Dual extrusion opens up a lot of possibilities for 3D printing. Beyond just multi-color prints, the ability to create designs that use two materials, like a solid component coupled with a flexible component, or a dedicated support material can take your creations to the next level. Dual extrusion comes with its own problems though; the second extruder can hang up on your prints or ooze excess material into your print. The BCN3D Sigma solves this problem by introducing a unique dual carriage design.

Each extruder on the Sigma is mounted to a separate carriage that runs on the same X-axis rail, keeping both extruders in line with each other. When an extruder is not in use, it is parked off to the side; when it’s time for the extruder to get back in the action, it passes over a wiper ensuring any ooze is wiped away for a clean print.

The Sigma pairs its dual extruders with a large enough print volume to suit most everyone’s needs. An LCD touchscreen makes controlling the printer and starting prints loaded via SD card effortless. Since the Sigma is an open machine, slicing profiles are available for Cura, Slic3r, and Simplify3D, and there’s no worry about proprietary filament.

Where the Sigma starts to fall down is on build quality. The ribbon cables that attach the X motor and end stop broke off during our testing, rendering the machine non-functional. The base of the machine is a thin piece of molded plastic that doubles as a spool holder. This piece is all that protects the electronics but it’s thin and flexes in a disconcerting fashion.

While none of these issues are total game stoppers for us, they were a let down for a machine that had so much potential. Despite these issues, the Sigma still scored well in our tests, further increasing our hopes that the build quality issues can be worked out in the next version.

The BCN3D Sigma has a decent worldwide following, with many of its users singing its praises. With its great feature set, we could see ourselves joining that crowd with just a few improvements.