Wheel blasting. (shot peening) and blasting questions.

1)Has anyone here used wheel blasting equipment? I was wondering if theres anyone that thought of or tried to make their own wheel blast system. I'm looking into shot blasting. I made my own sand blast cabinet, but might want to do shot peening or shot blasting some day with the wheel method.

2)I'm also curious, what media would be used to put a 1-1.5 mill profile on mild steel. I had a local shop blast some steel for me to put 2 mil profile on the steel, but i think they only used sand. I quit using their service due to lack of honesty and costomer care, so i never did ask them.

3)I have a lot of slag that im always cleening up from welding. If i were to start dumping this through a sifter instead of the trash, wouldnt this make a good blast media too? (im big on recycling)

Well, you COULD make anything- but the wheel blasting and shot blasting machines I have seen have been HUGE, heavy, powerful, and, no doubt, expensive.
The process itself destroys the machine- so the machines are made out of stuff like 1/2" plate, with big motors.

I just cant see it working very well on a small scale. I have seen some of these machines, and they are BEASTS. Conveyor systems to recycle the shot, of course- vacuum pressure wont pull shot, you are talking multihorsepower heavy duty systems just to move it around. Then, they dont just have one wheel throwing shot- usually 8 to 16 of em, each 10 to 20 hp. Normally they are as big as a small house.

The smallest ones I know about do only use one, 10hp wheel- and are made of 1/4" plate with 1/2" rubber inside- this size MIGHT be feasible to build- but its still a big momma.
here is Wheelabrator's spec sheet on it.

http://www.wheelabratorgroup.com/uploads/documents/WMT Table Machines.pdf

Its still gotta be heavy duty enough to throw 250lbs of abrasive per minute.

I havent realy thought this out much, other than the basics, but i was thinking of this heavy fly wheel i salvaged off of a nordic track. If it had scoops or divits machined around the circomference, and turned at high speed. Shot is then dropped vertically onto it and it catches in the cups or divits to be shot or sprayed in one direction. Sheilding could be made to vector it.

This of course would be stationary, so you need to make your work piece move, not the blast nozzle or blast stream of the shot.

The more complex part of this would be the augering, or retrieval system of the shot, so it is filtered and fed back to the wheel.

This application i have in mind i guess would be more for my application, and using it on the same parts all the time. So, no, im not thinking in terms of a commercial machine.

...hmm.

Yeah, the commercial ones are beasts,,

Ries, some one of the coolest surface finishes i ever saw was a steel plate that had been shot peened with something like 4 or 5 mil size shot. It was then nickel plated. It was beautiful. Have you ever tried that on some of your stuff?

"To invent, you need a good imagination and a pile of junk.” - Thomas Edison

Start calculating! How fast does the shot have to travel to give the effect you desire? How fast would the wheel have to be turning to impart that velocity? How does the shot stay on the wheel cups until it gets up to speed?

MAYBE.....and I don't claim to have thought this out completely, the wheel needs to be horizontal with the shot fed in near the center and it follows grooves or tubes out to the edge, picking up velocity as it moves farther from the center?

There must be expired patents you could use as inspiration.

Maybe the right thing to do is look in the Business-to-Business Yellow Pages and find a shop that can do the job for you.

When I lived in LA, I was friends with these guys who had 30,000 sq feet or so of sandblasting shop, with separate rooms and lines for steel grit blasting, shot blasting, glass bead, and sand.
I did have some stuff shot blasted, then plated, and it does look really cool.
Warps the hell out of thin sheet, though- even up to 1/8" aluminum will get oil canned by shot.

Nowadays, I get similar appearances from using air tools on stainless.
I use a needle scaler a lot, as well as grinding custom tips for an air chisel, and then selectively texturing the stainless.
I also do a fair amount of hot texturing, where we heat the metal, both mild and stainless, in a forge, and then texture it under a power hammer with custom tooling.

Both of these processes are more labor intensive than wheelabrators would be, but on small stuff, they work really well.

There is a free trade magazine that comes out quarterly for the shot peening/blast cleaning industry with articles, tips, advertisers, etc. You can sign up online at their website and they will mail you the latest copy to get started.

www.shotpeener.com

The way I see it, you never can know too much about a process, even if you don't ever get to build your own machine it makes you an informed customer if jobbing it out.

For what it's worth, I too would like to build my own machine for use on a product we manufacture but as Ries pointed out there is a lot to one of these machines.

