Sunlu FilaDryer S4 review

Sunlu FilaDryer S4

I started using 3D printers about three years ago, and what I learned first is that dry filament is essential to obtaining quality prints. As its name suggests, the Sunlu FilaDryer S4 allows simultaneous dehydration of four spools, making it unique in its market segment.

I just counted and found more than ten opened filament spools at home. Even if kept in their original packaging, they tend to absorb moisture and require drying before use. Depending on the material, moisture can penetrate only superficially or deeper into your filament. Also, some flexible materials like PVA are highly hygroscopic and tend to absorb much more moisture from the atmosphere than other types of filaments.

3D Printing problems example
3D Printing issues due to wet filament

Using “wet” materials can lead to various quality errors and even print failures. Some of the most common symptoms of moist filament are:

  • Excessive brittleness of the filament
  • Bubbling and popping as it exits the hot nozzle
  • Extrusion jams and other issues
  • Poor bed adhesion
  • Stringing (“hairy prints”)
  • Tiny blobs in print layers
  • Brittle, soft, and fragile results

Sunlu S4: Remove moisture from 4 filaments at a time!

Disclosure: I received this multi-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 shown in my article.

In addition to various printing materials (filaments and resins), SUNLU offers a wide range of 3D printing accessories (mates, as they call them), including filament dryers, vacuum bags, and enclosures. The S4 is the company’s third filament dryer. Here on FirstQuadcopter, we have reviewed the FilaDryer S2, a solid and well-designed moisture remover unit.



The FilaDryer S4 comes well-packed with thick protective foam. The box includes the following accessories:

  • 2 Teflon tubes (100cm)
  • 4 Teflon tubes (8cm)
  • 8 rubber plugs for unused filament-out holes
  • 8 metal clasps to hold output tubes in place
  • User manual

With the S4 dryer, SUNLU also sent me four spools of their new filaments: two high-speed PLAs, a Silk-PLA, and a PETG. These materials will be reviewed in a future article.

At a glance

The FilaDryer S4 has a cuboid form factor and measures 450x210x211 mm. The transparent, smoky gray acrylic front panel allows picking inside the drying chamber. On the sides of the display, a thin green LED strip animates while the dryer is turned on. At the bottom, two stainless steel bars serve as legs. The overall appearance of the unit is very elegant. If you were born in the 60s, you would probably find a resemblance between the S4 FilaDryer and a magnetophone (tape music recorder).

Two hinge lids

Two hinge lids

At the top, two hinged covers (see photo above) allow access to load the filament spools two by two. Each compartment has four bars installed on tiny bearings to run smoothly. In the center of the two drying zones, there is a small compartment for moisture absorber silica pouches. Inside the unit, three fans (only two visible) circulate hot air for uniform dehydration.

desiccant compartment
Moisture Absorber silica gel pouch compartment

The Sunlu FilaDryer S4 adopts a 330W PTC heater, allowing ultra-fast warming time. From 25°C to 70°C, it takes only 50 minutes. Built-in moisture sensor monitors internal humidity and adjusts operations accordingly.

In the stock configuration, you can load up to four filament roles. By adding an extra container on top of the unit (DIY project available here), you will be able to load giant 3KG spools or even dry a pair of shoes 🙂

Four spool filament dryer

Four spool filament dryer

The unit has eight filament outputs, four on the top and four on the sides, allowing you to feed your 3D machines in many configurations (positions). The included rubber plugs can be used to cover the unused holes, preventing moisture from entering the unit.

Eight filament exit holes

Eight filament exit holes

SUNLU S4 filament dryer: Controls and user interface

The unit has only one button, the power switch. The S4 is operated through the touch-screen LCD, with four virtual buttons at the bottom of the display. The FilaDryer 4 has six pre-configured filament profiles with set values, but users can adjust them according to their preferences. The available settings are:

  • Target temperature
  • Temperature units (°C or °F)
  • Program time
  • Drying mode (Timer – MO1 or Humidity control – MO2)
  • LED light bar mode
The table below shows the recommended temperature settings according to the filament type.
Time3-6 hours

Setting the appropriate filament profile is very important because you can damage temperature-sensitive materials, such as PCL filaments with shallow melting points (60-80°C). While testing the FilaDryer S4, I did not notice that I loaded a PCL spool, and after 20 minutes of drying, the filament started to drip like an ice cream.

Melted PCL Filament during drying
Low-temperature 3D filament melted in the drying unit

With a countdown timer function, you can set it to operate in constant heat mode for up to 24 hours. The heat automatically turns off once the timer runs out.

Touchscreen LCD
Big touchscreen LCD

During operation, actual (PV) and set (SV) temperatures are displayed on the left, and relative humidity (RH%) on the right.

Pricing and availability

The S4 Filadryer was initially revealed on Kickstarter, a crowdfunding platform. The project attracted 5,956 pledged backers and raised $620,000. A few months later, the project matured, and the finished product could be ordered directly from the manufacturer’s website for $159.99. Ordering now, you will receive one spool of white PLA filament for free.

Sunlu FilaDryer S4: Technical parameters

Filament capacityUp to four 1kg spools (1.75, 2.85 and 3.0 mm)
Max heating temperature70°C
Rated power320W
Supported filamentsPLA, ABS, PETG, TPU, PA, PC
Heating elementsPTC with three fans
Heating time (25–50 °C)30 min
Heating time (25–70 °C)50 min
Display5cm touchscreen LCD
Filament outputsEight (4xtop and 4xside)

For whom is this filament dryer suitable, and for whom not?

If you own multi-filament 3D machines such as the Bambu Lab X1, Elegoo OrangeStorm Giga, and Prusa i3 or use multiple 3D printers simultaneously, the FilaDryer 4 is an excellent alternative compared to four individual drying units as it saves space and allows centralized control. Being relatively airtight, the S4 is also suitable for storing unwrapped filaments until the next use.

On the other hand, if you print only occasionally using a single spool until you use it all, the price and power usage of the FilaDryer 4 are not justified.

Not all filament types require the same drying program (time and temperature), so you can’t mix them, or you may damage some of the filament, as I also experienced in my tests.

Eleggo Neptune 3 Pro printing directly from Sunlu S4 dryer
Eleggo Neptune 3 Pro printing directly from Sunlu S4 dryer

S4 Filadryer: Key features

  • [Large dying chamber] The FilaDryer S4 has an internal size of 450 x 210 x 211 mm and offers space for 4 x 1 kg filament spools (with a max. spool dimension of 75 x 206 mm).
  • [Intelligent PTC heating element] A 330-watt PTC heating element reaches a temperature of 50 °C in half an hour. The maximum heating temperature is 70 °C.
  • [Triple security protection] An integrated triple safety protection helps monitor the temperature in real time and warns of any anomalies:
    • At abnormal temperatures, the PTC element stops heating
    • A two-stage safety switch for temperature control interrupts the circuit when the temperature reaches too high a value.
    • Software protection warns of other abnormal occurrences.
  • [Dynamic temperature compensation] The FilaDryer S4 has an integrated triple fan system (two circulation fans + one heating fan) that ensures the heat inside the dryer is dynamically adjusted or balanced to a tolerance of ±3 ℃ to dry the filaments evenly.
  • [Automatic humidity control] To better meet the requirements of different types of materials, the humidity in the dryer can be adjusted as needed:
    • When the humidity reaches the preset value (30%-50%), the box automatically starts drying,
    • If the humidity drops to 25%, drying stops
  • [Wide compatibility] The FilaDryer S4 is compatible with most 3D printers and supports the simultaneous use of four devices.
Optimized by Optimole