Filament Spool Holder
A Lazy Susan style filament spool system seemed like a natural addition to this printer. The problem was the filament had to go down the center. This was solved by a nylon bolt with a hole drilled through it. That bolts a flange bearing to the top. A disk to support the spool is glued onto that. It then uses a tube attached to a piece on the side to guide the filament from the edge to the bolt. It also has 2 extra keeper to prevent the filament from a full spool from falling off the edge.
Magnetically attached bed
When a part is firmly attached to the bed, I get a little nervous pulling hard on it when it is attached to the rods and carriages. The answer was to attach it with a few Neodynium disk magnets. I used (3) 3/8″ x 1/16″ thick diameter N52 magnets. The magnets on the end effector are in pockets with 0.75mm thick base. This means the magnets never actually contact each other. The bed has them in pockets too, but the pocket is only as deep as the magnet.
I added a ring of LEDs. These LED ring lights are sold for use on cars. I bought mine on Amazon.com.
RAMPS controllers don’t have a lot of options for high current I/O so I hooked this to the unused bed heater output. You can control I/O pins M42 Pn Snnn command where Pn is the output pin number and Snnn is the PWM level. The bed heater pin is 8 on RAMPS. The Marlin firmware protects you from messing with “sensitive” IO pins, so you need to remove HEATER_BED_PIN from SENSITIVE_PINS which is defined near the end of the pins.h file. For some reason “M42 P8 S255″ only flashes the LEDs briefly. All other values below 255 work. You can put M42 P8 S254 at the beginning of the G-Code of your parts or in a script of the host program.