View Full Version : BIY Sand Blaster Questions
01-14-2012, 02:20 PM
I'm researching plans on a sand blaster I'm about to build. I have these references:
Build Your Own Grit Blasting Cabinet .: Articles (http://www.ford-trucks.com/article/idx/5/007/article/Build_Your_Own_Grit_Blasting_Cabinet.html)
There are a few questions I have -
1. The grit reclamation. It appears the flat-bottom cabinet requires you to scrape the grit on the bottom toward the seive. SO... what is under the seive? Do you just let the grit fall into a bucket or something? Doesn't that mean a bunch of air escapes the bottom of the cabinet? Not fully comprehending that part. THe BIY sites don't really show that part. Should I plan to make a funnel out of sheet metal or something to put underneath the seive?
2. Exhaust Fans. It looks like a cheap-o bathroom fan connected to an outside-vented duct will work?
3. Sand input. I have a blaster nozzle type that is intended for use with a bucket. It has a siphon tube about a foot long that is attached to a hose. You stick the tube into the media, the hose to the gun, and blast away. Like this one:
I am thinking that to use this with a cabinet, the siphon tube will pass through a hole cut in the cabinet. Is there a way I can connect this siphon tube and bucket into the grit seive so that the used sand can drain into the supply bucket? I have a limitless supply of 5-gallon plastic buckets... it seems I could make the supply bucket and the seive reclamation bucket one and the same and save some effort.
Any other advice is appreciated.
01-14-2012, 03:12 PM
Here's how my commercial cabinet works. The entire floor is expanded metal grate with the four sides of the cabinet underneath that coming together at a point, like an upside down pyramid. At the bottom is a sliding door so you can drain the media into a bucket, usually because you are tring to find a dropped part. The pyramid is sealed, part of the cabinet. The pickup tube is like yours, mounted to the side of the pyramid with the end a few inches off the bottom. The top end just sticks up through the floor. At the top back corner is a small fitting that takes a large shopvac hose. That hose is connected to a SKATBLAST version of a shopvac that sits on top of a small bbl and has a huge canvas filter. The bbl slowly fills up with media, and when full you just dump back into the cabinet. There is also a moisture filter on the airline, the kind used for commercial paint booths. It has what appears to be a toilet paper sized roll of the brown paper towel they use in restrooms. After an hour or so, it is saturated and you change it out, letting the old one dry out. To save your trigger finger, the air valve is a floor mounted pedal, the gun flows air anytime it is supplied. Get the ceramic or carbide nozzles, they wear out quick.
Were I building one, I would try to copy that as much as possible, it works. If you don't make a funnel shaped reservoir under the floor and go with just a drain, I would mount something like a toilet flange under there with a short length of capped off pipe under. That would seal it, yet you could unscrew the cap to drain. Or mount your bucket under there and use it for the supply and return, with a drain valve in the bottom. You want all openings sealed except the exhaust, grit will exit every opening otherwise. I would also keep the media supply internal to the cabinet, the system will clog occasionally and the cure for that is to put a finger over the nozzle and give it a short blast, forcing air back down the pickup tube and clearing the clog. Also blows the media out of the bucket. I would use a cheapie/old shopvac for exhaust, preferably with the exhaust hosed to the outside to keep grit out of your space. Besides saving the grit, the constant vacuum clears the cloud of dust inside and makes it easier to see. A shopvac also has the motor outside the grit stream, something like a bathroom fan the fine grit blowing across the motor will eventually scrub the insulation off the wire coil, ruin the bearings, etc.
01-15-2012, 02:21 AM
I'll have to look at those two links better later.
I was going to mention the upside down pyramid thing like Kernel mentioned, usually the media just sets in the bottom of the cabinet and is siphoned to the gun from there. Even if you want to set a bucket under it your going to need a way to get the media to flow to the bucket or bottom, so some type of tapered bottom should be used under a grate style floor.
I think you could do this design with plywood too, if your making it from wood, just remember to keep the smoothest side inside.
If you make a closed cabinet without the bucket, you could put as small as a 3/4" - 1" pipe flange on the bottom with a short nibble and cap as a drain so you can drain off the media when it needs changed. A larger diameter pipe would be better but I think 3/4" would be the smallest I'd use. And remember to leave enough space under the cabinet to put something under it (like a 5 gal bucket) when you do drain it.
The bucket siphon setup can work in the cabinet, as mentioned use the piece of steel tube and attach it to the cabinet and leave the bottom end of the tube off the bottom a little.
For venting the dust, put the exhaust vent up high on the back or side, and kind of box it in on the inside so the air has to go in the box from the top before it goes out the vent. This will help keep the larger heavier particals from getting into your filter setup.
