Manufacturing Glass Bubbles

And, what do you bring to the table?

I have a customer that is requesting this product, and I have equipment building experience.

Somebody here might know...

http://fusedglass.org/node/422

I would think you would have to make them in halves, then fuse them together...If you want to make them on a large scale, that would require automation, a lot of design and engineering, very expensive...or hire a bunch of unskilled workers and teach them glass blowing....

Thank you for your input. The large scale of this operation is why I came to this site looking for information and support. We will need large volumes of these little glass balls for a new project in the construction industry. This is all that I can say publicly.

You might find a consultant here that could help...

http://www.societyofglasstechnology.org.uk/cgi-bin/open.cgi?page=consult&sessionid=494210111

3M started marketing hollow glass microspheres because their solid (reflective) glass bead machines produced a lot of "rejects" that floated in water. Nothing wrong with them, but they weren't good reflectors.

The electronics packaging industry used them because they were light and had good electrical properties.

Beads of the sizes you want are probably hand blown now.

I have no knowledge of a high volume manufacturing process for spheres of this size.

But then, I have no knowledge of A LOT OF THINGS.

Many years ago as a student I worked in Rockware Glass where they made all kinds of glass containers, including tiny medicine or perfume bottles. I remember a large glass furnce and a channel with a slow moving stream of viscous glass which dripped in a vertical syruppy line.

This was cut off with some kind of jaws and the drop of glass fell into a tow part metal mould, a pipe with compressed air camein to the drop and inflated it inside the mould, The mould was on a rotating machine with maybe 20 stations, which moved at about 1 sec intervals. Machines made in USA were Owens and one called Lewis.

At the end of the cycle the jaws of the mould opened and the bottle or bottles dropped out onto a cooling belt, this moved along a slowly cooling tunnel, called a lehr until operators took off the bottles and packed them at he cool end.

Try a factory visit to http://www.ardaghgroup.com/

GA! I have seen the process you described in several glass factories.

Rotary blow molding equipment is what the OP needs. The design will be similar to that which is used to make Christmas tree ornaments or light bulbs. They both have thin glass envelopes. The difference is that this design will pinch off the opening rather than keeping it open. Because the balls that are being made are quite small, the amount of glass that is scrap may exceed the amount of glass that is used to make the ball. Of course the scrap will be recycled back into the process.

Process: (1) melt glass, (2) extrude through a spinneret, (3) cut a length as it is dropping into the closing mold, (4) pierce and inflate the glass to the shape of the mold, (5) pinch off and close the glass ball, (6) cool in mold until liquid becomes solid, (7) transfer to a layer loader cooling conveyer [this is actually a very long oven which is warm at the entry and cool at the exit], (8) inspect and pack

Any idea what kind of rate can be obtained?

Do you know the name of the company that makes the equipment? I would like to contact them to see what kind of investment requirement is needed by my client.

Google glass blowing machinery and you will find the names of several machine manufacturers. Here is a link to a Glass Blowing Machine.wmv on YouTube of a type that is similar to what I have worked with.

[That factory that I helped automate the process for made Libby drinking glasses. At the time they were upgrading old production lines to reduce the number of operators required to transfer the hot glass between machines wearing asbestos gloves. It was a worker safety issue. This was in the 1970's. My company provided the AC inverters and the control electronics to synchronize the equipment. The equipment was old and I believe was probably custom made their their designs.]

Good luck.

Contact a company that makes large marbles. The wall thickness will be 1/2 the diameter, but you say that doesn't matter.

I wonder if it would be easier to use broken glass that was originally heat tempered and when broken forms into near ball shapes and then your company would roll them in a hopper that is used to smooth pebbles for trading post souveniers.There may be other applications for these smoothers but I collect rocks so that is the one I have very little knowledge of.ds

Are these bubbles hollow or solid?

Have you ever seen a process like one of these?

http://www.hnscabravise.com/

I did some work and will be able to guide you through this. I am not sure what equipments you have but I can provide you list of the high pressure bubble blower. The optimizatin of glass composition along with pressure and and nozzle size is imprtant and can provide you full detail when you are ready

Please give me a call to discuss this further. thank you for your reply. Bob 505 864-8600.

If no real wall accuracy is required, crimp them out of extruded tube.

What kind of rate would this method yeild?

The cycle speed of all these systems (including the common blow molding others are referring to) is a function of the wall thickness of the product.

This is one reason the modern beer bottle is around 1.5 mm wall, as opposed to 4 to 5 mm as the older ones were.

So, to estimate a cycle time you need to know what sort of wall thickness you want and how much hotter the particular glass has to be when extruded, compared to how cooled the skin has to be on release from the mold, (so that it will retain its shape through the annealing stage)

Let's keep with what we know, like the 1.5 mm that you mentioned. This should be plenty thick enough for our study.

