Advanced 3D Printing

Most 3D printing guides treat all filament as roughly the same — just change the temperature and print. Engineering-grade polymers don't work like that. PEEK, PEKK, PA-CF, and their relatives have specific thermal, mechanical, and processing requirements that standard FDM printers simply cannot meet. This guide explains what those materials are, what they need, and why the gap between desktop and industrial printing has traditionally been so large — and how the Prusa Pro HT90 closes it. Why Engineering Polymers Are Different Standard filaments — PLA, PETG, ABS — are amorphous thermoplastics. They soften gradually as temperature rises and harden gradually as it falls. Processing them is relatively forgiving: get the temperature roughly right, keep the bed flat, and the print usually works. High-performance engineering polymers are semi-crystalline. This distinction matters enormously for 3D printing. Semi-crystalline polymers undergo a phase transition during solidification — they form ordered crystalline structures as they cool. This crystallisation releases heat (it's exothermic), changes the volume of the material, and happens rapidly at a specific temperature rather than gradually across a range. If the cooling rate is too fast, or the ambient temperature too low, the crystallisation is disrupted: the material doesn't achieve its designed mechanical properties, internal stresses build up, and interlayer adhesion suffers. This is why you cannot simply put PEEK in a standard desktop printer and raise the temperature. The material physics requires a controlled thermal environment throughout the entire print — not just a hot nozzle. The Materials — What Each One Is For PEEK (Polyether Ether Ketone) PEEK is the benchmark high-performance engineering polymer in FDM printing. Its mechanical properties are exceptional across a wide temperature range — tensile strength around 100 MPa, heat deflection temperature above 150°C (higher after annealing), excellent chemical resistance to most solvents, acids, and hydraulic fluids. It is biocompatible and can be autoclave-sterilised, which makes it valuable for medical devices and surgical tools. It is also used extensively in aerospace and defence for structural components, and in industrial machinery for bearings, seals, and bushings that must operate at elevated temperatures. PEEK requires a nozzle temperature of 360–400°C and a chamber temperature of 80–90°C for reliable printing. Without a heated chamber, parts warp severely and delaminate. PEKK (Polyether Ketone Ketone) PEKK is closely related to PEEK but with a different molecular structure that gives it some processing advantages. It has a wider processing window — the temperature range between its melting point and degradation temperature is broader than PEEK — which makes it slightly more forgiving to print. Its mechanical properties are comparable to PEEK, and it similarly requires a high-temperature chamber. PEKK is used in aerospace (it's qualified for structural applications on commercial aircraft), medical implants, and high-performance industrial components. PA-CF and PA-GF (Carbon Fibre and Glass Fibre Filled Polyamide) Polyamide (nylon) in its base form is already an engineering material — flexible, impact-resistant, chemically resistant to fuels and many solvents. Carbon fibre-filled and glass fibre-filled variants add stiffness and dimensional stability while largely retaining the toughness of the base material. PA-CF parts are lightweight with high specific stiffness — a key property for aerospace and automotive structural components where weight matters. Both require heated chambers (not as hot as PEEK — 60–80°C typically) and are highly hygroscopic, which means they must be dried thoroughly before printing and ideally fed from a dry box during printing. PPS (Polyphenylene Sulfide) PPS has outstanding chemical resistance — it is virtually unaffected by most organic solvents, acids, and bases at room temperature, and retains much of this resistance at elevated temperatures. It also has excellent flame retardancy (inherently V-0 rated) and dimensional stability. PPS is used in automotive (under-hood components, fuel system parts), electronics (connectors, insulators), and chemical processing equipment. It requires nozzle temperatures of 300–350°C and a heated chamber. PSU / PES / Ultem (Polysulfone / Polyethersulfone / Polyetherimide) This family of materials offers excellent thermal stability and transparency in some grades, good mechanical properties, and — for Ultem specifically — one of the best strength-to-weight ratios available in FDM printing. Ultem (PEI) is FAA-certified for use in aircraft interiors and is widely used in aerospace, defence, and medical applications. It requires nozzle temperatures around 360–420°C and a heated chamber at 70–90°C. What a Printer Actually Needs to Process These Materials Requirement Why it matters HT90 capability Nozzle temperature ≥ 380°C PEEK melts at ~343°C; reliable extrusion needs headroom above melt point Up to 500°C ✓ Heated chamber ≥ 80°C Semi-crystalline polymers require controlled ambient cooling to crystallise correctly Up to 90°C ✓ All-metal hotend PTFE degrades at temperatures above ~250°C, releasing toxic gases; must be entirely metal above the melt zone All-metal hotend ✓ Abrasion-resistant nozzle Carbon fibre and glass fibre fills are highly abrasive and destroy brass nozzles rapidly Hardened nozzle ✓ Controlled cooling Too much cooling disrupts crystallisation; too little causes sagging on overhangs Active, controllable ✓ Air filtration High-temp polymers generate VOCs and ultrafine particles; HEPA filtration required for safe operation Built-in HEPA ✓ Bed temperature ≥ 120°C PEEK requires a hot first layer to adhere reliably; PEI or garolite bed surfaces recommended High-temp bed ✓ The Drying Requirement All the materials in this guide are significantly hygroscopic — they absorb water from the air. Printing with moisture-contaminated filament causes hydrolysis: water molecules break apart polymer chains at processing temperatures, permanently degrading the material's mechanical properties. Unlike PLA where moisture causes cosmetic defects (stringing, surface roughness), moisture in PEEK or PA-CF causes structural degradation that cannot be fixed by post-processing. For engineering materials, drying is not optional. Specific recommendations vary by material but as a general guide: PEEK / PEKK: 120°C for 4–6 hours before printing PA-CF / PA-GF: 80–90°C for 6–12 hours; feed from a dry box during printing PPS: 120°C for 4–6 hours Ultem / PEI: 120°C for 4–6 hours Do not use a standard filament dryer set to 50–70°C for these materials — that temperature is insufficient. A dedicated high-temperature drying oven is required. Why the Gap Between Desktop and Industrial Has Been So Large Until recently, the practical barrier to printing high-performance engineering polymers was not the cost of the filament — PEEK and Ultem filament is expensive but not prohibitively so. The barrier was the printer. A machine that reliably meets all the requirements above — 500°C nozzle, 90°C chamber, all-metal hotend, HEPA filtration, high-temp bed, abrasion-resistant nozzle — has historically cost €50,000–€200,000. The engineering, the thermal management systems, the safety infrastructure all add up. The Prusa Pro HT90 is a genuine step change in that cost curve. It does not cut corners on the requirements that matter — chamber temperature, nozzle temperature, filtration, material compatibility. It brings them to a price point that small engineering firms, university labs, and serious professionals can actually reach. Material Comparison Summary Material Nozzle temp Chamber temp HDT Key use cases PEEK 360–400°C 80–90°C >150°C Medical, aerospace, industrial bearings PEKK 340–380°C 80–90°C >150°C Aerospace structures, medical implants PA-CF 260–290°C 60–80°C ~180°C Lightweight structural, automotive, jigs PPS 300–350°C 80–90°C >200°C Chemical processing, automotive, electronics Ultem (PEI) 360–420°C 70–90°C >170°C Aerospace interiors, medical, defence PSU / PES 340–380°C 70–80°C >180°C Medical sterilisation, chemical equipment Next in the Series Part 1: What the HT90 Is and Who It's For Part 3: Printing with the HT90 — Settings, Materials, and Practical Tips Part 4: HT90 vs Industrial 3D Printers — Is It Right for Your Business? View the Prusa Pro HT90 →