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Advantages of PEI in CNC Machining: Why It’s the Material of Choice

Discover the remarkable properties of Polyetherimide (PEI) in CNC machining and why it's the material of choice for diverse applications.

This blog post delves into PEI's unique characteristics, common grades, and its significant advantages in CNC machining.

Learn how industries leverage PEI's versatility to push the boundaries of innovation and performance.

Understanding PEI

Polyetherimide, often recognized by its abbreviation, PEI, stands out as a high-performance engineering plastic in the realm of thermoplastic polymers. Its impressive properties and extensive application scope have cemented its reputation in various industries.

PEI, an amorphous polymer, boasts a molecular structure that is randomly organized, distinguishing it from ordered or crystalline polymers. This unique structure endows PEI with certain noteworthy characteristics, such as its inherent transparency and lower shrinkage rate, particularly when juxtaposed with semi-crystalline polymers.

Among engineering plastics, PEI is a shining example of a material that embodies a harmonious balance of mechanical, thermal, and electrical properties. Its mechanical prowess is evident in its high tensile strength, making it an ideal choice for components that must withstand substantial stress or strain. Moreover, PEI showcases exceptional dimensional stability, ensuring its shape and size remain unchanged despite exposure to external forces or temperature fluctuations. This makes PEI a versatile engineering plastic, suitable for a plethora of demanding applications.

Mechanical Properties

cnc milled pei parts
CNC Milled PEI Parts

PEI sets itself apart with its remarkable tensile strength and the ability to retain its structural integrity under extreme heat and stress. This is a characteristic not typically associated with many plastics, and it allows PEI to replace metals in many applications. Furthermore, PEI exhibits significant chemical resistance, effectively withstanding exposure to a wide variety of substances, including potent acids, bases, and assorted solvents. This unique blend of properties enables PEI to serve as a viable metal replacement in numerous scenarios, offering lighter weight and comparable strength.

High Tensile Strength: PEI plastic exhibits excellent tensile strength, meaning it can withstand high levels of stress without breaking or deforming.

Superior Flexural Strength: PEI plastic shows an impressive ability to resist deformation under load, making it suitable for applications that require flexibility.

Good Impact Resistance: Despite its strength and rigidity, PEI can absorb shock and resist impact well, which helps prevent cracking or breaking upon impact.

High-Dimensional Stability: PEI maintains its shape and size under various conditions, including exposure to heat, humidity, and mechanical stress.

Creep Resistance: PEI plastic shows good resistance to creep, which means it doesn’t deform under long-term exposure to high temperatures and mechanical stress.

High Heat Deflection Temperature: PEI’s low thermal expansion allows it to sustain its mechanical properties, even in high-heat applications. It’s an ideal choice for temperature-sensitive environments.

Excellent Wear Resistance: PEI’s durability extends to excellent wear resistance, making it suitable for applications where the material may experience constant friction or abrasion.

Unique Characteristics

What sets PEI apart from other materials is its unique combination of characteristics. Its inherent flame resistance and low smoke production make it a go-to for high-risk industries. Furthermore, PEI’s transparency and UV resistance paves the way for various optical applications. And let’s not forget its excellent electrical properties, making it a preferred choice for a multitude of electrical and electronic components.

Chemical Resistance: PEI materials show exceptional resistance against a wide range of chemicals, including acids, bases, and solvents. This makes it suitable for harsh environments where exposure to such substances is common.

Flame Resistance: PEI is inherently flame-resistant and generates very little smoke when exposed to fire, making it a preferred material in industries where fire safety is crucial.

Transparency: Despite being a high-performance thermoplastic, PEI is naturally transparent, which enables its use in optical applications.

UV Resistance: PEI materials demonstrate excellent resistance to ultraviolet (UV) radiation, meaning it doesn’t degrade or discolor easily when exposed to sunlight over time.

Electrical Properties: Boasting excellent electrical insulation properties, PEI stands as an ideal material for a host of electrical and electronic components. Its low electrical conductivity contributes to its effectiveness as an insulator, thereby enhancing its suitability for applications in the electrical and electronics sector. This attribute further underscores PEI’s versatility and wide-ranging applicability.

Heat Resistance: PEI can maintain its properties at high temperatures, making it an excellent choice for applications involving elevated temperatures.

Low Moisture Absorption: PEI absorbs very little moisture, which helps maintain its properties in humid environments and makes it suitable for use in various outdoor applications.

Biocompatibility: Certain grades of PEI are biocompatible and can be used in medical applications where the material comes into contact with body tissues or fluids.

Ability to be Sterilized: PEI can be sterilized by most conventional methods, including autoclaving, ethylene oxide, gamma radiation, and electron beam processes. This is another reason why it’s often used in medical devices.

Meet the Different Grades of PEI Materials

PEI isn’t a one-size-fits-all material; it comes in various grades, each with unique features and applications. From the standard Ultem 1000 to glass-filled Ultem 2100, 2200, and 2300 variants, each grade brings something unique to the table. Ultem 4001 offers a unique PEI blend, while Ultem 5000 is favored for medical-grade applications. And for those requiring an extra strength boost, there’s the carbon fiber-filled Ultem.

