Rebuilding Wilhelm: Part 2

Read Part 1 here!

Once I had the frame squared and true, I had to wait for the new mounting hardware to finish printing. So I got to work on the build plate mounting system:

I knew that the Y axis that the build plate rides on was one of the weakest points on Wilhelm, so I thought that moving the linear bearing guides closer to the centerline would help keep the build plate mount true. And yes, that is a cut down aluminum cookie sheet! When I started 3D printing, it was a hobby. It was far less expensive to cut it down and drill my own holes than to have a custom aluminum plate made.

Next, I needed to fix the X axis. I knew the original X axis was too wide for the 500mm (20 inch) smooth rods I had, which made it wobbly. My solution was to mounted the X axis closer to the centerline. Of course, that meant that I had to completely rework the Z axis, too.

I tried to use Prusa’s MK3 X axis mounts, and I printed them with no modifications. It didn’t take me long to realize that the original Prusa mounts take a special plastic nut for the Z ball screws. I only had brass nuts, so I modified the Prusa design to use the brass nuts instead. I also modified one side of the mount so that the smooth rods could push all the way through, because it was far simpler than cutting solid stainless steel.

I put all of the linear motion components onto to the frame, and it was starting to look like a 3D printer again. I was feeling pretty good about the rebuild!

Alas, my confidence was short-lived.

It was at this point that I realized the Y axis that holds the build plate wasn’t going to work at all. The 8mm (5/16 inch) smooth rods that the bed was supposed to ride on were flexing nearly 7mm (1/4 inch) up and down! I should have known that the enormous 3.5kg (7lb+) build plate assembly would be too much, especially with the rods reaching nearly 700mm (28 inches) in length. I tried replacing the solid aluminum heated bed with a bare PCB heating circuit board to save weight, but it wasn’t enough to take the flex out of the linear rods. Even with just the mounting plate on the linear rods, there was far too much flex in the system.

After doing some research, I determined that dual linear rails should keep Wilhelm’s build plate stable. But now I have to wait for them to arrive in the mail.

Stay tuned for Rebuilding Wilhelm Part 3!

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