Heated bed glass plate idea -

Hi folks -
Just wondering if anyone knows if a recycled scanner - glass bed would be suitable
for using a a heated print plate. Is it borosilicate? I just broke my print plate prying a part
in a hurry. Boo! Otherwise I'll have to wait a couple of weeks for the ebay fairy to deliver.

Thanks! - JD

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Prusa I3 - Rework (home built)
w/ heated print bed. Borosilicate glass plate.
Ramps 1.4 board, Arduino 2650
Thermaltake 750watt power supply
Ulti-panel lcd controller
Marlin firmware
Cura - slicer/print software

Regular plate glass from a hardware store seems to work well for a lot of people.

Wow really? I thought the rapid temperature change would cause regular glass to shatter
but if a lot of people find success - that's a great low cost solution. I did take a look at an
old picture frame I have and examined the glass. It's pretty wobbly in terms of being flat.


cheers - JD

+1 - I've been using regular plate glass for the past 2 years and have never had an issue.

Well, regular glass may not be as flat as expected with some spare cups which can make bed leveling tricky if you don't have an auto bed leveling equipment. In my experience, mirror plates are a bit more expensive, but their surface are more flat. It also looks like thinner glass can twist under the action of the leveling screws. IMHO you want at last a 4mm thickness.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

I have used scanner glass on my printer, works great until you drop it. I have shattered regular glass due to heat expansion.

I am using 6mm float glass (also known in some parts as plate glass). It is perfectly flat.
Never had an issue with it. Never shattered and never had a chunk pull away.
A glass shop cut me 3 pieces 200mm x 200mm for 10 GBP. I got them to take the sharp edges off.
I have a standard Reprap bed. I just timed it heating up and from room temp 22 deg C to 110 deg C and it took 14 mins.
Don't know how this compares to thinner glass.
Don't know wher you live, but Ikea do mirror tiles which are the exact size for printing.

Perfectly Flat ---- NOT
unless it has been optically ground
Look at it with a laser or foucault edge tester
It will have hills and valleys
which get bigger and smaller under heating cooling

I have ground mirrors to 1/8 wavelength precision
your plate glass is far from perfect

Quote
dave3d
I am using 6mm float glass (also known in some parts as plate glass). It is perfectly flat.
Never had an issue with it. Never shattered and never had a chunk pull away.
A glass shop cut me 3 pieces 200mm x 200mm for 10 GBP. I got them to take the sharp edges off.
I have a standard Reprap bed. I just timed it heating up and from room temp 22 deg C to 110 deg C and it took 14 mins.
Don't know how this compares to thinner glass.
Don't know wher you live, but Ikea do mirror tiles which are the exact size for printing.

All good info.! - I just went in my attic and found a halogen construction work light I have.
This light is the kind with 2 square lamps that can be tilted in any direction for painting, etc.
Anyway, the tempered glass lens is the perfect fit for my standard Reprap Prusa I3 printbed.
It's a bit heavy though - 5mm thk. Might affect the machine during rapid infills. I'm noticing a lot
of step skipping now, but not sure it's related to the new added weight. I'm thinking that might be due to
a failing Stepper driver or Ramps board.

JD

cosmicray:

Thanks for the lesson on optics. I think you are splitting hairs. From your handle I assume you are a stargazer with precision optical equipment. For a Reprap printer like I (and most people) have got, the variation nozzle clearance across the bed with float glass is not detectable with a feeler gauge. It is less than 1 thou. inch. For all practical purposes for 3d printing it is flat.
Nothing is perfectly flat. Maybe I should have been more precise. It is down to semantics.

Quote
cozmicray
Perfectly Flat ---- NOT
unless it has been optically ground
Look at it with a laser or foucault edge tester
It will have hills and valleys
which get bigger and smaller under heating cooling

I have ground mirrors to 1/8 wavelength precision
your plate glass is far from perfect



Really not necessary for a 3D printer. Ordinary glass is plenty good enough.

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_______________________________________
Waitaki 3D Printer

I agree with waitaki, ordinary glass that can be purchased from a hardware store is suitable. Why would we be conserned with nanometer tolerances for the heatbed when the hot end z-axis has tolerances in the 1/10th of mm scale? We wouldnt or shouldnt.

On regular glass from homedepot-alike, 4 purchased, 3 ot them have a cup of about 0.3mm near the middle. Mirror plates have +-0.05mm cups and hills. That's managable.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

0.3mm is a lot. It must be poor quality picture glass. Maybe imported from China.
I print at 0.2mm layer height on top of 6mm float glass. Once the bed is levelled, the difference across the bed is not measureable using the sheet of paper test or a feeler gauge.

In the past I have also used a large piece of thick float glass as a surface plate. With some grinding paste it is ideal for making sure motorcycle crankcase halves are perfectly flat before reassembly.

I normally use 1/8" aluminum plates instead of glass they heat up much quicker and when I use my temp probe on it the edges heat more evenly.

I also have two pieces of tempered glass; they are 3/16" tempered glass. I bought one 8 X 16 rectangle for 12.99 plus tax at a pet store and took it to a glass shop and had them cut it for $3, so I have two perfect pieces with really nice smooth edges. I called the glass place before that and they didn't offer small tempered pieces just plate glass in small pieces and had to order tempered. So it opened up the door to letting me bring in a piece to cut. So all together I spent about $18 for two.

Edited 1 time(s). Last edit at 12/19/2014 08:12PM by AquaticsLive.

I managed to get a couple of borosilicate Glass sheets... but they are not flat enough to use.. but they wont shatter with heat. I measured 0.3mm across the 200 x 200 whish is quite poor.. I might try some aluminium sheet..

Edited 1 time(s). Last edit at 01/09/2015 12:42AM by moth4017.