New Dual Nozzle Hotend Assembly with Z Probe

This is really the trickiest and most unusual component in the Gemini 3D printer.
A lot of parts need to be assembled into a small space to pack all the hotend electronics into a chassis that can move smoothly and consistently.

Some of the features of the chassis design:

• 2x 0.4mm nozzle J-Head Mk V-BV hotends (from hotends.com)
• 2x 12v 25mm fans for cooling the fins in the PEEK portion of the J-Head (software controlled, triggered by hotend temperature)
• 2x Pneumatic pushfit connectors to fit 2mm ID/4mm OD PTFE tubing for bowden style extrusion

Thes features are new or improvements over the initial proof-of-concept prototypes:

• 3-point vertical sliding mechanism, spring loaded and running on PLA bushings. The guide rods are polished aluminum.
• Bolt-clamps for the aluminum rods.
• Fans are enclosed for better forced-airflow through the J-Head vents, and reduced air leakage towards the heating blocks
• Ducted air channels for targeted print cooling. The 12v high-CFM blower fan is mounted on the rear of the X carriage (not pictured)
• 1x Z endstop microswitch – when the primary (right) nozzle makes contact with the print bed, this triggers to inform the firmware that the print bed height has been found. It is manually adjustable by loosening the clamp bolt and sliding it up or down the guide rod. This design puts the switch even more inline with the motion of the chassis that the prototype models and allows the design to be more compact.
• By integrating the fan mounts, and hotend groove mounts together the design is easier to print and assemble, as well as being sturdier.
• pushfit bushings allow for easy replacement and reduces the complication of previous prototypes.

This chassis assembly will require some minor revisions to the existing X carriage mounting system. Although the M4 bolts are spaced the same as previous prototypes, the assembly mounts lower on the carriage.

More work still needs to be done on the X carriage, but this hotend chassis is a fairly stable design now and will soon be merged into the master git source.