The process of constructing our DIY wood etching machine was split into 3 different phases, as we moved from assembling the main structure of the machine, to editing Marlin to equip the 3D printer with new wood-burning functions, and lastly fixing the main pyrography kit onto the machine.
#1 Main Structure
Being provided with a deconstructed 3D printer, one of our team members painstakingly re-assembled it over the span of 2 full days in the lab. Certain components of the 3D printer were removed or replaced, such as the extruder, nozzle, and heater. Additionally, an Arduino board and LCD screen was also attached to the reconstructed 3D printer.
This presented us with a bare skeleton of a 3D printer which we could customise for our team’s specific needs.
Instead of using the existing heating element and thermistor that a regular 3D printer provided, we would separate this section of the wood etching machine by combining the skeleton with an external pyrography kit.
Why?
By using an external pyrography kit, this helps to increase the control that users will have over the temperature of the rod, and serves as a safety feature.
Firstly, depending on the type of wood used, e.g. softwood versus hardwood, the temperature control is crucial for the best quality of wood burning. Softwoods, such as spruce, typically take a shorter time, as well as lower temperature to burn and etch a design as compared to hardwoods, such as mahogany.
By installing an external heating element which can be manually controlled by the user, it allows the user to find the most suitable temperature that is required by the type of wood and design which they are aiming for. Furthermore, this helps to simplify the functions of the wood etching machine, making it more user-friendly, as users are not required to edit the Marlin code to set the temperature that they would like to use for the burning.
Lastly, an external heating element would allow for the power to be killed whenever necessary, such as when the heating rod becomes red hot. This would allow for the rod to cool to a safe temperature before continuing the design, without having to stop and restart the whole etching process.
#2 Coding
With regards to coding, the most work and effort may have gone into this phase of constructing our machine. We used Marlin to enable the required functions for wood burning, and disabled the unnecessary functions of the 3D printer.
Additionally, we had to learn how to convert an image into G-CODE to be processed by Arduino, such that users are able to upload digitally whichever design they wanted to be etched into the wood.
#3 Pyrography Kit
A pyrography kit was purchased from Shopee, which would serve as our external element. Some specifications of the kit are as follows: 220V input voltage, 3V output voltage, 60W power, adjustable voltage range of 0-220V, and temperature range of 0C-800C.
The external heating element is equipped with a variable resistor, allowing the user to adjust the voltage supplied by the machine, and hence adjust the temperature that the rod would be heated to.
Upon a few rounds of manual testing, we noted that the original tips that came with the pyrography kit were not able to produce burn marks that were smooth, and the rod had to be held at an angle to be able to burn the wood properly.
We purchased a new set of replacement tips that essentially had a metal ball-like attachment, which was more suitable for automated wood burning. The round tip allowed for more even streaks and burns to be made on the wood surface. The photos below show the differences in the sharp tip (left) and the rounded tip (right). The original sharp tip produced lines that were often choppy, and did not burn evenly on the wood; the rounded tip could produce much smoother and even lines on the surface.
The rounded tip also eliminated the problem of having to hold the heated rod at an angle, where the original problem arose due to the ergonomics of human-controlled pyrography equipment. The heated rod can now be held vertically (or at any angle) to be controlled by the machine, due to the even heating around the ball tip.
#4 Other Considerations
A manual kill-switch was chosen for our machine, over an automatic one. As mentioned above in section #1, this decision will greatly improve user experience, as they are not required to edit any code to set the desired temperature. For instance, if the user is attempting to burn a design on a thicker piece of hardwood, a much higher temperature is required, which may be hindered by an automatic kill-switch that switches off the machine when the temperature of the rod gets too high, yet the user’s desired temperature has not been reached.
Hence, to ensure safety of users while using the manual kill-switch, we attached a buzzer and an external thermistor to the machine. When the thermistor detects temperature above a threshold limit, it will cause the buzzer to sound off, prompting the user to turn off the heating tip and let the machine cool down. Visually, when the pen tip gets red hot (but a temperature is not considered dangerously high), the user can also choose to switch off the heating element, or lower the temperature to prevent sparking from occurring.