What is PEEK (polyether ether ketone)?
PEEK is an advanced thermoplastic containing good heat resistance, mechanical properties as well as chemical stability. PEEK is made up of polymer chains and ether ether ketone groups that distinguish it from other materials. Charles Poole discovered and then developed PEEK at ICI in 1982.
Properties of PEEK Plastic Material.
PEEK is a high-performance thermoplastic with many unique mechanical and chemical characteristics. Here are the key properties of PEEK plastic material:
- High-Temperature Stability:
PEKK has great stability at high temperatures and its working range is well above 250 degrees C which indicates its suitability for high temperature conditions.
- Mechanical Performance:
There are superior mechanical strengths and stiffness; that’s why it is suitable for applications with these properties.
- Chemical Resistance:
It has very high resistance to various corrosive substances like acids, alkalis, solvents, etc., for application in the chemical industry and medicine.
- Low Friction Coefficient:
The friction coefficient for PEEK is low which makes it ideal in several applications such as bearings and seals that have minimal friction requirements.
- Fatigue Resistance:
Demonstrates good fatigue resistance by having a constant performance regardless of long-term repetitive stresses.
- Electrical Insulation:
PEEK can act as a good electric and thermal insulator in electronic and electrical engineering.
Properly processed PEEK meets medical biocompatibility requirements and hence is good for medical implants and various biomedical applications.
- Processing Performance:
However, PEEK has a very high melting point (650 degrees Fahrenheit) as well as being extremely hard. Yet, processing PEAK efficiently can be attained with appropriate tools and cooling systems.
The density of PEEK is lower than that of metals but this material is good when considering the lightweight design of the applications involved.
- Wear Resistance:
PEEK has high wear resistance hence it is applicable in wear-resistant and durable applications.
The grades of PEEK plastic
Industrial Grade PEEK:
PEEK has been extensively applied in aerospace, automotive, electronic, petrochemical, and other industrial activities. It has superb wearability at high temperatures with good chemical stability. Hence, it is suitable for making highly efficient machine parts such as engine parts, seals, valves, and also pump bodies.
Medical Grade PEEK:
Highly biocompatible and biologically inert (stiff) for the production of medical devices & implants. It is employed in most surgical tools, bone screws, synthetic joints, and other medical orthopedics. Most medical grade PEEK will have gone through strict testing to meet the safety standards required by the medical industry.
The types of PEEK plastics
This is the commercial-grade PEEK material which does not contain additive filler and has no reinforcement. The material in question is extremely strong, rigid, and chemically resistant.
Glass-Fiber Reinforced PEEK:
The mechanical properties of these polymers can also be improved by adding filler materials such as glass fiber. These properties include enhanced tensile strength which includes of stiffness and dimensional stability which are enhanced as compared to glass fiber with similar properties.
Carbon-Fiber Reinforced PEEK:
Carbon fiber-reinforced PEEK is another option that offers greater strength and stiffness than glass fiber reinforcement PEEK. This material has excellent mechanical performance and it is therefore commonly used in those applications where high-grade performance is required.
Bearing Grade PEEK:
PEKK is made into customary bearing grades adapted for lower friction and wear-resistant applications. This group of grades is mostly applied in bearings and for wearing parts.
What are the advantages of machining PEEK?
Material advantages of peek plastic machining :
High Temperature Resistance:
PEEK retains its mechanical characteristics up to 499°F, which is why it is used in such areas as aerospace, and auto parts in high-temperature conditions.
The machined components have high tensile and flexural strength due to the PEEK material used therein.
PEEK is resistant to various chemicals hence suitable for applications in corrosive environments like chemical processing and oil and gas.
PEEK is used for machined parts experiencing friction and/or abrasion as it has exemplary wear resistance properties and extends lifespan.
Biocompatibility (Medical Grade):
Due to its bioactive properties, medical-grade PEEK can be used in various medical implantations and devices without harming the human body.
Process advantages of peek plastic machining :
The use of CNC machining of PEEK enables high accuracy and low tolerance for complicated shapes.
Versatility in Applications:
PEEK is a very versatile material as its properties can be used for many applications ranging from aerospace to medical, electronic devices to industrial parts.
Ease of Machinability:
In contrast to other high-performance plastics, it has a reasonably good machinability which leads to inexpensive production.
Reduced Friction and Lubrication Needs:
PEEK has a low coefficient of friction thereby minimizing the need for additional lubrication in applications and reducing overall maintenance costs.
Reduced Weight in Comparison to Metals:
PEEK in applications of high value, with consideration to the fact that its weight is very vital yet it holds out strong durability.
What are the Limitations of PEEK machining?
Compared to other materials, PEEK material may be more expensive; therefore, it affects the overall costs of machining processes.
Machining this material proves difficult as it is a high abrasive which results in higher tool wearing out. It may entail too many tool changes that affect production efficiency.
However, PEEK has a very high melting point with a low thermal conductivity which makes the machine difficult requiring specialized tools and machines.
Dimensional Stability Challenges:
Machining of PEEK can lead to dimensional variations because of its temperature-sensitive nature and hence attaining accurate tolerances could be difficult.
Smooth surface finishing of PEEK parts is sometimes more challenging requiring either additional processing or finishing steps.
