Small blasting cabinet with small compressor.

[gazzarose]

Evening all,

I'm about to start a restoration on a motorbike, nothing exciting just a 92' Suzuki Dr350, and my dad has just bought an old GasGas trials bike. Both of them will need so cleaning up of aluminium parts such as cars, engine casings and brake calipers as well as the odd steel bracket. Neither are particularly rusty, mostly old paint removal on steel parts and dirty or oxidised on the ali parts.

I've seen the small cheap blasting cabinets for just over £100 and the size would be perfect for the jobs in kind. The only concern I've got is my compressor. I've got a 1.5hp 25ltr Sip on that is around 4cfm FAD, but also an old similar size unit hanging about in work unused that I could tie in as well, either for just its air capacity or for the compressor part as well. I know I'd still be short on CFM to run constantly, the cabinet specs say around 10CFM, but if I don't mind waiting for the air to build back up, would I be fine for doing small parts? I don't intend doing any of the big parts like the frame, I'll likely be getting that powder coated so the coaters can blast that, but its all the little parts that that will be handy to just do at will.

This is the cabinet I was looking at
https://www.sgs-engineering.com/ssb100-shot-blast-...

Will the mainly Ali blasting I'll be doing, I'll probably go with glass beads, is it a case of start with a courser grade and work up to the finer grade, or does the grade mainly dictate the finish and not so much the ability to clean?

Any tips would be great, thank you.

[LunarOne]

I'm interested in that cabinet or the one up from it, and I was going to use my freebie 150L 15CFM compressor. I've been doing quite a lot of "research" into sand and shot blasting and watched countless videos on the subject, many of which are U.S. based and centred around their Harbor Freight cabinets. Most of the videos stress that you need a lot of air volume to make the process work reliably so I think you're going to struggle with a 4CFM compressor. You might get away with teaming two of them together, but then I imagine it's going to be a slow and laborious process as the air volume isn't going to pick up large volumes of media. The thread where I discussed it suggests that you need dry oil-free air, and you may also need a dust extractor if you want to see what you're doing!

See https://www.pistonheads.com/gassing/topic.asp?h=0&...

[gazzarose]

Thank you for the reply.

Both my new compressor and the one in work are oil free, and I saw a few guys putting a water Separator At the input to the cabinet. I'd also seen the issues with the dust coming out the side, and was thinking I could connect the good old Henry to the side. I think what I'll do first is have a check that the old compressor in work actually works before I go much further. I can't remember why it's out of use, I know we acquired a newer one, so maybe the old one is dead, in which case it'll have a new life as just an extra tank for my garage. My father in law is an upholsterer and has a couple of small compressors hanging about, so I could add 1 or more into the party, although that's probably gett all a bit heath Robinson then!

[droopsnoot]

A mate of mine used to have a Guyson blasting cabinet and a reasonably big compressor (three phase, probably 500l tank) and when I was using it, the compressor would be running all the time. I considered buying the blast cabinet when he recently closed his workshop down, but I figured that my 3hp 50l compressor would just be incapable of doing anything with it, and I couldn't justify a bigger compressor, nor have a three-phase one. That was a bigger cabinet, of course.

That said, cheers for the link, that looks interesting at the price, though I haven't compared prices. I wonder if it's a suction blaster though, in which case look out for a lot of stoppage time to unblock things.

Edited by droopsnoot on Wednesday 16th February 09:36

[tapkaJohnD]

The arithmetic seems simple. CFM needed is 10L/m, but compressor has a 25L tank and a 4L/m capacity. 25/10 + 4/10 = 2.9 mins, so your cabinet will run out in three minutes! Even ignoring the Heath Robinson aspect, does adding more small compressors add up like that? Don't know.

John

[LunarOne]

tapkaJohnD said:

The arithmetic seems simple. CFM needed is 10L/m, but compressor has a 25L tank and a 4L/m capacity. 25/10 + 4/10 = 2.9 mins, so your cabinet will run out in three minutes! Even ignoring the Heath Robinson aspect, does adding more small compressors add up like that? Don't know.

