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Old 10-19-2009, 07:27 PM   #1 (permalink)
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Name: gearsmithy
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How to build a media blasting cabinet out of junk

Since I got such a positive response from my fabrication howto, I figured I might as well put this one up here too. If you're like me, then you've probably been in at least 1 or 2 situations where you needed a sandblasting cabinet but just couldn't justify the $2000 price tag of a commercial unit. Before I decided to build this I used to joke to my friends "if I had a nickel for every time I needed a blasting cabinet, I could afford to buy one."

I literally built this cabinet out of junk, some of it I found in my alley, some of it was left over crap that we all have cluttering up our garages and basements.

Unfortunately I didn't own a camera until after I had built the thing, so there's no "in progress" shots, but the construction is soo simple anyone could take one look at this and reproduce it. The actual sandblaster is a generic gravity feed system, you can find these just about anywhere. You should also note that you'll need a shop vac, and an air compressor capable of running the blasting unit. These portable blasters have a dead man switch and can be had for around $100 from any major industrial supply shop. Enjoy

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I got the idea for this from some guys on the H.A.M.B. who've done something similar and I built this almost entirely out of scrap material that I had sitting around. The sandblaster unit is a clarke gravity feed system, you can get these pretty much anywhere. The arm holes are a couple of toilet-bowl flanges from Home Depot with a pair of harbor freight media blasting gloves hose-clamped clamped on. The stand is just spare lumber that I painted black.



I was originally going to make the window housing out of plywood but I found this website (The Barrel Blaster and The Blast Master - Affordable Bead Blasting Cabinets and Sandblasters) that makes these in a production capacity and just ordered one of their window units instead (it was much nicer than my original plywood model). Every bolt and joint in this thing is sealed with construction silicone to ensure that the cabinet is air-tight.



To make the door I cut out a "D" shape in the bottom of the barrel, and used the cutout piece as a backing to a piece of plywood.



The trickiest part of this project was getting the right hinges, you want the kind that can close completely flat on themselves, they'll usually run you a couple of bucks from Home Despot



The other thing you'll notice, is that I built this without welding anything. At the time, I had no electricity in my garage, so I built this by the light of a coleman lantern with nothing but an angle grinder, and an electric drill.



Those luevured (sp) holes are eve vents that I got from a siding place down the street stuffed with HVAC filter elements that I cut to shape. These are my intake ports that allow air to flow into the chamber and out into the shopvac. I was fortunate to have a couple of these oil drums sitting around, they had the perfect size holes for my input hose, and I was able to find a PVC fitting at home depot that "kind of" fit into the threaded bung on the lid (i wrapped that with tape, just be sure).



I picked up some automotive weather stripping from the hardware store to put around the door opening. The idea is to provide a tight seal. That green wire you see is a ground wire that attaches to the blaster nozzle and grounds to the conduit under the chamber (this prevents static charge buildup)




I went ahead and wired up a switch and an outlet underneath the blaster. One switch controls the outlet (which has my exhaust system [shop vac] and a hand sander [shaker for media tank] plugged into it), the other switch controls the light inside the chamber which is another 5 dollar dealeo from the hardware store. I used some big ass hose-clamps to attach an el cheapo hand sander to the media tank. These cheap models have a tendency to clog and it's nice to have something continuously shaking the tank. I wish I could take credit for that idea but some dude on the H.A.M.B beat me to it.



On the other side of the cabinet is the exhaust filtration. I made this from PVC piping, JB weld, and empty can of skoal.



Here's a closeup shot of it, I've photoshopped this to make it easier to see what's going on.



The shop vac is hooked up to the other end of this and forces air down through the main inlet tube. At the bottom of the inlet tube is a baffle (empty can of skoal). This baffle has about an 1/8" gap from its OD to the ID of the main reservoir. A couple inches of mineral oil sit at the bottom of the reservoir just under the opening of the main inlet tube at the baffle. This system forces fine particulates into to the oil where they are trapped and helps keep them out of the shop vac.

This system works pretty good, it's not as "perfect" as commercial systems but it's good enough for a chamber made of out of an oil drum. Originally, I had the oil above the line of the baffle, basically making this like a bong, but that didn't seem to work as well.

We were in the process of remodeling our house when I built this so most of the materials used were scrap/leftovers that were sitting around. The biggest expense is the blaster itself, which I think was around $100 or so.

I'd say this whole unit could be built for under $250 (including the cost of the sand blaster, shop vac, and hand sander) - your mileage will vary with size of your air compressor. If I had to do it over again, I'd probably use sections of 6" tubing for the arm holes and some sheet metal for a media trap on the bottom but I hadn't run electrical to the garage yet when I built this and couldn't run my welder.

I would also recommend ponying up the cash for a "gun" type nozzle and foot switch, you can make the foot switch yourself but mine was too unreliable to post a description of this process. Someday I'll spring for a commercial foot switch - and recommend you do to - your forearms will thank you.

Here's a resource to help you select blasting media, but there's tons of online resources to help you select the right media for the job:
McMaster-Carr

I'd stay away from coal slag, personally I use glass beads for fine work and crystalgrit (specularite) for the heavy stuff. I'm actually pretty happy with the crystalgrit since when it breaks down it forms sharp granuals which can be re-used.
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