Can peek be injection molded? Yes, Polyetheretherketone (PEEK) can absolutely be injection molded. In fact, injection molding is one of the most popular manufacturing processes for PEEK plastic parts across industries like medical, aerospace, automotive, and more. As a professional plastic injection molding manufacturer, I will discuss everything about PEEK injection molding in this post.
What is PEEK Plastic?
PEEK (polyether ether ketone) is a high-performance semi-crystalline thermoplastic known for its exceptional mechanical properties, heat resistance, and chemical inertness. The unique properties of peek make it an ideal material for demanding applications where reliability and durability matter.
PEEK has a unique molecular structure comprising benzene rings connected by ketone and ether functional groups. This arrangement imparts great thermal stability and mechanical strength to the material. PEEK offers the following benefits:
- High strength and stiffness
- Resistance to continuous use temperatures exceeding 250°C
- Inertness towards harsh chemicals and solvents
- Resists sterilization methods like autoclaving and radiation
- Dimensional stability under load
- Low smoke and toxic gas emission when burned
With its unmatched performance pedigree, PEEK has become the top choice for making plastic components across industries like aerospace, automotive, oil and gas, semiconductor manufacturing, and medical devices.
Why Injection Mold PEEK Parts?
Injection molding allows high-volume, cost-effective manufacturing of intricately shaped PEEK parts with tight tolerances. Although PEEK is expensive compared to commodity plastics, the per-part price becomes affordable when thousands of parts are molded.
Injection molded PEEK also offers benefits like:
- Flexibility to create complex geometries not possible with machining
- Option for multi-shot molding with overmolding
- Shorter lead times compared to CNC machining
- Near-net shaped parts to minimize machining
PEEK’s melt viscosity facilitates flow into thin walls and small features. Injection molded parts with ribbing or hollow internal structures are lighter in weight without compromising strength.
PEEK Injection Molding Process Overview
Though standard injection molding machines can mold PEEK, several critical process parameters need tight control:
Melt temperature – PEEK processing requires a melt temp between 360°C to 400°C to lower viscosity.
Mold temperature – Mold temps of 170°C to 200°C ensure proper crystallization kinetics.
Injection pressure – Pressures below 10MPa (1450psi) allow complete cavity fills.
Drying – PEEK must be dried for 2-3 hours at 150 deg C to a moisture content below 0.02% before molding.
Gate design – Large tab gates (> 1mm thickness) are preferred to fill PEEK’s faster freezing flow fronts.
Maintaining these optimal conditions leads to low-stress, dimensionally stable injection molded PEEK parts.
Applications of Injection Molded PEEK Parts
Thanks to its stellar performance, molded PEEK parts serve critical functions across industries:
Aerospace
Aircraft valves, fittings, electronic housings, engine wear rings
Medical Devices
Surgical instruments, orthopedic implants, MRI-compatible devices with peek plastic
Automotive
Gears, bushings, bearings, pump parts – under-the-hood components
Machinery
Valve bodies, conveyor parts, rollers, glide rings
Electronics
Connectors, insulators, sensors capable of withstanding high temps
Oil and Gas Exploration
Downhole tools, wellhead parts, pump components that resist corrosion
With innovative design, molded PEEK has the potential for groundbreaking new applications as well!
Design Rules for Injection Molding PEEK Parts
Proper design is key to molding dimensionally accurate PEEK parts without defects. Here are some design guidelines to follow:
Uniform wall thickness – Avoid thick-to-thin transitions to prevent sink marks. Keep variations below 20%.
Radius corners – Eliminate all sharp corners. Specify fillet radii equal to ~20-25% of wall thickness.
Draft angles – Incorporate draft angles between 0.5-1° on vertical walls to enable easy ejection.
Ribs and gussets – Add thickness in areas prone to warpage.
Textures and labels – Allow 0.5mm min. depth for engraved text or surface textures.
Furthermore, perform molflow simulation analysis to predict fill patterns, air traps, weld lines early. Fixing issues digitally prevents costly mold rework.
Why Injection Molding PEEK is Challenging
PEEK owes its phenomenal performance to a rigid chain-like molecular structure packed tightly via hydrogen bonding between polymer chains. Disrupting this ordered arrangement leads to inferior mechanical properties.
