Heated Glass Bed (Chinese production)

First, let me preface this with this isn't my first rodeo or printer, I have tweaked adjusted and cursed my fair share of 3d-printers and spools of filament. But I have to say I am EXTREMELY disappointed with the Boro bed on the Robo. Don't get me wrong it works fine for small parts, but I can use my soliddoodle for that. I wanted the robo for the larger envelope.

Unfortunately out of the box the variation in the bed which consists of a 1/8" thick piece of borosilicate glass is +/- 0.15mm across both the x and y axes. To Make matters worse it is not a simple bow either, the variation hit two peaks and valley's over the y-axis length of the glass. The x however is a simple bow. To try and get it flat enough to print a part that takes up the entire bed, I have installed a 1/4" ID C channel down each side of the y axis and slid in shims to flatten the glass (works good for the right and left third of the glass, but the middle section still has some variation which leads to the part coming loose).

OH YEA the heating element doesn't even heat the entire print zone, about 1.25" of the print zone on the front side of the printer never gets hot (glass is a poor conductor of heat).

Here are a few lessons I learned on my various heated bed printers in the past,

1) dont skimp use float glass at least 1/4" thick. It doesn't flex and is absolutly FLAT.
2) Frosted glass holds the work better than smooth glass
3) If using smooth glass, use hairspray to get the ABS/Acetone solution to stick to the glass
4) install the heater on an aluminum plate attached to the underside of the glass to heat the entire glass plate.

So has anyone else seen this, or am I the only one seeing this issue.?

 

I believe some one said that their Y belt was too tight and causes the bed to bow, Have you checked that?

 

That was the first thing I looked at, the measurements cited were taken with the y belt completely loose, besides that wouldn't account for the variation across the X. BTW I also loosened the mounting bolts to ensure I was measuring the actual variation in the glass and not some stress imposed during assembly.

I have, since the measurements were made (about three days ago), upgraded to the spring based bed mounts.

 

Yep thts exactly... well I didn't measure all around but i did use the card under the extruder measurement... \
and I had a upward bow of the glass in the center along the Y axis. But it mostly went away to wards the back of the glass... Also have noticed that the mounts for the glass are off center( i knocked my extruder against one of the screws) and the bed heater is not centered in the glass.