The SUNLU S1 Plus is a budget single-spool filament dryer for makers who want warmer, drier filament feeding directly into a printer without paying for a hotter or multi-spool machine. Its circulating fan, 35-55 C temperature range, live humidity display, and print-while-drying feed path make the most sense for routine PLA, PETG, TPU, and ABS upkeep.
The key boundary is just as important as the feature list: 55 C is useful common-material heat, but it is not the right tool for every soaked nylon, polycarbonate, or fiber-filled engineering spool. Think of the S1 Plus as an everyday moisture-control box, not a laboratory dryer or a substitute for sealed storage.
Check the SUNLU S1 Plus on Amazon
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SUNLU S1 Plus review: the short verdict
Buy the S1 Plus if you usually run one open spool at a time and want a low-cost way to warm it, monitor the chamber, and feed filament while printing. It is especially sensible for a beginner who has confirmed moisture symptoms in PLA or PETG, or for a TPU user who wants a shorter exposed path between dryer and extruder.
Skip it if your main job is deep recovery of very wet nylon or PC, if you regularly need two spools ready together, or if you expect the dryer to preserve filament indefinitely after power-off. A hotter dryer, a dual-spool box, or a dry-then-seal system is a better match for those jobs.
Key specifications and what they mean in practice
| Feature | Practical value | Important limit |
|---|---|---|
| 35-55 C adjustable heat | Useful range for everyday PLA, PETG, TPU, and ABS care | Not a high-heat recovery lane for every nylon or PC spool |
| Built-in circulating fan | Moves chamber air to reduce simple bottom-heater hot spots | Airflow cannot compensate for too little temperature or too little time |
| 2-inch LCD | Shows temperature, remaining time, and relative humidity together | Chamber humidity is a trend, not a direct measurement inside the filament |
| Dual temperature probes | Monitors chamber air and heating-element behavior for steadier control | Still follow the filament maker's drying guidance |
| 1.75, 2.85, and 3.00 mm feed support | Broad fit for external-spool FDM workflows | Check spool dimensions, outlet position, and your printer's feed path |
Who the SUNLU S1 Plus is best for
- PLA and PETG users in ordinary hobby rooms: it offers a practical first step after stringing, popping, rough surfaces, or brittle filament point to moisture.
- TPU users: feeding directly from a warm box can reduce the time flexible filament spends exposed before reaching the extruder.
- One-printer, one-spool setups: single-spool capacity is a benefit when it keeps the machine compact and affordable rather than unused capacity on the bench.
- Beginners who want readable feedback: temperature, time, and humidity on one display make the drying cycle easier to follow.
- Budget-minded makers: the S1 Plus fills the gap between passive storage and hotter premium recovery equipment.
It is a weaker fit for multi-material work where two or four spools must stay conditioned together. It also makes less sense for someone whose filament is already reliable and immediately returns to an airtight container with fresh desiccant after each print.
What the circulating fan changes
A heated box works by encouraging moisture to leave the filament and move into the surrounding air. A circulating fan helps distribute that warmth around the spool instead of relying only on the air directly above a heater. That matters because the outside of a stationary spool, the inner windings, and the top of the chamber do not warm identically.
The fan does not turn 55 C into 70 C, and it does not make a short cycle equivalent to a properly timed one. Its value is more ordinary: better chamber circulation can make common-material upkeep more consistent. The wrap-around heating layout and dual probes support the same goal, though users should still rotate an unusually dense spool if the product instructions recommend it.
Drying also requires somewhere for moisture-laden air to go. Follow SUNLU's current venting guidance for the selected material and model revision. Sealing a box perfectly during active heating can trap humid air; leaving it wide open can waste heat. The correct position is a product-specific operating detail, not a universal internet rule.
PLA, PETG, TPU, and ABS fit
PLA: not every PLA spool needs active drying, but damp PLA can become brittle, pop at the nozzle, or leave a rougher surface. The S1 Plus temperature range is well matched to conservative PLA upkeep. Avoid excessive temperature, which can soften a spool or filament depending on its formulation.
PETG: this is one of the strongest everyday use cases. PETG can string and print with tiny surface bubbles after absorbing moisture, symptoms that are often mistaken for retraction or temperature problems. A 55 C ceiling is useful for routine PETG drying, though a severely wet spool may need more time than a quick pre-print cycle.
TPU: flexible filament can absorb moisture quickly, and wet TPU may hiss, foam, or leave inconsistent extrusion. Printing from the box is valuable because it limits re-exposure during a long job. Make sure the outlet and guide path do not add sharp bends or drag.
ABS: the listing places ABS in the supported common-material lane, but drying is only one part of successful ABS printing. Enclosure temperature, drafts, ventilation, first-layer adhesion, and warping control remain separate issues.
Where the 55 C ceiling becomes the deciding factor
Temperature is the S1 Plus's most honest dividing line. For common PLA, PETG, TPU, and basic ABS upkeep, 35-55 C covers the work many hobbyists actually need. For moisture-sensitive engineering materials, the right drying temperature may be higher than the box can provide.
