blasting - pressure and flow - and setup (what's best on domestic power?)

[julianf]

I have a 14 cfm compressor.
I bought one of those machine mart venturi style guns.

It was pretty damn poor. I reckon a hand brush was about as effective.

Now was this due to the syphon style gun, or the compressor?

I would rather have 30 seconds of power, and then have to wait on recharge, than 20 mins of wasted time! But on this setup, it wasnt as if the performance dropped off as the tank emptied - it was rubbish from the start.

So is this a flow issue, or are those syphon fund just no good? And is it worth building a pot in a domestic setup?

Also, when I've finished it, I'll have another compressor, so, if need be, I can get more flow, but at 8 bar max, rather than the 10bar that the existing unit maxes out at.

I don't know if it's pressure or flow that I need though, or if the setup is just all wrong.

Can someone advise me? : )

 

[rtbcomp]

Go for a pot.

The pressure needed to drive a "domestic" pot is about 90psi so your 8 bar will be ample, but you do need the flow - the bigger the nozzle the more cfm required.

I had one of those MM blast guns and threw it away after about a week. I have a one from Anglo-Scott abrasives which is much better but not as good as a pot. I use the gun for going over the bits I miss after using the pot.

 

[brightspark]

get a pot with a 3 mm jet and preferably get another compressor and use both together when blasting . they work quite well on over 20cfm @ constant 90psi

 

[AndyStobbs]

Julian, what did you find let your gun down most?

I have a cabinet and venturi style gun but the flow of grit is very hit and miss. Generally good at first pressing the trigger, then within a moment no grit just air. Upon re-triggering the flow of grit is restored. Meaning constantly pulsing works best but wastes loads of air and time.
I ran the gun once with the pipe just buried in a drum of grit and it was fine, but seems to struggle with picking up grit from the bottom of the cabinet.

 

[rtbcomp]

Could be you haven't enough air, the grit is blocking the pick-up tube or the grit isn't falling down into the space left when some grit is picked up.

Mine worked best with the end of the pickup tube just below the surface of the grit.

 

[brightspark]

heres one solution mines simlar and overcomes the problem of pulsing u can also fit a tap to restrict the amount of air being sucked in from atmosphere http://www.nagara.co.uk/Blast2.htm

 

[AndyStobbs]

Mine is not like that at all. Maybe that's half of the problem, not having a pick up tube.
The bottom of my cabinet is basically an upside down pyramid. With the suck pipe connected at the bottom.

The air supply is ok, never dropping below 90psi.
Will have to apply myself and have a dabble. Thanks

 

[brightspark]

Mine is not like that at all. Maybe that's half of the problem, not having a pick up tube.
The bottom of my cabinet is basically an upside down pyramid. With the suck pipe connected at the bottom.

The air supply is ok, never dropping below 90psi.
Will have to apply myself and have a dabble. Thanks

Mine is not like that at all. Maybe that's half of the problem, not having a pick up tube.
The bottom of my cabinet is basically an upside down pyramid. With the suck pipe connected at the bottom.

The air supply is ok, never dropping below 90psi.
Will have to apply myself and have a dabble. Thanks

a quick fix , if u drill a smallish hole in the side of the pickup pipe just above the media height it will let air in and stop the pulsing and still pull the grit up

 

[Wallace]

Is it one of these guns Julian? if so, the nozzle is 6mm and needs over 15cfm flow and would probably be better on your compressor at 2.5-3mm.

Julian, what did you find let your gun down most?

I have a cabinet and venturi style gun but the flow of grit is very hit and miss. Generally good at first pressing the trigger, then within a moment no grit just air. Upon re-triggering the flow of grit is restored. Meaning constantly pulsing works best but wastes loads of air and time.
I ran the gun once with the pipe just buried in a drum of grit and it was fine, but seems to struggle with picking up grit from the bottom of the cabinet.

I had the same on a Clarke cabinet and now have it sat in the top of the grit where it works better.

 

[Gareth J]

I use one of those ^^ guns with (an ancient) 14cfm Clarke compressor and it's fine.

But I have chopped the pipe so it's only about a foot long, that way, I can jam it into wherever the pile of sand is in my cabinet and it's not so far for it to lift. Also, useful to be able to put your finger over the end (tightly) and blow back the tube in case it gets jammed. Likes more pressure, 100psi plus and you're cooking on gas.

It's pretty fussy with media, doesn't like any damp, tissue or big paint/rust flakes.

6mm hole is a tall order for the compressor to run and it won't keep up. I plug another small compressor inline if I have a lot to do which helps, but it's still not enough to run continuously.

The whole gun kit is about £12-15 on eBay with spare nozzles. The gun and nozzles wear plenty fast but cheap enough to be able to be treated as diaposable

I didn't get on with a small paint sprayer pot type.

Ultimately, I'd like to get a proper pot... Actually, ultimately, I'd like to never sandblast anything again.

 

[AndyStobbs]

Actually, ultimately, I'd like to never sandblast anything again.

Amen.
I can stand at the parts washer all day but 10 minutes at the blasting cabinet and I'm fed up.

 

[brightspark]

Amen.
I can stand at the parts washer all day but 10 minutes at the blasting cabinet and I'm fed up.

only because its a suction gun . use a pressurised pot with a decent air supply

I find washing stuff tedious, whereas I find blasting much more satisfying - the change in condition just does it for me...



Sometimes I think I'd like to not have to work on things, like just be able to have everything shiny-new.

But if I didn't have rusty old crap to cobble up what would I do with my time? I'm quite sure it would lead to a sore arm and blisters

is that a certain type of cramp beginning with a w