DIY Adjustable Hot Wire Cutter

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FIRST OF ALL: THANKS instructables for the this fucking website, just when i'm trying to put the finishing touches on this fucking project it decides to refresh the page and because it has no autosave it fucking removes everyhing I have written. thanks.

In this Instructable I an going to show you how to make a 'DIY hot wire cutter' to cut through styrofoam. Using a lot of DIY work and objects, lets begin!

DISCLAIMER: The wire you are going to use to cut will be around 300°C so be carefull to only let the styrofoam touch the wire! Safety is your own responsibility.

Step 1: Prerequisites

The things I used:

  • ATX PSU (see step 3 for more info).
  • Arduino UNO
  • Potentiometer
  • Button
  • LED
  • 300ohm resistor
  • Breadboard
  • lots of wires(also a few long ones)
  • 6.78ohm / meter nichrome wire
  • LEGO Technic axis
  • 4x wheels
  • 2x thread loops
  • wood to make the frame
  • some styrofoam to test and play around with!
  • tape

And you will need a hammer and some nails to hold the frame together

Step 2: Getting the Correct PSU/Nichrome Wire Configuration

Because you want the wire to be around 300°C you will need to figure out which combination of power supply and wire you will need.

Luckily you don't need to calculate this yourself. There are a lot of sites that will do this for you, I used this one.

You will probably want the wire thickness to be around 24gauage since this gives a nice balance between being small and not bending too much.

next you will look if you have a power supply at your disposal. I had a ATX PSU. They have a lot of different voltages (they have connectors: -12v, ground, 3.3v, 5v, 12v) so alot of combinations can be applied. I used the ground to 12v so filling in 12 volts in the calculator and setting the bullet point to length brought me to about 65cm.

So this is how you can figure out your configuration.

Step 3: Powering the ATX PSU

The first step should be getting your wire cutter to work, then we will make it adjustable.

A ATX Power Supply is not designed to be used outside of a computer, so we have to trick it into letting it think that its inside of a computer.

The first step is to connect its PWR_ON pin(the green one) to ground(the black one). this can be dont with a paperclip but we will use a Relay so arduino can turn it on and off.

When you connect the power supply's green and black wire and plug into the wall you should see the fan spinning up. if not, your power supply is probably broken.

Step 4: Wire Everything Up

as you can see, this is the circuit you should make.

Go ahead :)

Step 5: Create the Frame

now that the electronics are all wired up you can make the frame.

I made mine from two poles on a square board with a plate at the back for the drill

Step 6: Program Arduino

With the electonics wired up and the frame completed you can now tell arduino what to do! With the following program:

#include <Servo.h>

const int BUTTON = 9; const int RELAY = 10; const int POT_METER = A0; const int SERVO_PIN = 11; Servo servo; const float servo_div = ((float)1023) / ((float)180);

int buttonPressed = LOW; unsigned long lastPressed = 0; const int debounce = 200;

int oldVal = 0;

void setup() { Serial.begin(9600); // put your setup code here, to run once: pinMode(RELAY, OUTPUT); pinMode(BUTTON, INPUT_PULLUP); pinMode(LED_BUILTIN, OUTPUT); servo.attach(SERVO_PIN); pinMode(POT_METER, INPUT); }

void loop() { //read button input int buttonState = digitalRead(BUTTON);

unsigned long current = millis(); if(buttonState == HIGH && current - lastPressed > debounce){ lastPressed = current; buttonPressed = !buttonPressed; }

//write button state to relay digitalWrite(RELAY, buttonPressed); digitalWrite(LED_BUILTIN, buttonPressed);

//move relay to POT_METER value int val = analogRead(POT_METER); val = val / servo_div; Serial.println(val); servo.write(val); delay(abs(val-oldVal)*15); oldVal = val; }

Step 7: Install the Moving Axis

With the frame and circuit completed you should be able to create the moving axis.

I made by axis from LEGO Technic so the drill head with a + shape could fit in it with no problem.

Then you should connect a wire from each end of the servo to the end of the drilling machine trigger.

make sure that it is taped or glued on the trigger so when it pulls back it wont slide off.

Step 8: Setting Up the Cutting Wire.

Now with the moving axis in place. Its time to let your wire be moved.

First you should span a thread around each of the wheels vertically.

Then you should wrap around electric wire each thread so the wire stays at that position. Then wrap the Nichrome wire around the electric wire so it makes contact and doesn't fall off. no connect the other ends of the electric wire to the power supply, one side should go to the 12v pin (the yellow one) and the other to ground (the black one).

Step 9: Test It

Turn on the arduino, plug in the power supply and start cutting!

for the controls:

the button is for turning the power supply off (you will be able to smell if it is on for a while).

the potentiometer is for letting the servo turn which will let the drill turn which will let the axis turn which will let you move the cutting wire up and down!

now take a piece of styrofoam and try not to cut yourself! :D

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    Nice design. You could use this to cut really large objects.