Advanced 3D Printing

You've decided the HT90 is the right machine. This guide covers what you actually need to know to get reliable results: how to set up the machine, which head to use for which materials, settings per material class, bed adhesion, and the most common issues you'll encounter when printing high-performance polymers. First: Chamber Preheating For engineering and high-performance materials, chamber preheating is not optional — it is the first step in every print. Start heating the chamber before loading filament and before starting the print job. For PEEK and similar materials, allow the chamber to reach full temperature (90°C) and stabilise for at least 15–20 minutes before printing begins. Printing before the chamber is fully stabilised is one of the most common causes of first-layer delamination and warping in high-performance materials. For standard materials (PLA, PETG), the chamber can remain open or be heated to a lower temperature. There is no requirement to use the full 90°C for materials that don't need it. Head Selection The HT90 ships with two heads. Choosing the right one before printing is important — both are optimised for different conditions. Head Best for Max nozzle temp High-Flow Head PLA, PETG, ABS, ASA, PA — standard and engineering materials up to ~300°C ~300°C High-Temperature Head PEEK, PEKK, PPS, PSU, PEI (Ultem) — all materials requiring >300°C nozzle 500°C Swapping heads takes a few minutes without tools. The load cell sensor recalibrates the first layer automatically after each swap — no manual intervention needed. Settings by Material Class Standard Materials (PLA, PETG) Nozzle temperature PLA: 200–220°C / PETG: 230–245°C Bed temperature PLA: 50–60°C / PETG: 70–85°C Chamber Not required — can print with chamber open Print speed Up to 200–300 mm/s with Input Shaper enabled (PLA) Head High-Flow The HT90 with Input Shaper is extremely fast with standard materials. Use it for high-volume prototyping in PLA or PETG and you'll see throughput that rivals dedicated high-speed machines. Engineering Materials (ABS, ASA, PA, PA-CF, PCCF) Nozzle temperature ABS/ASA: 240–260°C / PA-CF: 260–290°C Bed temperature ABS/ASA: 100–110°C / PA-CF: 80–100°C Chamber temperature 50–80°C recommended Cooling fan Minimal or off for ABS/ASA; low (10–20%) for PA-CF Print speed 40–80 mm/s Head High-Flow (ABS/ASA) or High-Temperature (PA-CF with abrasive fill) ABS and ASA benefit substantially from the heated chamber even at 50–60°C. Warping disappears almost entirely. For PA-CF, ensure the filament is fully dry before printing — PA absorbs moisture aggressively and wet PA-CF prints will be brittle regardless of settings. High-Performance Materials (PEEK, PEKK, PPS, Ultem) Nozzle temperature PEEK: 370–400°C / PEKK: 340–380°C / PPS: 310–350°C / Ultem: 360–420°C Bed temperature 120–160°C (material dependent) Chamber temperature 80–90°C — must be fully stabilised before printing starts Cooling fan Off or minimal — semi-crystalline polymers need controlled cooling, not rapid cooling Print speed 20–50 mm/s — slower than engineering materials Head High-Temperature (required) Infill 40–80% for functional parts; rectilinear or gyroid Wall count 4–6 perimeters for structural parts Bed Surfaces for High-Temperature Materials Standard PEI surfaces are not ideal for PEEK and Ultem — adhesion can be inconsistent and removal difficult. The most reliable options: Garolite (G10/FR4): The gold standard for PEEK adhesion. Parts adhere well at temperature and release cleanly when cooled. Surface must be lightly sanded between prints to refresh adhesion. PEI with PEEK adhesion promoter: A high-temperature adhesion compound applied before printing. More consistent than bare PEI for PEEK. Borosilicate glass with PVA or PEEK adhesive: Works reliably but requires more preparation time per print. Do not use standard glue stick for PEEK prints — it will not survive the bed temperatures involved. Standard PLA/PETG adhesion solutions do not apply here. Drying — The Step Most People Skip Engineering polymer moisture absorption is not a minor issue — it is the single most common cause of print failures and substandard mechanical properties. Hydrolysis at printing temperatures permanently degrades polymer chains. Parts printed with wet PEEK or PA-CF will be brittle, regardless of how good the settings are. PEEK / PEKK / Ultem / PPS: Dry at 120°C for 4–6 hours minimum. Use a dedicated oven, not a standard filament dryer — 50–70°C is insufficient. PA-CF / PA-GF: Dry at 80–90°C for 6–12 hours. Feed from a sealed dry box during printing where possible. After drying, store in sealed containers with fresh desiccant. Do not leave spools of engineering materials on the printer between sessions. Annealing Finished Parts PEEK parts can be annealed after printing to further improve