Also, what about having the extruded glass come out of a mandrel that had air in the center like the blow molding machines I used to run for plastic, except not have a mold, just blow air into a space with cooling air blowing on the part to cause it to set. then just pinch off the hot side onto a surface to transport the balls for further cooling?

Or like #12

But rather than have me invent your solution via 20 questions, why not adapt the conventional approach?

. The word "bubbles" suggests a molten state at some point in the process. Is this a requirement? does the "trapped" gas need to be prevented from equilibrating with the atmosphere? Does the shape need to be spherical? If so, how close to round? Does your process allow a variation in size within each lot, or is a uniform sizing desirable? Is cost a significant consideration? mechanical strength? Are you setting up a continuous production, or batch processing with storage? The output seems low for a sophisticated design.

I would suspect that the glass would have to be molten at the point when the bubbles are formed, unless there is another technology that would allow glass that is not melted to be placed into the required shape and then heated? The trapped gas needs only to hold the round shape of the glass. the pressure inside can be the same as ambient. Spherical is important. Size variation would actually be a benefit in a range from 4 mm to 9 mm. The cost of the equipment is important, but the process cost is the real focus of the project. I believe that a continuous process would be the best as this reduces the start up and shut down costs. The estimated usage is low to start with as the project grows, so will the demand.

The bottleneck in an automated process would seem to be a way to crimp an extruder output while allowing the "balls" to be supported freely while cooling. Two rotating dies geared to mate with eadh other with hemispherical shaped hollows closing around the columnar output of a small (13mm?) OD extruder would trap ambient gas (air) and throw the crude spheres away. A high temperature, above the melting point, and a high rotation speed of the dies would be needed. If the spheres were thrown into a flame ( to polish the flashing at the die edges) then blown into a rapidly cooling air stream, so that the surface would cool and harden while the center remained liquid, the subsequent cooling would give the high strength of a "Prince Rupert drop" , but without the weak point of the PR drop, which is the pointed tip. The speed of the cooling, maintaining a very high thermal gradient (from surface to center) during the cooling would create the compression in the glass surface characteristic of ultra high strength glasses, like those produced by Corning with their ion-exchange process, but without needing that technology. Since this process by its basic nature needs to be fast, and the balls need to be suspended long enough to harden if the high strength is desired, the cooling tower needs to be fairly large, the output of this as envisioned by me would be above 200 tons per year (see #13). Now if variable sizes are desired, to allow for more efficient packing in the cement mix, different technology could be used, possibly cheaper, but in a higher output range.

Note that annealing is not used for the above (prince rupert drop) process. The internal stresses are what gives the high strength.

How would you move forward to build up this process equipment? I am working with an investor that wants to move on this rather quickly to establish the best route to make these little balls of glass.

200 tons annually. Over half a ton of melted materials per day seven days a week.

The furnaces I have worked near were using gas burners and furnaces were glowing red with white hot interiors. There's a separate mixing shed where the mix, called frit, is blended from crushed recycled glass, sand, and a few chemicals soda something. The sand pits and sand washing were at a separate site.

Dump trucks took this and tipped it into the furnace, where it started to fuse together and move into the main molten pool. The whole place is running 24/7 because it takes a long time to warm up or cool down. This is pretty standard for all the United States Glass Company members, St.Gobain and others.

I think your furnace will be at least 6 feet x 6 feet and the heat is extreme, depends on the glass but 900 C to 1100 C is about right. The surrounding area needs a clearance as the walls and roof get overheated. As far as I can tell the whole thing only lasts for 12 months and has to be relined with firebrick.

In your case molten glass is pouring into some kind of molding machine at a rate of about 60 lbs an hour for an annual 200 tons output, assuming no rejects or wastage. That's 60 lbs of material an hour to be cooled and carefully packed.

This isn't a homebuild in the shed, it's quite a big plant, I think fuel will be the main cost component as it is in pottery production.

Crimping tube is a shortcut but buying tube instead of sand will increase costs, but would simplify production. The machine should be fairly straightforward automation but getting rid of mold lines is quite challenging as any extra heat after forming could melt the whole bubble. I would experiment with bowls and cones and plasticine balls shot in at a tangent, rolling down an incline would tend to produce cylinders.

To what accuracy is "spherical" required? Ball bearings are spherical to a fraction of 1/1000 inch, so there's a further inspection problem. In the industry rejects are recycled back to the furnace and I would guess on glassware and bottles it can be as high as 25% rejects

If wall thinkness doesn't matter I would go for solid spheres. Depends what use these are being put to, do they have to float, or have a maximum density? The quantity of bubbles will vary with wall thickness, like twice as thick, half as many bubbles for the same weight.

Thank you for your insight. The raw material is waste glass from recycling. the plant will be located at the recycling center. The glass will be pulverized to a small particle size and then introduced into the furnace. The machine could be an extruder, like what they make tubing with, and have a tool at the end with an air source to inflate the bubbles just before they are cut. the balls could rotate on a cooling table so that they will not lose their shape.