Best Filament Dryers Compared: SUNLU S2, SUNLU S4, EIBOS, and More

How filament drying works: temperature targets by material

Filament drying works by heating the spool above the boiling point of water sufficiently to drive moisture out of the polymer matrix without reaching the glass transition temperature that would soften or deform the filament. The target temperature window is material-dependent and relatively narrow.

PLA: 45 to 55 degrees Celsius for four to six hours. PLA absorbs moisture slowly but the window to prevent deformation is narrow, above 60 degrees, PLA strands can fuse in the drying chamber. The SUNLU FilaDryer S2 handles PLA reliably at its 45 degree minimum setting.

PETG and TPU: 60 to 65 degrees Celsius for four to six hours. Both materials absorb moisture quickly and produce immediate print defects when wet. The S2 reaches 65 degrees and handles these materials at its upper temperature limit. The EIBOS Filament Dryer Box with its humidity display is more useful here because it confirms actual drying completion rather than relying on elapsed time.

ABS, ASA, and PC: 70 to 80 degrees Celsius for six to twelve hours. These engineering materials require higher temperatures and longer drying times. The SUNLU FilaDryer S4 reaches 70 degrees and handles ABS and ASA drying in its four-spool configuration. PC requires longer drying at the upper end of most consumer dryer temperature ranges.

Nylon (PA): 80 to 90 degrees Celsius for eight to twelve hours minimum. Nylon is the most moisture-sensitive FDM filament and the most demanding to dry thoroughly. Consumer-grade filament dryers that max out at 70 to 75 degrees Celsius will improve nylon print quality but may not fully restore severely wet nylon. A food dehydrator set to 80 degrees is a practical supplement for nylon drying when the dryer temperature ceiling falls short.

SUNLU FilaDryer S2: the best entry-level option

The SUNLU FilaDryer S2 earns its position as the most-recommended entry-level filament dryer through a combination of adequate temperature range, print-in-dryer operation, and a price under $50. Single-spool capacity is not a workflow limitation for most new users who print one material type at a time.

The S2 temperature dial is less precise than the digital controls on the EIBOS or S4, but the temperature accuracy at set point is adequate for PLA, PETG, and TPU targets. Users printing primarily these three materials and wanting the lowest-cost drying solution should start with the S2 and evaluate whether the capacity is limiting before upgrading.

Print-in-dryer operation, running the S2 continuously while printing from the dried spool, is the highest-value use mode for users in humid climates where filament re-absorbs moisture quickly after removal from the dryer. Thread the filament out through the S2 guide port directly into the printer extruder path to maintain dry conditions throughout a long print.

4.5 filament dryers

SUNLU FilaDryer S2

The SUNLU S2 is the most widely recommended entry-level filament dryer in the hobby. It accepts one spool, heats to between 35 and 70 degrees Celsius, and can run continuously during printing to prevent moisture re-absorption. The S2's temperature range covers PLA (45 to 55 degrees), PETG and TPU (60 to 65 degrees), and ABS and ASA (65 to 70 degrees). At under $50, it is the most accessible path to moisture-free printing.

$38 to $52 Check price

SUNLU FilaDryer S4: multi-spool for AMS and multi-material users

The SUNLU FilaDryer S4 solves the single-spool capacity limitation for users who run multi-material setups or rotate between multiple filament types. Four spools can be loaded simultaneously and dried in a single cycle, which is the practical requirement for Bambu AMS users who need all four slots conditioned before a multi-color print session.

Digital temperature control improves accuracy over the S2 dial, the S4 can be set to 65 degrees with confidence that it will maintain that temperature within a few degrees throughout the drying cycle. Two simultaneous feed ports allow two of the four spools to feed active printers while the other two dry.

The S4 footprint is significantly larger than the S2 and requires dedicated shelf space near the printer. Users who do not require multi-spool capacity should not buy the S4 for features they will not use. The capacity justification is specifically for AMS workflows and users who print four or more materials in regular rotation.

