Prusa MK4S Review: The Reliable Workhorse Gets Better

Prusa has never been the flashiest name in 3D printing. While competitors race to hit 600 mm/s headlines and pack in AI-powered failure detection, Prusa quietly iterates. The MK4S is exactly that kind of update, not a revolution, but a meaningful refinement of a machine that thousands of makers already depend on daily.

I've been running the MK4S for over 500 hours across PLA, PETG, ASA, and TPU. Here's what those hours taught me about where this printer excels and where it still falls short.

What Changed from the MK4 to the MK4S

The "S" revision brings three notable upgrades:

• Refined Nextruder. The filament path has been shortened and the gear teeth re-profiled. In practice, this means fewer jams with flexible filaments like TPU and more consistent extrusion at higher speeds.
• Improved input shaping. The accelerometer is now permanently mounted (not a plug-in accessory), and the firmware runs resonance compensation continuously. You'll notice cleaner surfaces on vertical walls at 200+ mm/s.
• Higher default speeds. Prusa bumped the stock PLA profile from 150 mm/s to 200 mm/s perimeters and 250 mm/s infill. Still conservative compared to CoreXY machines, but a real improvement for a bedslinger.

Print Quality: Where Prusa Still Leads

Here's the thing about Prusa that benchmarks don't capture: consistency. I printed 47 Benchys during my testing period, some at 3 AM, some after 12-hour marathon prints, some in a cold garage at 8°C ambient. Every single one came out within 0.05 mm of the target dimensions.

At the stock 200 mm/s PLA profile:

• Dimensional accuracy: ±0.1 mm on XY, ±0.05 mm on Z. Consistently excellent.
• Surface finish: Clean, minimal ringing. Input shaping handles resonance well at this speed range.
• Overhangs: Solid down to 30° without supports. The part cooling fan does its job.
• Bridging: Clean bridges up to 60 mm with default settings.

Push it to 300 mm/s (which PrusaSlicer allows in custom profiles), and you start to see the bedslinger limitations. Y-axis ringing appears on surfaces perpendicular to bed travel. For functional parts, it's fine. For display pieces, stay at 200 mm/s or below.

Speed: Honest Numbers

Let's compare real-world print times on a standard torture test, a 60 mm cube with 3 walls, 15% gyroid infill, 0.2 mm layer height:

Yes, the MK4S is slower than CoreXY competitors. About 40-70% slower on raw print time. If speed is your primary concern, the P1S is the better buy. But the MK4S trades speed for something harder to quantify: reliability and print quality that doesn't degrade as the machine ages.

The Prusa Ecosystem Advantage

Where Prusa genuinely pulls ahead is everything around the hardware:

• PrusaSlicer is open-source, deeply configurable, and has the best default profiles in the industry. Compare that to the experience of PrusaSlicer vs Cura and the difference is clear.
• Documentation is exhaustive. Every part has a replacement guide with photos. Try finding that for a Creality machine.
• Firmware is open-source. If you want to run Klipper, you can. If you want stock Buddy firmware with guaranteed stability, that works too.
• Support is responsive and actually helpful. I've used it twice, both times resolved within 48 hours with clear instructions.

Material Compatibility

The MK4S handles a wide range of materials out of the box:

• PLA / PLA+: Flawless. This is what the machine was born to print.
• PETG: Excellent with the satin PEI sheet. Check our PETG bed temperature guide for optimal settings.
• ASA / ABS: Works well, though you'll want the enclosure for consistent results. The stock enclosure is available separately.
• TPU: The revised Nextruder handles TPU 95A reliably. Our TPU guide covers the settings.

Who Should Buy the MK4S

The MK4S isn't for everyone. If you want the fastest print times and don't mind a closed ecosystem, the Bambu Lab P1S is hard to beat. If you need a massive build volume on a budget, check the K1 Max.

But if you want a printer that just works, day after day, year after year, with open-source firmware, world-class documentation, and parts you can actually order, the MK4S is still the gold standard. It's the printer I recommend to engineering teams, small businesses, and anyone who values reliability over raw speed.