The HF cabinet my friend did up had a vent tube the size of a shop vac tube. He got a lid that fit on a 5 gal bucket that had two hose hook ups (the size of the shop vac hose) and this turned a 5 gal bucket & a shop vac into a wet filter just by adding water to the bucket. Never got much dust into the shop vac itself, but the bucket would get nasty if the cabinet was used hard. And don't just hook a shop vac up to suck out the dust, it will destroy the vac very quickly.
And you really don't need a powered vent setup, just a vent will work, but it does help alot to keep the dust down in the cabinet so you can see what your doing.
01-15-2012, 08:02 AM
With the directions for the blaster given by kernelkrink & coils that should work well, my take on the dust removal was a bit different! On the large harbor freight blast cabinet, I hooked a 2 1/2" flex hose between the cabinet & a 4" header made of heavy duty cardboard shipping tube & DWV plastic pipe fittings that went from just above the cabinet to the outside of the shop. The tubing went parallel with the wall to where it turned 90 degrees & went outside as plastic to prevent rain damage. At the 90 degree turn, I placed a T instead of an ELL to allow another smaller pipe to be placed inside the T facing downstream with the end of the smaller pipe just past the the turn in the T. A shopvac blower was hooked to the smaller pipe to force air across the stream comming from the cabinet to act as eductor. You will have to adjust the small pipe in the T to get maximum air flow across it, but it scavenges all the air out of the cabinet & blows the dust outside of the shop, leaving the shop free of silica dust & no equipment is placed into the dust stream to be destroyed! The cabinet stays clear during blast sessions with no problems!
01-15-2012, 10:07 AM
I'm not sure if a bathroom fan would create enough draw.
I bought a 13 gallon exhaust blower from HF.
It was really the only decent thing to create enough negative pressure
inside the cabinet to keep dust down.
I was using a shop vac until the wife gave me dirty looks. (it was hers)
So, an old shop vac works great too.
I use a couple of old cartridge air filters stacked atop each other to keep heavier grit from leaving cabinet
and entering blower system. Periodically remove filters and take them outside and tap the dust out.
Portable Dust Collector - 13 Gallon (http://www.harborfreight.com/13-gallon-industrial-portable-dust-collector-31810.html)
01-15-2012, 10:56 AM
Thanks for the info, really helps! I am thinking about making the bottom flat simply because I don't plan to use it much, so scraping the grit back into the bucket should be OK for me.
I plan to make it big enough so that it just fits under the table, and a flat bottom will let me store it under it. The storage is really my big concern because it is starting to get crowded in my garage. Based on measurements plywood on hand, that should be a 4x2x2 box.
Another question - I forgot I had some glass shelving stored away. The glass appears to be the same kind you see in display cases. I think about 1/4" thick. Would normal wear and tear scratch that glass up beyond repair? Or is scratching something to worry about only with plexiglass?
01-15-2012, 01:38 PM
You'll need to sheild the glass with a clear material like they use on NASCAR windshields,"tear offs" it's pretty easy to get. Secondly now, exaust fans that dosn't have a sealed "squrirel cage", the dust will eat the motor alive, and in short order. I used a marine bildge blower with mine, a squirrel cage type, not an inline type, cheap, works great and 12 volt. A pre filter isn't a bad call eaither. If you make a wood cabinet, it's best to line the back and sides with sheet metal, well below the blasting screen level, it won't take long to burn up the plywood otherwise, It will last along time if your just using bead blast, but courser medias will eat them up in no time, and for sure a ceramic tip blower. I'd seen a bench top one someplace that was reasonable but needed the ceramic tip type blower, I think it was like 89 bucks or something like that, plenty for recevers , small parts, ect and maybe even a short barrel? Can't recall where I saw it, some store flyer like NAPA or one of those I think. Check places that have body shop tools and supplys, they'll be able to set you up I'll bet, and generally better then HF as far as quality goes.
04-19-2012, 02:55 PM
Brief update - after doing a little here, a little there, I have me a sand blaster! :D
I wanted to share something - I found that with the suction tubes there isn't much air intake. End result, the sand comes out in spurts, like a water line that has air in it... sand-air-sand-air. Really annoying.
Well, I FINALLY ran across a website where someone suggested opening up the snorkel tube so the suction has more air and less sand. Drilled a 1/8" hole just below where the rubber hose connects to the tube, PRESTO I have good sand flow! In fact I think I will drill a 2nd one to make it even better.
I'll have to post pics. I made it just large enough to fit underneath the other table in my garage, so the huge advantage vs. a commercial one is that I can slide it under the table and out of my way when I am done! :)
04-19-2012, 08:45 PM
Looking forward to the sand blaster pics. What size air compressor are you using for this ???
VD in AZ