Glass bed not flat

I have finally checked to see if glass bed was flat because I knew my bed was spot on level, and the glass bed varies around .005" which makes a bowl in the center. Belt tension changes it dramatically, both better in some areas and worse in others. Not exactly sure how to fix it, but without it flatter than that....prints over an inch around will be impossible.

 

Update:
Belt was tight, but I went tighter...kept trying, and measuring. I found the sweet spot and its extremely close to perfect now, should be fantastic once my new E3d arrives

I urge anyone that's having first layer issues to put a straight edge on the plate, then move belt while watching it(tighten belt with your fingers). it if gets flatter, that may be something you wanna do.

 

are you using boro glass or regular glass? I would get a piece of boro glass instead of regular glass if so. I have never seen one not flat..(boro glass that is)

 

Ive got the ABS version, so I would guess its boro.

Its certainly no where close to flat with no tension. (you must put true straight edge on it to tell)

 

well the question would be then... did the robo include boro glass or regular glass? boro doesn't warp like that.. and tension shouldn't matter, if the glass is flat it should be flat. boro glass just doesn't flex with tension not at this size.

are you talking about tension of the y axis causing the birch ply to flex?

 

Its the glass that comes on it....says robo 3d hot dont touch etc.

But if boro glass doesnt do that...this one is not boro. This one is easily changed with tension on the belt below the glass.

 

And the pic is terrible, but its without a shadow of a doubt bowl shaped. I would guess .007" or .008" with no tension. The picture is probably a gap of maybe .001"-.002". With decent tension, you could slid two sheets of paper under the straight edge in certain places. The straight edge doesn't lie, and the prints back it up. Im just very happy I would able to get it dialed in really close with just adjustments.

 

If your bed is more like a bowl, there are 2 ways you can fix it.
#1 Put something underneath the bed between the rail and the bed to see if it helps.
If it does, print something and attach it permanently.
#2 Put something underneath the bed between the rail and the bed and increase bed belt tension by couple of teeth to make it warp.
If bed warps down and gap gets bigger, put something thicker in between the bed and rails.

If your bed is warped only at one side, add couple of sheets of paper betwin the spacer and the bed, then tight the screw back on.


My bed was not perfectly flat until i flipped the screws upside down.
Here is how i setup my bed screws.

Works great for me

 

I flipped mine also. Once i added a lot more tension it pulled it pretty close to flat. Close enough that i dont wanna mess with it.