Build a SandBlaster with fixed Nozzle(s) small chamber to pass long material through

I would like to build a small sandblaster that would have at least one fixed nozzle, mabye several.

the general idea would me that there would be a small chamber, no need for gloves or view sheild, with very small openings on each end where either solid material, or tubing (small diameter) could be passed through slowly getting blasted from different angles. Maybe working with a power feeder... feeding through slowly is fine (no need for speed)... but want consistency.

The desired objective is to feed 20 ft pieces of material through and remove the mill scale. I figure first of all, someone may have already tried this.... But the main thing I am wondering about is the specifics of building the nozzles, and the different parts required.... I figured to use the carbide nozzles... but maybe the ceramic... I was thinking since it was going to be fixed nozzles that there would be no need for the traditional gun... curious about the size of the pipe used, and orifice requirement... Could it be as simple as taking a .5" Black metal TEE and .... Air in one side... Nozzle on the other, and suck media from the bottom? .... I assume a street type TEE would work better... but would a regular TEE work good enough?

Thanks in advance for any constructive input!

Just my constructive input that the sandblasting I've done with my 5hp air compressor makes it run nearly nonstop.

And that uses a lot of energy which shows up in the bill that DTE delivers every month.

So, to sandblast a 20ft round bar, lets say 1" dia for argument purposes...the sandblaster can probably remove a 1/4" wide pass at roughly 8 inches/min (my estimate based on no overlap, doing a good, slow job, plug in your own numbers to suit). So thats 2 in^2 per minute. The 1" dia round bar has a surface area of 3.14 x 20 x 12 = 750 in^2. So around 375 minutes, around 6 hours of blast time.

Meanwhile the motor is eating up 3.75kW for 6 hours straight. That's going to reflect in the electric bill as well as wear on the compressor. Not sure if the 5000 hour rebuild interval is standard for an air compressor (sort of means a recip IC engine is worn out at 5k hours) but you can see its going to eat into that pretty fast.

I'm just saying that there might be less costly methods of removing the mill scale, or maybe your intended use of the end product would have this cost factored in already.

Also to add, thats with glass beads which also get worn down as they fracture, etc, and lose effectiveness. There are other more aggressive medias like Staruolite (Star-Blast, etc) which work faster but with a different dimensional change and surface finish, which may work faster.

I think that for what you're doing you need to look into something more like an "airless" rotablast machine that uses steel shot and is much more energy efficient. I'm assuming when you say "mill scale" that we're talking about steel as our material of choice.

Consider making yourself a home made wheelabrader. In commercial ones there are at least three heads taking the shot and slinging it against the passing material. The one I started up years ago had three 50 horsepower motors that started up independently. Air is not very efficient as mentioned.

Why not do a homebrew pickling solution inside pvc tube capped on both ends?

He has not stated what material exactly he is trying to clean. He did mention small dia 20 footers, so that seems like full length raw barstock. Might be a LOT cheaper to just buy new cold rolled stock from the start instead of trying to clean up some hot rolled steel or old stock that had been rusting away outside in the elements.

A 20 ft long barrel type tumbler ? not so duumb if you've a lot to do, load up and leave it to get on with it, and as has been said compressed air is not cheap.

Air isn't cheap but neither is a shotblast machine that could do a 20ft bar.

At my work they sand blast mill scale off all sorts of steel all day long 2 shifts a day. Takes a big compressor as mentioned and a big work area. If you don't already have access to big air id be sure and factor that in.

Sealing the ends as the bar goes thru might be tough, but if you expect to loose media some rubber flats or something will keep the majority where it should be.

I'd be tempted to use pre built guns for the nozzle/Venturi more then anything.

If you have lots to do,its worth building a dedicated machine.For any kind of production,you will need 250cfm of air at 120psi,or as suggested a Wheelabrator.Standard nozzle(Borazon) ,1/4 dia,and use steel or iron grit.This is the only economical abrasive(unless you use white sand,which might get you into trouble with the EPA).Feed the rod thru with a rotator with skewed wheels,and adjust the rate to suit.I have been in the industry thirty years,and built many specialized devices for various jobs such as pipe internals,multiple small parts etc.Regards John.

Centrifugal blast is far less expensive than compressed air blast to operate.

A used, vented cast iron auto brake disk is the perfect configuration to propel the media and they're cheap.

A flanged coupling for say a 3/4HP motor shaft would make it easy to bolt on the disk. Tipped about 45° from the horizontal and encased in a "rubber" lined circular housing with a high velocity escape port in it's perifery, with media falling into it's center.

A blast box with pierced rubber diaphrams on each end and rubber covered wheels, skewed in pairs, form a dynamic "trough" that both rotates and drives the tubes through the box, under the media blast.

The above, including the media "slinger" wheel is a close approximation of the larger Wheelabrator I ran in the late 50's, for 20' X 4" to 12" tubular mandrels. Just load them on the skewed wheels on the right and watch them come out on the left as perfectly blasted tubes. The media was irregular iron shot. A "gallon" bag was very heavy.

A combined blast box and collection funnel under a vacuum, no dust from the system and it cleans the media. A small elevator to return the media to the feed bin over the wheel.