crystallinity and mechanical properties. Place finished parts in an oven at 150–180°C for 1–2 hours, then cool slowly (in the oven with the door closed). This increases crystallinity from the as-printed ~20–25% to 30–35%+, improving stiffness, chemical resistance, and dimensional stability. Allow 1–2% dimensional shrinkage during annealing — compensate at design stage for precision parts. Common Issues and Fixes First layer not adhering (PEEK) Almost always caused by insufficient bed temperature, insufficient chamber preheating time, or the wrong bed surface. Check that the chamber has been at 90°C for at least 15 minutes, bed is at the correct temperature for your surface, and that you're using garolite or an appropriate adhesion promoter. Clean the bed surface with IPA before printing. Delamination between layers Cooling too fast — either the chamber temperature is too low, the cooling fan is running at too high a percentage, or the print speed is too fast (too much time between layer depositions allows layers to cool). Reduce fan to zero for PEEK. Slow down print speed. Ensure chamber is fully stabilised before starting. Warping or lifting corners Thermal gradient too high — the part is cooling unevenly. Increase chamber temperature if not already at 90°C. Use a brim (5–8mm) for large flat parts. Ensure bed temperature is correct for your surface. Brittle parts despite correct settings Wet filament. Dry at the correct temperature (120°C for PEEK) for the full recommended time and reprint. This is nearly always the cause. Nozzle clogging Usually caused by incorrect temperature (too low for the material — under-melting), retraction that's too aggressive (pulling semi-crystalline material back into the cold zone), or contamination. Perform a cold pull with the High-Temperature head at ~250°C to clear. For PEEK, a purge with a lower-temperature material (PETG or ABS) can help clear residue. Slicers and Profiles PrusaSlicer has official profiles for the HT90 and is the recommended starting point. Bambu Studio and OrcaSlicer can also be configured for the HT90 but require manual profile creation. For PEEK and other high-performance polymers, start from Prusa's official profiles and adjust gradually — these materials are less forgiving than standard filaments and chasing settings changes one at a time makes it much easier to identify what is and isn't working. Continue Reading Part 1: What the HT90 Is and Who It's For Part 2: High-Temperature Filament Guide — PEEK, PEKK, PA-CF Part 4: HT90 vs Industrial 3D Printers — Is It Right for Your Business? View the Prusa Pro HT90 →

The Prusa Pro HT90 is not a faster version of the Prusa MK4S. It is a different machine for a different purpose — built around one capability that almost no desktop 3D printer offers: a fully enclosed chamber that heats to 90°C. This article explains what that means in practice, who the machine is designed for, and how it compares to the alternatives. The Problem with Engineering Materials on Standard Desktop Printers If you've ever tried to print PEEK, PA-CF, or even ABS reliably on a standard open-frame FDM printer, you'll know the frustration. Surface delamination. Warping that lifts corners off the bed mid-print. Internal stresses that cause parts to crack under load days after printing. These aren't settings problems. They're physics problems. High-performance engineering polymers crystallise — they form ordered molecular structures as they solidify. That process requires controlled, gradual cooling. When a part is being printed in an open environment at room temperature, the layers that have already been deposited cool too fast and too unevenly. The result is thermal stress, poor interlayer adhesion, and warping. The material is fighting the printing process. The solution is an enclosed, heated build chamber. Keep the ambient temperature around the part high enough throughout the print, and the material cools gradually and uniformly. Crystallisation happens correctly. Layers bond properly. The part comes out the way it was designed. This is exactly what the Prusa Pro HT90 provides. Its fully enclosed chamber heats to 90°C — high enough to enable reliable printing with the most demanding engineering polymers on the market. What Makes the HT90 Different A number of desktop printers now offer enclosed chambers — the Bambu Lab X1C being the most prominent. But most of these have passive enclosures or active heating capped at around 50–60°C. At that temperature range, you can improve ABS and ASA results meaningfully. You cannot reliably print PEEK or Ultem. 