SUNLU S4 Filament Dryer Review 2025: The Ultimate Fix
You’ve spent hours designing the perfect model with your SUNLU printer. You’ve sliced it with meticulous care, double-checking every setting. You hit “print,” filled with anticipation, only to return to a mess of stringy, fragile plastic that looks nothing like your digital creation. The layers are poorly bonded, the surface is rough, and the entire print is so brittle it cracks with the slightest pressure. It’s a frustrating, time-wasting, and expensive experience that almost every 3D printing enthusiast has faced.
What if I told you the problem might not be your printer, your settings, or even the filament brand? The culprit is likely an invisible enemy that silently sabotages your prints: moisture.
Filament, especially common types like PLA and PETG, is hygroscopic. This means it actively absorbs moisture from the surrounding air. Even a brand-new spool, left out for just a few days in a humid environment, can become “wet.” This absorbed water turns to steam in the hot end, causing a host of printing problems. But don’t throw away those “bad” spools just yet. There is a definitive solution, and it’s called the SUNLU S4 Filament Dryer. This device isn’t just an accessory; it’s an essential tool for anyone serious about achieving flawless 3D prints.
The Hidden Enemy of Perfect Prints: Filament Moisture Explained
Before we dive into the solution, it’s crucial to understand the problem. Moisture in your filament is the root cause of many common 3D printing headaches. It can turn a reliable, high-quality material into a useless tangle of plastic.
Why Does 3D Printing Filament Absorb Moisture?
As mentioned, materials like PLA, PETG, ABS, Nylon, and TPU are hygroscopic. They act like sponges for airborne water vapor. The rate of absorption depends on the material type and the ambient humidity. Nylon is notoriously bad, but even the workhorse of 3D printing, PLA, suffers significantly. In a room with 50% humidity, a PLA spool can become compromised in under a week. This process is silent and invisible, making it one of the most difficult issues for beginners to troubleshoot.
Telltale Signs Your SUNLU Filament Has Gone Bad
How can you tell if moisture is the cause of your print failures? Look for these classic symptoms during or after printing:
- Popping or Sizzling Sounds: As the wet filament enters the hot end, the trapped water instantly boils and turns to steam, creating audible popping, cracking, or hissing sounds from the nozzle.
- Excessive Stringing and Oozing: The steam pressure in the nozzle pushes out molten plastic erratically, leading to fine (or thick) strings between separate parts of your model.
- Brittle and Weak Prints: Steam creates voids and bubbles within the extruded filament, drastically weakening the final part and compromising layer adhesion. Prints may snap easily or layers may delaminate with little effort.
- Rough or Inconsistent Surface Finish: The small steam explosions at the nozzle tip disrupt the smooth flow of plastic, resulting in a fuzzy, bumpy, or even pockmarked surface.
- Poor Layer Adhesion: The bubbles and inconsistent extrusion prevent layers from bonding properly, making the final object structurally weak.
If you’re experiencing any of these issues, you’re not dealing with bad filament; you’re dealing with wet filament. Fortunately, this is a completely solvable problem.
Introducing the Ultimate Solution: The SUNLU S4 Filament Dryer
While DIY solutions like kitchen ovens exist, they are risky, inconsistent, and can easily ruin your filament by overheating it. For reliable, consistent, and safe results, you need a purpose-built tool. The SUNLU S4 Filament Dryer is engineered from the ground up to solve this exact problem, making it the best filament dryer for hobbyists and professionals alike.
This powerhouse device actively removes moisture from your spools, restoring them to their optimal printing condition and allowing you to print directly from the dry box. It’s a game-changer for improving 3D print quality.
What is the SUNLU S4 and How Does It Work?
The SUNLU S4 is a large-capacity filament drying station that uses a unique 360° surrounding heating system to evenly and efficiently dry your filament. Unlike other dryers that heat from the bottom up, the S4 employs a PTC heating element combined with dual fans to circulate hot air throughout the entire chamber. This ensures every part of every spool is dried consistently without creating hot spots that could damage the filament.
You simply place your spools inside, set the desired temperature and time on the intuitive touch screen, and let the S4 work its magic. A built-in humidity sensor shows you the progress in real-time, so you know exactly when your filament is perfectly dry and ready for printing.
A Deep Dive into the SUNLU S4 Features
The SUNLU S4 is packed with features designed for maximum efficiency and user-friendliness:
- Massive Capacity: The S4 can hold up to four 1kg spools of filament at once. This is perfect for users running multiple printers, working on large multi-color projects, or wanting to dry different material types simultaneously.
- High-Efficiency PTC Heater: The 350W PTC (Positive Temperature Coefficient) heating element is not only powerful but also safer and more energy-efficient than traditional heating coils. It heats up quickly and maintains a stable temperature.
- 360° Dual-Fan Circulation: This is the S4’s standout feature. Two fans ensure complete and even hot air circulation, eliminating the temperature gradients found in lesser models and drying your filament faster.
