PI

PI (Polyimide) is a high-performance engineering polymer known for its exceptional thermal stability, low outgassing, chemical resistance, electrical insulation, dimensional stability, and excellent performance under demanding temperature conditions.

Unlike commodity plastics such as HDPE, PP, and PVC, polyimide is designed for high-temperature, high-reliability engineering applications. CNC-machined PI components are widely adopted and customized by Evefab for aerospace, semiconductor equipment, electrical and electronics, vacuum systems, medical equipment, automotive systems, and precision industrial machinery.

PI is particularly valuable when conventional engineering plastics cannot maintain their mechanical, electrical, or dimensional performance at elevated temperatures. Depending on grade and formulation, polyimide can provide continuous-use temperatures in the ~200–260°C range, with specialized grades capable of substantially higher short-term or continuous exposure.

Because "PI" covers multiple thermoset and thermoplastic polyimide formulations, Evefab always verifies exact material properties against manufacturer datasheets and official specifications for every custom machining project to ensure engineering compliance.

1. Basic Material Information

Standard Material Designations & Classification

Unlike PEEK, PPS, PEI, and POM, polyimide does not have one universal commercial grade covering all applications. Commercial PI materials differ significantly based on polymer chemistry, molecular structure, manufacturing method, filler system, reinforcement and thermal treatment. Evefab provides targeted grade selection services to match accurate PI materials for different working conditions.

Common Polyimide Grade Types

Unfilled PI Features outstanding high-temperature stability, superior electrical insulation, ultra-low outgassing and excellent dimensional stability. It is the preferred material for precision insulators, positioning spacers, high-precision mechanical parts and semiconductor equipment components, widely customized by Evefab for high-reliability industrial projects.

Graphite-Filled PI Graphite filler effectively optimizes material wear resistance, friction performance and thermal conductivity. Evefab mainly processes this grade into high-temperature bushings, precision bearings and long-term sliding moving parts to improve component wear life.

PTFE-Filled PI PTFE modification significantly reduces material friction coefficient, eliminates stick-slip phenomenon and enhances wear resistance. It is suitable for processing high-performance sealing parts, precision sliding components and dry-running bearings, solving friction and wear problems of high-temperature moving equipment.

Carbon-Filled PI Carbon reinforcement improves the mechanical strength, wear resistance and dimensional stability of PI materials. The specific performance parameters vary with different formulas, and Evefab will select matching carbon-filled grades according to customer load and precision requirements.

Core Material Positioning

PI is a top-tier high-temperature and high-reliability engineering polymer. Its core engineering advantages integrate extreme temperature resistance, stable dimensional performance, excellent electrical insulation, low outgassing and superior chemical resistance.

Engineers and manufacturers choose PI processed by Evefab when standard plastics including POM, Nylon, HDPE and UHMW-PE fail to meet high-temperature and high-reliability operating requirements.

2. PI Physical Properties

Density

PI has a density of 1.4–1.6 g/cm³, far lighter than metal materials. While realizing lightweight equipment design, it has far better high-temperature comprehensive performance than ordinary commodity plastics, which is an important reason why Evefab widely uses PI for aerospace and precision lightweight component customization.

Tensile Strength & Modulus

The tensile strength of PI ranges from 70–120 MPa, and the tensile modulus is 2.5–4.0 GPa. Reinforced filled grades have higher rigidity and mechanical strength. Different from ordinary plastics, PI can maintain stable mechanical properties in high-temperature environments without obvious strength attenuation, meeting long-term high-load and high-temperature operating needs.

Thermal Stability

Excellent thermal stability is the core advantage of PI materials. Most commercial PI grades support continuous stable operation at 200–260°C, and special customized grades can withstand higher instantaneous high temperature impact. It is widely used in semiconductor processing, aerospace equipment, high-temperature electrical systems and vacuum equipment, and is a key high-temperature resistant material processed by Evefab for high-end precision equipment.

Dimensional Stability

Compared with most high-performance polymers, PI has excellent dimensional stability, which is very suitable for processing precision spacers, electrical insulators, high-temperature bushings and semiconductor precision fixtures. Evefab makes full use of this feature to ensure long-term dimensional accuracy of precision parts. It should be noted that temperature changes, moisture absorption, mechanical load and thermal cycling will still cause slight dimensional changes.

Wear Resistance

Pure PI has good wear resistance, and graphite, PTFE, carbon and other modified filled grades have greatly improved tribological properties. For dry friction working conditions, Evefab will select the most suitable PI formula according to actual load, sliding speed, matching materials, temperature and lubrication status to ensure optimal wear resistance.

