How CNC Prototyping Validate Special Plastic Materials (PPS)? – NDIR Sensor Frame Case

Project Background

Non-dispersive infrared (NDIR) sensors are precision instruments that detect the concentration of specific gases using infrared rays. By leveraging the property of infrared rays passing through gas, engineers design infrared emitters and receivers. These sensors, equipped with self-contained algorithms, calculate the amount of infrared absorption in the air to determine gas concentrations.

With growing concerns about air quality, these sensors are increasingly used in various applications, such as confined spaces, biosciences, and alcohol detection. As demand rises, more companies are entering the industry.

About the Customer

One of our customers, with 30 years of expertise in NDIR sensors, is dedicated to developing cost-effective, high-precision, and energy-efficient sensors. They have collaborated with WayKen on prototyping and production for many years. This time, the customer approached us to produce 10 PPS frames with a tolerance of 0.05 mm to verify assembly and material feasibility for subsequent injection molding production.

To meet the customer’s tight schedule, WayKen needed to complete 10 frames and deliver them to Europe within a week. After analyzing the structure and making a production plan, WayKen started the project.

Commonly Machined Plastic for Validating Sensor Frame

For general application scenarios, we recommend using ABS or ABS-like materials for producing plastic components with specific precision requirements. Our customer has previously made many ABS frames for sensors. Since their sensors are typically not intended for use in special environments, ABS is an ideal choice due to its excellent performance and cost-effectiveness.

A key advantage of ABS is that it can be split and glued without significantly affecting its strength. This makes it ideal for producing complex designs or large parts, as this approach reduces production time and saves costs.

Additionally, ABS plastic parts can be applied to various post-treatment processes, such as sanding, painting, polishing, and vacuum-plating, to meet specific appearance requirements.

Transitioning from ABS to PPS Plastic Machining

While ABS was commonly recommended for sensor frames, in this project, our customer highlighted specific machining requirements: the sensor would detect carbon dioxide and other toxic gases under high temperatures and in environments with chemical exposure. These conditions required a material resistant to both high temperatures and corrosion, which ABS can not achieve.

Since the sensor frame is used to test the feasibility before mass production, we recommended PPS, a more affordable alternative to PEEK. PPS has excellent heat resistance, allowing long-term use at 180–220°C, and strong chemical resistance, meeting the environmental demands of the sensor.

In addition, as the sensor frame will be assembled with other components, the precision requirement is extremely high, with a flatness of 0.05mm. PPS has excellent dimensional stability and mechanical properties, which means the deformation would be small after machining, ensuring the assembly is correct.

Challenges in Machining PPS Sensor Frame

Although PPS was chosen as the material for the sensor frame in this project, there were still some challenges in its machining.

• Brittle Nature: PPS is harder and more brittle than materials like ABS, making it prone to chipping or cracking during machining, especially when cutting intricate features.
• High Precision: Achieving a flatness tolerance of 0.05 mm demands highly precise machining, as even small deformations or errors could impact the sensor’s performance.
• Complex Geometry: The hollow frame of the sensor has structures spanning six sides, requiring multi-face machining with the least clamping to maintain accuracy and prevent distortion.
• Material Stability: PPS’s thermal properties, while advantageous for the end-use of the sensor, controlling heat generation in machining is also critical to avoid introducing internal stresses.

High-Precision Machining PPS

To address these challenges, we selected the Beijing Jingdiao 5-axis machine (JDGR400T), known for its ability to handle complex geometries with high precision. As the picture shows, the blue side has the least structure, we first used it as the clamping side and machined the structures on the other 5 sides. Then, with the strong machining capability of the 5-axis machine and professional operation, we efficiently produced the complex, multi-face hollow structure while maintaining the flatness tolerance of 0.05 mm.

Online Inspection in the CNC Machine

The red area specified above will be assembled with clips on the sensor’s outer casing, and then fix other components inside the sensor. Due to the sensor’s small cavity, this area requires a flatness of 0.05 mm and a verticality of 0.1 mm.

To ensure accuracy, the frame was inspected while still fixed on the machine. This is because it could deform when unconstrained due to material stress, leading to inaccurate inspection results. In addition, since the frame will be constrained by other structures inside the sensor during assembly, verifying the tolerances in the fixed state can ensure proper assembly.

5-axis machines at WayKen are equipped with probes that allow for in-process inspection of unfinished parts. These probes were utilized to measure all critical tolerances directly on the machine, ensuring the dimensional accuracy of the component.

Feedback

With the efficient production of 5-axis machines, we successfully shipped 10 pieces of frames to Europe within a week. The customers appreciated our full support in the project, ” Thank you for your support, these frames have successfully assembled and passed the function test. You are always a good and reliable partner.”

At WayKen, we specialize in offering precise and efficient CNC machining solutions for various industries. Our advanced CNC machines and expertise in handling different metal and plastic materials, ensure the high accuracy and quality of your components.

From prototyping to batch production, we keep trying our best to meet tight deadlines and strict tolerances. With years of industry experience, professional project management, and a customer-first approach, WayKen is always your trusted partner.