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> Question about Media Blasting and Compressors, Which is the correct combination?
ellisor3
post Jul 23 2014, 09:28 AM
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I recently bought a media cabinet and I already had a 30 gallon compressor. I started a trial run with the cabinet on a pair of calipers. I got no where. The media barely put a dent in the caliper paint. I sprayed for 30 minutes and completed an area about 3"x3". The media was glass bead 70 grit and the compressor was set at 100 psi.

I believe my issue may be the amount of air the compressor moves, and not the PSI. What is the recommended amount that will work on brake calipers? My compressor is a 5.2 CFM.

Is glass bead appropriate for enamel paint?
What size compressor do I need?
What is everyone else using?
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TheCabinetmaker
post Jul 23 2014, 09:41 AM
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What are the cabinet air requirments or recommendations?
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CptTripps
post Jul 23 2014, 09:47 AM
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Are you sure you are using the right media? What is the pressure set at?

Mine is a HF 21gal that only kicks out about 4CFM and I can blast the shit out of stuff...in short bursts
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bdstone914
post Jul 23 2014, 10:12 AM
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A long or small diameter hose from the compressor will reduce the pressure at the gun. I had that problem with impact tools. Made a 1 /2 inch Id hose and made a world of difference.
I tried to blast powder coat paint from Brembo calipers with no success. Have you tried blasting any dirty or rusted parts?
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ellisor3
post Jul 23 2014, 10:51 AM
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QUOTE(The Cabinetmaker @ Jul 23 2014, 11:41 AM) *

What are the cabinet air requirments or recommendations?


It is a HF 40 Lb cabinet. It says working PSI is 125 but the recommended PSI on the Glass Bead is 40-90 LBS. I have been running it at different pressures to check. I ran it at 60, 80 and 100 with little change in results. The inlet hose is 1/4 inch.
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Brian_Boss
post Jul 23 2014, 10:51 AM
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QUOTE(ellisor3 @ Jul 23 2014, 10:28 AM) *

My compressor is a 5.2 CFM.


I think this is the root of the problem.

No idea what sort of cabinet/gun you are running but the smallest blast gun nozzles I remember seeing use > 10 CFM.

QUOTE(ellisor3 @ Jul 23 2014, 10:28 AM) *

Is glass bead appropriate for enamel paint?
What size compressor do I need?
What is everyone else using?


1) If you don't have a pressure gauge at the cabinet, add one (better yet, gauge and reg). Without it you really don't know what the PSI at the gun is.
2) If you are trying blast continuously with that setup, you are almost certainly emptying the tank and running at something below the set reg pressure.
3) If you really are blasting with glass beads at 100 PSI, you are really hammering the blast media. I try to stay under 50 for best media life. Once the beads get pulverized, they are even slower cutting.
4) Glass beads, while leaving a nice surface finish, are not the fastest for stripping paint. For steel that will be repainted, I switch to garnet or Al Oxide media.


FWIW, I have a 5hp two stage rated ~18CFM @ 90 PSI and it still runs almost continuously while blasting.

Hope this helps
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ellisor3
post Jul 23 2014, 10:52 AM
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QUOTE(CptTripps @ Jul 23 2014, 11:47 AM) *

Are you sure you are using the right media? What is the pressure set at?

Mine is a HF 21gal that only kicks out about 4CFM and I can blast the shit out of stuff...in short bursts


I have Aluminum Oxide as well as glass bead, and neither seem to work all that well. The pressure has been set a 60, 80 and 100 without much results.
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ellisor3
post Jul 23 2014, 10:55 AM
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QUOTE(bdstone914 @ Jul 23 2014, 12:12 PM) *

A long or small diameter hose from the compressor will reduce the pressure at the gun. I had that problem with impact tools. Made a 1 /2 inch Id hose and made a world of difference.
I tried to blast powder coat paint from Brembo calipers with no success. Have you tried blasting any dirty or rusted parts?


I actually moved the compressor next to the cabinet and used a 3ft hose to attach the two. I to am trying to blast Brembo calipers. I have tried some other parts, the results are better but not by much.
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ellisor3
post Jul 23 2014, 11:01 AM
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QUOTE(Brian_Boss @ Jul 23 2014, 12:51 PM) *

QUOTE(ellisor3 @ Jul 23 2014, 10:28 AM) *

My compressor is a 5.2 CFM.


