Need to Build a Blast Cabinet

[Keith Outten]

I have decided to build something similar to a sand blasting cabinet that I can use to clean small Corian signs after they have been laser engraved. The engraving process leaves behind a sub-surface area that is filled with material from the heat process that needs to be cleaned. For years I have been brushing the engraved areas to clean them, the volume of work I have these days makes it necessary to make the cleaning process faster and improve the technique. A pressure washer would be the perfect machine for this job but I don't want even think about being outside in the Winter water blasting sign blanks.

I have intentionally placed this thread in this forum rather then the Engraving Forum because it really isn't about laser engraving, it is about water blasting or the combination of water and air blasting. Possibly there is a similar technique that someone is using to clean or process wooden parts using an air/? medium that I could adapt to this situation. Maybe I don't need air at all and would be better off looking for a small high pressure pump.

I have decided to purchase one of the plastic deep sinks from the local BORG and fabricate a new top with an acrylic window to contain the mess. What I need is any advice you might have concerning a blasting gun for lack of a better description. My first inclination is to try one of the air hose types of nozzles that has a siphon connection, these are used to air blast a cleaning solution of some kind. Rather than rely on just the siphon ability i have been considering attaching a water hose to the siphon connector which I would hope would provide a better mixture of air to water.

Under normal circumstances using a simple water hose to clean sign blanks works OK but it won't clean out areas that have very fine lines. These areas are also the big problem with brushing since you just can't purchase a brush that is stiff enough with bristles that are small enough to get into the very thin sub-surface areas.

I have also considered the possibility of using a traditional sand blasting gun connecting a water hose to the sand siphon connector. Another option might be to just use a paint sprayer type of gun.

Surely someone has been down this road before and can save me some time and testing that can recommend a nozzle they have used to clean metal parts or some other type of blasting technique.

Links, make and model numbers or whatever you have that will help would be appreciated.
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[Bill Huber]

What if.....
You got a plastic tank, the ones they use in motor homes for water tanks. Buy some sand blasting gloves and put in the side, make a basic sand blasting cabinet on out of plastic. Cut the top out and use a hinge and plexiglass for a cover. Then buy a small Karcher pressure washer and run the hose to the inside. Mount the whole thing on top of the sink you just got and drain the water out the bottom.

Those small pressure washers don't really use a lot of water so you would not be draining tons of it out. The plastic tanks are really easy to work on, cutting and screwing things to it.

Just a thought.

[Rich Engelhardt]

Take a long hard look at the blast cabinets from Harbor Freight.
They offer a lot of bang for the buck.
Once you factor in all the materials and start trying to configure the interior, the HF cabinets get real attractive real quick.

Also, check into soda blasting. Unlike sand blasting, soda blasting is non-destructive.

[Charles Lent]

Keith,

I have a friend that does commercial powder coating and has a huge sand blasting operation to support it.

He also has a large soda blaster in a separate room. He uses the soda blaster to remove paint from fiberglass, mostly Corvettes, because it removes the paint without damaging the fiberglass. If you would like to see the results on a small sample I'm sure that I could have it done for you. Send me a PM if you would like to do this.

Charley

[Aaron Berk]

Do you want to go the PRODUCTION route?

How about a commercial dishwasher, the conveyor type. You load one side and ta-da out it comes all clean and sparkly and you don't have to touch a thing. Just load a basket and send it through. You would be limited on height, but not length.

[Keith Outten]

Aaron, I doubt that a dishwasher will produce enough force to remove the caked material from the very thin lines.
Charles, the door signs have a contour line around the edge that is painted so I don't want to use any process that would remove paint. Come to think of it if I used water pressure that was very high it might also remove the paint.
Rich, I had not considered using a sand blast cabinet because they are metal and will probably start rusting quickly. I guess it would be possible to coat the interior of the cabinet with a bed liner type of material and it would be much cheaper than building a cabinet from scratch.
Bill, I will do a Google search on the Karcher pressure washer and see what turns up.
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[Aaron Berk]

Well it was a thought........
How many signs are we talking here?
Can you rig an electric pressure washer into a cabinet so it blasts downward, and then have it actuated by a foot switch. It would leave your 2 hands free to manipulate the sign beneath the spray. I think a sand blast cabinet would work well for this.

