FLSUN S1 Pro Review

A Comprehensive Analysis of the High‑Speed Delta 3D Printer

Introduction: FLSUN’s Speed Revolution

The FLSUN S1 Pro enters a competitive landscape where speed has become the defining metric for modern FDM printers. While competitors like Bambu Lab and Creality focus on CoreXY designs, FLSUN has doubled down on delta kinematics—a bold choice that delivers unique advantages for specific use cases.

This machine targets advanced hobbyists, engineers, and makers who need rapid prototyping capability without compromising on dimensional accuracy. At its price point of approximately $999 (regular sale) to $1,099 (early bird), it positions itself as a high-value alternative to premium speed printers.

The S1 Pro competes directly with machines like the Bambu Lab P1S and Creality K1, offering comparable speeds with the distinctive benefits of delta geometry—exceptional performance on circular prints, smooth curves, and impressive tall-object stability.

FLSUN S1 Pro Specifications at a Glance

Best Use Cases for the FLSUN S1 Pro

Unboxing and Setup Experience

What’s in the Box

• FLSUN S1 Pro printer (largely pre-assembled)
• Textured PEI build plate
• Power cable
• USB cable and storage media with test files
• Tool kit (hex keys, scraper, nozzle wrench)
• Spare nozzle
• Sample PLA filament
• PTFE tube and fittings
• Quick start guide and documentation

Assembly Process

Setup takes approximately 20–30 minutes for users familiar with 3D printers. The printer arrives mostly assembled—you’ll need to install the build plate, connect cables, and perform initial calibration.

First-time delta printer users should carefully follow the calibration wizard. The 7-inch touchscreen guides you through bed leveling and delta parameter tuning, though understanding these parameters helps achieve optimal results.

First Impressions

The build quality immediately impresses. The aluminum frame feels rigid with minimal flex. The delta arms move smoothly on carbon fiber rods with ball-joint connectors that operate silently and precisely.

The 7-inch color touchscreen is responsive with an intuitive interface. Navigation feels smooth, though the UI isn’t as polished as Bambu Lab’s system.

Build Quality and Design

Frame and Construction

The S1 Pro uses a robust aluminum frame with three vertical towers forming the delta structure. This design provides excellent rigidity while keeping the footprint relatively compact for the build volume offered.

The delta arms use carbon fiber rods with magnetic ball joints at each end. This lightweight yet strong construction enables the extreme accelerations (40,000 mm/s²) without compromising precision.

Hotend and Extruder

The direct drive dual-gear extruder provides strong filament grip essential for high-speed printing. The all-metal hotend reaches 350°C maximum temperature, enabling printing of engineering materials like polycarbonate and nylon.

The standard 0.4mm hardened steel nozzle is included and works well for most materials, including mildly abrasive filaments. Cooling comes from dual part-cooling fans providing excellent bridging and overhang performance even at high speeds.

Build Plate

The textured PEI heated plate reaches 120°C, suitable for ABS and other high-temperature materials. The textured PEI surface provides good adhesion for PLA and PETG without additional adhesives, and supports smart zone heating (inner Ø220mm zone and outer ring 220–320mm).

Auto-Leveling System

The S1 Pro features one-click automatic bed leveling with a comprehensive mesh system. This probing compensates for any bed irregularities and ensures consistent first layers across the entire build surface.

Noise Levels

At approximately 55 dB during normal operation, the S1 Pro runs at a reasonable noise level for home or office environments. The delta motion is inherently smooth, reducing mechanical noise. Stepper motors use TMC drivers for quiet operation.

Features and Performance

Actual Print Speed Performance

The claimed 1200 mm/s maximum speed is technically achievable but impractical for quality prints. Real-world usage centers around 600 mm/s for excellent results, which still represents significant speed advantages over traditional printers.

A test Benchy completed in approximately 14 minutes at 600mm/s with 0.2mm layers—exceptionally fast while maintaining recognizable detail. Pushing to 800mm/s produced usable results but with increased ringing on sharp corners.

Acceleration and Motion Control

The 40,000 mm/s² acceleration capability allows the printer to reach top speed quickly and handle direction changes without losing positioning accuracy. Input shaping helps minimize ringing, though some ghosting appears on sharp rectangular corners at maximum speeds.

For most prints, setting acceleration to 20,000–25,000 mm/s² provides an optimal balance between speed and surface quality.

AI Camera and Spaghetti Detection

The built-in camera supports real-time monitoring, timelapse recording, and AI-powered spaghetti detection that can pause printing on failure. In testing, the spaghetti detection caught obvious failures but sometimes missed subtle issues. It’s a useful safety net but shouldn’t replace periodic manual monitoring.

