Prusa's 400 °C HT Hotend is now available, and the more interesting part of the launch is what came with it. In an October 21 post on the Prusa blog, Jakub Kočí lays out the supporting cast: HighTemp print sheets for the CORE One+ and CORE One L+, three new high-temperature filaments in the Prusa e-shop, and a set of interlayer adhesion measurements that make a case for the hotend even if you never touch PEEK.
This piece looks at the ecosystem around the hotend, because a 400 °C heater block is only as useful as the sheets, materials and profiles that let you exploit it.
The Quiet Headline: Hotter Prints of Ordinary Materials
The most practically relevant numbers in Prusa's post have nothing to do with exotic polymers. Prusa says that printing several of its standard Prusament filaments above 300 °C with the HT hotend improved interlayer adhesion as follows:
- Prusament PA11 Carbon Fiber: +23%
- Prusament ASA: +18%
- Prusament PC Blend: +7%
- Prusament PC Blend Carbon Fiber: +7%
Z-axis strength is the chronic weak point of FFF parts, and a hotter melt is the likely mechanism for the gain: material that stays mobile longer as it lands on the previous layer has more time to bond across the boundary before it freezes. A 23% gain on PA11-CF is a sizeable improvement for a change that needs no redesign of the part. The PC results are more modest, but still worthwhile for anyone already running those materials.
These are Prusa's own figures, and the blog post does not publish full test methodology, specimen geometry or variance alongside them. Treat them as a credible direction and magnitude rather than design-allowable data. The product page also notes that the PC Blend Carbon Fiber figure comes from printing at 350 °C. It is also worth noting that Prusa's Knowledge Base lists ASA, PA11-CF, PC and PCCF as materials that run on either the standard or the HT hotend, so these gains are an optional upgrade path, not a requirement.
Three New Filaments, Each With a Job
Prusa has added three new high-temperature filaments to its store, and each targets a distinct use case rather than overlapping.
Siraya Tech Fibreheart PPA-CF Core is a polyphthalamide, a high-performance polyamide that Prusa says offers wear resistance under cyclic load. Prusa quotes thermal resistance up to 199 °C when annealed, resistance to oils and fuels, and carbon fiber only in the filament's core (what it calls Core-Shell technology). That construction, Prusa says, increases interlayer adhesion by 50% compared with regular PPA-CF filaments. Prusa suggests automotive uses, such as components that come in close contact with an engine.
Fiberon PPS-CF10 moves into polyphenylene sulfide territory, with 252 °C thermal resistance, a UL94 V0 rating as a self-extinguishing material, and insolubility in any known solvent below 200 °C. Prusa says the carbon fibers improve dimensional stability and that the chemical stability suits highly specialized use such as laboratory equipment.
Fiberon PPS-GF20 swaps carbon for glass fiber. The point is electrical: Prusa says the glass fibers improve electrical insulation, and the printed parts do not conduct charge or block radio signals such as Wi-Fi, Bluetooth and 5G. Prusa positions it for specialized electronics housings, and notes it can sit in direct contact with aluminum without causing galvanic corrosion.
The Knowledge Base adds a hardware detail that is easy to miss. PPS-CF, PPS-GF, PPA-GF, PEKK-CF, PPCF, PPSU and PEEK all require both the HT hotend and the modified extruder idler H, which uses a single bearing. The upgrade kit includes that idler alongside the standard idler S with two bearings. PLA, PETG, TPU, PVB and the standard-or-HT materials above use the standard idler. In other words, swapping materials across classes can mean swapping idlers too, so factor that into your workflow.
HighTemp Sheets Come to the CORE One Family
The HighTemp print sheet is not new; it already existed for the Prusa Pro HT90. What is new is a version for the CORE One+ and CORE One L+. Prusa says it provides the best adhesion to materials such as PEI, PEEK, PEKK, PPSU and PPS, and that it offers greater resistance to repeated high-temperature exposure, leading to a longer lifespan. The flip side is that you do not need it for standard Prusaments such as PC Blend Carbon Fiber, which Prusa says adhere poorly to this sheet's surface.
The Ceiling: A 60 °C Chamber
Prusa is unusually direct about the limits. The 400 °C hotend allows printing materials such as PPSU, PEKK, PEEK and PEI, but the 60 °C chamber temperature is the limiting factor, as these materials may require higher ambient temperatures to print properly. Prusa says small components may still be printed. Expect to be able to extrude these materials on a CORE One; do not assume parts that match what a heated-chamber industrial machine produces.
Two other cautions come straight from the post. Prusa highly recommends connecting the printer to a filtration system, since most high-temperature materials emit dangerous fumes, and it offers the Advanced Filtration System Upgrade for that purpose. It also recommends the Prusa USS Drybox, noting that advanced high-temperature materials are highly hygroscopic and that with filaments like PEI1010, moisture absorption takes mere hours.
Compatibility and Setup Constraints
According to the Knowledge Base, the HT hotend is compatible with the CORE One, CORE One+, CORE One+ (Gen 2), CORE One L and CORE One L+. It is not compatible with the MMU, and the blog post confirms it does not work with INDX either. The product page also rules out the MK4, XL and MINI.
Nozzle choice is locked down: Prusa specifies E3D ObXidian Standard Flow 500 nozzles only, in 0.4 or 0.6 mm. The documentation also warns against exceeding 30% print cooling fan power unless a validated material profile allows it, and says to use a filament profile matched to the HT Hotend and the material.
Prusa says the hotend swaps in under a minute, and it is available both as an upgrade and factory-mounted on new CORE One L+ printers. At the time of writing, the US-shipping view of the product page lists the upgrade at $184.26 with an estimated three-week lead time; pricing may differ by region and currency.
What It Means for Makers
For most CORE One owners, the strongest argument for this hotend is not PEEK. It is the measured adhesion gain on materials they already print, especially PA11-CF and ASA, combined with access to PPS and next-generation PPA-CF for parts that need real heat and chemical resistance. That is a meaningful expansion of what a desktop enclosed printer can deliver.
The PEKK, PEEK and PEI story is more aspirational. The hardware gets you to the melt temperature, the HighTemp sheet gets you adhesion, but the 60 °C chamber is the limiting factor Prusa itself names. If high-temperature polymers are your actual requirement, rather than an experiment, a machine built for hotter chambers is worth considering. Budget for filtration and a drybox either way.
