Potting of Ultrasonic Parking Distance Sensors

High Measurement Accuracy Resulting from Vibration-Damped Distance Sensors

Advanced Driver Assistance Systems, commonly referred to as ADAS, are becoming far more common in modern-day vehicles. The key to ADAS functionality is the cooperation between cameras, radar, and LiDAR (Light Imaging, Detection, and Ranging), as well as multiple ultrasonic sensor systems, which all work together to identify objects, pedestrians, and potential hazards for the driver, and thus ensure the safety of drivers, passengers, and pedestrians. Depending on the measurement accuracy of the driver assistance systems and the ultrasonic sensors, the recorded data is transmitted instantly to the vehicle’s onboard computer. Using this data, the connected control devices can trigger any necessary actions in real-time.

Today, most standard vehicle models have up to 8 distance sensors at the front and rear, and premium model vehicles use between 10 to 12 sensors. These sensors are constantly improving and can calculate distances even more accurately, helping improve safety in modern mobility and traffic systems, especially self-driving cars.

Using Henkel’s FERMASIL silicone foam helps to dampen the vibrational impact on the piezo, which improves the calculation of distances with the highest degree of precision helps to dampen the vibrational impact. The properties of FERMASIL silicone foams, tailored to requirements, are critical in ensuring reliable and functioning ultrasonic sensors. Our fully automatic mixing and dosing systems ensure highly accurate processing and dosing of these.

Are you faced with the task of encapsulating distance sensors with extreme accuracy in high quantities and at high process speeds with very small material quantities? Our dosing technology can help. Within the cycle times specified by our customers, we can apply even the smallest quantities with a highly repeatable accuracy of +/- 0.01 mm into the sensor housings.

Material

Reliable Ultrasonic Sensors Due to Vibration Damping

Ultrasonic Sensors Optimally Encapsulated with Silicone Foam Potting

Distance sensors work according to the ultrasonic echolocation principle. The sensors emit short ultrasonic pulses that are reflected by objects or obstacles. The echo signals are registered by the sensors and evaluated by a central control device. In this way, the sensitive systems of the sensors always provide the car’s onboard computer with accurate data.

The piezoelectric distance sensors offer the best conditions for generating and detecting ultrasonic waves. The piezo actuator works as a transmitter and receiver while emitting ultrasonic pulses. The required travel time of the resonant frequency is measured by the distance covered. So, the distance measurement is based on the travel time difference when ultrasonic pulses are alternately transmitted and received.

The piezo actuator is located on the cavity floor of the sensor housing and is potted with the two-component silicone foam FERMASIL A-33-4 and B-33-4 for vibration damping.

This image shows where the FERMASIL silicone foam is applied to the piezo in the ultrasonic distance sensor to ensure consistent vibrational damping.

The Different Reaction Phases of the Sealing Foam

After curing the silicone foam is characterized by a high level of elasticity, so that temperature differences from -60 to +180 °C can be met. FERMASIL is also weather-resistant and has very low water absorption levels thanks to its almost closed foam cell structure.

Our ultrasonic sensor encapsulation materials offer the perfect potting solution to keep the required properties of ultrasonic distance sensors consistent.

Reference Material

The 2K silicone foam reference materials shown below, meet the standard requirements of the ultrasonic parking distance sensors. Furthermore, our materials can be customized according to your part specifications and special technical demands. Henkel's Sonderhoff FERMASIL foam materials can be adjusted in their reactivity, hardness, viscosity, as well as color, and other chemical and physical properties.

	FERMASIL A-33-4 FERMASIL B-33-4
Mixing ratio	1 : 1
Pot life	280 sec.
Tack-free time	35 min.
Viscosity A component	9,000 mPas
Viscosity B component	5,200 mPas
Foam density	0.74 g/cm3
Hardness (Shore A)	24
Temperature resistance	from -60 to +180 °C

Process

Customer-Speciﬁc Mixing and Dosing Systems for Accurate and Eﬃcient Dosing Processes

Flexible and Fully Automatic – According to Your Requirements

As process experts, we support our customers with individual advice for the automation of your manufacturing processes. We offer numerous configuration and equipment options for semi-automatic or fully automatic production systems, using either the 3-axis linear robots or 6-axis robots.

The ultrasonic distance sensors are fed via a conveyor belt system that runs through the SMART-L dosing cell. The centering station then positions the sensor housing for the dosing of the sensors with FERMASIL silicone foam.

Despite high volumes of parts and process speeds, the dosing cell is able to dispense even the smallest quantities into the sensor housing via the MK 825 PRO precision mixing head with a positioning accuracy of +/- 0.01 mm, with high dosing accuracy and no deviations from the specified cycle times. Our innovative solutions ensure very reliable plant engineering, minimized maintenance times and consistent dosing quality. Thanks to the traceability of the dosing program data, all process data can be tracked while production is running.

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