SUNLU S4 Setup: Manual, Modes & Four-Spool Workflow

Confirm the original S4 before setup

Match the label, delivered manual, controls, and product name before applying any instruction. This page covers the original SUNLU FilaDryer S4. It does not cover the separate S4 Pro, whose manufacturer page specifies a different 45–85°C range and dual independent chambers. Instructions for the S2, S1, Plus, or another SUNLU dryer are not substitutes for the original S4 manual.

The current original-S4 product documentation describes one shared 35–70°C chamber for up to four one-kilogram spools, three circulation fans, and eight filament outlets. SUNLU gives overall internal dimensions of 450 × 210 × 211 mm, but those totals are not a promise that every four-spool combination will fit or rotate. Official SUNLU pages currently conflict on electrical wattage, so this guide does not publish one wattage figure. Confirm the rating plate and regional power instructions on the delivered unit.

Load only spools that can share one chamber

The manual instructs the user to place as many as four spools in the dryer and pass filament through the outlet holes. Fewer than four is a valid workload. For each reel, verify the complete loaded diameter, width, hub arrangement, and freedom to rotate in the intended position. Close the lid only after checking that no filament, tube, label, or adapter rubs another reel or becomes trapped.

All loaded spools share the selected chamber conditions. Before grouping them, find a supported temperature-and-time pair for each exact filament product and check the carrier-reel limit separately. Run different cycles when any product or reel cannot share the same supported process. Polymer-family labels and a vacant spool position do not resolve that conflict.

Route the eight outlets before applying heat

Choose the outlet and any supported PTFE path for every loaded spool while the machine is cool. The original S4 provides eight outlets so several printer directions can be planned; eight holes do not mean eight independent heaters or settings. Current store bundles may include different tube lengths, so verify the selected package instead of assuming every photographed accessory is included.

Make a cold feed-path test before the first drying or printing session. Pull a short length through each intended route and confirm that the reel turns freely, tubes do not cross moving printer axes, bends are not unusually sharp, and the dryer can remain in its required position with the lid and vents unobstructed. If routing creates resistance, correct the path rather than raising temperature or forcing the feeder.

Map the five controls and three indicator colors

The current one-page manual identifies ON/OFF as the run-or-stop control, M as the selector for Modes 1, 2, and 3, SET as the menu selector, and the up and down controls as parameter adjusters. Keep that page visible during the first session and confirm that the delivered screen and buttons behave the same way before saving a routine.

The same manual assigns yellow to drying operation, green to humidity-control operation, and red to an abnormal-temperature alarm. Treat red as a stop condition: end the run and consult SUNLU support for the exact unit and revision. Do not keep cycling the heater, disassemble the enclosure, bypass a protection, or transfer a fault-clearing sequence from another model.

Choose Mode 1, Mode 2, or Mode 3 by workflow

SUNLU labels Mode 1 as drying, Mode 2 as drying plus continuous constant temperature, and Mode 3 as humidity control. Use Mode 1 for a defined supported drying cycle. Use Mode 2 only when the current manual and your exact workflow call for its continuing temperature behavior; the label does not establish a universal storage cycle or an automatic transition that is not stated in the manual.

In Mode 3, the current product page says the user can select a 30–50% relative-humidity threshold: operation starts at the selected threshold and stops at 25%. That is a chamber-air control rule, not a direct measurement of water inside every layer of filament. It also does not turn the original S4 into the S4 Pro's two independently controlled chambers. Record the chosen mode so a later result can be compared meaningfully.

Treat presets and the shared 3–6-hour table as prompts

The original S4 accepts settings from 35°C through 70°C. Its manual also prints broad material-family temperature bands and a shared three-to-six-hour reference. Treat those rows as interface guidance, not a universal recipe. Modified, reinforced, and differently branded grades can require different paired conditions, and the carrier reel can impose a lower limit than the filament itself.

Start with the filament maker's current instruction for the exact product, including both temperature and duration, then verify that the S4 and loaded reel can follow it. Prusa's drying guide, for example, publishes named-product procedures and separate reel-generation limits rather than one rule for every polymer label. If a complete supported pair is unavailable or exceeds 70°C, stop and resolve it instead of choosing the nearest preset.

The S4 manual states an operating ambient range of 20–35°C and notes that below 10°C the unit may heat more slowly or fail to reach the set temperature, which it describes as normal. Do not compensate for a cold room by blocking airflow, insulating the appliance, modifying the enclosure, or increasing the filament setting. Move the equipment only as allowed by its instructions.

Start, monitor, record, and stop safely

Before pressing ON/OFF to run, record the model and manual revision, each loaded filament and reel, the outlet route, source for the material process, selected temperature, duration, mode, and room condition. During operation, confirm normal spool rotation and unobstructed airflow without opening or modifying the appliance. When a supported cycle ends, compare one repeatable print while keeping other variables stable.

Stop and contact SUNLU support when the red abnormal-temperature indicator appears, the screen or controls differ from the current manual, a spool or feed path jams, a fan or heater appears abnormal, or the unit cannot maintain the selected process in the documented operating environment. Do not open an electrical enclosure, remove a guard, drill an outlet, prop the lid, block a vent, add an internal fan, or improvise another heat source. Transfer unused prepared spools to suitable protected storage rather than assuming the chamber display proves that every winding will remain dry.