Prusa Core One+ Gen2 INDX (Assembled) Review: A Great, Unsteady Leap Forward for Toolchangers

Before we dive in, let’s stop things a second and agree to a new name for the purposes of this article. It is a slog to type out Prusa Core One+ (Gen 2) INDX, and is exactly the sort of convoluted name we’d make fun of Creality for (sorry, Creality). From this point on I’ll refer to this system under review (the 8-tool INDX-upgraded Prusa Core One+ Gen2) simply as the Core One INDX.

The Prusa Core One INDX is the company’s latest generation of printer, incorporating a very recent batch of minor updates, tweaks, and adjustments over the previous Core One+ machine. These updates, which include GT1.5 belts for finer surface quality, and a nozzle-wiper (a must for any purging printer, as this is) are also available to owners of the previous generation machine, either by upgrading their printer with the INDX conversion kit (which includes the Gen 2 changes, plus the INDX system) or by a straightforward Core One+ to Core One+ Gen 2 upgrade kit.

The complete, assembled Core One INDX is available in 4-tool and 8-tool versions, at $1,949 for the 4-tool and $2,249 for the 8-tool. Besides the number of toolheads available to you, there’s no difference between the two. Arguably, the 4-tool machine would be easier to live with, since you have unobstructed access to the waste bucket and the overall footprint shrinks.

For your money, you’re getting a 248 x 205 x 270 mm build volume – 15 mm off the build depth of the INDXless Core One+ Gen 2. The hot end heats to 300 °C, the bed 120 °C, with an actively managed chamber temperature that can reach 55 °C. There’s no dedicated heater in the chamber, mind you. It soaks up and traps heat from the heated bed. It’s often the case that there’s a warm-up period needed before hot prints can commence.

But enough about the Core One. The INDX bit is probably the only reason you’ve read this far. Despite the missteps that dominated the upgrade’s release, the INDX toolhead and the individual tools are miniature marvels. It is a clever piece of technology, having a single motor and mechanism handle all of the extrusion, locking, and unlocking of the tools, and the tools themselves go from cold to printing temperature in seconds.

The tools themselves are lightweight slips of inductively-heated metal nozzle with an integrated heatsink. The Core One INDX 4-tool and 8-tool variants ship with 0.4-mm high-flow CHT nozzles, respectively. Each tool has a short stretch of filament path left exposed, which is where the dynamic extruder pinches the material, feeding it from there.

The INDX nozzles are rated for general use – only ultra abrasives like high-filler glow-in-the-dark filaments or high volumes of carbon- or glass-filled materials will wear through the nozzle’s coating and distort them. This is the crux of the whole nozzlegate saga – that the nozzles aren’t as tough as initially sold to early adopters.

Prospective buyers reading this should approach the Core One INDX clear-eyed that until Bondtech’s production of the nozzles is back on track and solutions for tougher nozzles are found (like licensed third-parties, such as E3D, who have announced they’re working on it) then there’s a hard (hyuk) ceiling on how much you can print of super-abrasive filament before you need to switch in a fresh nozzle. I would guess that for the majority of users of the INDX, that’s never likely to be a problem, or if it is, it’s a long-term one. Fortunately, direct replacement nozzles are available from the Bondtech webstore for approx. $53 per tool.

The nozzles themselves feature Bondtech’s CHT technology, which is to say the filament path inside splits, heating the plastic faster and increasing the flow.

A replacement standard flow (which is to say non-CHT) tool costs approximately $45 from Bondtech directly. Nowhere else sells them currently. Not even Prusa itself.

As part of the Core One’s changes to accommodate the INDX, you get a bucket lid that fixes to the printer’s frame and has small locks to keep things secure. The eight filament guide tubes of the INDX pass through holes in this lid, rubbing on the sharp edge as the printhead pulls them back and forth. After only a day or two of use we could see dust from the tubes accumulating by the holes. If Prusa isn’t already shipping grommets with newer machines, they surely soon will. It’s worth checking Printables for a self-made fix in the meantime.

The coil for the INDX’s inductive heating of nozzles is quite visibly exposed in a way that clearly makes some folks uncomfortable, judging by online commentary about it. A big blob of death would be a pain to deal with, particularly if it reached the coil – it doesn’t heat up, and a filament build up blocks the printers ability to detect the nozzle’s temperature – so any attempt to remove it requires you to blow heat at it.

You can save some money by building the printer yourself – something everyone interested in the hobby of 3D printers as hardware should experience at least once in their life – but with the added complexity of the INDX, it’s a job that requires a seriously committed weekend of work – maybe longer.

