Stop Letting Moisture Ruin Your Prints: A Look at the SUNLU Filament Dryer S4
(Disclosure: This article is sponsored by SUNLU. I received this product for free to review, but all opinions regarding its performance are my own. This post contains affiliate links.)
If you have been 3D printing for any length of time, you know the sound: that faint pop and crackle as your nozzle extrudes filament. You know the look: stringing, blobs, and rough surface finishes.
The culprit isn’t usually your printer settings or your slicer profile—it’s moisture. Even “fresh” filament can be saturated with water, ruining your print quality and clogging your nozzle.
Today, I’m reviewing a solution from one of the most trusted names in the industry: the SUNLU Filament Dryer S4. This isn’t just a dryer; it’s a high-capacity station designed to keep your workflow smooth and your prints crisp.
The Capacity Game-Changer
Most dryers on the market hold one, maybe two spools. If you are running a multi-material setup (like an AMS or MMU) or just swap colors frequently, juggling single dryers is a hassle.
The SUNLU S4 holds four spools simultaneously. This is a massive workflow upgrade. You can dry your PLA, PETG, TPU, and ABS all at once, meaning your materials are ready to go the moment you need them. It doubles as a “dry box” storage solution, keeping dust and moisture away when you aren’t printing.
Power and Speed: 350W PTC Heating
Waiting for filament to dry can kill your momentum. The S4 is equipped with a 350W PTC heater, which is significantly more powerful than many standard dryers.
This heater heats up the internal space much faster, improving drying efficiency. It utilizes a built-in fan to circulate that heat 360°, ensuring every layer of the spool gets dried evenly, not just the outer strands.
Smart Humidity Control
One of the standout features of the S4 is the Auto Humidity Control. You don’t have to constantly monitor the box. If the humidity inside the box rises, the S4 detects it and automatically kicks on to lower the humidity back to your target level.
This “set it and forget it” feature is perfect for long prints where humidity might creep up overnight or during rainy weather.
Versatility for Advanced Materials
If you print with engineering-grade materials, you know they are thirsty. Nylon (PA), Polycarbonate (PC), and others need high heat to release moisture. The S4 reaches a max temperature of 70℃ (158°F), making it capable of handling a wide range of materials, from standard PLA to demanding industrial filaments.
Why SUNLU?
SUNLU has been a staple in the 3D printing community for years. They are a brand that understands the chemistry of filament. The S4 feels like a product designed by makers for makers, directly addressing the pain points of wet filament and limited storage space.
Final Verdict
If you are tired of brittle filament snapping in your Bowden tube or bubbly surface finishes ruining your aesthetic prints, you need a dryer. And if you value efficiency and volume, the SUNLU S4 is hard to beat. It solves the moisture problem at scale, letting you focus on what matters: creating.