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My boro plate came broken and I don't know how long it will take to replace it. I guess I can call sales Tue the 8th and buy a couple of extras to be sent with the replacement and ask for 2 day UPS if I pay the extra shipping over how ever that normally ship replacement parts
Or I can just head over to portland glass and get a 12.2" disc of window glass 1/8" i guess will be closest to 3mm and do my calibration with that

I expect that if I calibrate on 1/8" window glass I will need to do it all over when the pyrex gets here right?

based on what I got done tonight I think I will be ready to calibrate on Friday (with luck and if I don't break anything.)

SeeMe support suggested I try mirror glass when mine died. Same float glass as plate windows.

It shattered on the second heat cycle, just sitting on the Onyx with nothing else going on. I'm not saying it will happen to you, but my experience says "don't muck around, get borosilicate."

I then bought 5 replacements from an Australian glass manufacturer and, of course, now that I have spares I've never had another problem

Thanks Cap I will call them tomorrow and buy a pair of the pyrex to go with the one they owe me and perhaps in the spirit of the season if I ask nicely they will grab the freight for overnight or two day. whats another $70 when I am in this deep.

I bought cheap window glass from Menard's, and it worked well for quite a while. It was difficult to cut into a clean circle, though. It eventually cracked along one of the rough notches left from cutting a square into a circle.

I've had boro glass ever since, and have never had a problem (which has probably been 3-4 times as long).

Captain Starfish wrote:I then bought 5 replacements from an Australian glass manufacturer and, of course, now that I have spares I've never had another problem

That sounds like a good idea, I'm still on my original glass going on 1 1/2 years. Where did you get it from?

Don't remember anymore, sorry - but I get a suspicion that there's only one place in Aus that does borosilicate and these guys were it.

I wish folks would do a simple search here before doing something that could cause them pain or injury! A couple of things before I get to the show and tell good stuff.

1) Borosilicate glass is explicitly formulated to have low thermal expansion over a large range of temperatures. It's the thermal expansion that is the problem with normal glasses when heated on our heat beds.

2) Pyrex was originally formulated as a borosilicate glass. Corning sold the brand "Pyrex" and now several manufacturers make it. In the United States, the Pyrex name can and IS used for regular glass products. Unless the "Pyrex" item you purchase EXPLICITLY states "for use in oven" or an actual temperature range, it is not safe to use. The "Pyrex" bottom silicon baking pans that a few of us use on mini kisses is safe.

3) regular window glass and mirror glass is not safe to use. The thicker it is, the more dangerous it gets when thermally stressed.

Now for the show and tell.

Back in Feb of 2013 I too went down this path with window glass. I'm a chemist/material scientist and I knew better but I gave it a shot anyway. This happened:

[img]http://mhackney.zenfolio.com/img/s2/v72 ... 5760-4.jpg[/img]

[img]http://mhackney.zenfolio.com/img/s8/v83 ... 5640-3.jpg[/img]

I discovered a shard of glass stuck in the wall behind the printer a few weeks later. If I had been near the machine I could have taken a shard in the eye. It just isn't worth it folks, get the good stuff

Yep I called and ordered a pair of em to add to the one they owe me for it being broken in shipping

and I have requested that they do the 2 day shipping rather than charges the $17 for it but no word yet on if they will do that... or at least help with the shipping.

I did search on pyrex in the subject line but missed the facts of the matter... I did not know that pyrex no longer meant Borosilicate glass... I just thought like Kleenex and Xerox the name lapsed into generally use for heat/cold safe glass thanks for the heads up.

Hmmm... I've been running mirrors on my machines for a while now with no signs of any problems.... I wonder how much I should worry? I have a heat spreader on one and not on the other, but still seems fine. Did you have 24v heated bed, Michael? My beds take some time to heat up -- which I've always welcomed due to the non-borosilicate nature of my glass.

I don't recall if I was running 24V at the time. Slow heat up would be good as would printing PLA at 55°C bed. 100° and I'd be careful.

I've been printing at 115 lately (measured PEI surface temp)... so that's why I'm worried. Rostock takes about 1 hr to heat to 115, my new machine about 30-40 minutes. I figure thats long enough to not pose too much stress.

I would worry at 115°! But, the PEI will keep shards from flying so you are at least a little safer. No matter how slowly you heat, at that temperature there is a lot of stress in the glass.

You got me to look into it. I do certainly have to be careful. According to this page: https://en.wikipedia.org/wiki/Borosilic ... cteristics boro glass can be both in a freezer and at heatbed temperature without cracking. Normal glass will crack with a 37.22 °C temp difference. Luckily I have the bed well-insulated, and an aluminum heat spreader (on one of them). I also keep the room temperature and humidity controlled. I wonder if the cooling of layers fans on heated glass would be the main culprit of failures? Or drafts of cool air in general.