I think this is the root of the problem.

No idea what sort of cabinet/gun you are running but the smallest blast gun nozzles I remember seeing use > 10 CFM.

QUOTE(ellisor3 @ Jul 23 2014, 10:28 AM) *

Is glass bead appropriate for enamel paint?
What size compressor do I need?
What is everyone else using?


1) If you don't have a pressure gauge at the cabinet, add one (better yet, gauge and reg). Without it you really don't know what the PSI at the gun is.
2) If you are trying blast continuously with that setup, you are almost certainly emptying the tank and running at something below the set reg pressure.
3) If you really are blasting with glass beads at 100 PSI, you are really hammering the blast media. I try to stay under 50 for best media life. Once the beads get pulverized, they are even slower cutting.
4) Glass beads, while leaving a nice surface finish, are not the fastest for stripping paint. For steel that will be repainted, I switch to garnet or Al Oxide media.


FWIW, I have a 5hp two stage rated ~18CFM @ 90 PSI and it still runs almost continuously while blasting.

Hope this helps


I have tried it at lower PSI's (60-80) and I have not gotten any results
I also have Aluminum Oxide and it works a litter better but not by much.
I moved the compressor next to the cabinet and ran a 3ft hose to the cabinet to reduce the distance, but it did not seem to help.

I have started to look at compressors with much larger CFM ratings and they are a huge jump in cost.
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toolguy
post Jul 23 2014, 12:55 PM
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Most decent shop grade blast cabinets need a minimum of 15CFM and a constant over 100 psi. .
My Professional Curtis double stage compressor 20 CFM can barely keep up with my cabinet and drops to 90 psi running continuously on big blast jobs.
That is also affected by the size of air jet and nozzle your gun has . . Best to use a single stage compress , not double, on a blast cabinet as it will keep up pressure better. .
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Brian_Boss
post Jul 23 2014, 02:46 PM
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Can you do a quick test on a test piece that has a known paint on it?

As a baseline, I just popped out to shop and tried two things. First was a scrap of 914 body (factory paint and primer and second a can of rustoleum.

Holding the gun steady 3-4 inches from the surface, it took a count of four to hit steel with glass beads at 50 psi. Cranked it up to 80 PSI and same result in 2 seconds (this was the 914 piece. The rattle can was stripped as shown with as short a blast as I could do, probably 1 second at 50 PSI.

Attached Image

QUOTE(ellisor3 @ Jul 23 2014, 12:01 PM) *

I have started to look at compressors with much larger CFM ratings and they are a huge jump in cost.


If the compressor has cycled off, the blaster will work as well as it ever will for the first 30 seconds at least. If you are not getting good results for that first thirty seconds, there is an issue beyond the smallish compressor.

BTW, are these the alfa brembos, boxter caliper, 944 turbo, something else?? Just trying to get an idea of what you're up against.
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Brian_Boss
post Jul 23 2014, 03:08 PM
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More thoughts...

Can you see media coming out of the gun? Obviously some is but is it a solid stream, does it fluctuate, etc?

I just noticed you're in Florida. If your media is damp, that will cause problems with feeding.

Have you tried varying the amount of media in the hopper?

Way back when, I bought a HF sandblaster (no cabinet, just a bucket of media on the driveway). I'm pretty sure it used the same or similar gun as your cabinet. It was very fussy about media feed. I ended up making a new pickup tube.

Sorry to belabor this but I'm curious now. I know a lot of people are getting decent results from that cabinet, even with marginal air. We just need to figure out what's wrong.



P.S. According to HF web site, "Average Air Consumption 9.5 CFM @ 90 PSI" so you're looking at a duty cycle of less than 50% (i.e pull trigger for 30 seconds, wait 40 seconds ).
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cpavlenko
post Jul 23 2014, 03:46 PM
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Try 180 A.O., That's what I use. Leaves a nice finish. (Aluminum Oxide)
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ellisor3
post Jul 23 2014, 06:38 PM
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QUOTE(Brian_Boss @ Jul 23 2014, 04:46 PM) *

Can you do a quick test on a test piece that has a known paint on it?

