3D Filament Drying: Proper Drying Practices Make Perfect 3D Printed Parts

Water. It’s the foundation of all life on earth, but it’s a killer when it comes to the quality and consistency of 3D printed parts. The moisture content in thermoplastic extrusion materials used by 3D printers needs to be properly controlled during filament manufacture, storage, and when printing to achieve best results. Improper handling at any point in the production cycle can result in both visible and invisible defects in raw materials and the finished part.

Moisture can affect the tensile strength of 3D printed parts in several ways. If a spool of filament contains a high moisture content it can affect the melt viscosity of the polymer, leading to inconsistent extrusion and excessive stringing. When the material is heated, trace water molecules trapped inside the filament rapidly expand to form millions of microscopic bubbles inside each layer. These bubbles not only produce a poor surface finish, but also become internal voids that weaken the structure, leading to premature failure in finished parts. Some adverse changes to 3D printing materials are invisible under normal inspection. For example, many polymers heated with excess absorbed moisture change on a molecular level to be more brittle, reducing impact resistance. Before and after printing, materials absorb moisture from the surrounding air if left in ambient conditions. The effects can vary depending upon location — filaments will absorb more moisture in humid areas like Florida than in dry climates like Arizona, for example, affecting consistency.

Complicating matters further, the proper level of moisture content and upper temperature limit for drying vary by the type of material, and it is possible to over-dry thermoplastics to the point of negatively influencing its final properties. Heat is applied using several different methods to drive moisture out of spools before printing. This is typically accomplished in one of three ways: hot air drying, desiccant air drying, or vacuum drying. The chosen method is a function of the materials used, the temperature that must be achieved, the size of the spool, and customer preference for size, energy efficiency, and budget in a drying solution. All methods share one commonality: heat with a mechanism to remove moist air from an enclosed oven-type structure. But too much heat can result in an unusable solid donut of filament, or worse, can damage the material without any visible sign of degradation.

Therefore, it is very important to dry each polymer at the appropriate time and temperature recommended by the manufacturer. This is even more critical in today’s open platform environment in which users can purchase and print using any filament they choose. An end-to-end materials handling process that minimizes exposure to moisture is the best way to maintain quality. Here are a few best practices endorsed by our materials scientists at Essentium:

• New spools of material received from a manufacturer should arrive in vacuum-sealed packaging with a desiccant pouch inside to scavenge residual moisture not removed by the vacuum sealer. (If materials arrive in non-vacuum-sealed packaging, it will most certainly be wet and will require drying prior to use).
• Keep filament spools vacuum-sealed until needed for use. Immediately load the spool into a sealed dry canister to feed filament into the printer. If using more than one type of filament, swap materials between the dry feeding canister and the dry storage container as quickly as possible.
• Open vacuum-sealed spools in an environment with near-equal temperature and humidity in which it will be used to avoid condensation forming on the filament.
• Store vacuum-sealed filament spools in an off-line dry container. Essentium recommends its DryBox™ filament storage solution (pictured). This digitally-controlled cabinet has a humidity recovery time of less than 5 minutes after the door is closed and maintains a relative humidity level of under 1% for the proper, long-lasting storage of filament spools.
• If the filament appears wet or damp upon opening, re-dry the filament before using.
• Ovens with programmable time and temperature settings are preferable so that material is dried precisely the same way from batch to batch.
• Once a material is dry, it should be quickly transferred to the dry canister for feeding into the printer, or placed in an appropriate dry holding container (like the Essentium DryBox) for later use.
• Drying temperatures for high performance materials such as high temperature nylon are usually significantly higher than PTCG and PLA, up to 130°C. Make sure these materials arrive on PC/ABS, PC, or metal spools that can withstand higher temperatures.
• For the highest degree of quality control, routinely test the moisture content of a spool of filament with a loss of mass (LOM), moisture-specific, or Karl Fisher titration moisture analyzer.

Taking these steps at a minimum will help to create an environment that keeps materials dry, extends shelf life, and yields more consistent prints with better part quality. To learn more about how the Essentium HSE 180•S 3D printer and DryBox filament storage cabinet can maximize your investment in materials and deliver better results check out our industrial-grade materials.

Essentium, Inc. provides industrial 3D printing solutions that are disrupting traditional manufacturing processes by bringing product strength and production speed together, at scale, with an open ecosystem and material set. Essentium manufactures and delivers innovative industrial 3D printers and materials enabling the world’s top manufacturers to bridge the gap between 3D printing and machining to embrace the future of additive manufacturing.