Print Quality: Real Results

Benchmark Print Results

• Benchy: Excellent hull curves and smooth surfaces. Minor ringing on cabin corners at 600mm/s. Text remained readable. Completed in 14 minutes.
• Calibration Cube: Dimensional accuracy within ±0.15mm on all axes.
• Overhang Test: Handled 70° overhangs without support excellently.
• Bridging: Impressive bridging up to 60mm spans with minimal sagging.

Circular and Curved Surface Quality

This is where delta printers excel, and the S1 Pro didn’t disappoint. Vases, cylinders, and organic shapes printed with exceptional smoothness. The continuous motion of delta kinematics produces cleaner curves than the start-stop motion of Cartesian systems.

Material Compatibility

Consumer-Grade Filaments

• PLA: Prints beautifully with minimal effort. Excellent surface quality at 400–600mm/s speeds.
• PETG: Very good results with proper temperature tuning (240–250°C hotend, 80°C bed).
• TPU: The direct drive extruder makes flexible filaments practical. Print speeds must drop to 40–80mm/s.

Engineering-Grade Filaments

• ABS: Printable but challenging without added enclosure. Works best for smaller prints with draft shields.
• Nylon (PA): The 350°C hotend handles nylon at 260–280°C. Requires thorough filament drying.
• Polycarbonate: Printable at 280–300°C. Requires heated bed at 110–120°C.

Carbon Fiber and Abrasive Materials

The included hardened steel nozzle handles CF-PLA and CF-PETG. Print speeds should drop to 200–300mm/s for optimal results with abrasive materials.

Software and Slicer Compatibility

Supported Slicers

• FLSUN Slicer V2.0: Built on OrcaSlicer, optimized specifically for FLSUN printers. Recommended starting point.
• Cura: Fully supported with FLSUN-provided profiles.
• PrusaSlicer / SuperSlicer: Compatible with manual profile setup.
• OrcaSlicer: Growing popularity, good delta support, community developing profiles.

Mobile App and Cloud Features

The FLSUN World app provides remote control and monitoring: start/stop/pause prints, monitor via camera feed, upload G-code over Wi-Fi, and receive notifications. The app interface is functional though not as polished as Bambu Lab’s ecosystem.

Maintenance and Reliability

Routine Maintenance

• Delta Arm Inspection: Check ball joints monthly for wear or looseness.
• Carbon Rod Cleaning: Wipe carbon fiber rods weekly to remove dust.
• Belt Tensioning: Check belt tension every 100 hours of printing.
• Nozzle Cleaning: Perform cold pulls periodically to prevent clogs.
• Build Plate Cleaning: Clean PEI plate with isopropyl alcohol before prints.

Reliability and Known Issues

During 60+ hours of testing across PLA, PETG, and TPU, the S1 Pro demonstrated strong reliability with no missed steps or layer shifts at speeds up to 600mm/s. However, a few delta-specific quirks emerged:

• First-layer edge adhesion can be slightly weaker at the very outer rim (≥300mm diameter). A brim or raft helps for large base prints.
• Wi-Fi disconnects occasionally occur during long prints if the router signal is weak.
• Delta calibration drift may happen after shipping or physical bumps. Re-run auto-calibration if quality degrades suddenly.

FLSUN S1 Pro vs. Competitors

Note: The S1 Pro features a closed chamber per official specifications, which distinguishes it from many open-frame competitors and improves material compatibility for engineering filaments.

Final Verdict: Should You Buy the FLSUN S1 Pro?

The FLSUN S1 Pro isn’t for everyone—but for the right user, it’s exceptional value. It delivers professional-level speed, surprising print quality, and true engineering-grade material support at a price that undercuts some premium CoreXY printers.

If you understand delta kinetics, print tall or round objects, and want blazing-fast prototyping, the S1 Pro is one of the smartest buys in its class.

Frequently Asked Questions (FAQ)

Conclusion

The FLSUN S1 Pro proves that delta printers are far from obsolete. With modern firmware, high-speed motion systems, a closed chamber, and smart features like AI monitoring, the delta design is experiencing a renaissance built on speed, vertical efficiency, and elegant mechanics.

For makers who’ve outgrown entry-level printers and crave rapid iteration without sacrificing quality, the S1 Pro—with its 40,000 mm/s² acceleration, 350°C hotend, 120°C bed, and 55 dB noise profile—offers a compelling and often overlooked alternative to the CoreXY arms race. If your prints are tall, round, or simply need to be done fast, this delta workhorse deserves a serious look.

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