Help Request - Molding Glass Over Metal

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meat.paste
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Help Request - Molding Glass Over Metal

Postby meat.paste » Mon Jun 06, 2011 1:07 pm UTC

I have a project for work and I'm looking for a reliable way to mold glass over metal. The glass needs to reliably and precisely cover part of the metal. I have been searching for a few days and have discovered that glass makers use a completely different set of terminology than I do.

I have also learned that it is critical to match the coefficient of expansion of the glass and the metal, which I can do. I suppose it is possible to use traditional molding techniques (vacuum molding, pressing, etc.) Glass is much hotter and viscous than the plastic/metal examples I saw on the interwebs, so I'm not sure those methods are feasible.

Tl;dr summary...
If you know of any process to reliably mold glass or ceramic over metal in a way that is precise (within a mm) and can handle a thousand pieces or so without wearing out the mold, I would appreciate your help.
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Velifer
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Re: Help Request - Molding Glass Over Metal

Postby Velifer » Mon Jun 06, 2011 3:34 pm UTC

Ask an ancient Egyptian.

I'd also suggest dropping the notion of a direct metal-to-glass bond and looking into glues. Rearview mirror glue, E-6000, or plain old silicone aquarium sealant could do the trick, and that's not even getting into the exotic stuff like Hextal.
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meat.paste
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Re: Help Request - Molding Glass Over Metal

Postby meat.paste » Mon Jun 06, 2011 6:14 pm UTC

Thanks for the suggestion on the enamel. It won't work directly for what I need, but I'll see if I can find a way to use the technology. I need to have the metal in the glass but not completely covered in glass (electrical contact is needed, but the pieces of metal have to be isolated from each other.)

The glues aren't going to work for me. The part winds up in a vacuum chamber and it can't outgas anything. The temperature of the part is about 250C, which also constrains my options.

I can use vespel (pricey) or alumina (precision ground, so pricy) pieces with the metal inserts in them, but I'm trying to avoid them.
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Moose Hole
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Re: Help Request - Molding Glass Over Metal

Postby Moose Hole » Mon Jun 06, 2011 7:21 pm UTC

1) Put metal into molten glass.
2) Let the excess glass drip off.
3) Put the edges in strong acid to get rid of anything hanging over.

/I've never really worked with these materials, so I'm just guessing, but I think it'll work.

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Velifer
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Re: Help Request - Molding Glass Over Metal

Postby Velifer » Mon Jun 06, 2011 8:55 pm UTC

I've been to this guy's hot shop, and bought some of his work. He puts metal into some of his designs.
http://www.glassbyjm.com/

He's pretty cool, (very into education) and if you call him up and explain what you're doing, he may share some secrets.
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Seraph
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Re: Help Request - Molding Glass Over Metal

Postby Seraph » Mon Jun 06, 2011 10:09 pm UTC

Do you have a furnace of some sort? Controlled atmosphere?

You don't give much information but it sounds like you're looking for a ceramic to metal braze, but without some idea of what your metal is, and what your glass/ceramic is it's hard to make a suggestion. You'll need to find something you can melt, that doesn't react with what your trying to join, and that wets both the materials you're trying to join.

The enamel suggestion also sounds like a good one, it's sort of the same idea as the brazing, but using a glass rather then a metal as the 'glue'. I'm not an expert on glazes/glasses but based on what I've seen other people do you'd probably want to form your enamel in situ. That is, come up with a paste that forms an low temperature glass when fired, apply that paste to only the areas where your parts will contact, press the parts together and fire. Bonus points if your two parts will diffuse into it a little. I've seen this technique used to join two ceramic pieces so it might work for ceramic to metal.

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Qaanol
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Re: Help Request - Molding Glass Over Metal

Postby Qaanol » Tue Jun 07, 2011 12:15 am UTC

I don’t have first-hand experience, but would it be possible to use geometry to do the binding for you?

That is, shape the metal to have small hook-shaped (for example) protrusions that get engulfed in the glass. Then when the glass solidifies, it forms a sort of “jigsaw” interface with the metal. This may not work for you, especially if you require certain geometry-dependent electrical properties at the interface between materials.

This could also be done in reverse, with small holes drilled into the metal at various angles. When the glass fills them and then hardens, there is no single direction in which the glass can move, so it is firmly attached.
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ikrase
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Re: Help Request - Molding Glass Over Metal

Postby ikrase » Tue Jun 07, 2011 12:38 am UTC

Some ideas:
-Can you by any chance clamp the metal between two pieces of ceramic or glass, using a bolt?

