Ultem™ (PEI) in CNC Plastics: Key Properties, Benefits & Real-World Case Study

In the high-end manufacturing sector, where lightweight design, high strength, and stability under extreme conditions are key goals, material innovation has always been the core driver of technological breakthroughs. While traditional metals offer reliable performance, they often face limitations such as heavy weight, complex processing, and high costs.

Ultem™ (polyetherimide, PEI), as anoutstanding high-performance engineering plastic, is gradually becoming an ideal alternative to metals in industries such as aerospace, automotive, electronics, and healthcare. With its metal-like strength, excellent heat resistance, superior machinability, and lightweight properties, Ultem™ helps products achieve higher levels of performance and reliability.

Core Properties of Ultem

Ultem combines thermal stability, mechanical strength, and inherent safety features, making it a reliable material choice for demanding, high-performance applications.

Excellent High-Temperature and Flame Retardant Properties

Ultem materials can operate stably in long-term high-temperature environments ranging from 170°C to 210°C, with a heat deflection temperature exceeding 200°C. Additionally, it has inherent flame retardancy and meets the UL94 V-0 standard without the need for added flame retardants, fully complying with fire safety requirements for high-reliability applications.

High Strength, High Rigidity, and Dimensional Stability

Ultem exhibits mechanical properties close to those of metals, particularly the fiberglass-reinforced grades like Ultem 2300, which offer exceptional rigidity, creep resistance, and dimensional stability. It maintains its shape and performance even under continuous load or temperature fluctuations, making it ideal for structural and critical functional components.

During CNC machining, Ultem demonstrates excellent machinability and dimensional control, enabling high-precision and complex shape fabrication. The material achieves smooth surface finishes, high processing efficiency, and is well-suited for prototyping and small-batch production of precision parts.

Good Electrical Insulation and Chemical Stability

Ultem offers outstanding electrical insulation properties and arc resistance, along with high chemical stability. It can withstand a variety of hydrocarbons, alcohols, and acidic media, and is only sensitive to strong alkalis. This makes it widely applicable for precision components in electronics, electrical, and chemical environments.

Ultem Application Cases: From Prototypes to Functional Parts

Ultem has become one of the key solutions for high-demand customer projects, with its core advantages demonstrated in several cases. Next, I will analyze the application cases of two typical Ultem grades to specifically show how they meet stringent technical requirements.

Ultem 2300：Preferred Choice for High-Strength Structural Parts

Ultem 2300, reinforced with 30% glass fiber, excels in complex structural and load-bearing components. With CNC machining and sandblasting surface treatment, the parts not only offer dimensional stability and strong deformation resistance but also feature a fine matte finish that enhances the product’s appearance and durability.

In industries such as aerospace and high-end machinery, Ultem 2300 has successfully replaced traditional metal components, achieving both weight reduction and cost savings.

Precision Machining Strategy for a Complex Aerospace Housing

Below is a complex housing part made of Ultem 2300 used in the aerospace industry. The part has several critical dimensional tolerances that are extremely precise, which would be difficult to achieve even with metal CNC machining. To meet the requirements, we fully utilized the machinability of Ultem, combined with advanced machining technology, and developed a step-by-step machining strategy:

• Roughing Stage: A ball-end mill was used to rough out the sidewall arc, effectively controlling machining stress and deformation, while leaving a uniform allowance for finishing.
• Finishing Stage: A flat-end mill was used for the final shaping, achieving a high-quality surface finish and precise dimensions.

Overcoming Internal Complexity with 5-Axis Machining

Beyond tight tolerances, the main challenge of this part lies in its complex internal geometry, including hollow sections, deep grooves, and multiple cavities.

To address this, we implemented a dedicated machining plan using multi-position precision alignment and five-axis CNC machining. This allowed accurate multi-angle milling of internal features, ensuring full conformity with the design intent.

Other parts from the same production batch also passed quality inspection consistently, demonstrating the excellent machining stability of Ultem 2300. Additionally, the material adapts well to surface treatments. As shown below, the left part features a painted black finish, while the right part showcases a sandblasted surface.

Ultem 1000: The Ideal Material for Transparent Functional Prototypes

Ultem 1000 offers a unique combination of high transparency, mechanical strength, and thermal resistance, making it especially valuable for CNC-machined functional prototypes.

Its semi-transparent structure allows direct visual inspection of internal channels, airflow paths, and transmission states, while its high-temperature resistance and mechanical integrity ensure reliable short-term functional testing.

The amber-colored housing shown below is designed for demanding industrial environments, meeting requirements for heat resistance, chemical stability, and electrical insulation. Compared with other transparent plastics, Ultem 1000 provides clearer internal visibility while maintaining superior structural performance—making it ideal for R&D validation and engineering evaluation.

Conclusion

Ultem materials enable stable operation above 200°C, deliver metal-like strength with significant weight reduction, and offer excellent CNC machinability. With inherent flame retardancy and broad industrial applicability, Ultem is redefining what engineering plastics can achieve across aerospace, electronics, and medical manufacturing.

WayKen provides custom CNC machining for high-performance engineering plastics, including Ultem, with tight tolerances, expert DFM support, and reliable quality from prototyping to low-volume production.