Design Details of a Water Flosser – Learning-Oriented Case Study

In my previous two posts, I shared the overall product concept and direction, as well as the hardware design of a water flosser. Today, I’d like to dive into some key design details. Please note: this design is for learning purposes only and does not involve any infringement.

When designing a water flosser, we need to address several pain points:

1. Waterproofing

Our approach is to use sealing rings. Since the product shape is relatively regular, we typically apply O-rings (as shown in the diagram). Ultrasonic welding was also considered, but this method makes repair nearly impossible, because once the product is disassembled, it cannot be reassembled.

2. Water Pressure Control

The power source is the motor, and the water jet’s pressure is crucial to user experience. If the pressure is too strong, it may harm the gums; if it’s too weak, it won’t clean effectively. To solve this, we use control circuitry to stabilize motor speed. For higher-end designs, stepper motors can be considered, though they significantly increase costs.

3. Noise Reduction

To keep costs reasonable, we use a motor plus gear transmission. This requires precise gear meshing tolerances, which places strict demands on injection-molded gear quality and mold-making accuracy.

4. Cleaning of Water Tank and Water Path

One challenge engineers often face is preventing bacterial growth inside the water tank. In our initial design, we adopted a coating process to improve hygiene. Other high-cost solutions include using ceramic water tanks or adding filtration systems, but these come with substantial cost increases.

5. Cost and Manufacturability

From the beginning, it’s important to clarify whether the product will target the high-end market or focus on cost-effectiveness. In this case, we chose a brushed motor with two-stage gear transmission, avoided overly complex surface treatments, and only added antibacterial coating in the water tank to balance cost and function.