Avoiding Failures With Your 3D Prints - Drying Your 3D Printer Filament

How to Re-Dry Your 3D Printer Filament

PLA and PETG filaments are the go-to filaments for many 3D printing enthusiasts because they are easy to use, print well, and are pretty forgiving when it comes to your 3D printer settings. If you’re new to 3D printing, or if you’ve never had it explained to you, you’ll need to know that both PLA and PETG (and some other materials like Nylons and water solubles) are hygroscopic (they absorb moisture from the air). 

Different filaments absorb moisture at different rates, but there are a few common signs that you’ve got a wet spool:

• Popping/cracking sounds when extruding
• Severely reduced part strength and layer adhesion
• Uneven extrusion lines
• Uncharacteristically severe stringing, blobbing, or oozing
• Uncharacteristically textured or “fuzzy” surfaces on prints

When filament gets “wet” (the term we use to describe when 3D printer filament has absorbed too much moisture), it changes the normal characteristics of the filament to almost the opposite of what you would expect. Normally, you’d expect something with moisture in it to get soggy or soft. But with PLA, for example, the opposite is true. It gets brittle, almost like it is too dry. 

Additionally, wet filament can even cause pops and splatters as it prints. It’s not always that obvious, but you may hear popping sounds as the moisture in the filament gets hot in the extruder’s print head and the moisture in the filament turns into steam and expands. This bubbling can even appear in your prints and cause surface blemishes and weaken your 3D printed part.

The image below shows what wet PETG looks like when printed vs a dried product. Notice the rough texture of the "wet" filament vs the smoother surface of the dry filament when printed.

Another obvious result you’ll see is the filament breaking, sometimes before you even get it started in your printer or in the bowden tube. 

Many users are confused by this and feel they have a “bad” spool of filament, or that it has “expired” due to age. Some even worry about filament they receive having a production date on it because they are concerned about it “going out of date.” 

In reality, PLA or PETG filament should never expire or go out of date. It may, however, need to be dried in order to perform at peak levels.

A new user may receive their first PLA and open it from that pristine, vacuum sealed bag and print with it, then place it on a shelf or with a few others on an overhead filament storage system and leave it out in the open. Then, when they try to print with it again, they are surprised that it’s brittle. They may assume that they purchased bad filament. While it is possible that the filament is bad (especially if it’s a no-name brand) the more likely scenario is that the filament has absorbed too much moisture. 

So, what do you do about wet filament?

The obvious answer is that you dry it out. But how do you do that? There are a few ways to do this and we’ll discuss some of them here for you. These include industrial drying systems, small drying systems, homemade drying systems and even (if you’re extremely careful) your oven!

Which Type Do I Need?

If you are a production house and run a 3D printer farm, you may not even need a dryer because you generally open a spool and print until it’s gone, then open the next one. But you may have partial spools left over that you re-use and it would be nice to be able to dry them. 

If you’re like most 3d printer enthusiasts, you probably print a job or two from a spool, then change colors for the next job. This makes you a prime candidate for a drying system of some sort. 

Professional Dry Boxes

If you do a lot of printing, you may want to invest in a professional type drying box that can not only dry your filament, but keep it dry while you print from it. These range in price from about $150 to $400 or more depending on size and complexity of the dryer. Here are couple of photos to give you an idea of what these look like:

              

As you can see, these allow you to place multiple spools in the dryer and keep them in optimum condition even while you print. These are a great option… if money is not an issue. But for most hobbyists, these are a little steep in price. 

Single Spool Dry Boxes

The next option would be a dry box for a single spool at a time. These are great for storing your filament and for printing while using them. They generally hold only one spool of filament and are a little less expensive than the more professionally produced units. They range in price from about $40 for a passive system (uses reusable desiccant bags) to about $100 for the higher priced electric heated versions. Stacker3D has just released a nice passive unit that will even mount on your printer at $39.99.

            

     Stacker's F-BOX
     (Filament Dry Box)

Homemade Filament Dryers

You can also make your own electric/heated dryer by modifying either a yogurt maker or a food dehydrator to hold your filament spools. They have a temperature range that is suitable for drying filament and in general, you can’t over heat the filament. Here are a couple of examples of the types of products you can buy for $30-$75 to convert to filament driers:

    

With a food dehydrator you can remove the shelves and cut the middle part out. Depending on the unit, you can fit up to a 12” spool (4kg) in the dehydration unit and leave it for 2-4 hours. You can even leave it running overnight and should have no problems using the filament. The one on the left is a yogurt maker and you can simply remove the jars and holder and it holds a 1kg spool easily. 

Filament Drying with NO Budget

Of course, there is a final alternative for you. If you don’t want to, or can’t afford to, spend the money (though it’s probably worth it to have great prints and no lost filament), you can dry your filament in a conventional oven. 

The key is to make sure you don’t use too high a temperature. Most ovens today have digital settings. We have one that starts at 300°F when I turn it on, but I can reduce the temperature to something more appropriate. The biggest thing to keep in mind is that with full size ovens it can be difficult to precisely control the temperature. A toaster oven may be easier to control. Please use the temperatures outline below as guidelines. Just place the spool of filament on a clean baking sheet (to avoid any leftover pizza grease, etc.) on the middle rack and set the oven and leave it for an hour or two. 

• PLA - 40-45C (104-113F)
• PETG - 80-90C (176-194F)
• Water solubles - 40C (104F)

General Storage Recommendations

Even if you dry your filament, we recommend that you store your filament in resealable bags with desiccant. 3D-Fuel filament comes with a desiccant pack that can be placed in the bag with your filament when you finish printing. To provide your filament with even better storage life, re-dry your desiccant bags along with the filament. You can store the average 1kg spool of filament in a ziplock gallon bag, approximately 10 9/16” x 10 ¾”. So any zip top bag that size or larger should work fine. But watch for punctures in the bags. Getting a freezer bag that is a little thicker will help avoid the formation of holes that can allow moisture to seep through. 

Summary

Keeping your filament dry and in great condition will provide you with great printing experiences and help you get the most out of every spool of filament you buy. Don’t allow yourself to lose out on filament just because it gets wet. It’s one of the best lessons you can learn as a new 3D printer user, or even if you’ve been 3D printing for years.