Giving the heated bed some room to move

posted in: 3D Printing | 0

Physics and material science says that when you heat up a block of aluminum, it is going to expand. Now that expansion isnt a whole lot, but over a 330×330 plate going from room temp (20C) to 110C in a short period can really stress the material and does cause some expansion.

I timed the heat up from room temp on the heated bed today from 20C -> 90C and the new printer can do it is just a hair over 1min 45sec. That is due to the 750W heater under it. I was thinking about materials expansion, warping, and stresses this kind of heat up can cause. I also looked at what e3d is doing with their ultra high temp beds they make.

Photo of e3d’s heated bed

Note the 45deg cuts for the mounts. On a CoreXY style printer (or just a cube like mine) the heated bed moves in the printer very little, so you don’t need to crank it down (there is no lateral torque as it just moves up and down). Putting some 45 deg cuts to enable the material to expand in all directions ensures the plate itself isnt overly stressed, or distorted.

Because my 1/4″ thick aluminum plate cant be altered like that without a lot of work, I went about changing the mounting mechanism itself:

This is the heated bed mount for the Z table – the one on the left was the original one I designed. The one on the right is my new design with a 45deg slot for the screw.

Putting a 45 deg slot for the mounting screw ensures the table can slide as material expands if needed, and also keeps things stable since the table cant move on its own unless it moves in all 4 directions at the same time (heat expansion).

New on the Left, old on the right. excuse the under extrusion on the top layer… something changed and I am working to ID why it started happening on these parts.

When bolding the assembly together, I ensure there is enough tension on the lock nut holding the bed down onto the Z table that it doesn’t move, but the table with enough consistent force can slide in the slot. The hard fiber high temp spacers slide easily on the NylonX, and the lock nut under has a washer to help it slide as well.

Seems like an easy solution for a potentially frustrating issue. Figure i’d share. Now back to trying to figure out wtf happened with my top layers.

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