Best blasting pressure?

[rcx132]

I've tried a few blast pressures with my pressure pot and F60 alu oxide and a 3.5mm tip. Seems that 45 psi is working well, I'm getting most of the effect without the parts getting hot. My 18 CFM compressor is keeping ahead with this setup. I have a second 14 CFM compressor which kicks in if the main compressor can't keep up, and it's not even kicking in.

E.g. if I go above 45psi, e.g. 90 psi, I don't get that much more blast area, but the parts get hot. lf I go lower then the blast radius decreases.

 

[rtbcomp]

It's surprising how much heat is generated, keep the nozzle moving about over the workpiece and attack at a low angle to reduce the heat. Doing panels can be a nightmare, I just blasted the edges and any creases/folds and did the flat bits with a Polydisc, if possible using paint stripper first.

 

[brightspark]

depends on what u are blasting. also media size panels low pressure anything else 90+ for fast efficient cutting

 

[armalites]

There are so many factors at play, if you have something with an easy surface to clean keeping the nozzle away you'll find the overspray will do a good job of a pre blast. Sometimes you just need to be close. Even the atmosphere can affect things, sometimes everything goes lovely other times it feels like you are fighting an uphill battle.

My eldest had me blasting a scrap bike frame this evening so he can rebuild a bike, I made him degrease if first but there were some stickers, they took ages to clear, paint was gone in no time.

 

[Streetwerks]

Most of my blasting is done under 3psi, blasting should just be for prep in my opinion. Use chemicals to remove coating, much better finish with less effort

 

[rcx132]

Most of my blasting is done under 3psi, blasting should just be for prep in my opinion. Use chemicals to remove coating, much better finish with less effort

I thought this to. Four brackets that even at 90psi the paint would barely shift. But an hour in paint stripper and they are done. Tomorrow a quick blast to remove residue and done.

 

[rcx132]

Most of my blasting is done under 3psi, blasting should just be for prep in my opinion. Use chemicals to remove coating, much better finish with less effort

3 psi or 30 psi ?

 

[armalites]

I thought this to. Four brackets that even at 90psi the paint would barely shift. But an hour in paint stripper and they are done. Tomorrow a quick blast to remove residue and done.

How much grit flow do you have? Mine would be ripping stuff to bits at 90psi

 

[Streetwerks]

3 psi or 30 psi ?

3 bar, auto incorrect strikes again!

 

[Streetwerks]

How much grit flow do you have? Mine would be ripping stuff to bits at 90psi

Wears the cabinet away fast for sure, strip before blasting!

 

[james butler]

does having /using a smaller nozzle make a difference to required air pressure? or is it just flow thats more important?

 

[rcx132]

How much grit flow do you have? Mine would be ripping stuff to bits at 90psi

It does rip stuff at 90 psi, and makes things hot. But on these particular brackets the paint was shifting very slowly!

3 bar, auto incorrect strikes again!

That's 43 psi, so same as I found works best

does having /using a smaller nozzle make a difference to required air pressure? or is it just flow thats more important?

A smaller nozzle does two things:
1/ Smaller blast radius
2/ Requires less compressor air flow, i.e. less CFM, i.e. a smaller/weaker/cheaper compressor.

Here is a useful table, say you want to blast at 45 psi using a big 3.5mm nozzle. That means you need a compressor above 10cfm and below 14 cfm. Of course this table is probably a bit optimistic, I can't imagine a 14 cfm compressor keeping up with the value this table gives!

 

[rcx132]

Today, as a test, I only ran my 14 CFM compressor as that's what most people have. It kept up with blasting at 45 psi. So in my experience you can blast with the big 3.5mm nozzles with a 14 CFM single phase compressor. Appreciate others have said they can't, I don't know what we're doing different then. Maybe also depends how much wear is on the compressor?

Should also add, I've been blasting auto parts, so brackets, brake drums, calipers etc. I will do some bodywork blasting later but I only have rust in areas that won't easily warp.

 

[brightspark]

running at 45 psi is very inefficient. a lot of time wasted and more media used. after blasting a fair few hundred car wheels and a lot of motorcycle frames and parts and my pot is copied of the clemco mini pot using 6mm jet and a 90cfm comp I have got the general idea of what works best for speed and profitability the pot I have with a 3mm jet and using a 28cfm comp is ok for personal use if your in no great rush . herehttp://www.blast-one.com/technical-information/abrasive-blasting/nozzle-pressure-vs-blasting-efficiency

 

[rtbcomp]

^^ True but if you're doing a soft material like aluminium either reduce the pressure or hold the nozzle well away from the workpiece, it comes with practice.

 

[brightspark]

aluminium I used kiln dried sand and as u say held away from material so not to damage it just sufficient to remove surface corrosion or paint

 

[rcx132]

Today, as a test, I only ran my 14 CFM compressor as that's what most people have. It kept up with blasting at 45 psi. So in my experience you can blast with the big 3.5mm nozzles with a 14 CFM single phase compressor. Appreciate others have said they can't, I don't know what we're doing different then. Maybe also depends how much wear is on the compressor?

Should also add, I've been blasting auto parts, so brackets, brake drums, calipers etc. I will do some bodywork blasting later but I only have rust in areas that won't easily warp.

Ok correction, the 14 CFM compressor fell behind after a while...

 

[rcx132]

running at 45 psi is very inefficient. a lot of time wasted and more media used. after blasting a fair few hundred car wheels and a lot of motorcycle frames and parts and my pot is copied of the clemco mini pot using 6mm jet and a 90cfm comp I have got the general idea of what works best for speed and profitability the pot I have with a 3mm jet and using a 28cfm comp is ok for personal use if your in no great rush . herehttp://www.blast-one.com/technical-information/abrasive-blasting/nozzle-pressure-vs-blasting-efficiency

Dunno, at 90 psi the glass is quickly frosting and the nozzle is difficult to hold !! And the blast area doesn't seem to increase for me.

 

[brightspark]

blast aeria wont increase with pressure but will cut a lot faster and more efficient

 

[Streetwerks]

Im just peening with glass beads on pre wet blasted items so the low pressure gives a better sheen or giving profile with ao or grit whuch provides a better prepped surface than blasting at high pressure. High pressure is for coating removal or heavily rusted cast iron