And as good as the Wheelabrator brand performs, you can tell from their available update programs that they constantly look to improve their products. You have to admire that they appear to think of the people out in the world with their equipment when they design better parts that they can be retrofitted to older machines. I guess my point to this is that even they keep coming up with better design ideas.

If you build one for yourself, SHARE with us! I could use the encouragement! Actually, the foundry I used to use found a small one really, really inexpensive and so I keep thinking it would be smarter to find that deal myself.

Gus

Southbend.
Nice idea. I think i understand what your getting at. Sort of a centrifugal disc. I havent found much online yet that shows the inner workings of one, but im getting more curious now. I dont know of anyone in my area that does shot peening.

Ries. I havent used a needle scaler yet, but a friend of mine just dropped one off at my garage the other day for the hell of it. If i ever get my compressor going, ill try it out on some hot steel.

gusmadison. Thanks for the link, i may get on the list for shits and giggles. I DID share my blast cabinet design here http://www.practicalmachinist.com/vb/showthread.php?t=162128
if you are interested. I can get a pic of the prints too if you want them. I sent them to a couple other folks already. Its untested, but it was made very cheap. Since i got the cabinet set up and ready, and i have this fly wheel and a spare 3,000 rpm motor sitting around, i started thinking if i could also come close to getting shot peening done in there too.

I wonder how long a cast iron automotive disc brake rotor would last? Wouldn't have to last too long 'cause they are cheap at the auto recyclers, probably even cheaper at a large brake shop, where "too thin to resurface" wouldn't hurt them as shot slingers. I'd pick a very common, larger size or even several similar types with the same bolt pattern.

I've run Wheelabrators and they use a similar configuration on the wheels.

If needed, you could orient the wheel vertically and chute to the center hole, because the 'runners' (a little water turbine lingo) are enclosed, no place to fall out.

With the media simply floating through the runners, the wear factor would be much less than the parts that are being hit straight on.

Sheet 'rubber', like conveyor belting is a must for the scroll that directs the media.

I'd think that a 3/4 to 1Hp motor could handle all the media and air the rotor could pass through.

A small fabricated elevator that carried the media a foot or two above the supply bin, would allow dropping the media through a winnowing process that cleaned the media with fan or vacuum. A cyclone separator would minimize filter maintenance.

A gate to regulate the the media would be required, (obviously), I mention it because the mechanism that carries the media requires it to be loose and floating, (lotsa' air), that then carries the media around the scroll to it's outlet.

Several wheels, say 4, could be arranged to attack the parts from above, below and both sides, as they pass through the machine. Four shafts projecting into the chamber through simple seals and a disc on each shaft, just inside the chamber to throw the media away from the penetration, could all be run by one motor and a serpentine belt and five pulleys.

Of course the auto rotor version could not provide large volume abraiding. Adjusting part through-put would make that acceptable for many things.

My dad was the chief engineer at the huge manufacturing plant that employed the Wheelabrators I used and he did a study to compare abraiding the big rolls we constantly resurfaced for grip. The Wheelabrators were dramatically less costly to operate, compared to traditional shot blasters running on compressed air. The rolls were advanced past the single blast on biased rubber rollers that simultaneously spun and drove the rolls through. This was in the late '50's.

Bob

I had a customer who sold conveyor belting who gave the old stuff to someone who did shot blasting for liners. he was very happy to get rid of it.

I think ....design wise.....the wheel
(vented disc brake rotor....Fantastic idea....BTW)
needs to be vertically (ferris wheel) oriented.
Mounted on top of the "cabinet" so that if you stand in front of the cabinet, you're looking at the end of the shaft driving it.
That way, the grit flowing out the vent holes forms a curtain of shot across the inside of the cabinet, left to right.
Usually a chain belt or rotating table is inside to rotate or flip the parts around...

Course, the shot will be exiting the rotor slots in all directions, and thus the 'housing' that covers all but the bottom 1/3? -1/2? of the wheel would need to be stout enough to withstand that constant impact.....

I wonder if an exit "slot" of some sort at the top of the cabinet would be needed to concentrate the shot into a fairly narrow curtain?

I have seen the results these machines produce, and studied one years ago where I worked, but there were parts and areas i could not see....and I have thought over the years of how to "collect" one.....(find enough junk and parts to throw one together).
In the right shop area or neighborhood, a gas engine might not be a bad option for the drive.

dk

Hell YES! That is a great idea about the brake rotor. Using an existing part that would be trash anyway. You have a good supply of them around when they are useless otherwise. I like your train of thought.

