PEEK is a popular thermoplastic polymer found in objects as diverse as medical implants and electrical cable insulation.
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The plastic has excellent mechanical properties and a high level of resistance to corrosive substances, making it highly desirable for manufacturers across the world. Despite being regularly used for injection molding and 3D printing, PEEK has a high melting point, which would indicate its suitability for subtractive processes like CNC machining — although PEEK machining comes with its own set of challenges.
This article goes over the fundamentals of machining PEEK: the material properties of PEEK, the advantages of machining PEEK, common applications of machining PEEK, and tips for how to get the most out of machined PEEK parts.
What is PEEK (
polyether ether ketone)
?
PEEK, or polyether ether ketone, is a high-performance engineering thermoplastic and part of the PAEK family of materials. The semi-crystalline material is used for a wide range of industrial parts and components, exhibiting excellent strength, wear resistance, and abrasion resistance, and retaining its properties even at high temperatures.
PEEK grades offer chemical and water resistance similar to PPS. But with a melting point of 343°C, PEEK can operate at higher temperatures: it can be used continuously to 250°C and in hot water or steam without permanent loss in physical properties.
The high-performance PEEK plastic is available in granular form, in filament for 3D printing, and in bar / rod form for CNC machining. It is typically classified as either industrial-grade or medical-grade.
What are the Advantages of machining PEEK?
There are numerous advantages to PEEK machining, and these can be broken down into two categories: the inherent material advantages of PEEK, and the specific process advantages of using a CNC machine for machining PEEK material.
Material advantages of machining PEEK include:
Excellent chemical resistance
Very low moisture absorption
Wear and abrasion resistance
Unaffected by continuous hot water / steam exposure
Some grades biocompatible
Resistant to biodegradation
Process advantages of machining PEEK include:
What are the Limitations of PEEK machining?
Although many machinists use PEEK plastic as a reliable alternative to some metals, there are several limitations to machining the thermoplastic polymer. These include:
Special handling required to minimize internal stress and heat-related cracks
Annealing required
Doesn’t dissipate heat well
Can crack if drilled deeply
What are the Applications of PEEK machining?
PEEK is a material with a surprisingly diverse range of applications, some of which are best served by CNC machining over other manufacturing techniques. Industrial-grade PEEK plastic is used in the aerospace, automotive, chemical, electronics, and energy industries, while medical-grade PEEK plastic is used in healthcare and dentistry.
These common machined PEEK parts are here categorized by whether they use industrial-grade or medical-grade PEEK:
Industrial-grade
Medical-grade
Rollers and wheels
Implants
Bearings
Spinal fusion devices
Washers, seals & manifolds
Trauma fraction devices
Cable insulation
Orthopedic devices
Blocks
Dental healing caps
Bushings
Spiked washers
Rings
Drug delivery systems
PEEK machining tips
PEEK is a machinable thermoplastic, but critical steps must be taken before, during, and after machining to deliver the best end product.
Annealing: Annealing is a process performed on PEEK rods to relieve stress and reduce the chances of stresses and surface cracks in the PEEK material during machining. Annealed PEEK is also less likely to deform. Multiple annealing stages may be required depending on the time required for machining.
Cutting tools: In most circumstances, PEEK can be machined using silicon carbide cutting tools. If the PEEK is reinforced with carbon fiber, or if exceptionally tight tolerances are required, diamond tools should be used. Furthermore, contamination can be avoided if the cutting tools used are not also used on metals.
Wet or dry: Because PEEK doesn’t dissipate heat, it needs to be cooled during machining to prevent deformation or breakage. Standard liquid coolant can be used, unless e.g. medical parts are being machined, in which case the PEEK material needs to be cooled by pressurized air. This is because liquid coolant can affect the biocompatibility of PEEK.
Drilling: Deep hole drilling can cause cracks, since PEEK has a lower elongation than other plastics.
PEEK machining, PEEK 3D printing, or PEEK injection molding?
PEEK material is not limited to CNC machining. It can also be processed via additive manufacturing or injection molding. Choosing between the processes depends on the desired end product, as well as time and budget constraints.
For 3D printing PEEK, both FFF filaments and SLS powders are available. However, the availability of PEEK for CNC machining and injection molding still far outweighs the options for additive manufacturing. 3D printing is becoming increasingly popular for the printing of biocompatible medical implants, since complex (and partially hollow) geometries can be easily realized.
Injection molded PEEK resin is widely used for medical and aerospace applications and beyond. However, its melting point is at the upper end of many injection molding machine’s capabilities, and it may therefore be considered a specialty material. Learn more from our guide on Plastic CNC machining and how to choose the best type for your project.
Customers may also consider other high-temperature plastics besides PEEK, such as PEKK or Ultem.
Machining
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3D printing
Injection molding
Complex geometries
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3ERP in an experienced provider of PEEK machining, in addition to many other prototyping and plastic CNC Machining services and parts. Request a free quote for your next project.
