Technical Blast Cabinet Troubleshooting

A few years ago, I picked up a blast cabinet off of Craigslist. It’s an Economy version, not a Harbor Freight, but not the top of the line either.

It’s never worked like it is supposed to. I bought new media blew it all out, checked for obstructions etc. It sort of works, but the blast area is pretty small. It has a suction hose that looks like it is made out of emt conduit and has a slit cut in it.

I took the gun into a local dealer, thinking it may have been worn out, but they told me it was like new.

I have even removed the air regulator to see if maybe it was slowing it down too much. No bueno. I am saving up for a new compressor with a lot more cfm. I have a std box store 5 hp upright/ 60 gallon with 1/2” supply lines.

Any ideas? It’s basic physics, but nothing is making sense.

 

Is your media dry? It has to be 100 % dry. High Oklahoma humidity will clog it up. I store my stuff in sealed containers!








Bones

 

How many psi are you running?

 

1. Is your air regulated off the compressor? My compressor is 120psi, too high for work tools that want 80psi max generally. I split my air feed prior to the regulator so the blast cabinet gets 120psi my shop tools get 80psi.

2. My snap on clogs once in a while so I have to put a glove over the nozzle and pull the trigger to back flow the obstruction. That used to blow the hose out of the hole in the bottom of the cabinet so I put a worm drive clamp on it to prevent that from happening.

3. I find it works best if I heap the media over the outlet so it gravity feeds and you don't run out of media mid project.

4. Keep the exhaust bag clean and empty as possible

5. Water is the enemy, causes clogs. You need dry air and a dryer on the cabinet with a drain

6. When mine is working at peak proficiency, it is a dust storm in there. Hard to see what the hell you are doing. Thus I added a cheater valve on the air inlet to the cabinet to control the psi.

7. Remember to change the media once in a while, the used sand makes good filler on your putting green.

 

Yeah whats your compressor's psi and cfm output? Sandblasters take alot of cfm.

And what are you using for media? Sand? Slag ? Etc.

 

Yes to all the above, but you need volume and pressure so make sure the air supply to the cabinet is large enough, no wimpy 3/8" line
If you don't get a good media geyser when you block the nozzle and pull the trigger...a good indication of not enough air volume or a media delivery problem between the hopper and the gun

 

Hope it's not sand and a respirator is on hand in any case. Nasty disease, silicosis.

 

I am using glass bead media, the most aggressive size they sell. I can tell it’s not working as expected when there is no dust storm. I run about 120 psi on it.

I have 4 water drops between the compressor and the cabinet. I don’t have a drier, but it doesn’t act like it is a humidity issue. It acts the same when the media is brand new.

My shop is plumbed in 1/2” metal pipe for those asking about volume.

 

I put a couple of bags of silica desiccant in mine. Seems to make a difference down here in Florida. I'm using glass beads but would probably work with sand too.

 

You have a moisture problem , if you saw drops of water. Build or buy a dryer.






Bones

 

What does the air blast feel like coming out of the gun?

 

No, you misunderstood. I have 4 water down spouts with ball valves to drain the system
As the water condensates in the lines. It’s basically a T with a ball valve on it.

 

This has some very good suggestions. It worked for me.

8 MUST Have Modifications - Harbor Freight Blast Cabinet - YouTube

 

I use the coal slag they sell at tractor supply. I thought I had pretty fine media, but it turned out to be a little too coarse and kept stopping up. Moved to a finer grade of media and the problem cleared up........literally!
30-60 is fine. 40-80 is extra fine .

If your compressor doesn't have AT LEAST 10 ft between the compressor and the drier it doesn't remove water properly.More is better, but I'd try the finer slag.

 

pull that pick up tube out and check for a hole. they usually wear a hole at the bends.

 

Very good ideas, I brought it up for you. Notice that the pickup he shows has the hole drilled in the vent tube and the drawing has it in the siphon tube. It really does not matter since the outside hole is plugged anyway but it did have me going WTF for a second.

 

Another clever idea for a siphon fix (harbor freight).

 

Is the pickup tube supposed to be open on the end? Mine was and I installed a cap to see if anything changed and nothing really did. Mine has a slot cut in it to draw in media I suppose.

I literally unloaded 2-5 gallon buckets of media out of the cabinet when I bought it. I think the more is better mindset was out of control....

 

mine is open on the end.
can you pull the tube out and check it?

 

The pickup tube must be open on the end to allow sufficient air flow past the media inlet hole/slot to create adequate vacuum/suction to draw the media into the airstream....roughly similar to a venturi in a carburetor.

Actually, the blast 'gun' has the same arrangement (at least on the two I have) where the high pressure air line passes through the gun and flows past a port in the media line and draws the media into the airflow. That same suction past the port in the gun is what is drawing air through the media tube end and 'picks up' the media to feed the gun. .......clear explanation, huh?

Ray

 

Kinda what I figured. I found one that is very similar to mine. Of course, I didn't pay this for mine. https://www.fastenal.com/products/details/0829160

 

I used the pick up tube from T P tools in my home made blaster and it works GREAT

 

1;13 mark..."Here's the caulk, any caulk will do" I'll bet.

 

I noticed that too! Pronunciation is important.... I bet that guy uses duck tape as well.

 

I have several cabinets that I run different media thru each one . I bet that the large glass media is your problem. The media is clogging up in your gun and to large to pass through with the size of tip that you have .
Vic

 

When using a shop vac with a cyclone bucket it might not be too much of a concern. Any gaps or leaks will probably suck air in not out. The cheap HF gaskets should be enough.

 

I have tried different sizes of media. I need to start over and see what I can figure out. I am trying to buy a new compressor soon. That will be a good place to start.

 

I think you are describing drip legs for bleeding off the system. These get rid of large amounts of water. You need actual moisture filters..probably one just outside the tank and then another just before going into the cabinet. They remove the left over moisture and when it comes to media blasting, more filtering is better........

 

You may need to actually take the gun apart yourself and look inside where the media is siphoned up into the gun at the "Y" . I have seen where something larger than the media has been sucked into the gun or a small piece of paper from the media bag has gotten stuck in there .
Try this , take the suction hose off the gun , then pull the trigger with your finger over that fitting , you should feel a slight suction on your finger , if not your problem is in your gun.
Vic

 

Once all you guys get your blasters working properly, you might be interested in protecting the glass you are looking thru. They sell rolls of CLEAR mylar. Friend gave me a free roll thats about 12.5" wide. They sell them on Ebay for about $25 for 12' of it. What I have is .007 thick. I looked on Amazon and found some 40" x 25' x.005 I ordered some and I figure I can cut it into three pieces 13.333 wide. The extra width won't hurt a thing. The glass in my blaster is 24" long, so I figure that gives me about 36 replacements.

You make a little holder on one side of your viewing window and a long rod to go thru the center of the roll. Works kinda like a toilet paper holder mounted sideways. Remove your glass and pull a section of mylar out to cover the hole where the glass was. Then put the glass back. Its best if it is wider than the actual glass so when you put the bracket back on the glass, the mylar sticks out top and bottom. When it gets cloudy, remove the glass and unroll some more.
Might need a little punch to make holes in it to clear the bolts. Mylar isn't cheap but its a lot cheaper than buying glass.