In some way, air-machining PEEK could also produce certain hazardous fumes necessitating air-purifying arrangements inside the machining atmosphere.
Limited Color Options:
Because of this, PEEK is mostly available in a limited number of colors, which could limit its use in applications where color plays an important role.
Brittleness at Low Temperatures:
Unfortunately, it is possible to make PEEK brittle at very low temperatures which makes it not suitable for use in extremely cold surroundings.
PEEK is hygroscopic and thus it absorbs moisture with time. This could compromise its mechanical properties and dimensions in wet climates.
Limited Availability of Large Components:
The difficulty in acquiring sizeable PEEK pieces since they come in smaller formats.
What are the applications of PEEK machining?
PEEK machining finds extensive applications across various industries, leveraging its unique material properties for the production of high-performance components.
|Industry||Description||PEEK Component Examples|
|Medical Devices||Ideal for manufacturing surgical tools, implants, and medical device components due to its biocompatibility and chemical stability.||Bone screws, artificial joint components|
|Aerospace||Used in the production of engine components and interior structures for aircraft, offering lightweight and high-temperature resistance.||Engine thermal insulators, electronic equipment brackets|
|Automotive Manufacturing||Its high mechanical performance and chemical stability make it an ideal choice for automotive components such as engines and braking systems.||Spring washers, clutch components|
|Electronics Industry||Employed in the manufacturing of electronic components like connectors and insulation gaskets, boasting excellent insulation properties.||Electronic connectors, insulation gaskets|
|Wastewater Treatment||Widely applied in wastewater treatment equipment, such as valves and pump bodies, due to its corrosion resistance.||Valve sealing rings, pump body components|
|Oil and Gas||Resistant to chemical corrosion and high temperatures, suitable for components in petroleum exploration and production equipment.||Pump bodies, valve seat rings|
|Food and Beverage||Compliant with food safety standards, used in critical components for food processing equipment.||Conveyor components, food packaging machinery parts|
|Chemical Industry||Its corrosion resistance makes it widely used in chemical processing equipment, including pipe connections and pump components.||Pipe joints, pump impellers|
|Power Industry||With excellent insulation properties, it is suitable for manufacturing power equipment and insulation systems.||Insulation sleeves, power connectors|
|Telecommunications Technology||Ideal material for manufacturing antennas and connectors in communication devices, offering high-frequency characteristics and weather resistance.||Antenna brackets, communication connectors|
The suitable PEEK machining feeds and speeds
PEEK is a high-performance thermoplastic that can be challenging to machine due to its toughness and high melting temperature. When machining PEEK, it’s important to consider the cutting speeds, feeds, and other parameters to achieve optimal results. Here are general recommendations for machining feeds and speeds for PEEK:
Cutting Speed (Surface Speed):
Roughing: 200 to 300 feet per minute (61 to 91 meters per minute)
Finishing: 300 to 600 feet per minute (91 to 183 meters per minute)
Roughing: 0.005 to 0.015 inches per tooth (0.13 to 0.38 mm/tooth)
Finishing: 0.003 to 0.010 inches per tooth (0.08 to 0.25 mm/tooth)
Depth of Cut:
Roughing: Up to 0.250 inches (6.35 mm)
Finishing: Up to 0.060 inches (1.5 mm)
More PEEK machining tips for Accurate PEEK Machining
The properties of two common PEEK grades, industrial grade PEEK and medical grade PEEK, need to be considered, along with the corresponding processing methods and parameters. Depending on the desired end product properties, the processing strategy can be flexibly adapted.
- Select appropriate machining tools:
The reason for this is that PEEK is rigid thermoplastic and hence suitable tools would need to be picked which can be machined free of tears. Polycrystallin carbide tools are best suited for prolonged machining activities while carbide tools work well for general purposes.
- Avoid deep hole drilling:
PEEK has limited elastic properties hence deep hole drilling of a workpiece should be avoided as it may crack down the workpiece
- Keep clean during machining:
Wear gloves of cleanliness when machining medical grade PEEK since the parts may be contaminated.
- Use soft or pie fixtures:
Use a soft or a pie fixture for the creation of thin walls while supporting the workpiece properly.
- Drill :
When it comes to conditions that involve thread tapping, a spiral carbide tapping machine makes more sense.
These stresses often give rise to surface cracks and are reduced by annealing, which is a treatment process performed on PEEK rods. Multiple annealing treatments may be necessary depending on the machining time.
- Cutting tools:
Most commonly, PEEK can be machined using silicon carbide cutters. only diamond-cutting tools should be employed when adding carbon fibers to PEEK and in case of stringent tolerances. Furthermore, when you cut metals; try and have no contaminated cutting tool.
- Wet or dry machining:
It is important to cool PEEK since it does not conduct heat and can cause distortion and/or fracture. When machining medical parts, the use of liquid coolants is not recommended since the lubricity or the biocompatibility of the part should be maintained.
PEEK is a high-performance material engineering plastic used in the production of medical devices, aerospace engineering, and other fields. It is a must though complications in its machining make it hard. To tap into the latent strength of PEEK, precise strategies are required to unravel its potential as an innovative factor in manufacturing.
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