Nylon is the clearest example. Some nylon blends can be maintained at lower temperatures after they are dry, while a deeply wet spool may need hotter recovery based on the filament manufacturer's guidance. Polycarbonate and certain filled materials can also demand more. Running a 55 C dryer longer is not automatically equivalent to reaching the specified temperature.
That does not make the S1 Plus underpowered for its audience; it makes it specialized. Buying for the material on your shelf is smarter than buying the highest temperature on a spec sheet. If engineering materials are central to your work, start with our practical filament-drying guide and choose equipment that meets the exact material requirements.
Print-while-drying setup
- Inspect spool fit. The spool should rotate freely without rubbing the lid, walls, or feed outlet.
- Use a clean feed path. Route filament through the intended outlet and optional guide tube without a tight bend.
- Set temperature by material guidance. Do not default every spool to the maximum.
- Set enough time. A surface-warm spool is not necessarily dry through its inner windings.
- Watch chamber trends. Falling relative humidity can support the diagnosis, but print quality is the final check.
- Keep the box stable. Place it where spool pull cannot tip it or create an awkward angle into the printer.
- Run a controlled test. Compare the same model and settings before and after drying before changing retraction, flow, or temperature too.
For a direct product decision, the SUNLU S1 Plus versus SUNLU S2 comparison explains when the S1 Plus's fan-assisted 55 C workflow is enough and when the hotter 70 C S2 lane is worth buying instead.
Drying is not storage
The S1 Plus can condition a spool during a print, but filament can absorb moisture again after the cycle. Once the spool cools, move it to a genuinely sealed bag or box with maintained desiccant unless the dryer is specifically being operated as directed for storage. A humidity number on an unpowered dryer does not make the enclosure permanently airtight.
This distinction prevents a common cycle: dry a spool, leave it on an open machine for a week, then blame the dryer when stringing returns. Our dryer versus dry-box versus sealed-storage guide shows how active recovery and passive preservation fit together.
SUNLU S1 Plus versus common alternatives
SUNLU S2: choose the S2 when its higher 70 C ceiling matters more than the S1 Plus's circulating-fan value. It is the stronger step-up for buyers who routinely need hotter recovery, though the exact material instructions still rule.
Creality Space Pi: compare it when you want another mainstream single-spool dryer with a hotter lane and a more appliance-like interface. It usually makes sense as a mid-range alternative rather than the cheapest way to warm one active spool.
Sovol SH01: the SH01 is useful when budget dual-spool capacity matters more than higher temperature. Capacity alone is not better if you only ever print from one spool.
eSUN eBOX Lite: consider it for a familiar low-cost single-spool format. The S1 Plus's fan, live humidity view, and 55 C ceiling form the clearer argument when those operating details matter.
Likely downsides
- Single-spool capacity: multicolor or support-material workflows outgrow it quickly.
- 55 C maximum: not enough for every nylon, PC, or engineering-material recovery specification.
- No permanent moisture cure: dried filament still needs sealed storage afterward.
- Humidity interpretation: chamber RH is useful feedback but does not directly report core-spool moisture.
- Spool-fit variables: wide, oversized, cardboard, or unusually shaped rolls should be checked against current internal dimensions.
- Feed-path friction: a poorly placed dryer can add drag even when the box supports print-while-drying use.
- Marketplace drift: controls, accessories, color, or bundle details may change, so verify the selected listing before ordering.
Final verdict
The SUNLU S1 Plus is a sensible budget dryer when the real job is one-spool PLA, PETG, TPU, or ABS upkeep. Its circulating fan, readable display, dual-probe control, and 35-55 C range create a useful step above passive storage without pretending to be a high-temperature engineering-filament system.
The best buyer has a confirmed moisture problem, prints from one spool at a time, and will put that spool into sealed storage after use. The wrong buyer needs hotter nylon recovery, multi-spool capacity, or a complete dry-and-store ecosystem.
If that common-material workflow matches your bench, check the current SUNLU S1 Plus listing on Amazon. If the 55 C ceiling or single-spool capacity is already a compromise, move up before buying twice.
Frequently asked questions
How hot does the SUNLU S1 Plus get?
The verified listing range is freely adjustable from 35 C to 55 C. Use the filament maker's drying recommendation rather than automatically selecting the maximum.
Does the SUNLU S1 Plus have a fan?
Yes. The built-in circulating fan is intended to move heated air around the chamber for more even drying than a simple stationary bottom-heater layout.
Can you print directly from the dryer?
Yes. The box supports common 1.75, 2.85, and 3.00 mm feed paths. Confirm the spool rotates freely and route filament without sharp bends or excess drag.
Is 55 C enough for PETG and TPU?
It is a practical range for routine PETG and TPU upkeep when it matches the material manufacturer's directions. Extremely wet filament may need a longer cycle, while some engineering materials require a hotter dryer.
Is the SUNLU S1 Plus good for nylon?
It may help maintain some nylon after proper drying, but it should not be treated as a universal deep-recovery dryer. Many nylon formulations call for temperatures above 55 C, so check the exact spool guidance first.