Wet filament is one of the most common causes of print problems that people don't diagnose correctly. If your prints are stringing more than usual, making popping or crackling sounds during extrusion, producing rough or bubbly surfaces, or if your PETG or Nylon just won't cooperate - moisture is the likely culprit.
A filament dryer fixes this. You put the spool in, set the temperature, leave it for a few hours, and the filament prints like new. It's one of those purchases that most 3D printer owners resist for months, then wonder why they didn't buy sooner.
I put off buying a dryer for about a year. In that time I blamed my printer, my settings, and three perfectly good spools of filament for problems that were actually just moisture. The dryer I eventually bought cost £30 and has probably saved five times that in wasted filament since.
You need a filament dryer if:
PLA is relatively tolerant of moisture and can often be stored in dry conditions without issues. PETG, Nylon, TPU, and PC absorb moisture quickly and noticeably - these materials genuinely need a dryer or very airtight storage.
Temperature range. Different materials need different drying temperatures. PLA: 40-45°C. PETG: 55-65°C. Nylon: 70-80°C. A dryer that only goes to 50°C won't properly dry Nylon. Check the max temperature before buying.
Capacity. Most dryers hold one spool. Some hold two. If you regularly switch between materials mid-print, a two-spool dryer is worth the extra cost.
Print-while-drying. Some dryers have a filament exit hole so you can print directly from the dryer, keeping the filament dry during a long print. This is genuinely useful for Nylon and TPU.
Timer and display. A programmable timer is convenient. A temperature display lets you verify it's actually reaching the set temperature - cheap dryers sometimes run cooler than advertised.
The S4 is the current top recommendation in most 3D printing communities and for good reason. It holds two spools simultaneously, reaches up to 70°C (covering PLA, PETG, and most TPU - Nylon needs the full 80°C so push it to max), has a clear display with temperature readout, and has a filament exit port for printing while drying.
Price is around £35-45 depending on the seller. For the features you get, it's excellent value. The build quality is solid and the temperature is accurate in my experience.
Best for: Most people. Two-spool capacity and print-while-drying make it the most versatile option at this price.
If you only need one spool at a time and want to spend less, the S1 Plus is around £25-30 and does the job well for PLA, PETG, and TPU. Max temperature is 70°C. It has a filament exit hole and a basic display.
The original S1 (without "Plus") has a lower max temperature and less accurate thermostat - worth paying the small premium for the S1 Plus over the original.
Best for: Budget buyers, beginners, anyone who mostly prints PLA and PETG.
Nylon needs 70-80°C to dry properly, and not every dryer reliably reaches that. The EIBOS reaches 70°C accurately and maintains it consistently, making it a reliable choice if you print Nylon or PC regularly.
It holds one spool, has a digital display and timer, and a filament exit port. Slightly more expensive than the Sunlu options at £40-50, but the accurate high-temperature performance is worth it if you're printing engineering materials.
Best for: Nylon, PC, or anyone who needs reliable high-temperature drying.
Polymaker's PolyDryer Box is the premium option - it's designed as a combined storage and drying box. You dry the filament, then keep it in the box with integrated humidity monitoring and desiccant, printing directly from the sealed box. This is the best solution for keeping filament dry both during and between prints.
More expensive (around £50-60) and holds one spool, but if you're using moisture-sensitive materials like Nylon or PC for functional parts, the combined storage-and-drying approach is genuinely better than a dryer and separate storage container.
Best for: Nylon, PC, any material where you want the best possible moisture control.
Yes - with caveats.
Food dehydrator: Works well. Temperature range is suitable for most materials. The main limitation is that the wire racks can leave marks on the filament surface, and you'll need to check that the spool fits. Some people have great results with this approach at £20-30 for a basic dehydrator.
Oven: Works, but with risk. Most kitchen ovens don't hold low temperatures accurately - 50°C on the dial might be 65°C inside, which can warp PLA spools. If you use an oven, use an oven thermometer to verify the actual temperature, keep the door slightly ajar for airflow, and stay below 45°C for PLA.
A dedicated filament dryer is more convenient, more accurate, and doesn't mean your oven smells faintly of plastic. For £25-35 the Sunlu S1 Plus is better than the oven option for most people.
| Material | Temperature | Time |
|---|---|---|
| PLA | 40-45°C | 4-6 hours |
| PETG | 55-65°C | 4-8 hours |
| TPU | 50-60°C | 4-6 hours |
| ABS/ASA | 60-70°C | 4-6 hours |
| Nylon | 70-80°C | 8-12 hours |
| PC | 70-80°C | 8-12 hours |
For severely wet filament (you can hear crackling when printing), dry at the higher end of the temperature range for the longer time. For maintenance drying (just keeping filament fresh), shorter times at the lower end are fine.
I use the Sunlu S4 for day-to-day printing - one spool for the current print, one pre-drying the next material. For anything in Nylon or PC I leave it in the EIBOS overnight before the print starts.
The biggest change was printing PETG directly from the dryer. I had constant stringing issues with PETG for months before realising moisture was a significant part of the problem. First print out of the dryer was noticeably cleaner. It doesn't fix everything - retraction and temperature still need to be right - but it removes one variable from a material that has too many variables already.
Buy the Sunlu S4 if you want the best value option that covers most situations. The S1 Plus if you're on a tight budget. If you print Nylon seriously, spend the extra on the EIBOS or PolyDryer. A filament dryer is one of those purchases where the only regret is not buying sooner.