[Michael Mayo]

I was just in HF today and looked at the biggest blast cabinet they had on display. It sounds like it would be large enough for your needs. If I remember it was less than $250 and had a large interior size. It came on a nice metal stand and you could probably easily coat the inside with some type of water proofing. But why not just get a pressure washer and lay the items on the driveway and blast away? No need for the extra cost of a cabinet and it is only water. If the areas you have to blast are far enough from the painted areas then you should not have any issues with removing the paint. They have a wide assortment of different tips you can get for the blasters that will allow you to pin point the areas you need to clean up.

[Ted Calver]

I would experiment with a waterpik to see how well it does before building something on a larger scale. Mine sends out a pretty powerful jet of water. Just a thought :)

[Keith Outten]

Aaron, we are currently making 850 door signs and about 400 specialty signs for three new buildings. We have been machining sign blanks for weeks and have consumed 30 full sheets of Corian which now have to be laser engraved. I am considering a sand blast cabinet and a small pressure washer based on my research yesterday but I haven't found a small enough pressure washer yet.

Michael, given the number of signs we have in process and the Winter temperatures I hate to consider using a pressure washer outside.

Ted, the waterpik might work. I have an old one in my storage building that I can use to test whether it will do the job. I'm not sure that we can get any more pressure than from a standard hose with city water pressure but the small size would be easy to incorporate into a cabinet.
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[Rich Engelhardt]

These areas are also the big problem with brushing since you just can't purchase a brush that is stiff enough with bristles that are small enough to get into the very thin sub-surface areas.
A real low tech approach may be to take a cheap chip brush and cut the bristles down to short stubs.
I keep one of those on my table saw and use it to clean out the packed sawdust whenever I change blades.

They get real stiff once they get cut down to between a half and a quarter inch long.

[Bill White]

Need to Build a Blast CabinetDang! That got my attention. I thought you were tryin' to play with explosives.
Bill

[Scott T Smith]

Keith, I'm going to think out loud here...

Seems to me that a standard bead blasting cabinet is not a good solution because the blasting media may get stuck in your 'fine grooves', and you're also blasting downward, so everything builds up in the grooves.

Outside pressure washing is definitely a bummer too.

My idea is to take a poly type blasting cabinet, an electric pressure washer (such as the Karcher), and a length of pipe and build something well suited for your needs. In the pipe, mount three or four standard pressure washer tips, so that they are all pointed in the same direction.

Mount the pipe several inches below the grate in the blast cabinet, with the tips pointing up and the open end of the pipe passing through the cabinet wall. Place a quick disconnect on the outside, so that you can connect the pressure washer to it. You may need to cut a slot in the grate so as to not block the spray from the nozzles.

Run a drain hose from the bottom of the tank to a drain, and rig up a foot switch that turns the washer on and off. Load a blank from the side of the cabinet, with the side that needs cleaning facing down. Seal up the cabinet, and use the foot switch to activate the pressure washer, which will send blasts of water up through the nozzles. Using the rubber gloves move the corian piece as needed back and forth over the spray jets. The water and debris will fall to the bottom.

Here is a hdpe blast cabinet from Northern that will not rust: http://www.northerntool.com/shop/tools/product_200103074_200103074


When you're done, you can even convert the cabinet back to a standard blast configuration for other projects.

Scott

[Graham Wintersgill]

Keith

What about a power shower pump, they can you up to 4.5bar which is about 60psi

Regards

[Lisa Frendberg]

Years ago, I made my own blast cabinet out of a 275 gal. heating oil tank I got for free. I needed a large one for tractor fenders / hoods and such. I simply cut the openings with a sabre saw and closed the "window" with outdoor rated window shrink film. Everybody said that film wouldn't work, but it lasted four years and was replaced by simply duct taping on a new piece. As for the blast tool it's self...... In your case I would use an air powered engine cleaning wand - available at any well stocked auto parts store. Yes, it is a siphon, but crank up the air to 120psi and it works like a charm, very precise and using very little air / water.
My 2 cents.....

[Harry Hagan]

I like Scott’s idea of multiple washer tips. It looks like you have several issues if you decide to use water:



Containing the water and blow-back.
Having enough water pressure to supply multiple nozzles.
Seeing what you’re doing.
Handling 1250 signs.