Can you use an off the shelf item such as a light bulb filament support?

-Are there any cheaper ceramics you can use?

-McMaster Carr sells two-part castable alumina bisque ceramic, that is moldable. Look under castable ceramics

Can you insulate the wires with ceramic wool and then use another wire to bind this all together? (getting rather kludgy)

Can you cast metal into ceramic?
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Technical Ben
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Re: Help Request - Molding Glass Over Metal

Postby Technical Ben » Tue Jun 07, 2011 9:02 pm UTC

Velifer wrote:Ask an ancient Egyptian.

I'd also suggest dropping the notion of a direct metal-to-glass bond and looking into glues. Rearview mirror glue, E-6000, or plain old silicone aquarium sealant could do the trick, and that's not even getting into the exotic stuff like Hextal.


I so want to know how you know all those glass usable glues. :D
Aquariums and arts and crafts? ;)
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Velifer
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Re: Help Request - Molding Glass Over Metal

Postby Velifer » Wed Jun 08, 2011 12:28 pm UTC

I've built custom aquaria, had crappy old cars where the mirror dropped in my lap, worked with groups of artists including glass blowers, and have a Magical Knowifying Device.
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Re: Help Request - Molding Glass Over Metal

Postby Aelfyre » Wed Jun 08, 2011 12:37 pm UTC

Velifer wrote:...and have a Magical Knowifying Device.


You down with MKD? (yeah you know me!)
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Technical Ben
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Re: Help Request - Molding Glass Over Metal

Postby Technical Ben » Wed Jun 08, 2011 1:47 pm UTC

Velifer wrote:I've built custom aquaria, had crappy old cars where the mirror dropped in my lap, worked with groups of artists including glass blowers, and have a Magical Knowifying Device.


I was all with you until the MKD. It's all head knowledge if you have not put it into practice. But as you have done all the other stuff, you get an A* for application. :D
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Minerva
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Re: Help Request - Molding Glass Over Metal

Postby Minerva » Thu Jun 09, 2011 6:05 am UTC

If you can track down somebody who makes or repairs gas lasers, or makes specialized high-vacuum equipment for experimental physics, then you can probably find the resources needed to make a good glass-to-metal seal.

Glass-to-metal seals are not completely uncommon, when you start looking at gas lasers, vacuum tubes, CRTs, X-ray tubes, apparatus for atomic optics, stuff like that.

http://en.wikipedia.org/wiki/Glass-to-metal_seal
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gmalivuk
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Re: Help Request - Molding Glass Over Metal

Postby gmalivuk » Mon Jun 13, 2011 7:31 pm UTC

Technical Ben wrote:I was all with you until the MKD. It's all head knowledge if you have not put it into practice.
And what's wrong with head knowledge? The problem is that Google results are *secondhand* knowledge, not that it's head knowledge you didn't get from doing it yourself. For example, if I see someone else doing it, that's still head knowledge, since *I* never applied it or tried it. But that doesn't mean it's less valuable than that person's own practiced knowledge.
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meat.paste
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Re: Help Request - Molding Glass Over Metal

Postby meat.paste » Sat Jun 25, 2011 4:59 am UTC

Thanks fellow forumites. For the application I needed, I went with a traditional overmolding approach with metal inserts into plastic. My plastic just happens to be >700C and made of glass.
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Technical Ben
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Re: Help Request - Molding Glass Over Metal

Postby Technical Ben » Sat Jun 25, 2011 8:09 am UTC

gmalivuk wrote:
Technical Ben wrote:I was all with you until the MKD. It's all head knowledge if you have not put it into practice.
And what's wrong with head knowledge? The problem is that Google results are *secondhand* knowledge, not that it's head knowledge you didn't get from doing it yourself. For example, if I see someone else doing it, that's still head knowledge, since *I* never applied it or tried it. But that doesn't mean it's less valuable than that person's own practiced knowledge.

Nothing wrong. I just find it more interesting to see the results, then just get a description. That head knowledge is great, but practical application is better. So they are both good.
If you think all knowledge is equal then fine. But go try playing tennis with someone who has practices daily, and someone who only watched/read on the subject. :wink:
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