Media blasting

So I recently purchased a 40lb Harbor Freight blast cabinet. I have read around for some info on what media to use for what purpose.

Most places say using a round glass bead media is good for what I want to use it for, which would be stripping paint on/or corrosion off aluminum car parts, ie valve covers, bell housings, etc.

Started today with 80 grit Harbor Freight glass bead media and tried to do some stripping of old paint on a TRD supercharger for a 5VZ that is very loose due to corrosion destroying the bond.

Somewhere I’d gathered some information stated start at low pressure, 50-60 psi, but it had zero effect at stripping the paint, even in places it’s already lifting.

I then went all the way up to 110 psi, still, very little effect.

My thinking is the gun setup that came with the blast cabinet isn’t working well, has the siphon pipe that is dropped into the bottom of the hopper.

Everything is hooked up correctly, even installed a regulator mounted to the cabinet inline with the gun.

I am going to install a gravity fed metering valve to get rid of the pickup tube so hopefully things work better.

My question is does anyone have any tips for blast media? Think of anything I’m doing wrong? From experience, should the glass bead get the job done in this situation or should I maybe think of trying aluminum oxide media or something else?

Note: these are not my pics, borrowed from a guy on YouTube who was doing a vid on all his mods, but same cabinet

 

Nothing to add, but hope to one of these days.

What I mean is, there are a few guys that have posted specific media they run after having the exact issue you're running into (in my CNC groups).

Something about it being too big or something and impeding airflow among other things. That and adding a nice bright light inside the cabinet as well.

If I run into those posts I'll report back.

 

The glass beads may be a bit large, pressure low , not enough (air) volume.

OR you may need a harder sharper media.

Sand blasting is like that, mostly not like the book. You need try messing with parameters. Aluminum oxide/crust/paint may just look at with rounded glass media..............

 

How many cfm is your compressor?

You need around 8 cfm or more.

 

Depends on the paint you're trying to strip and the metal it's on. Glass beads don't have a lot of cutting power, but they leave a nice finish. They work great to strip Al scuba tanks.

I used 70-80 grit aluminum oxide to strip well adhered paint and anodizing. Have to be careful with it on aluminum because it will make gouges.

My go-to media was playground sand sifted through a screen. It's cheap, and has slightly less cutting power than Al oxide.

I had a non-cabinet Harbor freight sand blaster. It was hard to set up, I had to do a lot of fiddling with valves, pressure setting and finding the correct nozzle size, but eventually it worked great.

(yes, I used a full face respirator with the sand, silicosis is bad)

 

Glass bead is not very abrasive. Pick up some Garnet and it will work faster. Also air quality matters, you need completely dry air and a lot of CFM. We run a 6cft pressure pot at 240cfm and could still use more air. When it comes to blasting you want about 3 to 5 times the CFM you think you need.

 

Big rule / reminder.........Don't shoot your window!!!

 

Thanks for the replies, all things I need to look into. May be the compressor isn’t up to task. It’s a Craftsman 25 gallon but need to look into output.

Sounds like it’s possible a pressure pot would help and to try aluminum oxide.

 

So I put in a metering valve assembly to ditch the crappy suction tube on the harbor freight gun. Also bought a dryer assembly. Put in maybe 20 lbs aluminum oxide media, tried to get things going.

The compressor is a 25 gallon Craftsman, specs read directly from label- 150psi, 1.8 hp, 10.4 cfm displacement, volume of 7.4 scfm at 40psi/5.8 scfm at 90 psi.

I have it set at about 110psi. I also shortened the hoses so the distance the air has to travel is about 6 ft from the compressor to the dryer, then maybe 3 ft from the dryer to the regulator, 2 ft from regulator to the gun.

It now won’t spray ANY media, as an additional note, it wasn’t operating with the suction tube before I emptied the hopper and installed the metering valve.

There is now media in the low point of the siphon hose, and I’ve adjusted the metering valve from full open to full closed and points in between to adjust things, nada.

I’m hoping it’s the crappy harbor freight gun. l bought a small capacity Skat Blast gun, US made, so I’m hoping that’s it. If not, it’s gotta be the compressor, but seems strange it won’t spray any media at all. The paint is loose enough on the supercharger and the air flow is strong enough coming out of the gun that it’s blowing the paint off with air alone.

I’m frustrated, but there’s no stinking way I’m returning the whole cabinet, took too long to assemble and the cabinet doesn’t intuitively seem to be the source of the problem, correct me if I’m wrong, but how could it?

I’ll report back with good news hopefully after I get the new gun installed.

 

You added a dryer, and now it's not even pushing any media?

Any filtering you add acts as an inhibitor, whether it's a coalescing filter, refrigerated dryer, etc it'll kill your CFM's.

Got another air compressor you can run with your current one?

 

Actually you’re giving me a good idea to see if running the compressor directly to the regulator might work.

I had a single stage dryer installed from the beginning, switched to a two stage.

I have another compressor, more for running nail guns, 2 hp 4 cfm at 90 psi, twin stacked tank, I could make a double male splitter and try running both simultaneously. My thing is, I’m sure people have run this setup from harbor freight with less compressors, I think it’s the gun.

 

When you trigger the gun, does the siphon tube suck in the material? It sounds like that's where the problem is. Check to see if there's vaccuum there when the trigger is depressed. I had the same blast cabinet from HF back in the day and didn't have any problems running the system as is without a dryer. I also used glass media on some motorcycle parts without issues.