When it comes to processing high-performance plastics, people generally think of PEEK (Polyether Ether Ketone) CNC machining and PEI CNC machining. In the previous article, we have talked about PEEK CNC machining. Today’s article mainly talks about PEI (Ultem) CNC machining. PEI (Ultem) is a high-performance thermoplastic with high mechanical strength, high stiffness and good processability, making it the preferred processing material for many industry applications.
What is PEI(Ultem)?
PEI is an abbreviation for polyetherimide also known as Ultem. It is a thermoplastic polymer characterised by its ultrahigh performance, owing to its strength, thermal stability, and its capacity to withstand an extensive range of chemicals. The aerospace, automotive, electronics, and medical devices are some of the industries that utilise Ultem. Ultem is also CNC engineered, owing to its excellent mechanical properties and ability to create intricate structures.
Properties of Ultem
Tensile Strength
Ultem is known to have high tensile strength, found to be around 110 MPa. This enables Ultem parts to sustain structural integrity while experiencing the effects of gravity as well as maintaining enabled flexural strength and impact strength.
Thermal Stability
Ultem has high thermal expandability, being able to withstand temperatures of around 217 degrees Celsius. Coupled with rigidity, this ensures that Ultem remains reliably intact under high temperature exposure.
Chemical Resistance
Ultem’s resistance to acids, bases, and organic solvents undergoes strong resistance. This characteristic allows Ultem parts to withstand harsh environments without undergoing degradation.
Dimensional Stability
Ultem’s capability of retaining shape under long-term use as well as rapid temperature fluctuations is known as dimensional stability.
Flame Retardancy and Transparency
The transparency of Ultem is combined with its self-extinguishing capabilities. It can be used where flame retardant properties are required as well as where optical transparency is needed.
What are the grades of Ultem?
RPT 2100 LF
Ultem RPT 2100 LF is a low friction grade of Ultem designed for applications that require reduced wear and improved lubricity. Due to its enhanced durability, it is ideal for machined parts that operate under sliding or moving conditions, such as bearings or gears.
Ultem 1000
Ultem 1000 is a standard grade of Ultem that offers high strength and thermal stability. It is often used in aerospace and electronics.
Ultem 2100
Ultem 2100 has enhanced impact resistance compared to Ultem 1000, making it suitable for applications that require durability under high stress conditions.
Ultem 2300
Ultem 2300 is a reinforced grade of Ultem that combines improved mechanical properties and high strength with excellent heat resistance. It is often used in more demanding industrial applications where parts are exposed to mechanical stress and high temperatures.
Ultem 4000
Ultem 4000 is a clear grade of Ultem that contains glass fiber, PTFE and graphite powder fillers to increase its wear resistance and act as an internal lubricant. It is suitable for electronic equipment housings and personal accessories.
Properties Comparison of Ultem Grades
Property | RPT 2100 LF | Ultem 1000 | Ultem 2100 | Ultem 2300 | Ultem 4000 |
Tensile Strength, Yield (MPa) | 110-120 MPa | 90-100 MPa | 95-105 MPa | 95-105 MPa | 95-105 MPa |
Elongation at Break (%) | 5-10% | 6-10% | 5-8% | 5-8% | 6-10% |
Hardness (Rockwell M) | 120-130 | 120-130 | 120-130 | 120-130 | 120-130 |
Heat Deflection Temperature (°C) | 205°C | 217°C | 215°C | 215°C | 215°C |
Glass Transition Temperature (°C) | 200°C | 217°C | 216°C | 217°C | 217°C |
What are the methods for CNC machining PEI (Ultem)?
PEI Sawing
Sawing PEI (Ultem) is the action of cutting large sheets or blocks of the material into smaller, more usable pieces. Generally, a high-speed carbide blade is employed in order to achieve clean cuts. Sawing as a method proves to be beneficial when it comes to preparing Ultem stock for other machining operations, however, care should be taken in the form of heat management during the cutting operation so that the material does not deteriorate.
PEI Drilling
Drilling PEI requires meticulous attention to cutting speed and feed rates to avoid melting the material. It is imperative to utilise sharp and high-quality drill bits made out of either cobalt or carbide in order to produce clean holes without excessive heating. Furthermore, coolant or air blasts are utilised to maintain lower temperatures in the drilling zone as well as prevent cracking from occurring.
PEI Milling
When milling PEI, it is necessary to use complex machining methods to create features like contours, pockets, and slots. Both strength and thermal stability of the material require precise milling speeds and high-quality end mills. It is important to use coolant systems to prevent overheating from CNC machines, and cutting tools should be changed often to keep precision and surface finish smooth.
PEI Turning
When turning PEI, the material has to be rotated on a lathe, and a cutting tool is then used to get rid of material. Given Ultem’s hardness and wear resistance, carbide tools are used. Sharp tools and slow cutting speeds need to be enforced to achieve a smooth finish and to keep the material from overheating.
Key problems and effective techniques in Ultem CNC machining
Key Problems in Ultem CNC Machining:
1.Heat Generation
Ultem material has a high melting point and is prone to heat buildup during machining, which can cause thermal expansion, warping, or even melting of the material.
