There are over a dozen kinds of filament for 3D printing, from the most common ABA (Acrylonitrile Butadiene Styrene) and PLA (Polycystic Acid) filament to nylon, wood, metal, and even carbon fiber and glow-in-the dark options. These different products, and the range of available colors, equips makers to make a broad and growing range of parts and products. Makers increasingly move quickly between colors, products, and projects. Can you leave filament in a 3D printer?
Filament can be left in a 3D printer between uses, but doing so increases the risk of degrading that filament and undermining your projects. Filament that is not stored properly is exposed to moisture. That moisture will degrade the filament, weaken and mar your printed product, and interfere with the smooth operation of your 3D printer.
The best practice in 3D printing is to store your filament properly to preserve its performance and integrity, and the quality of the projects you’ll produce. We’ll break down the downside of failing to store your filament properly, and recommend some strategies for preserving filament without leaving it in your 3D printer.
Can you leave filament in a 3D printer?
Many makers who print with their 3D printers daily will leave filament in the extruder between printing sessions. Leaving filament in a properly maintained and operated 3D printer is not itself harmful to the printer. However, it means that the filament itself is left exposed to less than optimal conditions.
Filament that is left in the 3D printer and thus not stored properly is unnecessarily exposed to moisture. You may not expect that plastic materials would absorb moisture, but 3D printing thermoplastics — some more so than others — are hygroscopic, meaning that they will absorb moisture directly from the air if left exposed.
How does moisture and humidity affect filament?
Filament that is left exposed to moisture and humidity rather than being stored properly will experiencing the following impacts:
- It will become more brittle than usual prior to being heated
- It will degrade
- It will swell, i.e. its diameter will increase
- It will bubble and hiss steam at the hot end during printing
- It will require higher temperatures during extrusion
- It will break more easily during printing
There are several signs of excessive moisture in your filament while you’re printing, including: a popping sound during printing; obvious bubbles on the surface of your prints; excessive stringing; and clogged extruders. Each of those symptoms of excessive moisture in your filament because it was left in your printer rather than being stored has the capacity to undermine your project and bring a halt to your progress.
Technically, here’s what’s happening when your filament absorbs too much moisture because it wasn’t stored properly. The absorbed water vaporizes, leaving behind air bubbles in or on the filament. Those bubbles have the potential to break the polymer threads formed by your melted and printed filament strands. Rather than printing continuous chains of polymer material, you’re printing broken fragments. Your printed object ends up weaker and sprinkled with potential voids because fractured from those broken fragments. Layers will not adhere properly to successive layers, and the final surface layer will be marred by defects.
You can avoid these problems by storing your filament properly, including by not leaving it in your printer for prolonged periods when not in use. In this regard, not all filaments are created equal. Filament will always be better off stored properly rather than left in your printer for anything but the shortest periods, but this is more important for some filaments than others.
For example, one significant downside of the ubiquitous PLA filament is that it attracts moisture that can make it more brittle and make printing more difficult. Nylon filament is also a particularly good — or is it bad? —absorber of moisture, making it important to store it properly rather than letting it absorb moisture while exposed to the air or left in your printer. On the other hand, PolyEthylene Terephthalate (PET) filament is less likely to absorb moisture from the air.
How to properly store filament rather than leaving it in your printer
Do not “store” filament in your 3D printer by leaving it there between printing sessions, unless the interruption in your printing sessions is going to be very short. The longer that you leave your filament improperly stored and exposed to moisture and humidity, the greater the risk of damage to your filament, printer, and product. Here are four options for properly storing filament.
Filaments can safely be stored in vacuum-seal plastic bags. Not Zip-Loc freezer bags or the like, but storage bags with a built-in aperture for your vacuum cleaner’s nozzle to suck out air, moisture, and contaminants that might undermine your filament.
Sacs of silica gel
You’ve seen small sacs of silica beads in many purchases — shoes, bags, etc. Some filament products include bags of silica gel. Those beads of silica absorb moisture so the filament or other items won’t. When storing filament in ZipLoc bags, plastic containers, Tupperware or similar containers, place sacs of silica bags inside those containers. Purchase sacs of silica gel that indicate when they themselves are saturated and no longer effective. You can purchase silica gel for these purposes on Amazon. Silica gel is important when storing any filament, but especially important when storing PLA which absorbs much more moisture than ABS filament. It’ll also be much safer than simply storing your filament by leaving it in your printer for more than brief periods.
Build a “Dry Box”
A Dry Box can preserve filament from moisture and humidity, conveniently store spools of filament, and even dispense filament to your 3D printer. There are plans available online for building a Dry Box, including this design from Instructables.
If you operate your 3D printer and store your filament and materials in a compact and confined space, consider investing in a dehumidifier appropriate for the size of the space, and using it when humidity is at its highest. Reducing humidity in the space will preserve your product and prevent the degradation of your materials.
How to dry filament
Filament that has absorbed moisture because improperly stored can be dried and sometimes restored to its best performing condition, but not simply by properly storing it again. Storing filament that has absorbed excess moisture in the best airtight container with the best desiccants will not dry out that filament. Active drying strategies are required. How can you dry filament?
You can dry filament by baking it in an oven, while being careful not to overheat it and to produce toxic fumes. Doing this in food preparation areas is not recommended, but possible. Because they work by the constant circulation of air, convection ovens are a better option than a conventional oven. When using an oven to dry filament, be sure to preheat the oven to 160 to 180 degrees F before placing the spool of filament in the oven for four to six hours. Afterwards, store the newly dried filament in an appropriate airtight container with desiccant. You can also dry filament using a machine called the PrintDry, from which you can also feed dried filament directly to your 3D printer without storing it in any different storage device. The system comes with options for storing dried filament outside the PrintDry dryer as well.