SUNLU FilaDryer S4 Pro Review: A Dual-Zone Filament Dryer With Annealing Mode

Wet filament is one of the most common causes of stringing and weak prints. SUNLU built the FilaDryer S4 Pro to deal with that, with two separate drying zones and an annealing mode for engineering materials. Here's a closer look.

About SUNLU

SUNLU makes 3D printing filament, resin, filament dryers, dehumidifying cabinets and accessories for both FDM and resin printing.

What Is the FilaDryer S4 Pro?

The S4 Pro is a filament dryer that holds four 1kg spools across two chambers. Each chamber has independent temperature and time control, and the dryer reaches up to 85°C (185°F).

Key Features

Dual-zone control

You can run two different programs at once, for example drying PLA or PETG in one chamber while conditioning PA, PC or PP in the other.

Annealing mode

A built-in annealing mode is designed to improve strength, dimensional stability and heat resistance for printed parts made from engineering materials with an annealing temperature of 85°C or less.

Smart humidity management

Set a target humidity between 30% and 50% RH, and the dryer starts automatically when that level is reached and stops at 25% RH.

Wide material compatibility

SUNLU lists compatibility with PLA, PETG, TPU, ABS, ASA, PA (nylon), PC and carbon fiber or glass fiber filled variants.

Specs and Price

The S4 Pro measures 458 × 218 × 310 mm, weighs 4.7 kg and is rated at 380W. Each chamber fits 220 × 210 × 211 mm. The box includes a power cable, two 1m PTFE tubes, eight stainless steel shafts and 16 bearings. At the time of writing, it's listed at $139.99 for the US, Canada and Australia, and $149.99 for Europe.

Pros and Cons

Pros

• Two independently controlled drying zones
• Up to 85°C, suitable for engineering filaments
• Annealing mode for printed parts
• Automatic humidity start and stop
• Fits four 1kg spools

Cons

• Larger footprint than single-spool dryers
• 380W draw is higher than compact dryers
• More features than casual PLA-only printers may need

Who Is It Best For?

The S4 Pro is a strong fit for home studios, workshops and small print farms, and for anyone printing with moisture-sensitive materials like nylon or PC.

How to Save

SUNLU offers free shipping on orders over $40, and you can use our exclusive code ZUBA86 for 4% off your order.

Final Verdict

With dual zones, an annealing mode and hands-off humidity control, the SUNLU FilaDryer S4 Pro covers both everyday drying and advanced material workflows in one machine.

Shop the FilaDryer S4 Pro at SUNLU and save 4% with code ZUBA86