Friction

Pure PI has low friction coefficient, and modified filled PI can achieve ultra-low friction and self-lubricating properties. It is commonly processed by Evefab into high-temperature bushings, precision bearings, sealing parts, sliding rings and wear-resistant components for long-term dry friction operating scenarios.

Temperature Range

The conventional continuous service temperature of PI is 200–260°C, and short-term instantaneous temperature resistance is higher. The actual allowable operating temperature needs to be comprehensively evaluated in combination with mechanical load, sliding speed, atmospheric environment, vacuum state and thermal cycling frequency to avoid material performance failure.

Electrical Properties

PI is an excellent high-temperature insulating material, with high dielectric strength, high volume resistivity and low dielectric loss. Its excellent electrical insulation performance can remain stable in high-temperature environments, which cannot be achieved by ordinary plastics, and is widely used in high-end electrical and electronic precision equipment insulation parts.

Outgassing

High-purity PI grades have ultra-low outgassing characteristics, which meet the strict standards of vacuum and aerospace environments. Evefab specially matches low-outgassing PI materials for vacuum equipment, semiconductor production equipment and aerospace hardware customization projects to avoid gas volatilization affecting equipment precision.

3. PI Chemical Properties

Chemical Composition

The main elements of polyimide are carbon, hydrogen, nitrogen and oxygen. Different grades have different molecular structures. Modified functional grades added with graphite, PTFE, carbon fiber, mineral fillers and special additives have enhanced wear resistance, friction performance and mechanical properties to adapt to diverse industrial working conditions.

Chemical Resistance

PI has excellent resistance to oils, fuels, most organic solvents, hydrocarbons, partial acids and alkaline solutions. It can maintain stable performance in high-temperature and corrosive composite environments. Evefab will verify chemical compatibility one by one according to the customer's specific medium concentration, operating temperature and exposure time to ensure part service life.

Moisture Resistance

Compared with PTFE, PE, PEEK and other ultra-low water absorption materials, PI has slightly higher moisture absorption. Moisture will slightly affect its dimensional stability, electrical performance and mechanical properties. For high-precision electrical and semiconductor parts, Evefab will select low-moisture PI grades and optimize processing and storage environments.

Corrosion Resistance

As a polymer material, PI will not rust or produce electrochemical corrosion like metal materials, and does not need anti-corrosion coating protection. It is very suitable for electrical components and equipment parts exposed to chemical corrosive environments for a long time.

UV and Radiation Resistance

Special formula PI grades have excellent radiation and UV aging resistance, adapting to harsh aerospace and high-energy radiation environments. Evefab selects targeted anti-radiation PI materials for space equipment and aerospace component customization projects to ensure long-term stable operation of parts.

Welding and Bonding

Different from PE, PP and other thermoplastics, PI cannot be thermally welded conventionally. For PI assembly parts, Evefab mainly adopts mechanical fastening, professional special adhesive bonding and special thermal bonding processes, and carries out professional surface activation pretreatment to improve bonding strength and stability.

4. PI CNC Machinability Analysis

Machining Difficulty: Moderate–Difficult

PI CNC machining has higher process requirements than ordinary plastics. The core processing difficulties of PI include high material cost, fast tool wear, easy burr generation, concentrated cutting heat, thin-wall deformation and reinforced filler abrasion. Evefab has mature standardized processing technology to solve various PI machining problems and ensure part precision and surface quality.

Recommended Cutting Tools

Evefab's special tool configuration for PI processing: fine-grain sharp carbide tools, polished edge cutters; diamond tools for high-precision and high-volume processing scenarios. For carbon/graphite filled abrasive PI grades, wear-resistant tools are matched to reduce tool loss and ensure processing consistency.

General CNC Cutting Parameter Guidance

Due to the large performance difference of different PI grades, conservative and stable starting parameters are adopted uniformly. Evefab will dynamically optimize parameters according to material formula, filler content, tool specification, equipment rigidity and part structure.

CNC Milling PI

PI supports 3-axis, 4-axis and 5-axis CNC milling, suitable for profiling, pocketing, slotting and contouring processing. For thin-wall PI parts that are easy to deform, Evefab adopts multiple light cutting passes, full-area auxiliary support, low clamping force and stable tool engagement technology to avoid thin-wall deformation and size deviation.