- Smart Touch Screen & Humidity Sensor: The large, easy-to-read LCD touch screen allows you to precisely control temperature (up to 70°C) and drying time. The integrated sensor provides live feedback on the chamber’s humidity level.
- Print While You Dry: The S4 is designed with multiple filament exit holes, allowing you to feed filament directly to your printer while it’s drying. This is the best way to handle extremely hygroscopic materials like Nylon and ensures your filament stays perfectly dry throughout the entire printing process.
- Broad Compatibility: It accommodates spools up to 210mm in diameter and is compatible with all common filament types, including PLA, PETG, ABS, TPU, Nylon, and more.
Ready to see what this machine can do for your prints? Don’t forget to check our SUNLU coupon page to get the best possible deal on this essential tool.
A Comprehensive SUNLU S4 Review: Putting It to the Test
We couldn’t just talk about the features; we had to see the SUNLU S4 in action. We took a spool of PLA that had been intentionally left out in a humid garage for two weeks—it was a brittle, stringy mess.
From Brittle PLA to Perfect Prints
Before drying, a test print with this PLA was a disaster. It was fuzzy, had terrible layer lines, and the finished piece snapped with almost no effort. The filament itself was so brittle that it would break just trying to load it into the printer.
We placed the spool in the S4, set it to 50°C for 6 hours, and watched the humidity reading drop from a starting point of 65% down to 20%. The result was nothing short of miraculous. We reran the exact same G-code file on the same printer. This time, the print was flawless. The surface finish was smooth as glass, there was zero stringing, and the layer adhesion was so strong we couldn’t break the part with our hands. The SUNLU S4 had completely resurrected a spool we would have otherwise thrown away. This is the ultimate fix for brittle filament.
Tackling Tougher Materials like PETG and Nylon
Where the SUNLU S4 truly shines is with more challenging materials. We tested a spool of PETG that was making loud popping sounds from the nozzle. After a cycle in the S4 at 65°C, the popping completely vanished. The resulting prints were stronger, clearer, and had a beautiful glossy finish. For anyone struggling with the common PETG popping sound, this device is a must-have.
Why You Need a Dedicated Dryer (and Why the SUNLU S4 is the Best Choice)
Some makers try to use their kitchen oven or a modified food dehydrator to dry filament. While these methods can work, they come with significant drawbacks that make a dedicated dryer like the S4 a far superior choice.
The Oven Method vs. The SUNLU S4
Using a kitchen oven is risky. Most ovens have poor temperature regulation at the low temperatures required for plastic, with swings of 10-20 degrees being common. This can easily exceed the glass transition temperature of your filament, partially melting it and fusing the windings on the spool, rendering it completely useless. The SUNLU S4 provides precise, stable temperature control designed specifically for the delicate nature of 3D printing filaments.
Long-Term Savings: How the S4 Prevents Wasted Filament
Think about the cost of a failed 12-hour print. You’ve wasted time, electricity, and a significant amount of filament. A single roll of specialty filament can cost $40-$50. By salvaging wet spools and preventing print failures, the SUNLU S4 pays for itself very quickly. It’s an investment that saves you money and frustration in the long run, transforming your 3D printing troubleshooting from a guessing game into a science.
Getting the Most Out of Your SUNLU Filaments and Dryer
Pairing the S4 dryer with high-quality materials is the key to perfect prints every time. SUNLU is renowned not just for its accessories but also for its vast range of affordable and reliable filaments.
Recommended Drying Settings for Common SUNLU Filaments
Here are some great starting points for drying your filament in the S4:
- PLA/PLA+: 45-55°C for 4-6 hours
- ABS/ASA: 60-65°C for 4-8 hours
- PETG: 60-65°C for 6-8 hours
- TPU (Flexible): 50-55°C for 8-12 hours
- Nylon (PA): 65-70°C for over 12 hours
Always start with a dry spool for the best chance of success. When you combine perfectly dried material with excellent printers and filaments from a trusted brand like SUNLU, you create an ecosystem for success.
Final Verdict: Stop Guessing and Start Printing Perfectly
Stop letting moisture dictate the quality of your 3D prints. Stop wasting filament, time, and energy on failed projects. The stringing, the brittleness, and the poor layer adhesion are not problems you have to live with.
The SUNLU S4 Filament Dryer is the definitive, must-have solution. Its large capacity, efficient 360° heating, and user-friendly design make it the single best upgrade you can buy to improve your 3D print quality. It turns unreliable, wet filament back into the high-performance material you paid for.
Take control of your printing environment and unlock the true potential of your 3D printer.
Ready to achieve flawless prints? Order your SUNLU S4 Filament Dryer today and say goodbye to moisture-related failures for good. And before you buy, be sure to visit our exclusive SUNLU deals page to ensure you’re getting the absolute best price! You can also find a wide range of SUNLU products on their official Amazon store.
