SUNLU S4 Filament Dryer — 4-Spool 3D Filament Dehydrator
Product description
This SUNLU S4 filament dryer is built to hold up to four standard 1kg spools simultaneously. The internal chamber measures approximately 450 x 210 x 211 mm, providing space for full-size reels and enabling multi-color or multi-printer workflows without constant spool swapping.
Heating is provided by a 350W PTC heater that delivers steady, controllable warmth up to 70°C across the chamber. Three circulation fans distribute air for 360° surround heating, promoting even moisture removal from all loaded spools. The dryer also supports direct filament feeding, so you can run filament from the unit straight into an FDM printer while it stays dry.
Safety and monitoring are built in: the unit combines the PTC heater with a backup thermal cutout and software-based temperature supervision, offering multiple layers of protection and alerts if temperatures stray beyond set limits. Humidity control is automated — the system engages drying when ambient relative humidity is between roughly 30–50% and continues until it reaches a target below about 25% RH to maintain a dry storage environment.
Compatibility is broad: the S4 accepts common filament diameters (1.75 mm, 2.85 mm, 3.0 mm) and can serve up to four printers or spools at once, making it suitable for small labs, schools, or multi-printer hobby setups. The exterior and build quality support frequent use, with features aimed at making filament prep and storage straightforward.
Pros
- Holds four full-size 1kg spools for continuous use
- 350W PTC heater with three fans for even drying up to 70°C
- Automated humidity control and multi-layer temperature safety
Cons
- Not fully sealed — filaments can slowly reabsorb humidity if left long-term
- Control knobs and latch feel small and awkward to operate
- Minor display quirks reported with some material labels
VerdictA practical solution for keeping moisture-sensitive filaments ready for printing. Large capacity and reliable heating make it ideal for multi-printer setups or makers handling several materials, though the enclosure isn’t fully airtight and some controls feel fiddly.
Reviews
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Bob H. 5/5
User-friendly and well made
Fantastic device — I no longer need to occupy other drying equipment. It can dry four spools while other systems feed printers. Fit and finish are excellent, with stable rubber feet and intuitive controls. Switching materials and adjusting temperatures is simple. One of my better purchases for the shop.
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Matt 5/5
Solid option for clubs and hobbyists
I bought this for personal use and for my college printing club. It’s a cost-effective way to prepare and store filaments long-term and works well with filaments from different manufacturers. I mainly use it for PLA and it has helped with bed adhesion and reducing stringing. Highly recommended for anyone into 3D printing.
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Brandi Kae 5/5
Essential for multi-spool printing
Very pleased with the SUNLU 4-spool dryer — it noticeably improves prints using PETG, TPU, Nylon and PLA in humid conditions. Drying four spools at once saves a lot of time compared to single-spool units. The temperature is straightforward to set on the digital panel, and I can feed filament straight from the box while printing. It runs quietly, heats evenly, and reduced stringing and extrusion issues after drying moisture-prone materials.
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Andy K. 5/5
Great value and improved print quality
Well built and it has improved our prints substantially. Living in a humid area caused filament moisture issues before; being able to store four spools means we always have commonly used materials ready. A simple but effective upgrade for our setup.
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Ashley B 5/5
Keeps multiple filaments ready and organized
This dryer has been great for managing various filament types at once. Holding four rolls simplifies larger or multi-material jobs and keeps everything ready without constant swapping. Feeding filament directly into the printer makes prints more consistent in humid environments. The adjustable settings let you tailor drying for different materials.
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Jesse 5/5
Really useful and dependable
So far the unit has been reliable and the temperature accuracy is good. It keeps filament dry and the unit looks tidy. One small quirk is a display typo that mislabels PETG, but otherwise it’s an excellent tool that saves time and reduces wasted material.
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B. Marshall 4/5
Good performance, two notable annoyances
Performance and value are solid, but there are two drawbacks: it isn’t fully sealed, so filaments left inside can slowly pick up moisture again — a lid gasket would have helped. Also, the small, nearly flush knobs and the latch are awkward to operate and frustrating in daily use.
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