Proposal for End of Term Project: Sand Plotter

Introduction

Many designs of sand plotters are found on the Internet. When I first thought of doing this, I was unaware of how well trodden the path is, however I am not discouraged because it will be a good test of fabrication and still leave plenty of scope for designing patterns that can also be interactive to external environmental factors.

Movement or sound could modify the emerging pattern of the plotter, which may run continuously for extended periods. Thus, patterns can be drawn in a circular (it could be square also) enclosed chamber with a steel ball or cylinder.

Construction

Under the enclosed chamber is a revolving double rail, powered by a high torque stepper motor. The double rail will have a magnet mounted, pulled in the y axis by another stepper motor. The control board will be an Arduino mega with a Ramps shield board (or similar) comprising polulu stepper drivers.

So, with one circular motion and one lateral motion, circular patterns can be drawn in the sand.

Software to control the Ramps board will be developed and also some runtime scripts developed to demonstrate the sand plotter.

Prototype

First stage will be to construct a frame without enclosure, mounting the mechanical parts. A very simple test script to move the turntable and lateral axis with be the first stage.

Second stage is to provide accurate control of the stepper motors

Third stage is to fabricate the sand enclosure and outer box (laser cut)

Fourth stage (possibly too much in the time alotted) – to build some interactivity with external sensors, thus modulating the sand pattern in real time.

Dimensions

I do not want to build anything too large, it becomes impractical, however it must be large enough to look impressive in a gallery setting. So, at least 50 cms diameter.

Examples:

I am not the first…

https://youtu.be/7SyORW-bhLQ

http://forums.jjrobots.com/forum-34.html

Main Parts list:

Laser cut enclosure

Bearings for circular movement

2 x Nema high torque stepper motors

toothed belt, possibly 3d printed gears, metal belt pulleys,steel rods and linear bearings (I have most of these parts from building a 3d printer)

limit switches – these may not be mechanical but optical sensors

Ramps shield and Arduino Mega, polulu stepper drivers

Steel rods and 3d printed supports

Neodymium magnet

15-20 mm diameter steel ball

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