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PEEK is a well-known thermoplastic polymer found in various objects, such as medical implants and insulations for electric cables.
The popularity of PEEK stems from its excellent mechanical properties and high resistance to corrosive substances products. Furthermore, its high melting point makes it suitable for subtractive processes such as CNC machining.
This article guides you through PEEK properties, components, and industry applications. Here, we’ll share tips to help you get the best from your PEEK machining process. Let’s go right to it!
What is PEEK?
PEEK Parts
PEEK is a thermoplastic polymer of Polyether ether ketone. It is a semi-crystalline high-performance engineering thermoplastic. This semi-crystalline material is used in diverse industrial parts and components due to its excellent mechanical properties, wear resistance, high chemical resistance, water resistance, and abrasion resistance.
PEEK plastics have the exceptional advantage of retaining their properties even at high temperatures. They melt at about 343oC and operate perfectly at higher temperatures. Therefore, it can be used in hot water or steam and progressively to a temperature high temperature up to 250oC.
The semi-crystalline thermoplastic polymer occurs in different forms. It is available in granular form, bar forms for CNC machining, and filaments. The two major classifications of PEEK are:
Industrial-Grade PEEK: This is a strong, abrasion-resistant plastic with increased impact strength. It also has a low coefficient of friction, with its biggest attribute being its ability to retain its mechanical and physical properties even in extreme conditions.
PEEK Bearing
As you may have guessed, the common uses of industrial-grade PEEK are for industrial applications. It is useful in the aerospace, chemical, automotive, petroleum, electronics, and food and beverage industries.
Medical-Grade PEEK: In addition to its inherent properties, medical-grade PEEK includes biocompatibility, sterilization compatibilities, and resistance to biodegradation. This thermoplastic is also radiolucent. This means that it is not visible under CT, X-ray, or MRI scans.
Medical Grade PEEK Parts
This PEEK grade includes polymers used for medical implants to mimic the stiffness of bones. Thus, they can be in contact with tissues and blood. Other medical-grade PEEK variations are useful for custom components and applications like spinal devices and articulating joints.
Your application will determine the grade of PEEK you choose to machine.
Properties of PEEK Plastic Material
Industries producing diverse objects, such as medical implants, use PEEK widely in their productions. This is due to the excellent and exceptional properties of Peek plastic.
Manufacturers widely appreciate the following properties of this thermoplastic:
1. Excellent Chemical, Electrical, and Temperature Resistance
PEEK material gives high resistance against corrosive chemicals. It provides resistance similar to nickel steel and can retain its non-corrosive and chemical structure with most metals, even at high temperatures. During normal conditions, only concentrated sulphuric acid can dissolve this plastic.
Also, PEEK has high electrical performance over high temperatures and frequencies. Since it has a stable chemical structure when chemically attacked, the material can operate perfectly under high doses of ionization radiation.
In addition, it has high resistance to gamma radiations, more significant than that of polystyrene (material with the most resistance to radiations in general-purpose resin use). This property makes it suitable for high-performance wire use to ensure good insulation.
Furthermore, PEEK material is highly durable and has a high melting point. Therefore, it works perfectly well during peak machining at elevated temperatures and does not deform at higher temperatures.
2. High Workability Rate and Consistent Performance Even at High Temperatures
PEEK material assures high workability during plastic CNC machining due to its good processing performance. Although it’s a super high-temperature thermoplastic material, it can be processed with different material processing methods.
These methods include injection moulding, extrusion moulding, melt spinning, etc. The high-temperature workability and high thermal decomposition properties of PEEK ensure this compatibility. In addition, this thermoplastic is a self-extinguishing material during combustion; it produces little or no toxic gas and smoke.
3. Excellent Mechanical Properties, Creep Resistance, Wear, and Friction Resistance.
PEEK and other high-temperature thermoplastics have high impact strength and retain their size at elevated temperatures. It has a low linear expansion coefficient and good dimensional stability.
PEEK has the highest fatigue and stress-retaining properties of all other plastics. Also, it has excellent creep resistance properties (the ability of a substance to deform slowly over a long period of exposure to stress). This property makes it a suitable material to withstand great pressure during machining.
Furthermore, PEEK provides excellent wear resistance with a low coefficient of friction. Therefore, it can maintain high wear resistance with various physical pressure conditions, surface roughness, temperature, and speed relative to the contact surface.
4. Low Absorption of Water and Resistance to Radiation
Using PEEK for making machine or instrument components helps these parts retain their chemical structure and properties in wet areas. Even at increased temperatures, its resistance to hydrolysis makes it ideal in wet environments, pressurized hot water, or steam.
Also, PEEK parts can operate under intense ionizing radiation. As previously stated, it has better resistance to gamma radiation than polystyrene.
PEEK Components, Applications & Industries
Despite being an essential material for manufacturing, it is crucial to use PEEK only, where you will get operational benefits from its applications. Here, we will mention some components and industries where PEEK is appropriate.
