Where's the Glass?

[Randolph]

To anyone building a Hadron,
What glass are you using on the heated bed and where did you get it?
Especially if you are using a LAVA heated bed. The LAVA is 216mm x 216mm;(8.5 x 8.5 in.)
The only borosilicate glass I can find is 8.5in. x 7.8 in. (at Lulzbot.com for $25 plus $14.90 shipping).
I can order a piece cut to size from the local glass shop for $68.50. Pricey.
Thanks,
Randolph

[orcinus]

I'm using a cheap mirror.

I used to subscribe to the idea that borosilicate is the only way to go. But so far, absolutely no problems with a mirror. Haven't gone over 70deg C yet, though.

It does have an issue i'm pretty annoyed with, though - the surface isn't flat. If i set up the nozzle to 0.2 mm from its surface, and let it travel along X, it'll float in and out of contact with the glass surface about once every 4-5 times over the whole 200mm range.

It could be that my gantry is wavey (the V wheels or the Makerslide), but i doubt it. It's far more likely the glass was rolled unevenly. Another thing to watch out for when buying glass for your ORDBot.

[Enraged]

I walked into a local glass shop (the kind that does windows, mirrors, showers, etc) and got 4 pieces of 8.5" x 8.5" glass for $10. There is no need to order online and pay shipping, just find a local glass shop.

[frob]

Hi Randolph,
You don't really need borosilicate glass, because the temperatures involved are well withing the "safe" zone for plain window glass. If you're worried about the strength of the glass,
you can get tempered glass, which is also available at any glass shop. I walked to the nearest one 4 blocks from here and got some lightly frosted glass which looks cool and i thought might help the plastic stick better- and had them bevel/ polish the edges and corners to make them safer to handle. the beveling and polishing is expensive, but the glass is not - the total was $25 per piece of 5mm thick frosted /beveled/polished tempered glass. If you have a belt sander and some fine emery belts (240-320 grit works well) you can do the polishing yourself- and pay about $5 per piece for 3mm plain window glass.
On a side note, i am looking into trying some of the special glass-ceramic used on franklin stoves and cooktops to try out, just to see if it makes any difference in performace - these materials are engineered to be especially transparent at longwave IR (heat) so may help speed up things, in theory at least.

To anyone building a Hadron, What glass are you using on the heated bed and where did you get it?....
Thanks, Randolph

[Randolph]

4 pieces of 8.5" x 8.5" glass for $10.

Hmmm. Another case where ignorance cost money. I paid $39.90, including shipping, to get the borosilicate glass from Lulzbot. AND, it's .7 in. too narrow to fit the LAVA when it gets here.
I should have thought of the "plain window glass" solution. If I break one, it's cheap. Since I like to experiment, I'll pick up some of that anyway. I have a 6" x 48" belt sander that will take care of the edges. I have worried about regular glass not being flat enough, but I have a 18" x 18" granite surface plate that I can use to lap it perfectly flat if it isn't already good enough.
I know. I will have more invested in time than it would cost to buy, but I have to have some of the fun.

[macona]

How big of a piece of glass do you guys need?

You might look at old IC Masks. They are usually 6"x6" and either 1/8" or 1/4" thick. They are usually made from quartz/fused silica and are very tough and highly heat resistant. Once side is clear and the other has a layer of chromium where the mask is etched. They are very, very flat.

A friend of mine sells them at his surplus store for about $5 a piece. If any one is interested I can get some.

[Randolph]

How big of a piece of glass do you guys need?

It depends on the heated bed being used. I have one of Fantz's LAVA beds and it is 8.5in. x 8.5in.
I think the usable area is 8" x 8".