Timelapse by using SeaStarNC generated toolpath
SeaStar NC
Framework For a Democratic 6-Axis Robot
Year
2019
My Role
Research Resident @SPACE10
Programming, Mechanical Design, Prototyping, Electronics
Industrial 6-axis printing belongs almost exclusively to factory-scale budgets — articulated robots, proprietary controllers, closed firmware. SEASTAR compresses that stack onto a consumer printer. Over a three-month residency at SPACE10, my work produces three open repositories that compose into one platform:
CoaxialSPM, a 3-DOF spherical-parallel end-effector printed on a desktop SLA, geared 1:40 through a 2-start worm and assembled with fasteners alone; Repetier6X, a fork of the Repetier firmware extended for six axes plus extrusion on an Azteeg X3 Pro controller; SeastarNC, a Grasshopper plugin that streams toolpaths and machine state to the printer in real time, opening it to sensor- and image-driven routines.
The total bill of materials lands near $360. The argument is procedural rather than mechanical — that multi-axis fabrication can be unbundled from industrial robotics, and that the design environment, the firmware, and the hardware can be authored by a single hand.
A 6-axis robot needs a wrist that can orient the end effector without dragging mass through the workspace. This platform uses a 3-DOF spherical parallel mechanism(SPM) — three closed kinematic chains, each driven by its own motor, that meet at a single virtual centre coincident with the end effector. Pitch, yaw, and tool-roll resolve at that point; the three motors stay fixed to the upper plate, so almost none of the actuator mass moves with the tool. Compared to an equivalent serial wrist, parallel manipulators dominate on positioning accuracy, repeatability, and payload-to-weight ratio, the three metrics a print head cares about most.
The geometry is purposefully coaxial. A flexible drive shaft for the filament feed threads down the wrist's central axis — the head can tip and yaw freely without disturbing the filament path. Three 2-start worm-and-spur stages reduce the inputs 1:40 and self-lock against back-drive. Everything — worm gear, ring gear, curved linkages, triangular coupler platform, motor seats — is SLA-printed on a Formlabs machine in a single overnight run. Assembly takes fasteners, three NEMA steppers, and the drive shaft, and nothing else. No ball bearings, no machined parts, no jigs. The completed end-effector is roughly the size of a fist and bolts onto an lightly modified $300 Anycubic Linear Plus.
Light Weight
Multi-axis End Effector
Direct Control From Grasshopper
Most robotic 3D-printing pipelines treat the design environment and the machine as separate stages — toolpaths are authored in Grasshopper, exported as a static G-code file, and fired at a printer that has no way to talk back. SeastarNC collapses that separation. The plugin is a real-time link between Grasshopper and the Repetier6X firmware: motion, extrusion, and machine state are streamed to the printer from inside the canvas, and the printer's responses are read back into the same graph. Roughly fifteen components cover behaviour, machine setup, six-axis toolpath generation, streaming, and an in-canvas simulator that previews motion against the kinematic model before anything moves. Because the loop stays open, the printer can be conditioned on inputs a slicer cannot see — a camera reading the last layer, a load cell on the bed, or geometry recomputed mid-print. The plugin's value is less that it drives a printer, and more that it makes the printer addressable from the place where designers already think.