CNC Turning PI

Turning process is widely used for customized processing of PI bushings, sealing rings, positioning spacers, sealing parts and cylindrical insulators. Evefab uses ultra-sharp precision turning tools to avoid material tearing, surface smearing and edge burrs, ensuring high roundness and smooth surface of rotary parts.

Drilling PI

Precision drilling of PI requires strict control of cutting heat and chip removal. Common processing problems include heat accumulation, hole edge burrs, layered delamination of filled grades and hole size deviation. Evefab adopts sharp special drills, stable low-speed feeding and efficient chip removal technology to ensure hole position accuracy and smooth hole wall.

Tapping PI

PI can realize threading processing, but its mechanical strength is lower than metal materials. For heavy-load threaded connection parts, Evefab optimizes thread engagement length and wall thickness, and matches metal thread inserts and through-bolt structures to improve connection firmness and avoid thread sliding and deformation.

Common PI CNC Machining Problems & Solutions

1. Burr Formation Burrs are easy to appear at hole outlets, thin edges and groove intersections. Evefab solves the problem by configuring sharp professional tools, optimizing matching feed parameters and adding fine finishing passes.

2. Heat Buildup Although PI has high temperature resistance, local cutting heat will affect dimensional accuracy, surface finish and tool life. Evefab strengthens air blast cooling, optimizes chip removal paths, avoids tool friction and rubbing, and controls cutting heat stably.

3. Tool Wear Carbon, graphite and mineral fillers in modified PI have strong abrasion, which accelerates tool wear. Evefab uses fine-grain wear-resistant carbide tools, optimizes tool geometric angles, monitors tool life in real time, and configures diamond tools for mass processing to reduce cost and improve efficiency.

4. Thin-Wall Deformation Thin-wall PI parts are prone to elastic deformation under cutting force. Evefab reduces single cutting volume through multiple fine cutting processes, adds full-area auxiliary support fixtures, optimizes clamping scheme and eliminates thin-wall deformation.

5. Dimensional Variation Temperature change, moisture absorption and processing residual stress will cause dimensional deviation of PI parts. Evefab arranges parts to stand and stabilize after processing, controls constant-temperature processing and inspection environment, reserves reasonable finishing allowance, and ensures dimensional consistency of key features.

CNC Tolerance Capability

With Evefab's professional process control, the stable precision tolerance of PI precision parts can reach ±0.02–0.05 mm. The ultimate tolerance is affected by part size, wall thickness, PI grade, filler content, equipment precision and temperature environment. For ultra-precision parts, we formulate exclusive processing schemes according to actual working conditions.

Surface Finish

The conventional CNC machining surface roughness of PI can reach Ra 0.8–3.2 μm. Evefab optimizes tools and cutting parameters according to part requirements, and matches fine grinding and polishing processes for high-surface-quality parts to achieve ultra-smooth surface effect.

5. Typical PI Applications & Part Scenarios

Semiconductor Equipment

PI is a core high-performance material for semiconductor manufacturing equipment. Evefab customizes insulating spacers, wafer handling parts, vacuum-compatible precision fixtures, high-temperature bushings and precision support components for semiconductor industry customers. Its low outgassing, high temperature resistance, insulation and dimensional stability fully meet semiconductor ultra-precision production standards.

Aerospace

In aerospace equipment, PI processed by Evefab is made into lightweight electrical insulators, high-temperature bushings, positioning spacers and precision support parts. It integrates lightweight, high-temperature stability, chemical corrosion resistance and electrical insulation, meeting the high-reliability requirements of aerospace equipment.

Electrical & Electronics

PI can maintain stable electrical insulation performance in high-temperature environments where ordinary plastics fail. It is widely processed into equipment insulating parts, coil accessories, precision connectors, high-temperature spacers and electrical isolation baffles for high-end electronic and electrical equipment.

Vacuum Equipment

High-purity low-outgassing PI grades are suitable for vacuum equipment manufacturing. Evefab customizes insulating rings, precision bushings, positioning spacers and vacuum special fixtures to ensure no gas volatilization and stable operation of vacuum equipment.

Automotive

PI is used for high-demand automotive parts, including high-temperature resistant bushings, precision sensor components, electrical insulating parts and wear-resistant moving components. Modified filled PI grades are used for long-term friction and high-temperature working scenarios of automotive core parts.

Medical Equipment

Certified medical-grade PI can be processed into precision insulators, surgical equipment accessories, high-temperature disinfection equipment parts and laboratory precision components. Evefab strictly verifies material medical certification qualifications to meet medical industry safety standards.

