Cyclops

Cyclops introduces a new way of printing multiple materials not yet seen before in commercially available hotends. By taking 2 input materials and printing them alternately from a single nozzle Cyclops is able to eliminate ooze problems that are inherent in most conventional dual extrusion systems. 

More info - video.

Cyclops requires some care and precautions with regards to slicing settings and setup. The main point to understand is that if a filament is not present in both heatbreaks and fully towards the bottom of the heatbreaks into the heated zone then there nothing stopping liquid plastic from back-flowing up the empty heatbreak and making a horrible mess of the cold side of the hotend. Always ensure filament is present in both heatbreaks before attempting to extrude in order to prevent back-flow.

Cyclops requires somewhat more extrusion force than a standard hotend will normally, and geared extruders are our recommendation. Particularly http://www.thingiverse.com/thing:60531 which is what we use internally for bowden extrusion.

When inserting filament for the first time it is a good idea to insert the filament into the hotend as far as they will go when cold, and then heat up the hotend to printing temperature.

When configuring your slicer for dual extrusion pay attention to the length of retraction used on tool change. Slicers often assume that you are using a fairly conventional hotend and attempt to fully retract the filament out of the hot zone of the hotend with a long retraction when switching hotends. This can cause the filament to be retracted too far out of the idle heatbreak and allow back-flow.

In general we have found that a 1mm standard retraction works well for most situations. Retraction on tool change works well when set to a value of around 1.5-2mm. Any longer than this and back-flow may occurr.

Cura has a useful dual extrusion feature called “Wipe and Prime Tower”. This feature creates a sacrificial tower-object which when the printer has to change extruders the printer will use to purge out the old colour before continuing with the next part of the print. Cyclops works well with values of around 25-35 mm^3 depending on the type of filament being used and the strength of the colours, if you see slow transitions a purge volume of 50 mm^3 may help. In general we find ABS produces much crisper switches than PLA with lower purge volumes, and also seems to produce slightly better quality prints.