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18/04/2013
CNC Etch-A-Sketch

Computer Numerical Control (CNC) machines are a popular method for automating precision machining processes. Combining precision and repeatability at low cost, CNC machines are now commonplace in industry.

A typical CNC machine may feature three axes, each driven by a ball screw coupled to a motor. Often, two axes are used for X and Y movement along a horizontal plane, while the third is used to control height of the machinery from the material.


A typical 3-axis CNC router

Some common applications:

  • Plasma Cutting
  • Drilling
  • Lathes
  • Printing
  • PCB Manufacture
  • 3D Printing
  • Laser Cutting
  • Routing

And now: Etch-A-Sketch!

The Etch-A-Sketch is a drawing toy, featuring a screen and stylus controlled by two rotary knobs. One knob moves the stylus horizontally (the X plane), the other vertically (the Y plane).

Two axes direction control make the Etch-A-Sketch a perfect candidate for CNC. Rather than attempting to draw by hand, the computer can be employed to automate the task with precision.

Step-A-Sketch

The Setup:

The control signals are generated by the CNC software and sent out of the computer's parallel port. The DB25 cable couples these signals to the KTA-205, which boosts the weak port signals to a level required by the stepper drivers. The stepper signals are then sent to their respective drivers. The drivers interpret the control signals and energise the coils of the motor to generate movement.

Learning To Draw

The CNC software runs a control language known as G-Code, a commonly used programming language for Computer Numerical Control. We obtained our automation script from a plugin for Inkscape, known as gcodetools. We simply imported pictures to Inkscape, then exported the G-code via the interpreter. This left us with about 2500 lines of movement commands for our Etch-A-Sketch.



Drawing the Ocean Controls Logo



Drawing Da Vinci's Vitruvian Man (double speed)


The Etch-A-Sketch Arcade

The Etch-A-Sketch is currently setup in our shop as a demo. Rather than running G-Code, we have employed the SFJ-004 long handle arcade joystick for user input. The KTA-276 Step Pulser receives the direction commands from the joystick, outputting control signals directly to the stepper drivers. Stepper motor speed is set by a potentiometer on the board.


The Etch-A-Sketch Arcade
The KTA-276 Step Pulser can be seen to the right of the joystick.

Getting Involved in CNC

If you are interested in CNC automation, we stock a range of all-inclusive kits to retrofit almost any size machine.

You are also not limited to G-Code, with these versatile stepper motor controllers.

Computer Numerical Control is finding applications outside the process industries; we have helped out customers on a range of custom projects. Get creative!


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-BS



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