SUNLU FilaDryer S4 Review: Auto Humidity Control Will Dry Your 3D Printing Tears

My son has a name for when 3D prints fail. One time is a fluke; twice is unfortunate, but if they fail more than twice, they become what he calls “cursed prints.” One of the main reasons a print can fail is if the filament is too wet from ambient humidity. So, I was extremely excited to test out the SUNLU FilaDryer S4. Did drier filaments and uncursed prints await us?

The sneaky thing about humidity and prints is that you may not realize the filament is too humid. Most people don’t have specialized tools to change the relative humidity of their home or their filaments. But even if you don’t think it’s too humid, it can make your prints TERRIBLE.

Humidity keeps the layers from coming in cleanly. It prevents proper adhesion, so you get weak prints that don’t hold together, stringing spots instead of clean edges, and even weird bubbles and other textural issues.

There are many DIY ways to dehydrate your filaments, from popping them in the oven to keeping them in sealed boxes with little silica packets. But if you really want to keep your filament in perfect condition, you need a filament dehydrator, and that’s what the SUNLU FilaDryer is for.

If you can 3D print it, the SUNLU FilaDryer S4 can dry it.

3D printing can go from simple to complex in a hurry, but the SUNLU FilaDryer S4 is pretty straightforward. It can hold up to 4 rolls of filament at a time, and you can program the parameters of what you want.

So you can tell the SUNLU FilaDryer S4 that you’re putting PLA in the dryer and ask it to dry it out for at least 4 hours and bring it to a set value between 30% and 50%. Then, you can just start it and go about your day.

Or, if you’ve already dehydrated the filament and you want it to stay perfect while you’re printing, you can use the provided TPU tubes to run the filament from inside the SUNLU FilaDryer S4 right into your 3D printer, with almost no chance for outside air to interfere and undo the dryer’s hard work.

The inside of the dryer has rollers to keep the filament moving, and the TPU tubes are smooth and easily accommodate the filament without anything getting jammed.

The only issue I ran into with running the filament directly from the SUNLU FilaDryer S4 to my printer was that it only really worked if I used the side closest to the printer.

That’s mostly because I have the dryer on one side of the printer; if you did them back to back, there’d be less stretching across the dryer and less of an issue with the motor having to tug the filament at an odd angle.

That was the only time I had any issues with printing directly from the dryer to the printer, though, and otherwise, I found it to be an efficient way to print. However, I should mention that the FilaDryer S4’s fans can be loud depending on where you place the device.

It also looks aesthetically a little cleaner since you don’t see big spools hanging out on top, just the tubes running between the machines.

I decided to give the SUNLU FilaDryer S4 a tough test. See, I have an almost full roll of Amazon Basics PETG filament, and the reason it’s practically full is because I’ve never gotten a successful print from it.

PETG is great when it works right, but it can be a finicky beast. It requires a higher starting temperature and ongoing nozzle temperature than PLA and is notorious for being super sensitive to humidity.

When I bought this roll, I mistakenly trusted Amazon Basics over a more established brand, but if anything could make it usable, it was the SUNLU FilaDryer S4!

The Titanic of benchys.

It should be illegal to write about a 3D printer, even tangentially, without including a benchy, so I made one with the cursed PETG before it went into the SUNLU FilaDryer S4. As you can see, that benchy was a disaster.

The bottom got stuck to the print bed, the little smokestack on top just yeeted itself off the rest of the benchy out of embarrassment, and the whole thing was very creaky and definitely not seaworthy.

It’s not perfect, but there’s definitely an enormous improvement!

I popped the roll of filament into the SUNLU FilaDryer S4 and left it there overnight. I printed the same benchy with the newly dried filament the next day.

The second benchy isn’t 100% perfect; there are a few stringy spots and some bubbling along the hull, but the difference is NIGHT AND DAY compared to the prior benchy.

Again, this filament was not the best quality from the start, but the SUNLU FilaDryer S4 took it from disaster to usable, which honestly feels like a miracle after I had almost completely given up on it.

SUNLU was also kind enough to send us several of their filaments as part of the kit. Their PLA is top-notch and creates excellent prints right out of the box and after a trip through the FilaDryer S4.

I’ve used SUNLU’s filaments in the past, and they’re always consistently great. My son was especially delighted because we received both red and white filament, so we immediately had to get to work printing Pokeballs!

3D printing is a fantastic hobby, and like all hobbies, the tools you use help shape your experience. If you’re doing any serious 3D printing, the SUNLU FilaDryer S4 should be on your radar. Its price is more than reasonable, considering how it can save a roll of otherwise unusable filament.

Think of it this way: a roll of decent PLA costs between $20-30, so for the cost of 5-7 rolls of filament, you have a tool that will let you use every last bit of the rolls you have. It’s a no-brainer to save money and frustration! Now, if it could only solve nozzle clogs at the same time…

The SUNLU FilaDryer S4 retails for $159.99; it is available directly from the manufacturer and other retailers, including Amazon.

Source: Manufacturer provided review sample

What I Liked: It is easy to set up; You can leave filament inside and feed it right to the printer; It can resurrect even the most hopeless of filaments; It’s an affordable way to keep supplies in good shape

What Needs Improvement: The fans can be loud depending on where you place the device