Note: my first NXT Pin-Plotter was released on March 2007. This page describes a second release which never entered into serious action.
Important: my LEGO® bricks index page is here!
NXT Pin-Plotter I (March 2007):
- maximum resolution 82x104
- needle (and partial drawing) always well visible while printing
- parses a PBM image bitmap contained in the NXT filesystem
- 100% LEGO parts except needle
- clean design.
- paper sheet must be taped
- low printing speed (two motors already on 95-100% power)
- before printing, needle position calibration is required
- needle sync on rotation count (not recommended for thicker paper).
- the NXT brick is on the moving tool
- software is single-task and only requires a bitmap on the NXT
- I think that transferring a bitmap via bluetooth is not worth the work.
- plotted six bitmaps only (I was about to move)
- was able complete a bitmap without human assistance
- I will show one of the plotted bitmaps as soon as I will find one (maybe they also were "lost in translation").
NXT Pin-Plotter II (July 2008):
- higher resolution
- supports thicker sheets and other materials
- 100% LEGO parts except needle.
- pneumatic paper locking (no need to tape it)
- improved gearing and overall printing speed
- no calibration required before printing
- touch sensors on all three restart limits
- software optimization on large white areas.
- needle (and partial drawing) hardly visible while printing
- moving tool should be reengineered to get rid of "half stud quirks"
- a few last-minute patches are still visible near the motors
- less robust structure.
- software routines resemble some "stepper motor" style - NXT brick may be detached from the moving tool (plotter still works; I had it on because it seems nicer).
NXT Pin-Plotter III: what should be improved
Maintain all "pro's" and defeat all "con's":
- no "half stud" quirks
- clean design, no last minute patches
- robust structure
- moving tools should have 4-wheels drive (improved stepping precision)
- sensors should be "on board" (on moving tool) to reduce cable drag
- X/Y motors should remain on their own structure (not external), to reduce drag and friction.
Let users see how it works:
- needle always visible
- partial drawing always visible
- motor rotating parts (at least the orange wheel of NXT motors) also should be always visible.
Paper size and printing area
Sheets should be exactly 105mm tall (13 holes: half an A4 sheet) and at least 137mm wide (17 holes). Two holes are reserved for the margin (the rubber band and the internal "border"), thus the printing area is a bit smaller than 11x15 holes.
Taller sheets are difficult to place because their borders would bend in the yellow tree-shaped guide.
Sheets wider than minimum may be a bit easier to place.
Cutting an A4 sheet in four parts works fine.
NXT Pin-Plotter II: current status
Errors in design made me rework again everything.
It proved to be terribly hard to configure correctly step values for plotting, because of the "soft sliding" method chosen. In fact, the sliding parts rely on Technic arms: there is thus some friction and a less exact axis movement, making impossible a final tuning.
The sliding part must navigate on its own wheels (actually gears), using sliders only for navigation error correction.
Interestingly, this will lead to a complete redesign of the sliding tool, without consistent changes to the base structure.