A mechanical arm that writes the time on a small board and wipes it clean once a minute — a remix of Joo's Plot Clock.
BuiltFirst try mid-2016 · Second April 2017
ByAlex Lim & Mark Bala
Field3D printing
The assembled plot clock writing out the time.
We 3D-printed and assembled a "plot clock" — a mechanical arm that writes and erases the time at fixed intervals, using a remixed version of Joo's Plot Clock from Thingiverse.
How it works
Every plastic part is 3D-printed.
Three servos drive movement along the x, y and z axes.
An Arduino is the brain: once a minute it instructs the servos to move the arms.
The arms guide a pen to write the time, then lift it into a cap, which is dragged in a sweeping motion to erase the previous minute.
With the board clean, it returns home and waits for the next minute.
The code can be calibrated for writing speed, lift and positioning.
First attempt
Before we owned a printer, we sent the original Joo STL files to a shop to print, then assembled and calibrated it over two evenings.
Snags:
No tap drill, and the holes were too small for screws — we shaved plastic and forced screws through with an electric screwdriver.
Calibration wasn't great, so some numbers printed strangely.
The marker cap wouldn't fit into its resting slot.
Second attempt
We reprinted every part on our own FLSUN Kossel Delta and got it running reliably this time.