A little back story to start with, I had a need to do a lot of shot blasting a few years ago, I purchased a hand gun and lift tube which I was able to connect up to my air compressor.
I started off lifting the blast media from a plastic box surrounded by a large cardboard box...This resulted in blast media everywhere including all over me, this needed to be rethought! I built a cabinet to do the job.
When I moved house the poor old cabinet spent months outside with, as it turned out, a pretty poor cover over it, when I finally got round to housing it and using it I discovered that the elements had played havoc with the woodwork, warping and splitting it, the hinges were rusted solid and some of the framing was made from faced chipboard which had sucked up lots of water and turned to mush, it was a mess, you can see it in the background of the last photo, under the white cover.
I will go through what I built back then and explain why and how I modified it to make it work well after the rebuild.
Step 1: What Do I Need to Make This Work?
The first picture shows 1 of 2 old coffee machine cabinets that I found locally, the one you can see is my welding bench. The other one, without its door, is what I built the shot blasting cabinet with. A floor standing build worked for me but there is no need for it to be so big, you could equaly well make a bench mounted version out of sheets of plywood, what you will get here are the important bits to get a successful shot blasting cabinet.
You will also need:
- 2 flue flanges (large enough to get your arm into (I used galvanised ones, much cheaper))
- A pair of arm length gloves (not just rubber gloves, proper industrial ones)
- Tie wraps
- 20mm square weld mesh
- Small hole perforated sheet
- Perspex for a window
- 2 lengths of piano hinge
- Plastic packing box for blast media
- Wood of various sizes and shapes, mainly sheet ply 12mm thick.
- Silicon sealant
- Wood screws and PVA glue
Step 2: The Design, Bottom End First
The size of this is down to you, my build is quite large... so I put castors under it so that I can move it around. You could start by building an open fronted plywood box.
I cut a bottom plate that fitted into the cabinet and cut out a hole to fit the plastic box, supported by its top lip.
Next came a front panel, which sits on the bottom plate, and with a piano hinge attached to its top edge.
To make sure that the blasting media ends up back in the plastic box, once it has left the gun, cut pieces of ply to fit round the four sides of the box out to the walls of the cabinet creating 4 sloped sides, these need to be sealed all round with silicon sealant.
The glove panel is a piece of ply with 2 holes cut to suit the flue flanges, this attaches to the piano hinge on the front panel. Attach strips of ply to both side panels to stop it from over closing (You will see these strips on the next step). The gloves are held in place with tie wraps.
Step 3: The Design, Top End
You will need a window to look through, cut a frame to fit the box with a cutout, 20mm smaller than the perspex, for it to fit behind. Frame the perspex all round to locate it, clamp it in place top and bottom. The bottom of the frame will need to sit on top of the glove panel and will be attached with a piano hinge at the top. Add an overlapping piece of ply along the bottom edge to overlap the glove panel. Attach strips of ply to side panels to prevent over-closing.
I have used a greenhouse window support to keep the window up when in the open position, I also added magnetic catches just to keep the flappy bits in place when the unit is in use.
The double, switched, wall socket on the side has the compressor and the internal light plugged into it for ease of access.
Step 4: The Internals
To support the gun and any item being blasted you will need a simple wooden frame with a weld mesh cover in 2 pieces so that it can be swung up when needed.
I used a bulkhead fitting to bring the airline into the box and added a light at the top of the box as it is a bit dark inside when you stand in front looking in.
This was how I first used it but found I had a problem with the gun blocking with flakes of paint in the media and even when the paint was cleared out the gun sometimes wouldn't lift the media.
Step 5: Modifications
So I have 2 problems to address:
- Ensuring that the media keeps flowing to the gun
- Preventing the gun from blocking
The plastic box is quite large and the media dribbles back into it around the edges, much of it a long way from the pick up tube. Using some thin MDF I created baffles to direct the flow to the pick up tube, these pieces were sealed in place with silicon sealant.
To stop flakes of paint getting back into the plastic box I siliconed an MDF frame to the top of the box, this supports the perforated steel which allows the media through but holds the paint flakes back. It is easy enough to take the internals out to remove the paint flakes as and when required.
Step 6: Finishing Touches
Blasting media is quite heavy so I made a support to go under the plastic box, this is where I store spare blasting media and all the spares for the gun so that I know where they are.
To help with getting the media through the small holes in the perforated steel and back to the pick up tube I have pushed the cabinet over until it touches the frame of the compressor, the gentle vibrations transferred to cabinet help to keep the media flowing!
Step 7: Health and Safety
A safety note is needed here, in the past Media blasting was commonly called "sand blasting" due to the use of silica sand, breathing in the dust produced by the process can cause silicosis, a long-term lung disease caused by inhaling large amounts of crystalline silica dust. Do not use sand! There are other, safer, medias available Aluminium Silicate for instance, but by their very nature and the process being used there will always be some dust around, I always wear a face mask when blasting, better to be safe than sorry . The right kind of gloves are important too, do not use just ordinary long rubber gloves, the rubber will perish and weaken over time, media blasting your skin is not a good idea
...Oh and if your compressor is as noisy as mine, wear ear defenders too :)