I run standard window glass (1/8th inch I think) on all my printers with square beds.
I've yet to break a piece of glass, but it certainly can happen, and the likely hood increases with the bed size.
I also usually have Either Kapton or PET tape on the beds, which greatly reduces the hazard from breaking.
The one advantage of window glass is it tends to be flatter than borosilicate glass.
Short version if I broke my build plate and I needed to print something that would fit on one of my existing glass plates, I'd make do with one of the pieces of window glass I have on hand.

Also thickness. 1/8" is much better at dealing with stress than 3/16" for instance.

I have to add my two cents in here and that is not to use mirrors or plate glass on the Rostock Max or Orion.
I have tried both and the most I got was three heating cycles before both the mirror and plate glass fractured.
There is a possibility of glass flying off the bed with some force and I do not wish to see someone getting hurt.
They use special safety glass in cars for your protection and they use Borosilicate glass on printers for the same reason.

If my glass build plate (from SeeMeCNC ) has chunks pulled out with the print does that indicate it is not "real" boo glass, or maybe inferior quality?
I was shocked the first time this happened, I did not think boro would do that.
This is with Aquanet hairspray and ABS.

Is there any way to test or tell if build plate is really borosilicate glass?

bvandiepenbos wrote:If my glass build plate (from SeeMeCNC ) has chunks pulled out with the print does that indicate it is not "real" boo glass, or maybe inferior quality?
I was shocked the first time this happened, I did not think boro would do that.
This is with Aquanet hairspray and ABS.

Is there any way to test or tell if build plate is really borosilicate glass?

Here is one link: http://glassshop.sites.yale.edu/helpful-glass-facts

Eaglezsoar wrote:

bvandiepenbos wrote:If my glass build plate (from SeeMeCNC ) has chunks pulled out with the print does that indicate it is not "real" boo glass, or maybe inferior quality?
I was shocked the first time this happened, I did not think boro would do that.
This is with Aquanet hairspray and ABS.

Is there any way to test or tell if build plate is really borosilicate glass?

Here is one link: http://glassshop.sites.yale.edu/helpful-glass-facts

So, we all need quartz build plates!!

Or ditch the glass altogether, use 1/4" MIC-6 with a PEI layer on top. You get a flat, rigid heat dissipating plate with arguably the best print surface for PLA and ABS.

bvandiepenbos wrote:If my glass build plate (from SeeMeCNC ) has chunks pulled out with the print does that indicate it is not "real" boo glass, or maybe inferior quality?
I was shocked the first time this happened, I did not think boro would do that.
This is with Aquanet hairspray and ABS.

Is there any way to test or tell if build plate is really borosilicate glass?

One way to test would be to heat the plate up to 100 celsius then dump it straight into cold water. In theory, boro should not suffer any damage.

My mirror is 3.6mm thick, over 1/8" so maybe I'm a bit safer due to the thickness. I'll still keep the temperature deltas minimal.

bvandiepenbos wrote:Is there any way to test or tell if build plate is really borosilicate glass?

Use it. If it explodes in your face, it probably wasn't borosilicate.

Actually thick is worse than thin when it comes to thermal stress in glass. Be careful.

bot wrote:

bvandiepenbos wrote:If my glass build plate (from SeeMeCNC ) has chunks pulled out with the print does that indicate it is not "real" boo glass, or maybe inferior quality?
I was shocked the first time this happened, I did not think boro would do that.
This is with Aquanet hairspray and ABS.

Is there any way to test or tell if build plate is really borosilicate glass?

One way to test would be to heat the plate up to 100 celsius then dump it straight into cold water. In theory, boro should not suffer any damage.

My mirror is 3.6mm thick, over 1/8" so maybe I'm a bit safer due to the thickness. I'll still keep the temperature deltas minimal.

Borosilicate glass will explode with rapid cooling.
In a moment of utter stupidity I once ran cold water over a pyrex baking container in my sink when it was at perhaps 300F, I was picking up shards of pyrex from all over my kitchen floor for months afterwards.
It's less likely to break under heating and cooling, but it isn't magic, and if the expansion is fast enough you'll break it.

mhackney wrote:Or ditch the glass altogether, use 1/4" MIC-6 with a PEI layer on top. You get a flat, rigid heat dissipating plate with arguably the best print surface for PLA and ABS.

what are the plusses and minuses of using the MIC-6 in this way...

its easy enough for me to slap the 12x12x1/4 inch MIC-6 plates i see sold on eBay for $25 each on to my bridgeport and trim them into a circle.
so cheaper than boro and unlikely to break... it can't be that simple or everyone would be using them and SeeMeCNC would be provided them in the kit rather than the breakable boro
and selling them with the PEI bonded on them should be a product found at places like tricklaser yes? no?