We decided to make a pen plotter for our project, inspired by the letter drawer example, but graphing rectangular equations. It will function via two stepper motors controlling the movement of a pen module on the x and y axes. The pen module will move along a track, itself moving along two tracks, perpendicular to the top track. The tracks will be made of extruded aluminum linear rail and the module will move via a pulley system using GT2 timing belt. The pen will be lifted from the paper via a solenoid.
- 30.5in Linear Rail/Extruded Aluminum
- 39(?)in GT2 Timing Belt
- 2x Stepper Motor
- 1x Solenoid
- 1x Ballpoint Pen
- 1x Metro M4
- 1x Prototyping Shield (probably)
- misc. standard fasteners (to be updated later)
- Acrylic for lasercut baseplate
- Filament for 3d printed track carriage
- Movement on two axes
- Libraries for graphing & how to get coordinates for plotting out of them
| Week of 3/4 | Week of 3/11 | Week of 3/18 | Week of 3/25 | Week of 4/1 | Week of 4/8 | Week of 4/15 | Week of 4/22 | Week of 4/29 | Week of 5/6 | Week of 5/13 | Week of 5/20 | Week of 5/27 | Week of 6/3 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Planning/Initial model acquisition | Axes Prototype | CAD for Pen Module | Assemble Complete Prototype/Fix Issues | Spring Break | Research Code/Code | Coding | Finish Code? | Integration/Work Out Issues | Documentation | Extensions/Fixing Issues | Extensions/Fixing Issues | Extensions/Fixing Issues | Extensions/Fixing Issues |
We will know we are successful if the plotter can plot linear graphs with possible extension to polynomials, rational equations, etc. and/or letters and/or svgs.
Coming out of spring break we were running a bit behind, having not quite completed the axes prototype or pen module. We still needed to design most of the pen module, figure out a working end cap design (the initial one failed), and cut the third axis.
As of the penultimate week of school, we are most of the way there, lacking only the motor for the top(X) axis, although much of it is untested. We decided to use a servo to actuate the pen, instead of the planned solenoid. We also abandoned the hard stops at the end, as it would be too much work to figure out a working model, and decided to implement them in code. A contributor to our lack of finishing was the amount of time spent searching for a suitable library for graphing (~1-2 weeks), instead of jumping into the code ourselves. Another issue we had was that we forgot to account for the placement of the motors in our original design.
- 30.5in Linear Rail/Extruded Aluminum
- ~5in GT2 Timing Belt
- 1x Stepper Motor
- 1x Servo
- 1x Golf Pencil
- 1x Metro M4
- 1x Breadboard
- 5 Bolts & 2 Nuts
- Acrylic for lasercut baseplate
- Filament for 3d printed sliders, pen module, and motor enclosure
Back view of design
Front view of design
Top view of assembled project