I don’t think you’re going to be able to see what you’re doing with all that water and material flying around so having a view port won’t be of much use.

I propose keeping the nozzles stationary and move the signs past them at the correct distance and speed.

See my drawing for the basic concept. I’m thinking this design will enable you to build a very simple and small blast cabinet. With some experimentation you’ll be able to determine the appropriate offset, angle, distance and number of nozzles. It might be necessary to supply both ends of the supply pipe to achieve even water flow. You’ll hopefully be able to shove signs using the guide rails into the cabinet and out the other side without getting yourself too wet.

Rubber inserts around the entrance and exit holes should help contain the water. I’ve also included a shroud around the spray mechanism to redirect the blast back onto the sign which should help with cleaning, require less water pressure, and further contain the back-blast.



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[Ken Dolph]

Keith,

Water will be messy. Have you thought of an air knife. It would run off your air compressor. There are many commercially available. I am sure that you could build one easily. Just make sure that you use a tear drop shape for the housing. This will maximize the laminar flow. See http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CIMBEBYwAA&url=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FAir_kni fe&ei=g65DT_-GDIbr0gGzrqnFBw&usg=AFQjCNFFFSfHD5dlYSsDZz1xeuLwK8cPag&sig2=gbZRL9bzsaMvhnCkDWGGjw

To see a tear drop shape see http://air-knives.com/air-knife-design

Easy to build and no cabinet necessary, except for noise and or dust collection.

I hope this helps.

[Perry Holbrook]

Keith, Cyclone Mfg makes a bench top blast cabinet that is made of tough plastic, I've got the Model E500 (I think) that I use daily as a sand blaster, if that helps any.

Perry

[Keith Outten]

Lots of good ideas in this thread.

I found an old air nozzle that has a siphon connector, the type you use for engine cleaning. Lisa suggested this might work so I will try to round up the fittings I need to connect it to a garden hose and use about 90 psi of air. If it works well the next step would be to get a plastic blast cabinet and install the nozzle. If the combination of city water pressure and air won't do the job then I will have to find a pump that can deliver more pressure. Due to space limitations I really hope that I don't have to use a pressure washer. Even though I know it will do the job the "washing machine" will take up space that I just don't have in the sign shop at CNU.

I am almost convinced that I will have to use water because of the very fine details we engrave in some plaques. The lines are so thin I can't find a brush that will clean them and I have sharpened a pick to the point it looks like a needle. Although it will get into most of the areas it is a very slow process.

I hope to have something working by early next week. We will start engraving AutoCad Drawings that almost always have a lot of very fine lines, the drawings are stairwell signs for Fire Evacuation purposes. I will take some pictures to share with everyone as soon as I have something that works efficiently.

Thanks..........
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[Ken Deckelman]

Keith,
I built mine last year with parts from http://www.tptools.com/ , specifically this kit: http://www.tptools.com/p/335,142_Build-Your-Own-Cabinet-Foot-Pedal-Operated-System.html

There are a bunch of pictures in my Picasa album: https://picasaweb.google.com/113966569709555812037/Blaster#

I use this cabinet a lot and it works very well.

Edit: I see that you really are looking for a water base solution and not abrasive, sorry.

[Keith Outten]

We decided to purchase a small electric pressure washer. Since the weather right now is perfect and were running out of time we bought the pressure washer yesterday and started cleaning the signs we had already engraved. It works perfectly, each sign took less than 30 seconds to clean and they air dried in about an hour. Before the cold weather comes back we need to design a cabinet and find a short handle gun so we can move the washing effort inside the shop.

FWIW I tried the engine cleaner gun with 100 pounds of air pressure and water. It wouldn't do the job so I new I had to have a lot of pressure to get the sign blanks clean.

Ken, I built a small plywood sandblast cabinet years ago that worked good, then I gave it to a friend who needed it for a job. I have a commercial blast cabinet now that I got in a trade for some web design work a few years ago. When I get the chance I want to connect my pressure pot to the cabinet so it will not need as much air volume. I have been kicking around the idea of using walnut shells to polish Corian but my early testing didn't go well. The siphon system won't deliver enough shell media to do the job so I am thinking that I can deliver more volume with a pressure delivery system hooked to my blast cabinet.
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