SUNLU S2 Filament Dryer: Moistureless 360° Surround Heating

SUNLU S2 FilaDryer

Many 3D printing filaments are hygroscopic, which means they readily absorb moisture from the environment when they are removed from the original package. Moisture can turn into steam in the hot end, leading to issues like poor layer adhesion, bubbling, or even clogging of the nozzle. Using a filament dryer box such as the SUNLU S2 is essential to ensure the quality, consistency, and reliability of your 3D prints.

Different 3D filaments absorb water at different rates, depending on their chemical composition. The S2 FilaDryer monitors in real-time the inside humidity and allows temperature level setting between 35℃ and 70℃. The dryer uses two heating elements that turn moisture into vapor, which is discharged through the filament outlet.

The SUNLU S2 Filament Dryer is compatible with 99% of FDM 3D printer materials regardless of brand, diameter ( 1.75mm/2.85mm/3.00mm), or type (PLA/PLA+, PETG, ABS, TPU, Nylon, and PA/PC).

SUNLU S2 drying box

SUNLU S2 FilaDryer review

Disclosure: I received this filament dryer as part of a product review collaboration with SUNLU. Product specs and quality may vary according to the manufacturer’s reliability, so I cannot guarantee that you will get products that perform the same as seen in my article.

The brand name “SUNLU” is inspired by the word “sunshine” -the thing that is among the most treasured in our world, bringing vitality and vigor to all beings. The company was founded ten years ago by Jack, a man with a broad vision and a hardcore enthusiasm for 3D printing. Besides a wide range of printing materials (filaments and resins), the company also has a few FDM machines and 3D printer accessories. 

This year, I already reviewed the SUNLU T3 printer and some of the company’s filaments, and I was happy when they contacted me to test their latest drying box. The S2 is SUNLU’s third and most versatile drying solution.


At a glance

The S2 FilaDryer comes in a nice storage box with an included 24V/2A power adapter, spare Teflon rings, and a quick start guide. For further details, you can consult the product’s detailed multilingual online user manual here.

two metal rollers support the filament spool

The drying box has a slightly egg-shaped form with four feet on the bottom. The top shell is semi-transparent, smoky black, and can be opened to load the filament. Inside the unit, there is a generous space. I tested it with five different spool types; all fit without issues. SUNLU says that you can load bobbins with sizes of up to φ210*85mm. The filament rests in two metal rolls, getting heat from all sides via two heating surfaces. It has filament exit points on both sides, so it can be positioned on the left or right of your 3D printer.

SUNLU S2 LED animation

Around the large (6x4cm) monochrome LCD is a cool LED ring. It does not have any physical buttons. After the 24V AC/DC adapter is plugged in, all the controls are accessible from the touch screen. You must double-tap the “ON/OFF” icon in order to power it on. Navigating the settings can be done by using the UP, Down, and SET virtual touch buttons. You can toggle between Celsius and Fahrenheit display modes. From top to bottom, you have Measured temperature, Configured temperature, Material (PLA/PETG/TPU/ABS/PA/PC), and LED. Relative humidity (RH%) is displayed in the right-up corner -the value should go down as the temperature increases. The humidity and temperature sensors are inside, on the back of the LCD screen, and you should avoid covering them.

Filament exits

According to your material, you configure working temperatures between 35 °C and 70 °C. The default drying program is set to 6 hours -if needed, you can lower it or increase it up to 24 hours. When changing from one material to another, the appropriate temperature will be automatically set. The preset temperature is reached fast thanks to the 48Watt 360° heating elements.

During my test, from a 970-gram filament spool that stayed installed on my Neptune 3 Pro printer for more than a month, a 6-hour drying program managed to eliminate about 3 grams of water. When you remove the moisture from the filament, it behaves the same as the day it was first bought without being too brittle.

Bottom heating plate

SUNLU S2 filament dryer box key features:

  • [Big Touch Screen] It features a big 4.6-inch LCD touch screen. You can easily see all settings like Heating Temp, Time, Filament Type, and LED Light. All settings need one click.
  • [360° Circular Heating] 3D surround heating way can fully dry moisture filaments and improve printing effects greatly—rapid drying, breaking through the heating temperature to 35℃~70℃.
  • [Moisture is not a problem at all] A completely dry filament eliminates printing problems like Clogging, Layer shift, Stringing, and Adhesion to print sheet.
  • [Real-time Humidity Detection] Built-in high-precision humidity detection sensor, displaying real-time humidity inside the filament dryer. Assist in judging the drying effect. Automatic sleep standby after drying.
  • [Suitable for most 3D printing filaments] Compatible with all the mainstream 3D filament brands and all standard filament diameters 1.75mm/2.85mm/3.00mm; Works perfectly with PLA, PLA+, PETG, TPU, ABS, PA, PC, etc.
  • [Dry, Store, and Print] The SUNLU S2 is designed to dry and store your 3D filament and even print directly from it.

Price and availability

The S2 FilaDryer can be ordered from the manufacturer’s online store for $69.99 (discounted from $79.99). For an extra $19.99, you can opt for a Vacuum Bag kit to store your opened filaments without absorbing moisture. You can opt for Europe, USA, Australia, or Canada warehouse. SUNLU products can also be ordered from their Amazon or Aliexpress official store. Spoiler alert: The new FilaDryer S4 with a box design will be officially released on 13 September 2023, and it has a promo price of just $79.99 for the first 300 backers on Kickstarter.

Technical specifications

Dimensions 265x274x118mm
Weight 1190 grams
Max spool size φ210*85mm
Power of heater 48Watt
DC input 24V / 2A
Display size 6.4-inch
Filament diameter 1.75mm/2.85mm/3mm
Temperature setting range 35℃~70℃
The table below shows the recommended temperature settings according to the filament type.
Temp 45-50°C 50-55°C 60-70°C
Time 3-6 hours

How do you know when the filament needs to be dried?

As far as I know, no dedicated tool can measure the filament’s moisture level. Instead, there are some specific signs when your filament is too wet. You need to dry your filament if:

  • The filament gets brittle or loses its flexibility.
  • Hotend makes a lot of sounds when the filament is extruded.
  • The melted thermoplastic continues to ooze even after the 3D printer turns off.
  • The 3D prints have quality issues like stringing, blobbing, and poor adhesion between layers.
Price/performance ratio
Design and build quality
Heating temperature settings
Extra features
sunlu-s2-filament-dryerIf you’re a 3D printer enthusiast, this dryer is a must have. For high quality prints it's a must using moistureless materials. The SUNLU S2 is compatible with most common filaments including hygroscopic materials such as Nylon, PVA and PETG. Temperature can be set between 35 and 70 °C. <br> Pros <br> +Built-in humidity sensor <br> +Moisture-proof and dustproof case <br> +Filament outlet for on-the-fly printing <br> +Silent operation <br> + Low standby power 0.05W <br> Cons <br> - Low visibility inside the unit (you can't see how much filament is left) <br>


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