DrawBot – Onwards and Upwards!

A few thoughts about operating a DrawBot, in semi-organized fashion:

  • Vertical Surface Drawing.  There is an interesting tension in the design of a vertical line-driven drawing robot.  As the drawing surface orientation approaches horizontal, the easier time the robot will have using a standard pen to draw, the more difficult it will be to control the drawing component via a line system, the  greater the weight that would be required,1 a greater weight puts a greater stress on the line and the motor and has some effect on the responsiveness of the drawing component, and the more the weights on the drawing component would be in contact with the drawing surface – possibly causing smudges.  The closer the surface is to vertical, the easier it will be to actually operate as a line-driven robot, the less weight required,2 but the more difficult it would be to have a pressure from the drawing component on the drawing surface.
  • Robot Portability.  Right now my robot is quite portable – and, of course, there are costs and benefits associated with this.  Right now I’m limited to the “size” of my robot at 2’x4′ since that’s the size of the piece of plywood I bought and on which the motors are mounted.  However, it is very easy to just move the robot by putting the plywood in a different location in the house.
  • Robot Location.  This is, in some senses, the flip side to robot portability.  I’d love to put the ‘bot up on the wall and draw something really really huge.  I don’t see that happening until I’m more comfortable running the robot, have found a better pen/paper combination, and – perhaps most importantly – figured out how to run the robot wirelessly or off an SD card.
  • Drawing To-Do’s:  Ideally, I’d like to put the robot to work drawing something on an epic scale.  A high resolution photograph of earth, moon, or pretty much anything from NASA.  Perhaps a map of middle earth, the 100 acre woods, or the Princess Bride story?  A photograph of the world at night, with highlights of the world’s electricity consumption.  Or, some of the INSANELY awesome super sweet posters from various XKCD comics.

  1. This my theory, anyhow.  My reasoning is that as the surface approaches horizontal, the more weight you’d need to pull at the drawing component because more of the force of the weight would be absorbed directly by the drawing surface itself – along with some friction as it passes over the surface as well. []
  2. See reasoning regarding weight above. []

7 Responses to “DrawBot – Onwards and Upwards!”

  1. lanthan says:

    There might be other ways to increase the pen pressure against the paper while keeping the vertical orientation. I am thinking of a metallic board (or any surface coated with magnetic paint) and some magnets on the gondola…

  2. MakerBlock says:

    @Lanthan: I had considered such an apparatus – but a big problem would be the increased force required to move the pen.

  3. lanthan says:

    Yes, the motor shield gives barely enough power to drive higher loads, or a bigger machine with more belt tension. Knowing this beforehand (from some previous diy eggbot experience), I went straight with a couple of stepstick/pololu drivers and some small mods to the firmware. This has been working great.
    The quest is still on for “the ideal pen”

  4. Sandy Noble says:

    I think adding more weight / applying more force (bigger motor) will always give some rewards, because the weight of the gondola will increase while the size of the contact area of the pen tip will remain static

    The obvious solution that most people suggest is to run cords from the bottom corners of the machine too, to have four points of connection, and that way you can add pressure by increasing the tension of the cords, as Viktor does with great aplomb. But I’ve never been excited about that solution – seems a bit like cheating to me! And I suspect not nearly as simple as it sounds!

  5. lanthan says:

    The beauty and power of this device resides in its simplicity… yes, one could add cords/belts and pulleys and get it stabilized that way. On the other hand the more complexity increases, the more the balance might shift in favor of a conventional X-Y table…

  6. natko says:

    Have you considered a small giroscope on the gondola for stabilty, it could be as simple as a dc motor with whell which runs all the time.

    Just a thought.

  7. MakerBlock says:

    @natko: That’s an interesting idea! Overall, the gondola is actually pretty stable. I haven’t had any wobble issues. For the most part it goes where it needs to, it’s relatively precise. Adding and subtracting weight seems to make a difference. However, I suppose that if you need the weight anyhow, it might be interesting to try a gyroscope. Then again, do you think it would the gyroscope prevent it from being as responsive?

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