2.Surface Quality
Because Ultem tends to melt or chip when not machined properly, it is difficult to achieve a smooth surface finish.
3.Tool Wear
The abrasive nature of Ultem can accelerate tool wear, especially when inappropriate cutting speeds or tools are used.
4.Brittleness
Despite its strength, Ultem can be somewhat brittle, especially in thin cross-sections or under high cutting forces, leading to cracking or breaking.
5.Chip Control
Ultem produces long, sticky chips that can clog cutting tools or machines if not properly controlled.
6.Dimensional Stability
The material’s sensitivity to heat can affect its dimensional accuracy if cooling is not properly managed.
Effective Techniques for Ultem CNC Machining
1.Proper Tool Selection
Use sharp carbide or diamond-coated tools to reduce friction and tool wear. These materials can handle the abrasive nature of Ultem better than standard high-speed steel (HSS).
2.Cutting Speeds and Feeds
Use lower cutting speeds to minimize heat buildup, but maintain medium-to-high feed rates. Typical cutting speeds range between 1,000 and 3,000 RPM with feed rates of 0.005 to 0.020 inches per tooth.
3.Cooling and Lubrication
Use air cooling or a light coolant mist to effectively dissipate heat. Avoid excessive use of coolant, as Ultem is a thermoplastic that can absorb moisture, which can cause dimensional instability.
4.Chip Management
Use proper tool geometry with a high rake angle and optimized chipbreakers to help manage the long, thin chips produced by Ultem. High helix end mills promote effective chip evacuation.
5.Annealing After Machining
To relieve machining-induced residual stresses, consider annealing Ultem parts after machining. A typical annealing process involves heating the material to around 300°F to 400°F (150°C to 200°C) for several hours, followed by slow cooling.
Industries Utilizing Machined Ultem Parts
Aerospace
- Aircraft interiors (panels, brackets)
- Electrical housings
- Structural components (supports, clamps)
- Medical Devices
Automotive
- Fuel system parts (fuel injectors)
- Brake components (brake housings)
- Electrical connectors
- Electronics
Medical Devices
- Surgical instruments
- Diagnostic devices
- Implantable components (dental implants, pacemaker housings)
Electronics
- Connectors
- Circuit boards
- Insulators
Defense
- Protective casings (equipment housings)
- Munitions components (guidance systems)
- Communications gear
Consumer Goods
- Kitchen appliances (blender parts, appliance casings)
- Sporting equipment (bike parts, helmets)
- Home electronics (computers, remote controls)
What are the Differences between PEEK vs. Ultem Machining?
Feature | PEEK (Polyetheretherketone) | Ultem (Polyetherimide) |
Thermal Stability | Higher heat resistance (Tg ~ 143°C) | Moderate heat resistance (Tg ~ 217°C) |
Chemical Resistance | Excellent resistance to a wide range of chemicals | Good chemical resistance, but not as strong as PEEK |
Strength | Very high tensile strength and stiffness | High strength, but slightly lower than PEEK |
Machinability | Easier to machine, but slower feed rates are needed | Slightly tougher to machine, requires more care |
Moisture Absorption | Very low moisture absorption | Low moisture absorption |
Electrical Insulation | Excellent electrical insulation properties | Good electrical insulating properties |
Cost | Generally more expensive | Slightly more affordable than PEEK |
Applications | Aerospace, medical devices, automotive, electronics | Aerospace, medical devices, automotive, electronics |
Surface Finish | Can achieve smooth surface finishes easily | May require more effort for smooth finishes |
Weight | Slightly heavier than Ultem | Lighter than PEEK |
Custom Ultem CNC Machined Parts At EASIAHOME
Ultem is a high performance thermoplastic that offers processability, high strength, thermal and chemical stability.At EASIAHOME, we specialize in delivering high-quality custom CNC machined Ultem parts, tailored to meet the unique requirements of industries like aerospace, medical devices, automotive, electronics, and more.
Q: Is PEI the same as Ultem?
A: Yes, PEI (Polyetherimide) and Ultem are essentially the same material. Ultem is the brand name for PEI, manufactured by SABIC. Both terms are used interchangeably to refer to the same high-performance thermoplastic known for its thermal stability, strength, and chemical resistance.
Q: What surface finishes are available for Ultem Machined Parts?
A: CNC machined Ultem parts can achieve a variety of surface finishes depending on the application. Common options include: machined finish, ground or polished finish, sandblasted, etc.
Q: What types of CNC machines are best suited for machining PEI (Ultem)?
A:CNC machines with high-speed spindles, rigid setups, and coolant systems are best suited for machining PEI. Common machines include CNC mills, lathes, and drilling machines equipped with carbide or diamond-coated tools.
Q: Can PEI (Ultem) parts be machined to tight tolerances?
A: Yes, with proper machining techniques and equipment, PEI can achieve tight tolerances. This makes it suitable for applications requiring high precision, such as medical devices and aerospace components.
Q: Does machining PEI (Ultem) require cooling or lubrication?
A:Yes, coolants or air blasts are often necessary to dissipate heat during machining. This prevents material softening or melting and ensures a cleaner finish.