Several peculiarities of PEEK make its processing tricky:
Narrow processing window – With a melting point of 343°C and glass transition temperature of 143°C, only a narrow temperature range allows proper viscosity for molding. Temp fluctuations easily take the melt outside this window.
Poor heat transfer – The melt cools slowly due to poor thermal conductivity. Combined with high crystallization rates, this makes uneven cooling and freeze-off likely.
Moisture sensitivity – Although chemically inert, PEEK readily absorbs atmospheric moisture. Just 0.2% moisture content causes internal bubbles and void defects.
Shear sensitivity – Excessive shear from high screw RPM damages polymer chains. This drastically increases melt viscosity.
Despite these challenges, injection molding know-how makes processing PEEK rather straightforward.
How to Injection Mold PEEK Parts Successfully
Follow these vital pointers to injection mold defect-free PEEK components consistently:
1. Select The Right Grade of PEEK
Various grades are available depending on required mechanical properties and cost:
- Unfilled standard grades – For electrical insulation and FDA compliance. Most economic option.
- Glass fiber reinforced – 30% glass fibers boost strength and stiffness while lowering CLTE.
- Carbon fiber reinforced – 30% carbon fibers optimize strength along load directions. Add conductivity.
- Wear resistant grades – PTFE or silicone lubricant filled PEEK cuts friction and wear rate.
- Flame retardant grades – Includes phosphorous additive that quenches fires. Food contact compliant.
Always get material certificates from your supplier outlining exact mechanical properties and polymer quality metrics.
2. Dry The PEEK Material Thoroughly
Although PEEK arrives predried from suppliers, exposure to humidity in storage affects processing:
- Dump PEEK pellets in a hot air hopper drier set at 150 deg C.
- Dry pellets for 3 hours or until moisture level reaches 0.02% maximum.
- Use nitrogen blanketing while drying to prevent reabsorption of moisture.
- Feed the injection press using a closed, continuous material conveyance system.
3. Setup The Injection Molding Machine
Configuring the press appropriately is vital for defect-free molding:
- Heaters – Install ceramic heater bands and thermocouples rated for 400+ deg C.
- Barrel – Use bimetallic barrels with nitride steel surface hardness.
- Check ring – Must withstand high injection pressures without leaks.
- Screw – Hardened steel alloy screw with polished finish to prevent hang-ups.
- Mold – Use beryllium-copper or aluminum molds with uniform temperature across all cavities.
4. Adhere To Recommended Process Settings
Refer to your chosen PEEK grade’s datasheet for its optimal molding window:
- Melt temp – 390±10 deg C for unfilled, 380±10 deg C for glass filled PEEK
- Mold temp – 180-210 deg C for glass-filled, 170-200 deg C for other grades
- Injection pressure – Maximum 14MPa (2,000psi) to fill complex geometries
- Injection speed – Fast injection along with high mold temperature improves surface finish.
- Holding pressure – 90% of injection pressure prevents shrinkage related defects.
5. Inspect And Package Parts Correctly
Once molded, adhere to industry-specific quality protocols while handling PEEK parts:
- Visually inspect parts for any short shots, sink marks, warpage, or surface defects
- Use non-abrasive packaging materials to avoid scratching
- Seal molded components in moisture-proof packaging with desiccant bags
Follow these guidelines, and you will find injection molding PEEK quite undemanding. With practice, automating the entire molding sequence allows further fine-tuning for zero-defect output.
Conclusion – Leveraging PEEK’s Potential with Injection Molding
This guide covers the essentials of injection molding high-performance PEEK plastic components. When optimally molded, PEEK parts provide game-changing advantages like light weight, environmental stability, mechanical toughness, and long service life without compromises.
Injection is the ideal manufacturing route to unlock PEEK’s immense potential while keeping costs reasonable. With informed design and tight process control, intricate geometries with demanding tolerance requirements are achievable.
As automation makes lights-out 24/7 production feasible, consistent high-quality and rapid scale-up become reality, propelling next-gen product development. Supporting the production of complex shapes in PEEK via injection molding pushes the boundaries of possibility across industries!
