---

Tools used

• Old electric fryer
• Wire cutter

---

Software Used

• Arduino IDE

---

Introduction

In Molding and casting week I had a problem. I needed machinable wax quickly. I had not ordered it ahead, and judging by the delivery time of other consumables, I would not receive it in time at a reasonable cost.

So my decision was easy: in this week's assignment, I will be making a machine that helps me make my own machinable wax.

So yes, I will be using the knowledge acquired in the previous weeks, and even some of the hardware, to achieve a digitally manufactured machinable wax.

---

Safety first

Read this first!! Extracted from Shamrock Candles website and lightly modified.

Can paraffin wax catch fire? Yes, highly-flammable paraffin wax generally ignites at the following temperatures, depending upon its melting point, and the hardeners you mix into it:

1. Paraffin wax without additives: 199°C (390.2°F).
2. Paraffin wax with additives: 249°C (480.2°F).

Because of the additives used in the process we are doing, the mix will exceed 100 degrees, so using a double boiler, which prevents the wax from exceeding the temperature of boiling water, becomes impossible.

So in my project I don't want to use an open flame (gas stove, etc...). The flammability of paraffin causes a problem when melting wax directly on the stove. Watch for signs of overheating: candle wax turns brown, smells bitter, smokes and sizzles some time before it approaches the point of auto-ignition.

How to Put out a Paraffin Wax Fire

So, if paraffin (or candle wax) combusts, how do you extinguish the fire? Do not pour water over burning wax. This impulsive action might be the first thing one thinks of, but it simply accelerates the fire and causes an explosion. Instead, switch your electricity mains off. Stick a lid onto the pot with the flaming wax. This smothers the flames and causes the fire to die down naturally.

---

The process of building the machine and making the Machinable Wax:

1-What I learned from input devices

In Input Devices I made a thermometer, so I wanted to use it to take the temperature reading in order to activate/deactivate the heater resistance and obtain a controlled temperature.

2- The code used

The code I used is for a reflow soldering oven, and it required minimal changes to perform the test.

The problem was the size: it was too big, and in order to use it on the ATtiny45 it loses software serial, so I had to use an Arduino instead. Luckily Zaggo, the author, had a debug mode and all went flawlessly.

I could then use his debug mode to view the changes in temperature.

The project of the reflow oven can be found on GitHub.

3- The build process

You will be amazed what you can find in the trash.

Of course my dumpster diving impulses are much more contained now, in times of a pandemic, but hopefully one day I will be able to go back to one of my preferred activities.

So some time ago I found this fryer.

The brand is UFESA, and I couldn't find much information online except some 2nd hand websites from Southeast Asia.

In Malaysia it sells used for around 20 Euros :)

Turning it upside down, I opened the first cover; there the mains cable could be reattached, as the original was cut.

The second cover revealed much more interesting stuff, let's see:

1. a lever that is connected to some type of current-adjusting mechanism I couldn't identify;
2. a temperature fuse;
3. the resistance;
4. a light bulb.

I believe in the future I could have a servo attached to the lever, or another way to adjust the max current.

The temperature fuse is rated at 228 degrees, adding another level of safety to the project. Nice!

I couldn't find its datasheet, but its part# is DNKD226P.

The heater resistance reads 30 ohms, so it was working, as it matches its label (1600W 220V~).

I calculated it with the following formula:

R = Resistance (Ohms)
V = Voltage (Volts)
I = Current (amps)
P = Power (watts)

I = P / V
I = 1600 / 220
I =~ 7.27 Amps (Thats the current drawn at 220 Volts)

R = V / I
R = 220 / 7.27
R = ~30.26 Ohms

This result matches the reading of the multimeter almost perfectly.

So with the previous information checked, I could continue with the project without the fear of doing it for nothing if the resistance was broken. After all, I found it in the trash.

Next I attached a thermistor with processor thermal paste and Kapton tape.

The 100k thermistor was then soldered to my thermistor board, replacing the SMD thermistor I had used in Input devices.

In the photo below you can see:

1. Mains plug;
2. Thermistor board;
3. Ammeter for future additional safety with current reading;
4. Relay;
5. Arduino Uno.

---

4- Making the wax

As a reference I read the following pages on how to make machinable wax:

1. Instructables
2. Hackaday
3. And this video

I liked the first page the most; they use an electric fryer and that makes all the difference in safety.

Ingredients:

1. Paraffin Wax 80%
2. Plastic Shopping Bags (LDPE, Recycle symbol #4; HDPE is #2) 20%

I tried using HDPE first; it did not work well, it requires a higher temperature and I ended up having to remove it as it would not melt, so in my experience I advise using plastic bags (LDPE), symbol #4.

Here you can see me placing entire bags, no need to cut them.

There is a lot of stirring needed; do it until you can't notice the solid plastic.

When you have a homogeneous mix, add the coloring (not required). I used kids' crayons.

It's nice to see the crayons getting mixed; watch until the end for the effect.

Pour the mix through a strainer; use a better one than mine.

Then, last, pour it into a mold. I unnecessarily placed this paper, as I was afraid of it sticking to the mold; it won't stick to glass.

Success, ready for machining! See the results in molding and casting week.

← (May 20) Mechanical Design, Machine Design · all weeks · Invention, Intellectual Property, and Income (Jun 03) →

Related: Input Devices, Molding and Casting