As a baseline, I just popped out to shop and tried two things. First was a scrap of 914 body (factory paint and primer and second a can of rustoleum.

Holding the gun steady 3-4 inches from the surface, it took a count of four to hit steel with glass beads at 50 psi. Cranked it up to 80 PSI and same result in 2 seconds (this was the 914 piece. The rattle can was stripped as shown with as short a blast as I could do, probably 1 second at 50 PSI.

Attached Image

QUOTE(ellisor3 @ Jul 23 2014, 12:01 PM) *

I have started to look at compressors with much larger CFM ratings and they are a huge jump in cost.


If the compressor has cycled off, the blaster will work as well as it ever will for the first 30 seconds at least. If you are not getting good results for that first thirty seconds, there is an issue beyond the smallish compressor.

BTW, are these the alfa brembos, boxter caliper, 944 turbo, something else?? Just trying to get an idea of what you're up against.


Thanks for the advice, that is a good test, I will try that tomorrow.

The calipers are 993 twin turbo Big Reds. The enamel is pretty thick to begin with.
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ellisor3
post Jul 23 2014, 06:47 PM
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QUOTE(Brian_Boss @ Jul 23 2014, 05:08 PM) *

More thoughts...

Can you see media coming out of the gun? Obviously some is but is it a solid stream, does it fluctuate, etc?

I just noticed you're in Florida. If your media is damp, that will cause problems with feeding.

Have you tried varying the amount of media in the hopper?

Way back when, I bought a HF sandblaster (no cabinet, just a bucket of media on the driveway). I'm pretty sure it used the same or similar gun as your cabinet. It was very fussy about media feed. I ended up making a new pickup tube.

Sorry to belabor this but I'm curious now. I know a lot of people are getting decent results from that cabinet, even with marginal air. We just need to figure out what's wrong.



P.S. According to HF web site, "Average Air Consumption 9.5 CFM @ 90 PSI" so you're looking at a duty cycle of less than 50% (i.e pull trigger for 30 seconds, wait 40 seconds ).


I do have a filter built on to the cabinet, so the media is very dry. I do get a pretty constant stream from the gun. I changed the siphon hose to one that is less prone to kinking and I reduced the amount of product in the hopper. That did get somewhat better results. Should I use a larger pick up tube?

Thanks for all the help
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Jeffs9146
post Jul 23 2014, 07:02 PM
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I had a similar problem with my compressor and it turned out the adjustable pressure regulator wouldn't let enough CFM through it to use the tools I needed to use.

I ended up adding a seperate full pressure hose connection before the regulator! I use the regulator for things that don't require high CFM's!
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Jeff Hail
post Jul 23 2014, 08:46 PM
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Like the famous SNL skit.. "Gotta have more cow bell". You will need CFM to push any media fast enough to get it airborne.

Aluminum Oxide is pretty useless for blasting parts other than aluminum. After one cycle on hard parts the media profile turns round, beats itself into dust then its done. Its soft material which just does not strip well.

On the other hand its a dangerous material once it becomes pulverized into fine dust, leaks from the cabinet and lands everywhere.

I didn't believe the danger until one of my special effects buddies put on a pyro show to prove a point. It didn't take much. Google it and you will see why it really should not be used for heavy stripping. AO dust inhalation hazard is the least of your worries. Once you get enough you wont have any worries at all.

If you want to remove paint, crud whatever fast try Dupont Starblast comes in three grades from fine to course depending on the finish texture you are attempting to achieve. Starblast XL really turns out nice and uniform.

You can always shoot a finer media after initial strip with glass, ceramic, walnut, soda for finer degrees of surface finish.

For aluminum parts walnut, corn cob media and soda work very well.

If you have way too much time on your hands and like standing around for hours holding your gun by all means go with the Aluminum and breath deeply.
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dan_the _body_guy
post Jul 26 2014, 04:20 AM
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are we 100% sure its enamel paint and not powdercoating youre attempting to strip? enamel paint is fairly soft and should blast off pretty quick with just about any media. it sounds like powdercoating youre fighting against. try hitting it with a torch to burn the coating then blast it off with a course garnet
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