90°C is the threshold that matters for true high-performance polymer processing. At 90°C ambient chamber temperature, combined with a nozzle capable of reaching 500°C, you have the full thermal profile that materials like PEEK and PEKK require. No desktop machine in this price bracket offers this combination out of the box. Most industrial machines that do cost €50,000–€200,000. The Prusa Pro HT90 does not. Key Specifications Build volume Ø300 × 400 mm (cylindrical) Kinematics Delta Chamber temperature Up to 90°C (active, fully enclosed) Nozzle temperature Up to 500°C Print heads included 2 — High-Flow and High-Temperature (swappable, no tools) Filtration Built-in HEPA air recirculation Extruder Direct drive with load cell sensor (auto bed levelling) Resonance compensation Input Shaper Connectivity Online and offline, remote monitoring The Delta Architecture The HT90 uses delta kinematics — three arms arranged around a central column, moving a print head in a cylindrical build volume. This is worth understanding because it explains several characteristics of the machine. Delta printers tend to be faster than Cartesian printers at equivalent quality because the effector (print head) is lighter and the movement geometry allows high accelerations with less vibration. The Input Shaper resonance compensation built into the HT90 further extends this advantage — it measures and compensates for mechanical resonances in real time, allowing fast prints without ringing artefacts. The cylindrical build volume — Ø300mm diameter, 400mm tall — is particularly well suited to tall parts, round components, and anything with rotational symmetry. The 400mm height is exceptional for a machine in this class and enables large single-piece prints that would require splitting on most desktop machines. The Two Print Heads One of the HT90's most practical features is that it ships with two specialised heads that swap without tools in a few minutes: The High-Flow Head is optimised for standard and mid-range materials — PLA, PETG, ABS, ASA, PA. It prioritises throughput and surface quality. For rapid prototyping in standard materials, this is the head to use. Combined with Input Shaper, it enables very fast print speeds without visible quality loss. The High-Temperature Head is built for PEEK, PEKK, PPS, PSU, PES, and PEI (Ultem). It reaches 500°C and is constructed from materials that can withstand sustained operation at that temperature. This is not a modified standard head — it is engineered specifically for engineering polymers. The load cell sensor in the extruder system handles first layer calibration automatically at the start of every print. No manual bed levelling is required, which is particularly important when the chamber is at 90°C and you don't want to reach inside. HEPA Filtration — Why It Matters for Engineering Materials PEEK, Ultem, and similar polymers release volatile organic compounds (VOCs) and ultrafine particles when printed at high temperatures. These are not benign. Without adequate filtration, printing engineering polymers in an enclosed space represents a genuine occupational health concern. The HT90 integrates a HEPA air recirculation system directly into the machine. It is not an optional add-on or an aftermarket upgrade — it is active whenever the chamber is enclosed and printing. This makes the HT90 substantially safer to use in professional environments — offices, labs, shared workspaces — than a machine without active filtration. Who Should Buy the HT90 The HT90 is the right machine for a specific set of buyers. It is not the right machine for everyone. It is right for you if: You need to print PEEK, PEKK, PPS, PSU, or PEI (Ultem) for functional end-use parts You are prototyping medical devices that require biocompatible, autoclave-sterilisable materials You are producing automotive or aerospace components that must survive thermal cycling or sustained high temperatures You need a large build volume — Ø300 × 400mm — for single-piece industrial-scale parts You are currently paying for bureau printing in engineering materials and want to bring that capability in-house You have a research lab that needs engineering polymer capability without an industrial machine budget It is probably not right for you if: You primarily print PLA, PETG, or standard materials — a Prusa MK4S or Core One will serve you better at lower cost You need multi-material printing — the HT90 is a single-material machine per print Your highest temperature requirement is ABS or ASA — a Bambu Lab X1C or similar is a more cost-effective solution for those materials Where to Buy The Prusa Pro HT90 is available from Eolas Prints — authorised Prusa resellers based in Cantabria, Spain, serving customers across Europe. EU-compliant warranty and support included. Continue Reading Part 2: High-Temperature Filament Guide — PEEK, PEKK, PA-CF and What They Need from a Printer Part 3: Printing with the HT90 — Settings, Materials, and Practical Tips Part 4: Prusa Pro HT90 vs Industrial 3D Printers — Is It the Right Tool for Your Business?