Egg Decorating CNC Lathe (easy to Build)

I have seen some very sophisticated egg decorating machines, but all of them needed precise positioning components, so they are not especially easy to build. Further more your creativity is not involved in the painting any more.

With my solution you still have the possibility to add your personality to the decoration, and it is also very easy to build.

It is basically a lathe, where the rotation is controlled by an exact motor. You hold the pen in your hand, that is the tool for the lathe. You can choose from different rotation patters while you control the pen movement by yourself to preserve the creativity.

Step 1: Requirements

Parts needed

cheep stepper motor with motor driver,
an Arduino microcontroller,
PCD8544 display, aka Nokia 5110 display,
a rotary encoder, a push button,
some scrap wood pieces and a piece of wooden rod,
a nail,
a spring from a ballpen,
a piece thin hard wire and a piece of thick (steady) wire.

Tools involved

saw,
drill with regular drill bits and a bigger one,
pliers,
screws, screwdriver.

Step 2: Preparing the Posts

First the base and the two posts should be formed. Choose pieces are seems to fit for the project.

Drill a center hole in one of the posts, fit the motor shaft in this hole. Now you can mark and drill the mounting point of the motor. After this you can extend the hole with a bigger drill-bit. Attach the motor.

Drill the other post central hole with a much smaller drill-bit. Only a nail will be driven through it.

Step 3: Build the Chuck

Cut two pieces out of the rod. One should be a bit longer, that will fit on the motor.

Drill though this longer one with the drill bit matching the shaft of the motor. Drill a very narrow hole onto the other one, just to prevent it from splitting, when the nail is hammered into it.

Drill three diagonal holes in the rod pieces for the thin wire, and apply the small wires.

Drive the nail through the post, add a spring from a ball-pen, gently hammer the nail in the smaller rod piece.

Attach the other assembled rod-piece in the motor shaft (mounted on the other post).

Step 4: Finalyzing the Frame

Fix one of the post, find the right place for the other post with an egg. You need to go for a distance where the spring holds the egg steady, and nail has some extending end, that you can pull when changing eggs.

Fix the other post in this place.

Form a thick wire as a tool-rest. Fix the tool-rest.

Step 5: Electronics

Connect the electronic parts:

stepper motor the motor driver
motor driver A, B, C, D pins to Arduino pins 9, 10, 13, 11
rotary encoder A, B, Push pins ground and to Arduino pins A4, A5, A3
push button pin to ground and Arduino pin A2
LCD screen SCLK, DATA, CS, RST, CSE pins to Arduino 2, 3, 4, 6, 5 pins

It's a good idea to mount the electronics into a box.

Step 6: Software

Of course you can create your own software for the job, but you can download my software from my project page: https://sharedinventions.com/?p=288

Note, that there is a Program interface. With implementing this interface you can define your own pattern extending my ones.

class ZigzagProgram : public Program<br>{
  public:
    virtual unsigned long next(Stepper8Task* task);
    virtual void callLater(Stepper8Task* task);
  private:
    short _direction = 1;
};