Buy a heated dryer with circulating air and venting when PETG, TPU, nylon, or idle multi-color spools keep picking up moisture. Skip a dryer when sealed PLA still prints clean. Skip a sealed warmer with no exhaust, and skip vacuum-only storage when the spool still needs heat to move water out of the core.
Heat, circulating air, and venting
Hygroscopic filament takes on water from room air. In a hot nozzle that water flashes to steam. The usual signs are stringing, surface pockmarks, popping, and weaker layer bonds. Moisture is one cause; confirm the PETG, TPU, or ASA profile before blaming storage.
A dryer has three jobs. Heat drives moisture from the filament core toward the surface. Circulating air reduces hot spots. Venting or active exhaust carries vapor out of the chamber. Without airflow and a way out, a heated box becomes a sauna: water leaves the spool and sits in the air until it condenses back.
Vacuum without heat mainly affects surface moisture. CNC Kitchen’s mass tests showed a vacuum chamber plateauing while a heated dehydrator with circulating air dried faster. FilamentSetup has not repeated those measurements and does not publish recovery curves.
Stay below the spool’s heat limit and use the filament maker’s drying temperature. Creality warns that high-temperature drying must consider spool heat resistance. Polymaker notes PolyDryer temperature varies around the spool; its published peak range is 68–73°C, not a single setpoint.
Which dryer fits the job?
Choose by spool count, whether you need sealed storage after the cycle, and whether the unit can reach the temperature your filament maker specifies. There is no ranked winner on this page.
| Your job | Start with | Skip when |
|---|---|---|
| Several 1 kg spools, mixed materials | Space Pi X4 or SUNLU S4 | You only dry one roll now and then. |
| Dry, then keep the same spool sealed | PolyDryer complete system | You only need the dock, or you need 3 kg in the original box. |
| Bambu AMS lid upgrade | EIBOS Tetras, official store | You do not have AMS 1 or AMS 2 Pro. |
| One budget spool | SUNLU S2 or Space Pi | You need 85°C engineering temps or 3 kg spools. |
| 3 kg spools | EIBOS Polyphemus | Your spools already fit a 1 kg dryer and you do not need rotation. |
Check current seller, variant, and price on the retailer page. Some links are affiliate links, which may earn us a commission at no extra cost to you. How we assess products.
Compare dryers for the job
Several spools at once
Use a four-spool unit when you keep PETG, TPU, or nylon on deck for multi-color or several printers. The Space Pi X4 is the one in this set whose manufacturer page lists 85°C. The S4 is the high-volume 70°C box.
Four-spool dryer
Creality Space Pi X4 Filament Dryer, four-spool, dual chamber
View on AmazonFour-spool dryer
SUNLU FilaDryer S4, four-spool
View on AmazonCreality’s Space Pi X4 page specifies dual independent chambers, active dehumidification, and spool diameter ≤200 mm / width ≤150 mm. SUNLU’s S4 page lists 70°C, circulating fans, and humidity-control cycling; the same page says 350 W PTC in prose and 300 W rated power. Confirm the selected Amazon child against the generation you want. FilamentSetup has not measured chamber uniformity or dry-down time.
Dry, then store
Use PolyDryer when the job is dry-then-keep-sealed, not an always-on sauna. The complete system is the dock plus a gasketed box. The dock-only accessory is a different listing; do not buy it as a first dryer.
Polymaker’s PolyDryer wiki describes modular sealed boxes, three power levels, and a separate XL box for 3 kg spools. Confirm the Amazon bundle includes the box, not only the dock. Do not treat hygrometer RH as a measured moisture content.
Bambu AMS lid upgrade
Tetras replaces the AMS lid with four independently controlled chambers. EIBOS sells it from its store, not as a FilamentSetup Amazon ASIN. It is an AMS add-on, not a standalone dryer for a printer without AMS.
AMS dryer lid
EIBOS Tetras AMS dryer, four chambers
View at EIBOSEIBOS states Tetras/Dyas fit Bambu Lab AMS 1 and AMS 2 Pro, with a self-printed adapter required for AMS 2 Pro. Temperature is capped at 65°C to protect the AMS chassis. Ordinary TPU 95A still does not belong in AMS lite; Tetras does not change that feeder rule.
One budget spool
Use a single-spool 70°C box when you dry one roll at a time. These are print-through dryers first. They are not a substitute for a gasketed storage box after you power them down.
Single-spool dryer
SUNLU FilaDryer S2, single-spool
View on AmazonSingle-spool dryer
Creality Space Pi Filament Dryer, single-spool
View on AmazonSUNLU’s S2 page lists 70°C and 48 W. Creality’s Space Pi page lists 45–70°C. Third-party reviews report the single Space Pi as a print-through unit rather than long-term sealed storage. We have not measured reabsorption after power-off. Do not use those 70°C ceilings as a nylon/PA-CF recovery promise.
3 kg spools
Polyphemus is the 3 kg path in this catalog because of its rotating spool and optional expansion parts. Confirm the Amazon listing includes the 3 kg kit if that is why you are buying it.
Large-spool dryer
EIBOS Polyphemus filament dryer, rotary
View on AmazonEIBOS’s Polyphemus page lists 130 W, adjustable exhaust, a rotating motor, and 3 kg capacity after expansion parts that grow the opening to about ø250 × 170 mm. Bundle contents on Amazon are unknown until you check the selected variant. FilamentSetup has not measured hot-spot reduction from rotation.
| Check | What the maker states | Unknown here |
|---|---|---|
| Space Pi X4 | Four spools, 45–85°C, dual chambers, 360 W rated. | Whether the live Amazon child matches this generation. |
| SUNLU S4 | Four 1 kg spools, 70°C, humidity-control mode. | Which wattage figure (300 W rated vs 350 W PTC copy) applies to the listing. |
| PolyDryer | 68 W dock, 68–73°C peak range, sealed box, 1 kg original box. | Dock-only vs complete-system bundle on the selected child. |
| Tetras | Four 60 W chambers, 20–65°C, AMS 1 / AMS 2 Pro. | Hands-on dry-down time for nylon. No Amazon ASIN on this page. |
| S2 / Space Pi | Single spool, 70°C class, circulating / PTC air. | Sealed-storage performance after power-off. |
| Polyphemus | 130 W, 30–80°C, rotation, 3 kg with expansion kit. | Whether the Amazon SKU includes that kit. |
Check the selected variant, seller, and price on Amazon before ordering. Some links are affiliate links, which may earn us a commission at no extra cost to you. Tetras is linked to EIBOS, not Amazon. How we assess products.
Before you buy a dryer
Confirm the filament maker’s drying temperature, the spool diameter and width, and whether you need storage after the cycle. Then pick the job row above. A lower price is not evidence of even heat or a working exhaust path.
- Match max temperature to the material: PLA/PETG often sit in the 50–60°C band on manufacturer charts; nylon and some PA-CF lines ask for higher heat. Use the spool instructions.
- Measure spool outer diameter and width against the dryer spec. 1 kg mass is not a size.
- Decide print-through vs sealed storage. A unit without a gasket still dries while powered; it is not a dry box once it is off.
- For AMS, confirm the exact AMS model. Tetras is not an AMS lite lid.
- For 3 kg, confirm expansion parts are in the bundle you are buying.
Related material decisions
Drying does not replace a matching print profile. Solve stringing on PETG in order: profile, dryness, temperature, then retraction. Keep TPU dry and on a guided feed path. Plan enclosure and ventilation for ASA before you add a dryer. PLA often only needs sealed storage unless the spool is already noisy or brittle.