Update on 7 March 2017
This page has not been updated since the very early days of Hangprinter development. Until someone gives this wiki-page an overhaul, use refer to dev blog (https://vitana.se/opr3d/tbear/) and Github repo (https://github.com/tobbelobb/hangprinter) instead. -tobben
Ideas the design is meant to implement
- A print-head that hangs down in a string from the ceiling.
- Put all the hardware (except AC/DC-converter) in one single unit.
It should be possible to install in a house by simply by attaching strings to anchor points in walls and ceiling, power wire to circuit board and filament to extruder.
Assumed advantages from using house as frame
- Low part count
- Easy to print, assemble, install and distribute
- Huge build volume (especially height).
- When printer is idle, one could retract all the strings. Hanging it in the z-achor point (the ceiling) with no dangeling strings might be elegant storage solution. Could make it popular in big cities, where indoor area is scarce.
- Special geometry-compensating firmware
- Keeping strings tight
- Keeping rotation at zero
- Finding a reasonable home position
- Convincing people to put anchor points (screws) in walls...
Geometry compencating firmware
Converting from Cartesian coordinates to the four wire lengths we need is just a matter of using Pythagoras' Theorem. The maths needed to regulate the velocities properly has not been worked out.
Keeping strings tight
Keeping rotation at Zero
Things that will produce forces
- Dragging filament around
- Dragging power cable around
- Accelerating motors
Rotation around z-axis might be considered less harmfull since one could place the hotend in the rotational midpoint. All motors probably need to be downshifted heavily, and accelerations kept minimal. It might have to be a very slow printer. Will it help to keep all motor shafts in paralell with the z-direction in order to avoid induced xy-torque? Will it need a very thought out extruder?
Finding Home Position
All wires have a markers (ferrite bead? Something black?) that can be recognized with sensors at their max-length. The optical sensors are situated near the motors. Max-lengt and home-length of each wire are set in firmware.
- All motors release wire until max length markers are found.
- All motors roll in wire until home length is reached. Mechanism that keeps wires tight near motor shaft is needed for this.
Motors are working. (Tobben, 17 dec 2014)
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