Current Project

Etch A Sketch + CNC

Started following the success of the core xy gantry after realizing that an Etch A Sketch is a child friendly gantry. With the intent of increasing my understanding of CNC systems without requiring any custom belt system while also developing experience with 3D printing and design.

Concept:

Diagram of Etch A Sketch internals

While playing with an Etch A Sketch in the Walmart toy isle I realized that the toy is effectively a plotting device. Turning one knob moves the stylus along the X-axis while turning the other moves it along the Y-axis. This is the basis of many gantry systems. After preforming some research I determined it would likely be possible to control the Etch A Sketch with the help of a computer.

The specific layout of an Etch A Sketch is most like a cross gantry, used in many 3D printers specifically UltiMaker S series devices. With this goal in mind, to control an Etch A Sketch with a computer, I set out refining the requirements of the device.

Requirements:

Functional Requirements

CNC Plotting: The system shall precisely control the horizontal and vertical knobs of a standard Etch A Sketch to plot two-dimensional designs.
G-Code Compatibility: The system shall interpret and execute standard G-code commands to control the plotting process.
Etch A Sketch Preservation: The system shall attach to the Etch A Sketch without causing permanent modification or damage to its housing, knobs, or internal mechanisms.
Modularity: The system's mechanical interface shall allow for the a standard Etch A Sketch to be easily installed and removed without tools in under 5 minutes.
Data Saving: The system shall be capable of storing at least one complete G-code program on a non-volatile memory device for recall and execution.

Non-Functional Requirements

Durability: The system shall withstand an accidental drop from a height of 1 meter onto a hard surface without suffering critical failure.
Power: The system shall be powered by a single DC voltage source between 5V and 24V DC.
Safety: All moving gears, electrical connections, and power systems shall be enclosed within a protective housing that prevents accidental contact by the user.
Alternative Control: The system shall include an auxiliary input port to allow for the connection of an external joystick or control device, providing manual control of the plotter's axes.

Proof of Concept:

A proof of concept was developed utilizing materials that were already on hand to keep down development cost and time. This proof of concept used an Arduino Uno with a CNC shield paired with a pair of NEMA-17 stepper motors. The motors and knobs of the Etch A Sketch were equipped with 3D printed gears printed on a Anycubic M3 Photon Premium to ensure quality. The motors were attached to the Etch A Sketch using two mounting brackets printed out of PLA. The brackets were then glued to the Etch A Sketch.

Initial Proof of Concept

This proof of concept did succeed at the main goal of using an Etch A Sketch as a CNC plotting device it failed in almost all other requirements. The proof of concept was attached to the Etch A Sketch and could not be removed. The gears are press fit to the knobs and can not be easily removed. The gears are exposed making it easy to touch and the controls were not protected. The motors are also bulky and require significant amounts of power.

Changes needed:

A frame to avoid gluing anything to the Etch A Sketch
Avoid gears to prevent possible pinch points and to avoid attaching them to the Etch A Sketch
Smaller motors to decrease size and power requirement
Custom controls to reduce size and power requirement
- Current controls contain unneeded features adding to the size, processing, and power requirement

Updated Model:

Utilizing Smaller motors and a slide in design the newly updated model allows the Etch A Sketch to be slid into the device where it can be clipped in to ensure contact with the new gear-less drawing system.

Changes and Benefits:

Smaller motors
- Allow smaller form factor
- Allows for decreased power demands
- Allows for smaller more compact controls
New frame
- No longer requires glue to keep device attached
Wheels vs gears
- Wheels use friction as opposed to gears to reduce pinching
- No longer require gears to be attached to the Etch A Sketch

Drawbacks and Changes Needed:

Material for wheels needs to be determined
An enclosure is needed to eliminate pinching
Frame required the development of clips to hold Etch A Sketch in place

Wheel Material Research:

The first idea was to use TPU. TPU is very bendy and that the wheels would be 3D printed slightly bigger than needed hopefully allowing them to squish around the knobs of the Etch A Sketch. TPU is also slippery, this led to the wheels riding up on the knob, they work for small periods of time and at very slow speeds.

To attempt to solve this issue, a few concepts have been developed:

Place a PETG "core" inside the TPU wheel to hopefully add rigidity
Use silicone molding in conjunction with SLA 3D printing to make a wheel with a hard inner section and a soft squishy outer shell.
Return to gears and use some other attachment method besides press fitting such as using butyl rubber as a temporary adhesive.

The PETG core did lead to better behavior, the wheel stayed in contact with the knob longer and did not slip off as quicky. However, the wheel did eventually ride up on the knob as the pure TPU wheel did.

Next is to try silicone molding, this method requires designing a 3D printable mold in which to inject silicone around a 3D printed center piece to hopefully acquire a wheel with a hard center and squishy outside.

A TPU Wheel Riding On a knob

From left to right, a PETG and TPU wheel with a TPU center, a PETG and TPU wheel without a TPU center, and a PETG and TPU wheel without any PETG

A Silicone Mold Model

To be continued, printing and attempting to mold silicone as of 12/5/2025

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