I was not happy with the glass bed , I could not get things to stick to it and it took an age to heat to even 50'C, its 240w heat way too small for such a large piece of glass.
While watching the Prusa XL launch , I was taken by the idea of a segmented bed , so decided to build one for the FrogSpawn. While sourcing a suitable piece of cast tooling plate from the 'works' my friend overheard what I wanted it for and promptly donated ten 120x100 heater pads - :-) perfect.
The mod involves bending the front of the existing Z plate , to remove a nice little 'finger-shear' between the plate and the front of the frame. and mounting it below the ball-screw nuts to increase Z range. Four rectangular bars fixed to the underside of the Z-plate and a rear support , stiffen the Z-plate and provide mounting points for the Kastal 300 bed-plates
The heated bed-plates will mount on springs at each corner , with screws for adjustment. Once properly adjusted the bed should stay trammed and level.
The nine 240vac 120w heaters will be controlled from a RaspberryPi Pico with a 9 way PID written in microPython .
The problem I have yet to solve is how to control the bed temperature from Marlin or, via g-code, from the BTT display controller.
Ideally, Marlin would be able to talk to the Pico via a spare serial port and report temperatures back to the display. However, I found no way to do this in Marlin :-(
My work around plan , is to intercept or monitor the serial data between the BTT LCD and the BTT Octopus board and intercept the appropriate M-codes .
Interception , means breaking the like between the two boards and inserting the Pico , but now the Pico would have to handle all the traffic and could be a potential bottleneck.
Monitoring means just sniffing the data going to the Octopus board and picking up the bed control M-codes as they pass by. In order to let Marlin know the bed temperature , the centre plate's thermistor would have to be paralleled with both the Pico and the Octopus . Any thoughts?