The assembled version of the printer ships calibrated and ready to print right out of the box. And they really mean right out of the box – you can skip all of the networking stuff when you first boot it up and dive immediately into one of the dozen or so ambitious test prints that come with the printer.

Unboxing is a cinch thanks to the use of a lift-away box. Prusa made particular efforts with its Core One L launch to highlight its virtually all-cardboard packaging – better for the environment, and really quite cleverly done. In the unit we were shipped, that’s all gone with packing foam holding the Core One INDX and all its pieces in place. I hope they revisit the elegance of that cardboard packaging in the future.

The company’s bet on a distinctive steel exoskeleton and stamped metal plating for the Core One’s body lends the printer a utility and ruggedness that’s difficult to argue against. The door and windows are plastic, so be mindful of what you clean it with – IPA will melt them.

Despite the totality of metal shrouding the Core One INDX, it’s a light printer – just 24.5 kg when equipped with the 8-tool INDX (without filament – 8 spools will add 8 kg+). The Core One has a clever design that makes it easy to pick up by the recesses in its sides. A consequence of this design is that the internal volume of the printer is barely any bigger that the actual print volume. It’s lean.

New for the Core One INDX is a dedicated purge area, where the printhead with INDX tools wipes itself off to eject its little Wonka Nerd-like priming nuggets (see photo in next section). (If Prusa doesn’t park the Haribo gummy bears for the kit version and ship boxes of Nerd candy instead, they’re missing a trick.)

The printer presents a massive improvement over single-nozzle filament changing machines, including Prusa’s own MMU, and even goes a step further than other full on toolchangers. At default values, the Core One INDX doesn’t print a prime tower, only the Nerds. I’ve found it takes between 9 and 12 seconds, from parking a tool, picking the next and priming, returning to the print.

Calibration is mercifully improved over what we saw with Prusa’s first generation toolchanger, the XL – that machine used a manual screw-in pin that seemed borrowed from the world of CNC toolchanging in concept, but not considered enough for the hands-off direction 3D printing has clearly evolved toward. Included as part of the Gen 2 upgrade for the Core One, a nifty eddy current-based calibration board sits off the main print area, always there and available when the printer decides to check the X/Y positioning of the tools.

The recess on the right-hand side – where the spool would sit on an unINDXed Core One – is now taken up by a bucket that neatly slots in to collect the INDX’s priming waste as it drops through a hole in the top surface of the recess. One downside introduced with the INDX upgrade is that the other recess, which Prusa previously encouraged hacking to add extra functionality to your machines, becomes inaccessible and largely out of bounds for anything other that infrequent use storage when the printer has a full complement of eight spools loaded up.

A new injection molded spool holder design does a job, and can extend to accommodate larger 2 kg spools as needed. Throughout testing I frequently found filament jumping off the spools and looping around the holders. There’s something between the weight of a full, fresh spool, and the way tension is held in the filament pathing that making this happen, and I’m finding a little more caution than is typical is needed when loading to keep it from happening.

Feeding the filament is manual – a pain the occasional time you have to do it, but with 8 spools loaded up, you might not even need to all that often. There are filament sensors on the outside of the printer that are supposed to detect material as you feed it and prompt the printer into its “load” wizard, but ours didn’t. Others have reported similar issues. These things, in aggregate, point to a feeling that, in order to accommodate the INDX, balls have been dropped elsehere.

While writing this review, a firmware update went partway to addressing one of my older criticisms of the printer – that the hardware doesn’t really know much about the filament you use. You could tell it the material type only, in service of the printer preventing you from setting a print with the wrong material. On a single-material machine like an unINDXed Core One, it didn’t matter, but for the wide possibilities of color printing, knowing which color material is loaded where becomes pretty useful. Now, the Core One can be told which color is where, and that information ripples through the software to Connect and the Prusa app (but not PrusaSlicer).

Prusa also released an OpenPrintTag upgrade for the Core One, which can read the NFC tag inside every spool of Prusament filament (or your own filament you’ve manually tagged them) automatically, passing its information and writing updates to the filament remaining.

Except that upgrade is only designed to fit the Core One’s recessed spool holder – right now it’s good only for non-INDX machines.

It’s a setup and process that’s not at all suited to situations like ours, flitting between materials and colors frequently. For everyone else sticking to a low number of preferred materials and kinds of prints, this “issue” is not really much of an issue.

All the pieces are there or nearby for the printer be the buttery smooth, psychic experience that other brands have more or less accomplished. Prusa doesn’t fit that mold.