Great ideas dkmc and Robert. I might just start some preliminary sketches on this.

I think i would like to get ahold of the the brake rotor first, and make some temporary plywood sheilding, shrouds and what not, just to test how well it would work, and how to vector it. Spray area, etc, etc. If all checks out, begin building a cabinet, or retrofit mine with rubber liner. I have cheap vinyl flooring i bought to make a wrap around layout template out of, i might use that to line the inside.

If i come accross a brake shop that would give away an old one, i might use that motor and get started on this little experiment.

IF, i get that far, ill share the results. Maybe some different perspectives can help fine tune it. We can keep it public domain also.

Maybe this has all been done before, but hell, its starting to sound a little more do-able for the (dont wanna spend a penny, do it your-selfer) like me.

dkmc said:

...... the shot will be exiting the rotor slots in all directions, and thus the 'housing' that covers all but the bottom 1/3? -1/2? of the wheel would need to be stout enough to withstand that constant impact.....

I wonder if an exit "slot" of some sort at the top of the cabinet would be needed to concentrate the shot into a fairly narrow curtain?
dk

Click to expand...

dkmc, thanks for the kind words. Regarding the quote above, that's what I meant by "scroll", the name of the snail shape you find wrapped around centrifugal superchargers and squirrel cage fans. The outlet of the scroll would be configured for the most effective discharge. By the way, your idea of having it fan down the width of the cabinet sounds good, though most tend to concentrate the output and move the part under the stream.

A scroll has it's 'fan' eccentric and has a constant radius increase as it turns toward the outlet, a volute. The idea is that as the wheel turns, discharging air/media at 360°, the scroll constantly opens up to receive more and more of the wheels discharge.

Scrolls are easy to fashion out of flat stock and it wouldn't be necessary to use anything heavier than 1/8", as long as it was protected by a resilient cover.

As far as your "slot" goes, a vented brake disc is maybe 1-1/2" wide, max. A close scroll would create a narrow aperture. It might be most effective if it narrowed even further, to the width of the openings on the rotor. The scroll would have to have one of the sides and the curved part welded together with a flange, on which to bolt the second side, allowing access to install and replace the resilient material.

A brake rotor spins at something like 1,100RPM at 80MPH, never heard of one exploding from centrifugal force. Should be quite safe at 1,000RPM.

This would need some experimentation re; RPM, % and shape of opening in the scroll, flow of media, media reclamation and so on. It's got me intrigued.....

Bob
Edit, Booster, you posted while I was typing, I here stand and nominate you the experimenter!

By the way, your idea of having it fan down the width of the cabinet sounds good, though most tend to concentrate the output and move the part under the stream.

Click to expand...

It's possible some of the designs do, but watch this video....
I think this machine clearly emits a 'cabinet wide' pattern, that's adjustable.
Lots of other interesting Shot Blast videos on their site as well....

http://www.blastabrade.com/setblastpattern.html

I would think there would be a -time out- on rotor wear.
If it got too thin it could 'blow up'.
And I'm wondering if a cast iron rotor would wear surprisingly fast? Although expressed in hours, and work accomplished, probably a low cost replacement 'wear part'. I think mid-size trucks have vented rotors now-a-days also...so if a larger 'capacity' wheel is needed, maybe need to look beyond the car or pickup size category.

dk

Edit:

I here stand and nominate you the experimenter!

Click to expand...

I second the motion.

Booster, like SurplusJohn said, they give used conveyor belting away, the back side is usually pretty good. Rock and sand quarry's use a lot of it. I've also been given short, waste chunks of new belting. I fear your thin vinyl would die a fast and ugly death under the media blast. Probably best to find some conveyor belting first, so that you can make allowances for it's thickness as you build the parts. I've seen 1/4", 3/8" and 1/2", at least.

Warning, you wont cut it with your pocket knife. I've used circular saws, hand and table saws, and others. I've made low speed universal joints with crossed tees welded to the ends of opposing shafts with a 1/2" c.b. disc cut with a hole saw bolted between them.

Nothing I've tried makes a really easy cut but that says good things for the material as an abrasives liner. Ask the maintenance man at the quarry how he cuts it. Maybe SurplusJohn has some ideas of how to cut it.

