That helped immensely with the sand delivery, but........It uses a lot of air. I was controlling the air with a ball valve and the gun trigger. But when I made this mod, the air was always on to the siphon tube. Well that didn't work well, used too much air and was draining the tank too quickly because it was always on.
So...... Time for a foot valve, but no foot valve on the shelf. But I did find an old Parker 3/8'', 5 port solenoid valve on the shelf. OK, that'll work.....Look around for a foot switch, nope, no foot switches....So off to Harbor Freight. The valve only draws 17 Watts so the HF switch foot switch will probably live.
After about a hundred valve cycles, it quit working. I had removed this valve from a machine about 30 years ago because it wasn't reliable. Well today it failed completely. This is really a new valve, I replaced it during testing of a new machine. These valves are not rocket science, and I found there was no pressure to the pilot port. But it was working, now it's not????????? WTH?????
What I found was that the factory assembled the valve with the wrong size check ball in the pilot pressure port, and it dropped into the port and jammed, thus blocking the port. I punched this one out, and dropped in a 3mm ball and end of problem. (The little ball is sitting on a dime).
So now I'm back to work
But........Still using too much air.About a year ago my air 5 HP compressor motor finally failed after about 25 years. So I replaced the motor with a new one, but I made a slight mistake, the original motor was a 3450 RPM motor and I ordered a 1725 RPM motor. OOPS
So I effectively turned my 5 HP compressor into a 2.5 HP compressor, but it runs at half speed and will probably last forever this way. It keeps up with everything but sandblasting.I traded about 20 minutes of labor for this compressor, but it has a bad motor so I can't just hook it up and go. It says 7 HP on it, it ain't, but it is a true 5 HP. I think they rate these at start load, not running load.
So the next question is what do I do to fix my air problems? I have a few options. The motor on the other compressor would run both of these pumps at half speed and double the current airflow and get me back to a full 5 HP.
So I could build a dual pump system with parts I have.
Or, I could just buy a replacement motor for the black compressor, and switch it on when needed.
Or, I found a 5 HP, 3 phase, 3450 RPM motor on Craigslist for $125, a pretty good deal. I have a 15 HP VFD that is currently running the 3 HP vacuum pump on my router. So I could pull the 3 HP VFD off of my mill and run the vacuum pump with that. Then replace the mill VFD with a new sensor-less vector VFD to facilitate my direct drive conversion later. Then I can use the 15 HP VFD to run the black compressor. I've always wanted to try running a compressor with a VFD and vary the speed based on air use to maintain a constant pressure.
Decisions, Decisions
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