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I just got to the portion of the build where you use the framing square to level and tighten the towers. I noticed that my heated plate is slightly convex (upside down bowl shaped) and I am thinking this might affect print quality down the road. I loosened the hot plate screws and it still seems to have a slight curve to it. I tried adding the glass plate and it seemed to straighten it out for the most part, however I would like to try and fix the root of the issue. Any body else experience this? What are your suggestions to fix it?

Thanks guys,

Ryan

Weight it down in the center to flatten it and re-tighten the screws using the pattern I specify in the manual. (The docs have been updated to reflect this, but pending further changes haven't been uploaded yet.)

g.

I just finished building my V2 last week and I have the same problem. FIRST OFF - I squared the towers to the top melamine plate with the heated bed out of the way. The headed bed is NOT flat, it is convex and on top of that the glass plate is NOT flat,it has a cylindrical curve to it to the extent of .038" across the width in one direction, but fairly flat in the other direction at 90 degrees to it. I also tried to 'flatten' the bed as per the instructions from Gene, but this doesnt work because the screws go into countersunk holes in the plate. The countersunk holes will cause the screws and the bed to sit in exactly the same place every time. My experience and knowledge as a machinist tells me this, so don't listen to the others that say they can do this. IF the screws were not flat head, then yes that process could work to some degree. But that wont work as the glass plate interferes if you use pan head screws.

Another option would be to have a screw in the center of the plate to help pull it down flat - better yet, just get the guys that make the plates, to make them flat, it isn't impossible to do.

So to get around the problem my solution was to insert some brass shims, about 1/2" wide x 3/4" long - thickness as required, between the glass plate and the heated bed. I had the heated bed fastened down, then with the glass plate sitting free, but with a light weight in the center of the glass plate to help hold it in place, I went around the edges and checked the gaps between the plates, using a feeler gauge. I did this in the 6 areas between the screws, where you would place the binder clamps. I got clearances ranging from .016" to 0.25". I then cut up some pieces of thin brass shim stock to make up the thicknesses that i needed for each spot. You have to be careful that you also deburr the edges of the brass where you cut them as the burr will increase the effective thickness on each piece of brass, so polish the edges of the brass with a fine file, or rub it on some fine sandpaper etc to get rid of ALL of the burrs on all pieces.

Carefully stack the brass shims where you need them and then install the binder clamps. Check the flatness of the glass plate now, using the edge of a STRAIGHT metal ruler, and carefully see if you can get it to rock up and down at the ends. If not then you should be close to flat. If you are not happy then put in more shims or take them out if need be. Once you are finished figuring out the thickness, you could glue them together lightly with a drop of THIN CA glue. Use a black sharpie felt marker to mark the position where each shim goes. Use a silver felt marker on the bed.

Now you can go ahead and try setting your Z0 height and tower heights etc. with better success.

One issue that comes from doing this is that you will end up with some air gaps between the heated bed and the glass. i dont know if this is going to be an issue or not, I havent gotten that far. Maybe you will need to crank up the bed heat? IF the heat transfer becomes a big issue, then one solution is to install some of the white heat sink compound that is used on electronics and smear this across the entire underside of the glass. This will transfer the heat, but it is somewhat messy when you take it off.

Anyway, I hope this helps.
Pete