Bob
Edit, again caught by the bell, dkmc, re wear on the rotor, there is no doubt in my mind that the "fins" would wear much the fastest. If all of them separated, the outside ring of the disc would be set loose, not a good thing! Frequent examination would be in order, at least until wear factor is determined. Maybe a little heavier on the scroll metal would be a good thing as well. With heavy belting as a buffer, the loose disc would soon wind down. The question is, would you still be within a mile or so of it to shut it off?

A simple,cheap 'excessive vibration shutdown' switch would be a good safety feature....

Well, if i just got nominated, i think i might take a shot at this. Keep in mind, i have other priorities, but they are all being done in the same shop so it may get pieced together as i go along. I do things home made, cheap and scrappy, but lets see how far i can get before getting stumped or to broke to proceed. I'll revive the thread when it comes time.

I did reach a personal mile stone tonight. I have my compressor cleaned up, wired up, oiled up, and running. Next week i will finish making the cabinet air tight and attaching the gloves and lighting. Next priortity for me is making a dust collector. After that, i have plenty of room to take on this experiment. I finally found the tag on the compressor under a layer of dirt and oil. It was made in 1944, so im a bit gun shy letting it charge up. I keep thumping the metal and listening for thin spots. Not sure if what im hearing sounds good, yikes!

Give me a grociery list...

I have the
2 HP motor. rated at something like 3,100 rpm. (its a spare compressor motor)
I have plywood and some scrap steel for the make shift barriers.
I have a v belt and pully.
I have steel plate for mounting motor and supporting members.
I have a 1/2"x35" shaft salvaged from sump pump. If needed.

Need..
Several Brake rotors.
Steel shot.
Conveyor belting.
..anything else?

Any tips on balancing something like this before turning it on high speed? I know how to grind, or drill out metal to balance one side, but isnt there some other techniques for fine balancing?

My application will be for removing paint from old propane tanks. I recycle them and turn them into something else, so i may put a turn table, or lazy suzan in the finished model, if i get that far.

It will also be used to profile the steel for new paint job.

One of those laser thermal readers would be neat addition. You could tell if your material is getting too hot. Oh that reminds, me, i need to ground my work, same with my blast cabinet!

Hey, i have had a couple ideas since starting this thread.

Two other options for propelling the shot come to mind.

Howabout running two tires pressed together tread to tread, and feeding the shot into them. They would propel the shot without the friction and damage that shot hitting a metal wheel would.

The second question..... Is there a guass gun, or rail gun method that might work for this. If so, i'm wondering if the (efficiency)energy spent on electro magnets would be higher than an electric motor. Not to mention developing it and putting it together.

Third....I might start looking on craigslist for one of those free washers or driers, just to use for some of the materials here. I could canabalize the sheet metal and line it with the rubber, or conveyor belting. Would the motor in a tyical drier be up to task for this? Ries's spec sheet indicates 3600 rpm, so the motor i already have seems to be in the realm, but what about the drier motors? (BTW) thanks for that link Ries.

Your thoughts please?

In the mean time, i typed vented rotor brake into google images, and found some examples to examine.











If i use the vented disc brake method. I would like to design it so that changing them out can be easy, since they may be one of the "consumables." For that matter, i would like to minimize all the "consumable surfaces", and make them easily replacable. Im thinking of angled plates used to vector the shot, that are isolated from heat buildup, and easy to get too. I would think that they will act like a blower, so that could aid in cooling down the surfaces that are being heated. Thats a bit of a design challenge, but it will be fun to try to come up with something.

Also, what would one of the most common vented disk rotors be? If this is used, i would want to find a VERY common size and style. Any thoughts on this?

On the topic of dust collectors. I've seen that shot is cleaned with a blast of air through it, not so much like in a cyclone, but since i need to build a cyclone or dust collector for my blast cabinet anyway,,i found these online yesterday, and will try to build one of them...
I cant decide which one to build yet though.

Check out this guys design.. very cool
http://www.youtube.com/watch?v=hOi-CUx4v6U

And this one looks easy to build, but i hope it works.
http://www.cgallery.com/jpthien/cy.htm

dkmc said:

A simple,cheap 'excessive vibration shutdown' switch would be a good safety feature....

Click to expand...

Do you have an example? A link? Is there an inexpmensive way of making one that you can think of? Something comes to mind, but i would have to sketch it to explain.