Precision Machinery

Evefab processes high-performance PI into precision bearings, wear-resistant bushings, sealing parts, wear rings, positioning spacers and insulating components, which are suitable for precision machinery scenarios where traditional metal lubrication parts are not applicable, realizing maintenance-free and high-reliability operation of equipment.

6. Our PI CNC Machining Advantages

Professional PI Grade Selection

Evefab's professional engineering team provides one-stop PI material matching services, accurately selecting unfilled PI, graphite-filled PI, PTFE-filled PI, carbon-filled PI and special customized grades according to working temperature, friction and wear conditions, mechanical load, electrical insulation requirements, vacuum standards and chemical exposure environment.

Controlled PI CNC Machining

Aiming at PI's processing characteristics of easy burr, heat accumulation and tool wear, we formulate exclusive processing schemes: configure sharp special tools, strictly control cutting heat, optimize fixture positioning stability, monitor tool life in real time and realize part dimensional stability control, especially suitable for high-precision semiconductor and aerospace components.

Precision PI Components

We support customized production of all kinds of high-precision PI parts, including precision bushings, sealing rings, positioning spacers, electrical insulators, sealing parts, wear-resistant components and complex special-shaped precision parts, meeting high-end equipment precision assembly standards.

Multi-Axis CNC Machining

Equipped with complete 3-axis, 4-axis and 5-axis CNC processing equipment, Evefab selects corresponding processing schemes according to part complexity. Multi-axis integrated processing reduces clamping times, avoids benchmark conversion errors and accumulative position deviation, and improves the overall precision consistency of complex PI parts.

Prototype to Batch Manufacturing

We cover the whole production cycle from engineering prototype verification, small-batch trial production, replacement parts customization to mass batch manufacturing. For recurring batch orders, we develop special production fixtures and optimize processes to improve production efficiency and product repeatability.

Quality Inspection & Documentation

Full-process quality assurance system includes CMM three-dimensional precision detection, dimensional full inspection, GD&T geometric tolerance verification, surface finish detection and key feature special inspection. Evefab can provide complete material certificates, conformity certificates and industry-specific certification documents for aerospace, semiconductor and medical projects.

PI CNC Machining Material Selection Summary

PI vs. PEEK vs. PAI vs. PPS vs. PTFE

When Should Engineers Choose PI?

Choose PI when you need: Long-term continuous high-temperature performance, high-temperature electrical insulation, ultra-high dimensional stability, low vacuum outgassing, high wear resistance, low friction coefficient, excellent chemical resistance and high reliability in harsh working environments.

Choose PEEK when: High mechanical strength and comprehensive chemical resistance are required, high-performance thermoplastics with stable supply are needed, and flexible processing methods such as injection molding and CNC machining are required.

Choose PAI when: Ultra-high structural rigidity and wear resistance are required for precision parts under high mechanical load.

Choose PPS when: Excellent chemical resistance, low water absorption and high dimensional stability are required for high-temperature electrical parts with cost control needs.

Choose PTFE when: Ultra-low friction and non-stick performance are core requirements, and rigidity and dimensional stability requirements are relatively low.

Final Engineering Recommendation

PI (Polyimide) is a premium high-performance engineering polymer, specially used for extreme working scenarios where temperature resistance, operational reliability, electrical performance, dimensional stability, wear resistance and low outgassing exceed the bearing range of ordinary and conventional high-performance plastics.

Its core advantages include ultra-high thermal stability, excellent electrical insulation, superior chemical resistance, grade-dependent low outgassing performance, excellent tribological properties and ultra-high dimensional stability, adapting to various harsh high-temperature and high-reliability industrial environments.

Material limitations are high raw material cost, large performance difference between different grades, high CNC machining process requirements, partial grades with general impact toughness and inability of conventional thermal welding.

In engineering design and procurement, it is not allowed to simply mark "PI" for material specification. It is necessary to clarify the specific grade, filler type, dimensional tolerance standard, operating temperature, load condition, friction and wear environment, electrical performance index, vacuum requirement and industry certification standard.

Contact Evefab now to obtain professional PI CNC machining quotation and DFM design optimization consultation. We customize high-temperature bushings, precision spacers, semiconductor fixtures, electrical insulators, sealing parts, wear-resistant components and complex high-precision PI parts, providing one-stop customized manufacturing solutions from prototype verification to batch mass production.

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