So I have a new project to build a new 3D printer for myself. My Makerbot is close to it's last days and I wanted a bigger/better replacement. Here it is.
Print envelope is x=24" y=12" z=12". Most of the design and fabrication is complete except for the heated bed.



The problem I am having is dealing with the heated bed expansion based on temperature changes. I haven't even designed the bed because I am struggling with how to attach the bed to the 3 screw/bearing mounts. I have examined other printers that are a little smaller. Most of them put a slot in the bed in the direction of the expansion and then loosely bolt it down. Since my bed will be twice the size of theirs the expansion joint will have to allow about .030" expansion in the X axis, and about .015" in Y.

The second issue is deciding how to attach the bed loosely enough that if the steppers go haywire the bed will not be bent if the 3 steppers are at drastically different heights.

So that is my issue. I expect to use 6061 aluminum .25" thickness bed with a heater attached to the underside. Depending on what we come up with for an attachment there may need to be a minimal frame attached to the bottom of the bed plate.

Here is a close up of the screw/bearing carriage. These can come off an have more holes drilled if needed.



Any of your idea or recommendations are welcome.