Prusa Core One L vs Bambu H2S — Engineering Filament Showdown

Enclosed 3D printers have pushed the hobby well past PLA and PETG. But when it comes to ABS, ASA, and polycarbonate — the materials that actually hold up under heat and load — not all enclosures are built equal. Thomas Sanladerer recently put four enclosed machines through a head-to-head engineering filament test: the Prusa Core One, Prusa Core One L, Bambu Lab P2S, and Bambu Lab H2S. The results reveal where active chamber heating matters, where it falls short, and which printer delivers the most consistent high-temperature prints out of the box.

The Contestants

Sanladerer tested four printers across two families. On the Prusa side, the standard Core One and the larger Core One L — both featuring a closable front vent grill and rear exhaust fans. The Core One L adds a 230-volt heated bed that doubles as an active chamber heater, using a pair of fans beneath the bed to push heat into the enclosure. It also uses satin PEI sheets for engineering materials and, notably, swaps the original Core One's steel side panels for aluminum.

On the Bambu Lab side, the P2S and H2S follow a similar small-to-large pattern. The H2S is the larger machine and includes active chamber heating, but through a dedicated fan heater rather than repurposing the bed. Both Bambu machines can draw fresh air or recirculate chamber air through their filtration systems. Sanladerer used Bambu's standard textured PEI sheets, which the company greenlights for nearly all materials.

The Test: Four Filaments, Identical Settings

The test part was a filter holder box — a practical print with enough surface area to reveal warping tendencies. Four materials were run on each machine using the closest stock filament presets available:

• ColorFabb XT — a hardcore PETG variant
• Azurefilm ABS — standard ABS
• Prusament PC Blend — a polycarbonate blend formulated for easier printing
• Polymaker PC Plus — much closer to pure polycarbonate

Every print used the same settings across machines, with no manual tuning for the baseline comparison. The parts were then ranked blind — Sanladerer examined them without knowing which printer produced which.

ColorFabb XT and ABS: The Gap Narrows

With ColorFabb XT, the results were close among three of the four machines. The P2S struggled noticeably — its hotend appeared to be printing too cold, even on the same profile used by the H2S. The Core One produced a slightly warped but acceptable part. At the top, the H2S and Core One L were nearly identical, with the Core One L warping marginally less.

ABS widened the spread. The Core One and P2S — neither with active chamber heating — showed clear overfilling at the top of the part, a sign that warping had pushed the layers up into the nozzle's path. The Core One was the worst of the group on this material, with distinct separation lines where the part stuck to the bed and where it lifted. The P2S warped more evenly but was still visibly crooked. Between the actively heated printers, the H2S edged out the Core One L by the smallest of margins.

Across both PETG and ABS, the pattern was consistent: the passively heated chambers of the Core One and P2S topped out around 40–45 °C, while the H2S and Core One L reached roughly 60 °C. That 15–20 °C gap translated directly to reduced warping.

Polycarbonate: Where the Core One L Stumbles

Prusament PC Blend exposed the limits of all four machines. Every printer produced some warp, but the ranking was clear. The Core One L was the worst performer — Sanladerer measured 3–4 mm of lift on the PC Blend part. The P2S and standard Core One both warped heavily, though the Core One held on slightly better. The H2S produced the only reasonably flat part, though even it showed slight lifting at the edges.

Things got worse with Polymaker PC Plus, the near-pure polycarbonate. On stock settings, the Core One L failed entirely — all three attempts came loose from the bed mid-print. The P2S and Core One both warped severely. Only the H2S produced a flat, usable part on the first try with generic settings.

Sanladerer identified two compounding issues on the Core One L. First, grease from the factory-lubricated linear rail was liquefying as the chamber heated up and dripping onto the print bed — visible as small dots that killed bed adhesion. He noted the front door became coated in a grease film after several failed PC prints, and cleaning with ethanol did not resolve it. Second, the hybrid bed-heater design introduced a trade-off: the more the fans pulled heat from the bed to warm the chamber, the more the bed surface temperature dropped.

Measured Temperatures Tell the Story

To quantify what was happening, Sanladerer applied gaffer's tape to all four beds for consistent thermal camera readings and measured actual surface temperatures against what each machine reported:

Printer	Displayed Bed Temp	Actual Bed Surface	Chamber Temp (Active)
Bambu Lab H2S	110 °C	110 °C	~60 °C
Bambu Lab P2S	100 °C	105 °C	~40–45 °C (passive)
Prusa Core One	100 °C	~95 °C	~40–45 °C (passive)
Prusa Core One L	110 °C	96–98 °C	~56–57 °C

The Core One L's bed ran 12–14 °C below its displayed temperature, with visible cold spots where the chamber-heating fans blew against the underside. The sides of the bed were 5–10 °C hotter, creating an uneven heating surface. Meanwhile, the H2S hit its set temperature exactly.

The aluminum side panels on the Core One L also worked against it — they conduct more heat out of the enclosure than the steel panels on the standard Core One. Sanladerer noted that at his controlled 18 °C ambient, the Core One L's chamber struggled past 56–57 °C and would likely only reach the full 60 °C in a warmer room (around 22 °C). The chamber temperature also scales with the bed setting — lowering the bed below its 120 °C maximum proportionally reduces the maximum chamber temperature achievable.

Stock Profiles vs. Manual Intervention

After diagnosing the issues, Sanladerer retried the PC Plus print on the Core One L with manual adjustments: bed and chamber set to their maximums of 120 °C and 60 °C, respectively, and the part positioned in the center of the bed oriented toward the hottest zones. This time, the print succeeded and compared well against the other machines.

This raises the question of whether print profiles are part of the product. Sanladerer's position is that they are — predictable results from stock settings are what you pay for in a printer. The fact that all three other machines handled polycarbonate better on their generic, out-of-the-box profiles, including the technically simpler P2S and Core One, suggests the Core One L's hybrid heating approach carries a real usability cost. A dedicated chamber heater — the kind available as a standalone PTC unit with fan and temperature regulation for under ten dollars — would have sidestepped the bed-temperature trade-off entirely.

What This Means for Engineering Filaments

Despite the Core One L's struggles with polycarbonate, Sanladerer's broader takeaway was positive: all four enclosed printers performed surprisingly well compared to the benchmark of an open-frame machine. He stated plainly that he does not believe any open-frame printer — including something like a Prusa MK4S — could have printed this part in any of these materials.

The jump from passive to active chamber heating, whether on the Prusa side (Core One to Core One L) or the Bambu side (P2S to H2S), makes a meaningful difference. Small parts on the smaller machines can work with careful brim usage, but larger parts warp more aggressively and demand active temperature control. The H2S was the most consistent performer across every material tested, while the Core One L's hybrid design introduces complications that Prusa's stock profiles do not yet account for.

For anyone looking to print ABS, ASA, or polycarbonate regularly, the data points toward a dedicated chamber heater as the more reliable path — and toward the H2S as the printer that currently delivers the most predictable results with the least manual tuning.