A Comprehensive Guide to PEI (Ultem) CNC Machining

Table of Contents

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.

PEI (Ultem) CNC Machining

What is PEI(Ultem)?

PEI (Polyetherimide), commonly known as Ultem, is a high-performance thermoplastic polymer renowned for its exceptional strength, thermal stability, and chemical resistance. Ultem is widely used in CNC machining due to its excellent mechanical properties and versatility in manufacturing complex parts. This polymer is often found in industries like aerospace, medical devices, automotive, and electronics.

Properties of Ultem

High Tensile Strength

Ultem has high tensile strength, with a tensile strength of 110 MPa. This property ensures that Ultem parts maintain their structural integrity even under the effects of gravity, with high flexural and impact strength.

 

Thermal Stability

Ultem has excellent thermal stability, with a high glass transition temperature (Tg) of around 217°C. This allows it to perform reliably in environments exposed to high temperatures without deforming, maintaining its rigidity.

 

Chemical Resistance

Ultem has a strong resistance to a wide range of chemicals, including acids, bases, and organic solvents. This property ensures that Ultem parts can withstand harsh environments without degradation.

 

Dimensional Stability

Ultem has excellent dimensional stability, meaning it retains its shape even with temperature fluctuations and long-term use.

 

Transparency and flame retardancy

Ultem has both transparency and self-extinguishing properties. It can meet flame retardant requirements and can also be used in applications that require optical transparency.

 

 

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) involves cutting large sheets or blocks of the material into smaller, more manageable pieces. A high-speed carbide blade is typically used to achieve clean cuts. Sawing is an effective method for preparing Ultem stock for further machining operations, though care must be taken to manage heat buildup during the cutting process to prevent material degradation.

 

PEI Drilling

Drilling PEI requires precise control of cutting parameters, including speed and feed rates, to prevent the material from melting. It is essential to use sharp, high-quality drill bits made from carbide or cobalt to ensure clean holes without excessive heat generation. Coolant or air blasts are often used to keep the drilling area cool and reduce the risk of cracking.

 

PEI Milling

Milling PEI is a common process used to create complex shapes and features, such as pockets, slots, and contours. The material’s high strength and thermal stability require slow, controlled milling speeds with high-quality end mills. CNC milling machines with coolant systems are essential to prevent overheating, and cutting tools should be replaced regularly to maintain precision and surface finish.

 

PEI Turning

Turning PEI involves rotating the material on a lathe while a cutting tool removes material to shape the part. Due to Ultem’s hardness and resistance to wear, carbide tools are commonly used. Low cutting speeds and sharp tools are necessary to achieve smooth finishes and prevent the material from overheating.

Ultem CNC machining parts

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)
ultem CNC machining

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.

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