4.6 filament dryers

SUNLU FilaDryer S4

The S4 is SUNLU's four-spool dryer, offering the same temperature range as the S2 but scaling to users who rotate multiple materials. Two spools can feed simultaneously, making the S4 practical for multi-material setups like the Bambu AMS where several filaments need to be conditioned at the same time. Digital temperature and timer controls are more precise than the S2's dial.

$60 to $85 Check price

EIBOS Filament Dryer: the humidity-verified option

The EIBOS Filament Dryer Box differentiates itself with a live humidity display that shows the actual moisture level inside the drying chamber. This is a meaningful feature rather than marketing: knowing when the humidity inside the chamber has dropped to a stable low level confirms that drying is complete, rather than relying on elapsed time at a set temperature as a proxy.

The practical value is highest for materials where incomplete drying is costly, nylon and engineering materials where a partially dry spool still produces print failures. The EIBOS humidity readout tells you definitively whether another two hours of drying is warranted rather than requiring a test print to check.

Brushless internal circulation fan in the EIBOS distributes heat more evenly than the natural convection in the SUNLU S2. Even heat distribution matters for large spools where the center of the spool is further from the heating element than the outer windings. Single-spool capacity matches the S2; choose between them based on whether the humidity display justifies the price difference for your typical materials.

4.5 filament dryers

EIBOS Filament Dryer Box

EIBOS positions itself above the SUNLU S2 with a brushless motor internal circulation fan, precise PTC heating element, and a humidity display showing real-time moisture level inside the chamber. The humidity readout is the differentiating feature, it tells you when the spool is actually dry rather than requiring you to guess based on elapsed time at temperature.

$45 to $65 Check price

Passive dry storage: the complement to active drying

Active dryers restore wet filament and maintain dry conditions during printing. For spools not in use, passive dry storage in airtight containers with desiccant is the cost-effective complement. PrintDry Filament Container with Desiccant containers with Dry and Dry Rechargeable Silica Gel Desiccant provide multi-month moisture protection between print sessions.

The workflow: dry the spool in the S2 or EIBOS before first use, verify humidity drop on the EIBOS display or allow adequate time at temperature, then transfer to a sealed PrintDry container with fresh desiccant for storage. The Govee Temperature and Humidity Monitor placed inside the storage area confirms that the desiccant is maintaining the target humidity level below 20 percent relative humidity.

In climates with humidity below 50 percent year-round, passive storage with rechargeable desiccant is often sufficient for PLA and PETG without an active dryer. In climates with seasonal humidity above 70 percent, active drying before each multi-hour print session is the more reliable approach.

4.3 filament dryers

PrintDry Filament Container with Desiccant

PrintDry's dry storage containers provide passive moisture protection for spools not currently in use. Each container holds one spool, includes a desiccant packet holder, and seals with a silicone gasket. For users who do not print nylon or engineering materials but want to protect their PLA and PETG collection between print sessions, passive dry storage is a lower-cost solution than an active dryer.

$14 to $20 Check price

4.4 tools maintenance

Dry and Dry Rechargeable Silica Gel Desiccant

Rechargeable silica gel packets that absorb moisture inside filament storage containers and sealed storage boxes. When saturated, the indicator beads change color from orange to clear, signaling time to recharge by heating the packet in an oven at 120 to 150 degrees Celsius for two to three hours. Reusable indefinitely, making them more cost-effective than single-use desiccant over a filament collection of any size.

$12 to $20 Check price

4.5 tools maintenance

Govee Temperature and Humidity Monitor

A wireless temperature and humidity sensor for monitoring the environment inside a printer enclosure or filament storage area. The Govee sensor logs data to the app over Bluetooth, enabling trend analysis of how humidity changes in a print space through the day. Knowing the relative humidity near your filament storage helps calibrate how often desiccant needs recharging and whether an active dryer is necessary for your climate.

$14 to $20 Check price