Solid buffer screen for Pika buffer

Had a bit of an issue with the endless spool and Pika buffer. When a runout is detected, a bowden lengths worth of filament is retracted into the pika buffer. 

However it cannot coil itself around the wheel, since the runout meant the end of the filament was reached in the pre-gate sensor, hence all of it was uncoiled from the buffer. This resulted in the filament escaping its cage and wandering in the neighbouring cartridges. 

This can cause a big tangle as the filament can get caught in the unwound buffered part of the neighbouring cartridge. 

A way to mitigate this is to make the rear cartridge plate solid so the filament cannot escape into the next cartridge but rather be forced to stay in its own. 

This remix aims to address this shortcoming by creating a 3 layer tall solid wall for the rear side of each cartridge. In addition, this also reduces the probability of filament wandering into its neighbours if during retraction the buffering process fails.

This is only the rear panel for each cartridge. For the rest of the files please visit the Pika GitHub below: https://github.com/geoffrey-young/pika-filament-buffer 

A remix of the Pika buffer screen to prevent filament escaping from the cartridge and tangling with its neighbour.