Filament Drying
Filament dryer cabinets and four-spool units
When the problem is eight spools rather than one, capacity matters more than any other specification. That changes what you should buy.
By Michael W. · Published October 5, 2026
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When capacity is the right thing to buy
When you print multi-color. Drying one spool while three sit reabsorbing moisture is close to pointless on a four-color job. You need the set dry together.
When you run more than one printer. Two machines consume spools faster than a single-spool dryer can cycle them.
When the problem is "I have eight spools and half are damp." That is a throughput problem, and a hotter single-spool dryer does not solve it.
Not when the problem is nylon or polycarbonate. Then the ceiling is the constraint, and a bigger standard-temperature box is the wrong purchase.
What a large unit costs you day to day
Long cycles
Four spools is four times the thermal mass. The unit takes considerably longer to reach temperature and considerably longer to drive moisture out of the whole load. In practice four-spool drying is an overnight activity, not something you do between two prints.
That is not a fault, it is physics, and it changes how you use the thing: you run it on a schedule rather than reactively.
Space
Four-spool dryers are physically large and they want to live next to the printer, which is already the most contested shelf in the room. Measure before ordering — this is the most common regret with capacity purchases.
Running cost if you leave it on
An infinite timer is genuinely useful and it is also a continuous power draw. A sealed box with desiccant maintains dryness at zero running cost. The sensible division of labor: heat to dry, seal to store.
The hybrid that is usually cheapest
One good dryer plus several cheap airtight containers with rechargeable desiccant. You dry a set when needed, then store everything sealed. This beats a large cabinet on cost and often on total space, because stacked tubs are denser than a cabinet with air gaps.
Put a cheap hygrometer in each tub. Desiccant saturates silently, and the whole system is only as good as the desiccant in it. Dryer boxes and sealed storage.
If you own an enclosed Bambu machine
Price an AMS 2 Pro before a four-spool cabinet. It holds four spools, dries them actively, and feeds the printer from inside the sealed box — which closes the reabsorption gap a cabinet leaves open. It also does four-color printing, which a cabinet does not.
It costs more and it does more. If you were going to buy both a dryer and multi-color capability, it is one purchase instead of two.
Where to go next
The full roundup for picks by temperature and capacity. Printing while drying for the reabsorption problem. Whether you need one at all.
What to buy
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1. Best four-spool unit
SUNLU FilaDryer S4
Cited as best for multi-color and multiple printers, drying the whole set together.
Four spools at once, cited as best for multi-color and for owners running more than one printer. For a four-color workflow this is the capacity that matches reality rather than the brochure.
Cheapest per spool of anything in the category. Two costs: a large footprint, and long cycles because four spools of thermal mass heat slowly.
What it gets right
- Four spools at once is the only capacity that matches a four-color workflow
- Dries the whole set you are about to print with, rather than one spool at a time while three re-absorb
- Cheaper per spool than any single-spool dryer
What it does not
- It is a big box; four-spool dryers need shelf space you may not have next to the printer
- Standard-temperature drying is not enough for nylon or PC — that needs a high-temp unit
- Four spools heat more slowly than one, so cycles are long
| Capacity | Four spools |
|---|---|
| Positioning (cited) | Best for multi-color and multiple printers |
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2. Best for permanent dry storage
EIBOS Cyclopes
Four spools, a 100 W PTC heater and an infinite timer, so it can stay on as storage.
Four spools with a cited 100 W PTC heater and an infinite timer. The timer is what sets it apart: the unit can act as ongoing dry storage rather than a cycle appliance.
Direct competitor to the S4 at comparable capacity, so price both. A 100 W heater is efficient for the volume, and running any heated unit indefinitely is still a continuous power draw a sealed box does not have.
What it gets right
- An infinite timer means the unit can simply stay on as dry storage, not just run a cycle
- Four spools at a 100 W PTC heater is efficient for the volume it holds
- Direct competitor to the SUNLU S4 at a similar capacity, so shop both
What it does not
- Running a dryer continuously as storage costs power — consider a sealed box with desiccant for long-term storage instead
- Standard-temperature class, so nylon and PC are not its job
- Four-spool footprint again: measure the shelf first
| Capacity | Four spools |
|---|---|
| Heater (cited) | 100 W PTC |
| Timer (cited) | Infinite |
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3. Best if capacity is not the real problem
SUNLU E2 FilaDryer
A cited 35-110 C range, which no amount of four-spool capacity substitutes for.
Included here as the honest counterpoint. If your spools are nylon or polycarbonate, no four-spool standard-temperature cabinet solves your problem, because the ceiling is the constraint rather than the capacity.
A cited 35-110 C range with a 500 W PTC heater, named for PA6-CF, PA12-CF, PC, ABS and ASA, with annealing as a second use.
What it gets right
- 110 C is the first number on this page that is genuinely enough for nylon and PC
- A 500 W PTC heater gets to temperature fast instead of creeping there over an hour
- Doubles as an annealing oven, which is a second real use rather than a marketing bullet
What it does not
- Overkill and over-priced if PLA and PETG are all you print
- A 500 W heater is not a quiet, low-draw appliance
- Annealing shrinks and distorts parts — it is a technique to learn, not a button to press
| Temperature range (cited) | 35-110 C |
|---|---|
| Heater (cited) | 500 W PTC |
| Second function | Annealing as well as drying |
| Materials cited | PA6-CF, PA12-CF, PC, ABS, ASA |
Questions people actually ask
Do I need a four-spool filament dryer?
If you print multi-color or run more than one printer, yes - drying one spool while three others reabsorb moisture does not match a four-color workflow. If you print one material at a time, a single-spool unit is cheaper, smaller and heats faster.
How long does a four-spool dryer take?
Longer than a single-spool unit, because four spools is four times the thermal mass. We do not publish cycle times because measuring them needs a controlled rig this site does not have. Practically, treat four-spool drying as an overnight activity run on a schedule rather than something reactive.
Is a dryer cabinet better than sealed boxes?
Different jobs. A cabinet dries; sealed boxes keep filament dry at no running cost. The cheapest effective setup for most workshops is one good dryer plus several airtight containers with rechargeable desiccant, which usually beats a large cabinet on both cost and total space.
Will a bigger dryer help with nylon?
No. Nylon and polycarbonate are limited by temperature, not capacity - they need a unit reaching around 110 C, and a four-spool standard-temperature cabinet cannot get there regardless of size.
Should I leave a four-spool dryer running all the time?
You can if it has an infinite timer, and it works. It also draws power continuously, where a sealed box with desiccant maintains dryness for nothing. Heat to dry, seal to store is the cheaper division of labor.
Sources
Read this next
- The best filament dryers in 2026Dryer picks split by temperature range and capacity, because a 70 C unit and a 110 C unit are different products for different materials.
- Filament dryer boxesHow per-spool sealed boxes differ from four-spool dryers, the humidity figure that matters, and where the modular approach stops scaling.
- Printing while dryingWhat the reabsorption gap costs per material, which units let you print from them, and when closing the gap is worth paying for.
- Bambu Lab AMS 2 ProWhy active drying makes the AMS 2 Pro a different product from the original AMS, and the case for buying it instead of a new printer.
- Is a filament dryer worth it?Who a dryer genuinely pays for, who should buy sealed storage instead, and the free test that settles it before you spend.