While 3D printing has been around for many years, it has only become a veritable sensation in recent times. The growing number of many DIY kits, low-cost parts, and hundreds of suppliers for plastic filaments have made 3D printing much more accessible.
Of course, not everyone wants to use a large computer-controlled machine to make a small model. This has led to the invention of the 3D printing pen.
This pen has two buttons for extrusion and withdrawing of the plastic filament, a slider for motor speed control, LEDs for temperature indication, a power jack input, a filament input, and a pre-set pot for adjusting the temperature.
The 3D pen
The two buttons that extrude and withdraw the filament
The motor speed slider
The two indicator LEDs and the pre-set pot (under black plastic)
DC jack and filament feed hole
Pre-set pot revealed
The head, itself, is built in a similar fashion to hot glue guns with a black heat-resistant casing surrounding the heater element. The nib is made of plastic which is also heat-resistant and guides the plastic to exactly where it is needed.
The extruder at the front surrounded by a protective plastic case
Opening the Pen
Getting access to the inside of the 3D pen was very easy as no screws are used to keep the unit together. Instead, the lid is held in place with tabs that can be undone with a small flat-head screwdriver. The opened unit shows a white tube that is used to guide the filament to the extruder, a motor assembly unit, and a PCB underneath the tube.
The 3D pen's innards!
Close-up of the guide tube that directs the filament
The extruder unit is held in place with just one very small screw and a plastic tab. Removing the extruder reveals multiple connections which handle the current needed to heat the unit, as well as a thermostat which is used to ensure that the temperature of the extruder is where it needs to be.
The extruding head removed from the 3D-printing pen
The connector point for the extruder
The Motor Mechanism and Slider
The pen has a very small motor mechanism that consists of a sharp tooth gear and a roller (which is unconnected to anything powered). The gap between the roller and toothed gear is slightly smaller than the diameter of the filament. This results in the gear biting into the filament. When the motor assembly operates (which is geared down), the toothed gear slowly rotates and drags the filament in.
The filament drawing system
The filament guide removed, showing the gearbox and motor
The motor speed control is done using a slider potentiometer that directly connects to the plastic slider found on the side of the pen. This is a very important feature as trying to make a 3D model with a pen that extrudes plastic too fast can be difficult.
The main PCB uses a blue solder mask, is double-sided, and is made of FR4 (fiberglass).
Considering the number of IO present on the PCB and the need for temperature control, there is a good chance that there is a microcontroller somewhere to be found! But will this controller be a generic Chinese IC that no one can identify? Or will it be a commonly used micro?
The PCB with peripherals attached
Motor driving in this pen is done with the L9110 IC. The main features are as follows:
- Capable of working with a wide range of voltages (2.5V – 12V)
- 800mA of continuous current draw per channel
- TTL and CMOS level compatible
- High-voltage input protection
All inside a small package.
The L9110S motor driver IC
Now for the brain of the PCB, the ST 8S003F3P6! This is an 8-bit generic micro made by ST and features FLASH memory of 8KB, 1KB of RAM, 128 bytes of ROM, I2C, UART, SPI, 16 IO, and a 3V to 5V operation—all for under a dollar!
The main controller – ST 8S003F3P6
The pre-set potentiometer used for setting the extruder temperature
Overall, the 3D pen is a classic example of electronic and mechanical miniaturization. An extruder, motor feed, and computer all fit in a device the size of a large pen while being very light weight. Even if 3D pen printed models have much to be desired, they provide great entertainment for all ages!
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