Ultem 1000

ultem 1000 cnc parts
Ultem 1000 CNC Parts

This is the standard, unfilled grade of PEI, offering the highest elongation and toughness of all the Ultem grades. Ultem 1000 exhibits excellent thermal properties and high chemical resistance. This grade is often used in applications like automotive, aerospace, and electrical/electronics where strength and heat resistance are required.

Ultem 2100, 2200, and 2300

ultem 2300
ultem 2300

These are glass-filled grades of PEI that offer enhanced rigidity and dimensional stability compared to Ultem 1000. The number following “Ultem” indicates the percentage of glass fiber filling – 10%, 20%, and 30%, respectively. Glass-filled Ultem grades are used in structural components requiring high strength and stiffness at elevated temperatures.

Ultem 4001

This grade is a blend of PEI and polycarbonate (PC). Ultem 4001 provides the high heat resistance and strength of PEI while gaining the improved processability and toughness of PC. This blend is typically used in applications where a balance of strength, heat resistance, and processability is needed.

Ultem 5000

pei part
PEI Part

This is a medical-grade PEI, specifically designed for applications in the healthcare industry. Ultem 5000 is biocompatible, can be sterilized, and offers excellent heat and chemical resistance. It’s commonly used for medical devices and instruments that require repeated sterilization.

Carbon fiber-filled Ultem

This grade of Ultem is filled with carbon fibers to increase its strength, stiffness, and dimensional stability even further. Carbon fiber-filled Ultem is used in applications requiring extreme strength and rigidity, and it’s often found in aerospace and automotive industries for high-performance parts.

Introduction to CNC Machining

CNC machining is a subtractive manufacturing process where a computer controls the movement of machinery, allowing for high precision and repeatability. Material selection plays a significant role in CNC machining, as the chosen material must withstand the rigors of the process while delivering the desired final product characteristics.

Advantages of PEI CNC Machining

PEI plastic machining brings distinct advantages to the table, thanks to its superior mechanical and thermal properties. This makes it an unbeatable choice for crafting precision parts that can resist the most challenging conditions.

The machinability of PEI allows fabricators to create intricate parts with rigorous tolerances, making it a preferred material for industries where precision is key. The aerospace sector, for instance, leans heavily on PEI plastic machining. Here, components are frequently subjected to extreme temperatures and stresses, and the demand for precision and durability is paramount.

In essence, PEI plastic machining presents an unparalleled combination of resilience, precision, and adaptability, answering the demanding requirements of numerous industries.

High Precision: CNC machining can produce parts with high precision, and this is particularly true when using PEI. Its dimensional stability under heat and load makes it ideal for applications that demand exactness. For instance, in the electronics industry, PEI is used for manufacturing precision components like connectors, switches, and insulators.

Excellent Surface Finish: PEI can be machined to a high-quality surface finish, eliminating the need for post-processing in many cases. This quality is beneficial in optics, where PEI is used to create transparent, optically clear components such as lenses and light guides.

Complex Geometries: CNC machining can create complex shapes and designs, and with PEI’s excellent machinability, even intricate parts can be produced. In the aerospace industry, this allows for the creation of custom, complex components for aircraft systems.

Consistency and Repeatability: CNC machining allows for consistent and repeatable production of parts. This characteristic, combined with PEI’s consistent properties, is crucial in industries like medical technology, where PEI is used to create identical, high-quality components like surgical tools and implants.

Speed of Production: CNC machining PEI is relatively quick, allowing for faster turnaround times. In the automotive industry, where speed of production is critical, this advantage allows for the rapid prototyping and manufacturing of parts such as sensors and interior components.

Durability and Longevity: Given PEI’s mechanical strength and heat resistance, CNC-machined PEI parts are highly durable and can withstand harsh conditions over time. This durability is beneficial in industries like oil and gas, where PEI is used to create components that can withstand the demanding conditions of exploration and extraction operations.


In the world of manufacturing, PEI truly shines, especially when paired with CNC machining. Its unique properties make it an excellent material choice for a range of applications, offering durability, precision, and versatility. While no material is perfect, the benefits of PEI significantly outweigh any potential drawbacks, making it a standout choice in the realm of CNC machining.

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As your trusted CNC machining partner, AT-Machining is poised to bring your project to life. Based in China, we pride ourselves on our capacity to provide CNC machining services across various grades of metal, plastic, and ceramic materials. We don’t just stop at machining; we also offer a range of finishing services for machined parts, including nitriding, plating, anodizing, and more.

If you’re looking to leverage the exceptional properties of materials like PEI in your next project, don’t hesitate to reach out to us. We’re here to provide you with the high-quality, precision-machined parts you need. Take the next step towards quality and precision – contact AT-Machining today!

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From AT-Machining, I’m a CNC Machining Expert in this field for more than 20 years.  We offer cost-effective machining services from China. Ask for a quote for your ongoing or upcoming projects now!

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