German company INDMATEC has begun offering 200gm rolls of 1.75mm PEEK filament on its website for €140.00. This is a significant step toward printing industrial materials on relatively inexpensive desktop 3D printers.
PEEK (Polyether ether ketone) is a semicrystalline thermoplastic with good chemical and mechanical resistance properties that hold up at high temperatures. Its tensile strength is 90 to 100 MPa and its melting point is 343°C (662°F). It is resistant to thermal, organic and water degradation. The material is often used in the aerospace, energy, automotive, electronics and medical industries for the creation of bearings, piston parts, valves, gaskets, low-noise gears and medical implants. Its wear and abrasion properties are better than titanium or steel.
ABS and PLA melting temperatures are 100+°C lower than PEEK and some FDM extruders use PEEK as thermal insulation. This means an average desktop FDM printer isn't capable of using the material. Certain manufacturers are working to achieve the pressure temperatures required to extrude it and PEEK-ready machines should be available within a year. In the meantime, aftermarket printer modifications are required.
INDMATEC offers both technical support and hardware components to aid in the conversion. For those interested in doing it themselves, an E3D v6 all-metal HotEnd is able to reach over 400°C by swapping the thermistor for a thermocouple, which is capable of measuring higher temperatures. RepRap guru and 3D printing author Rich Cameron explains the difference.
"A thermistor is a resistor that changes its resistance based on temperature. Actually, all of them do, but thermistors are designed to have a large, predictable change in resistance based on temperature within a useful range of temperatures," says Cameron. "A thermocouple is a point of contact between wires of two unlike metals. Due to the Seebeck effect, this junction produces a voltage on the order of millivolts. This requires an external reference temperature and an additional chip to amplify this signal to something that a microcontroller can read."
The hot end, electronics and chip code aren't the sole areas of focus for printing Peek. While significantly less moisture absorbent than ABS (its water absorption saturation is 0.45 percent at 23°C), it can still warp during printing due to thermal gradient effects. Put simply, the temperature difference between the material's melting point and previously printed layers can be very high.
Dr. Brando Okolo, a materials professor and the CTO of INDMATEC says five things are required to print with PEEK filament.
"To successfully print this material you need an enclosed printer, an all metal hot end that attains 400°C, a good heating bed, a printing speed optimized for the particular printer and the patience to understand the material," says Okolo.
Does that mean a Stratasys-style temperature controlled build chamber? Not necessarily. Between a high temp print bed and a 400°C hot end, any enclosure is going to get pretty warm. Limiting air circulation between the build area and room would be crucial.