The only downside, if you limit the blast cabinet to about 5' in length and the clearance to load and unload the tubing on each end, 20 footers take up about 50' of wall space. Keep it outside?

My dad designed the vacuum pump that cleaned the media on the machine that I ran and I've sketched it to the best of my memory, been close to sixty years.... The water and ports may have been a little higher.

The dirt simple impeller is the only moving part, other than the water which in this case, is a second mechanical part as well as the seal and dirt catching medium. The exhaust was tall (out of the roof), to give any upward propelled water a chance to fall back into the pump.

The centrifugal force and the turbulance between the impeller blades assured that all the significant waste particles got captured by the water.

Bob

Re: Build a SandB with fixed Nozzle(s) small chamber to pass long material through

We run multiple automatic peening machines at the shop I work at. Most are rotary carousel with ~12 guns (aircraft parts).

You will need a massive amount of air to run multiple nozzles. You will also need some kind of media classifier/delivery device to keep several nozzles fed. And lastly I don't see an easy way to seal your cabinet while running long pieces of various cross sections. Not saying it can't be done, but there's some serious obstacles.

IMHO you don't need to own the machine, Most steel suppliers in the uk can get beams Shot blasted and primed. The shot blast set-up is exactly what your describing. Im sure if its a reasonable qty they will happily run you some lengths of pipe through. The cost on the beams is surprisingly little, Like we can not buy the paint + brush for the cost!

Something like this,

https://www.youtube.com/watch?v=U7jXn8o-i9w

YOu need a lot of demand to justify owning one, but its so cheep to get done, just buy the tube in pre blasted + primed.

Thank you all for the good input:

Yes, the material is "Mild Steel" ...

In reference to the "cold roll" suggestion... I really need the hot roll, both price and the cold roll is a little too hard for my process...

i don't paint the product until it is finished... and sometimes not at all... so don't want to order it primed...

@adama --> Yes, that process shown in the video would great.... just smaller scale....

I will look more into your suggestions.... they all sound good.....

I am not looking at super high production rates... but also looking at a regular flow of material and a decent rate ...

If you are going to pursue this, keep your nozzles small and well aimed to reduce air consumption (nozzles get big all by themselves)
Line the inside of your chamber with rubber to make it last longer and reduce sound levels.
Garnet has a pretty good tooth and always breaks down sharp, steel media has the highest reclaim rate, but is very aggressive.

One thing to consider is the stressed skin that can form on the surface of the metal from the blasting. This can cause problems when machining the bar afterwards such as slots that spring closed during cutting.

There was a very small rotoblast machine over at Mckean last year.

dead simple, never could find a linky on google. something like "Fred's blasters"

Had the impeller wheel maybe 1 h.p., flung the abrasive straight UP into
rotating mesh basket, that was run with maybe a 1/4hp 90 vdc motor.

No lift bucket conveyor, no metering valves, dead simple.

Taking Robert Campbel's advice, for a simple wheel, you could make the pass thru
up above, and a simple blower to remove the dust. The "good" abrasive falls back down
(to the impeller) the dust flys up and the fan sucks it out.

http://www.lsindustries.com/products_services.php?page=airless_blasters-tumble_blasters-mb_2000
Looks like the machine.

herrmc said:

I would like to build a small sandblaster that would have at least one fixed nozzle, mabye several.

the general idea would me that there would be a small chamber, no need for gloves or view sheild, with very small openings on each end where either solid material, or tubing (small diameter) could be passed through slowly getting blasted from different angles. Maybe working with a power feeder... feeding through slowly is fine (no need for speed)... but want consistency.

The desired objective is to feed 20 ft pieces of material through and remove the mill scale. I figure first of all, someone may have already tried this.... But the main thing I am wondering about is the specifics of building the nozzles, and the different parts required.... I figured to use the carbide nozzles... but maybe the ceramic... I was thinking since it was going to be fixed nozzles that there would be no need for the traditional gun... curious about the size of the pipe used, and orifice requirement... Could it be as simple as taking a .5" Black metal TEE and .... Air in one side... Nozzle on the other, and suck media from the bottom? .... I assume a street type TEE would work better... but would a regular TEE work good enough?

Thanks in advance for any constructive input!

Click to expand...

I've been thinking of doing something like this as well, but not as much length, with at least a 24" width, (I want mine to do the parts off the plasma cutter)

what I have not figured out if making this all from scratch is a good way to keep from all the sand from destroying the drive system, I really would like to have it blast from top and bottom or parts

If you figure out how to stop the abrasive from destroying everything mechanical,you will be the first.One particle of steel grit destroys the hydraulic steering on a crane.New Orbitroll at $1500.Garnet in a ball bearing cuts out the seal and seizes it completely.By the way ,garnet is a very expensive blast media,as it lasts only three passes on average,and the dust resulting requires a much larger collecting system.Steel grit lasts nearly indefinitely,with only carryout losses.But it will cause rust spots on stainless,if youre not careful.Grit is the only practical media with a wheel machine.Regards John.

john.k said:

Grit is the only practical media with a wheel machine.Regards John.

Click to expand...

Auto part re-builders worldwide would probably dis-agree with this statement.....