However, you must note that this list is not exhaustive. You may need to talk to our experts to get you through your projects.
PEEK Plastic Part
Oil and Gas
Downhole tools in the oil and gas sector endure harsh conditions like high temperatures and aggressive chemicals. Where traditional materials fail, PEEK valves excel due to their superior chemical resistance and heat tolerance. These valves efficiently regulate fluid flow, enhancing extraction safety. Their durability leads to extended operational life, reducing frequent replacements and upkeep.
Medical
In the medical field, PEEK is prominently used for orthopaedic and spinal implants, especially in spinal fusion surgeries for conditions like degenerative disc disease. Damaged discs are replaced with PEEK cages, often filled with bone grafts to encourage fusion. PEEK’s biocompatibility prevents adverse reactions, and its radiolucent nature allows clear imaging post-surgery. Its mechanical properties mimic natural bone, ensuring support and flexibility.
Aerospace
Aircraft components, especially those in the engine and cabin areas, must withstand extreme conditions while being lightweight. PEEK is used to manufacture cable sheaths and insulation in aircraft. Its lightweight nature contributes to fuel efficiency, while its heat resistance ensures safety and durability. For instance, PEEK composites replace metal in certain aircraft parts, reducing weight without compromising strength.
Electronics
PEEK’s excellent electrical insulation properties make it a prime choice for connectors, insulators, and cable insulation in electronics. For instance, PEEK wafer carriers are used in semiconductor production because they can withstand aggressive chemicals and high temperatures in chip fabrication.
Automotive
The automotive industry continuously seeks materials to reduce vehicle weight and improve fuel efficiency. PEEK makes components like gears, thrust washers, and seal rings. Its ability to reduce friction and wear, combined with its thermal stability, makes it ideal for parts that experience high stress in engines and transmissions.
Tips for PEEK Plastic Machining
As we mentioned earlier, PEEK is a machinable material. However, you need to take critical steps before, during, and after the machining process.
Here are some tips to help you if you want to get the best end product from machining PEEK.
Annealing: The annealing process on PEEK rods helps reduce any chances of internal stresses and surface cracks. It also helps minimize internal stress in the material while machining. It will also be difficult to deform an annealed PEEK. Depending on the required time for machining, you may need additional intermediate annealing steps.
Cutting Tools: Silicon carbide cutting tools are among the best choices for machining PEEK. In other circumstances, you should use diamond tools. Such cases include when the thermoplastic is reinforced with carbon fiber. Diamond tools will also be useful when the required tolerances are very tight. You can prevent contamination by avoiding using the same cutting tools used on metals.
Wet or dry: PEEK does not dissipate heat. Therefore, it requires cooling during the machining process. Doing this will prevent breakage or deformation. You can choose to use a standard liquid coolant. However, pressurized air will be the best option for machining medical parts. Why? Liquid coolant may affect PEEK’s biocompatibility.
Drilling: Drilling deep holes into heavy cross-sections on PEEK can cause cracks because its elongation is much lower than other plastics.
Features of PEEK Machining Services at AT-Machining
As an industry leader in custom CNC machining services, our clients across several industries appreciate the following features of our PEEK machining services:
PEEK CNC Machining Services
- In-house fabrication of PEEK plastic parts machining at our well-equipped facility
- A wide range of engineering services, such as product design and tooling, as well as CAM/CAD
- We can effectively work on prototypes from medium-sized and low-production runs.
- Our plastic CNC machining services comply with RoHS, MIL specifications, and AMS standard.
- Our qualified professionals inspect every machined part before delivery, ensuring optimum quality and avoiding product recalls.
- We also offer secondary finishes on PEEK machined parts, such as polishing, edge finishing, etc.
- Our experts will work closely with you to understand your requirements and offer you the best materials, machining processes, and finishing suggestions.
FAQ
Custom PEEK CNC Milled Part
Is PEEK Hard to the Machine?
PEEK is a difficult plastic material to machine. It requires special handling with high expertise and experience. Despite being machinable thermoplastic, the manufacturer must take critical steps before, during, and after machining for the best results.
Can You EDM PEEK?
Electrical Discharge Machining (EDM) works well on PEEK. The unique properties ensure the adequate creation of complex geometries, some of which are impossible with other technologies.
Is PEEK Stronger Than Aluminium?
Aluminium is stronger than PEEK, with a tensile strength of 45,000 psi. However, PEEK is a high-performance polymer with a high strength-to-weight ratio among other thermoplastics. It is an excellent alternative to other materials like steel, glass, and aluminium.
Conclusion
PEEK is an excellent thermoplastic with applications in several industries. Properties such as excellent chemical resistance, biocompatibility, tight tolerances, and more make it popular for many applications. The tips we discussed in this article will help you get excellent results from machining PEEK.
Contact us at AT Machining to get the best PEEK CNC machining services. Let’s help you bring the best out of your next project.
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