PROCESS OVERVIEW
My first Making Studio assignment involved disassembling an old AquaSonic electric toothbrush. It appears that this model is no longer available for sale on the AquaSonic e-commerce website.
As this was my first teardown, there was a lot to learn! I struggled to find full teardown examples of electric toothbrushes, but was able to use some common sense and guessing to get started. Other than encountering some unfortunate toothbrush-related gunk, I was pleasantly surprised at how smoothly the first half of the process unfolded. However, I ran into quite a bit of trouble removing the circuit board (16) and Li-Ion battery (15) from the interior plastic framework (20). I was hesitant to exert too much brute force as I was fearful of damaging the battery.
Here is a visual breakdown of my chronological process. The parts are numbered in the order in which they were taken apart, and can be referenced in the parts section further down.
While attempting to remove the Printed Circuit Board/PCB (16), a lot of LED indicators (PCB 04) lit up, and I was unable to turn them off for a while. The intensity of the light was surprisingly bright.
I eventually used wirecutters and a larger screwdriver to remove the PCB (16) from the plastic framework (20), and the Li-Ion battery (15) was easily removable after that.
COMPONENTS
1. Outer Case: plastic
2. Brush Connector Base: plastic
3. Motor Shaft Bearing: steel?
4. Top Gasket: plastic
5. Button Covers: silicon or rubber
6. Screws: stainless steel
7. Top Ring: rubber
8. Motor O-ring: rubber
9. Motor Gasket: rubber
10. Motor Case: steel
11. Small Brush Motor O-ring: plastic or rubber
12. Charging Base Clip: plastic + metal (copper?)
13. TBD Brush Motor Part: plastic?
14. Brush Motor Rotor + Vibrating Rod: copper coil, steel
15. 14500 Li-Ion Battery Cell: lithium, nickel, cobalt, maybe manganese(?)
16. PCB: copper, fiberglass, resin
17. Base O-ring Seal: silicon or rubber
18. Charger Coil: copper
19. Base: plastic
20. Inner Frame: plastic
PCB Components/Chip Details
01. Power Button (S1)
02. Secondary Button (S2)
03. Coil Connectors (M)
04. LED Indicators (LED)
05. Transistors (Q), Diodes (D), Resistors (R), Capacitors (C)
06. Battery Connections (B-, B+)
07. Chip 1, MCU? (U2)
08. Chip 2, PW? (U1)
Chip Details
I was unable to locate any part numbers on the chips. Some research suggests that they are surface-mounted Integrated Chips (IC) with Dual in-Line Package (DIP) form factors. It seems that the larger one is likely a Microcontroller (MCU), which controls motor speed, timing, LED indicators, charging, etc. The other is possibly a Power Management chip, controlling battery charging and protection from overcharging.
Type: TBD
Manufacturer: TBD
MANUFACTURING
01. Plastic Injection Molding is used to create the internal plastic pieces (frame, button covers) and outer case. This involves melting plastic pellets (polycarbonate, polypropylene, ABS) and injecting them into precision molds. Parts are removed after cooling. This technique is used to ensure precision and water resistance.
02. PCB Manufacturing + Assembly involves photolithography, surface-mount technology (SMT), and solder mask application
03. Metal Stamping/Machining is used to create motor shafts and other metal components. Sheet metal stamping, turning, and precision machining are techniques that are used in this process.
04. Li-Ion Battery Cell Manufacturing happens under very controlled conditions. It involves various steps that conclude with packaging.
05. Motor Assembly is crucial to ensuring the brush will vibrate. Copper wires are coiled around rotors, and all motor-related parts (rings, gaskets, bearings, etc.) are assembled.
06. Final Assembly occurs when all components are combined using manual or automated assembly methods. Adhesive sealing or ultrasonic welding techniques are used to waterproof.
TOOLS/TECHNIQUES
01. Wire Cutter: Used to remove the PCB (16) from the plastic frame (20), also used to remove the base (19) from the plastic frame (20)
02. Screwdriver: used to pry apart larger/more unwieldy pieces (like removing the PCB board from the plastic framework)
03. Small Steel Screwdriver: used to unscrew screws (06) and to pry apart small pieces that were glued together
04. Wrench: Used to grip and remove larger parts that were glued together
05. My Hand (Not Pictured): Used during the entire teardown process to manipulate tools, etc.
DESIGN ELEMENTS
01. I found it interesting that the interface is very simple (compared with most of their current models). There are two buttons (05); the top one is the power button and is labeled “ON/OFF”. As it no longer functions, I am inferring that the second “button” is a charging indicator. This simple interface is representative of the limited capabilities/modes.
02. Indented arch shapes on the back of the outer case (01) seem to be placed where one’s fingers would go when gripping the toothbrush. It is a nice ergonomic touch.
03. (Not Picture) Overall, it is clear that this was not designed to be taken apart. I’m curious how much of this is due to capitalism, discouraging DIY fixes and encouraging new purchases, and if any of it has to do with safety due to the lithium battery.