John

I'm not sure it quite works like that, because the free air delivered rating is only at the maximum pressure. Most 24/25-litre compressors go to 8 bar maximum, but when the receiver is half drained, the pressure will also be half as much and the FAD also much reduced. So even if you could sand blast with 4CFM FAD, you could only do it when the receiver is at maximum pressure, which it will only be if you're not blasting. Any other time, you'll be below max pressure and below maximum FAD. Adding more compressors will increase the total FAD but will not increase the maximum pressure that can be achieved. And when delivering 4CFM each, both compressors will drop below 8 bar very quickly, indeed if my Wold 24-litre compressor is anything to go by, the pressure will drop to half its max of 8 bar in just a few seconds, by which time the FAD will be far too low to power a blaster. That's one of the reasons I wanted a big compressor, but even my 150L 15CFM compressor seems barely up to the task.

Also beware not to confuse CFM with litres per minute. 4CFM = 113.2L/min. So if you could ignore pressure and hypothetically maintain 4CFM or 113L/min FAD until the receiver were empty, a 24 litre tank would be empty in 13 seconds. That's with the compressor off and not refilling the receiver. If the compressor is running, then I'd imagine you'd get a little longer, but not much!

[paintman]

I had a play with one of the small spot blasting guns a few years ago with a small compressor (2hp 50 litre)

Would have done better throwing the medium by hand.
'Meaningful' delivery with full tank (straight after motor stopping) was a couple of seconds, not even enough to take the shine off the paint never mind remove anything.

The cabinet you list requires AT LEAST 10cfm at a SUSTAINED 8 bar (116psi). That's big garage size compressors, not small diy types which simply aren't capable.

Edited by paintman on Wednesday 16th February 14:10

[Hi]

I have a blasting cabinet I got from amazon, coupled with a massive 3 phase 42cfm compressor and the sandblaster is still rubbish. I say rubbish, it works, but takes forever to do anything of any size.
I'm trying to find an affordable pressure pot blasting cabinet as I think thats the only option for a decent machine which can do wheels etc.

(I've never tried a wheel in my cabinet, but given the time taken to do other parts I imagine a single wheel would take 1-2 hours)

[Hi]

As an example, this ecu bracket and dipstick tube took about 45 mins to clean up in the sandblaster.

And then 10 mins to powdercoat! If you are restoring a motorbike I can highly recommend the easycoat powdercoating kit from electrostaticmagic (no affiliation) as it works brilliantly and I just use a household oven I got free from gumtree to bake the parts (180c for 20 mins).

[peterperkins]

You basically need the biggest compressor/receiver you can afford with a minimum of 14cfm/100L to make it reasonably practicable.

14/15CFM ~3kw is about the max you can get from a standard 13amp socket.

[Hi]

The powdercoating gun really is good (and only requires the tiniest bit of air to run), i've done a lot of parts with it but nothing large as I just have a household oven.

I find it takes ages to blast anything, maybe 45 mins was a bit high, closer to 30 min perhaps (it was a few months ago). Yes I use crushed glass, it was the most abrasive medium I could find.
I think both are issues, the area out of the gun is very small and the ferocity is crap, the pickup of medium from the tube is very inconsistent etc. I'm sure there are things I could do to imorove it but I think I'd rather put the money towards getting a pressure pot machine.

[LunarOne]

You might be able to improve the airflow and make the blaster much more effective, but you'll probably need an even greater air capacity to really make use of it.

[gazzarose]

Hmm, looks like I need to do some thinking. Annoyingly I only had my compressor for Xmas, a d at the time thought a small one would be fine for just tyres and blowing through the odd carb. I'll have to see if there are any other compressors I can aquire, otherwise I may have to farm any blasting out. I can't really justify not just the money, but the space of a bigger compressor.