There is a quiet failure mode that affects more industrial FDM work than anyone admits: wet filament. Engineering thermoplastics, particularly the nylons (PA6, PA12, PA-CF and PA-GF), TPU, PETG and to a lesser extent ABS and ASA, all absorb moisture from atmospheric humidity. Once a spool has sat in open Perth air for a few weeks, the material has changed in ways the print process cannot fully recover.
Wet filament prints with foaming, voids, poor interlayer adhesion and dramatically reduced mechanical properties. A bracket that should hold 130 MPa might hold 80 MPa, with no obvious external sign that anything is wrong. Moisture control is therefore one of the most consequential aspects of industrial FDM printing.
Why filament absorbs moisture
Most engineering thermoplastics are polar polymers, with molecular features that attract water. Nylons are particularly aggressive moisture absorbers, picking up 3 to 8 percent by weight from saturated atmosphere over a few days. When that moisture laden filament is melted at the nozzle, the water flashes to steam, creating bubbles, voids and disrupted polymer flow.
The resulting part has compromised structure that no post processing can fully recover. The strength loss is permanent for that print. The only fix is to dry the spool, retune the slicer and try again, which is why catching wet filament early matters so much for production schedules.
How to tell if filament is wet
Surface roughness on overhangs and travel zones
Excessive stringing between print features
Audible hissing or popping during extrusion
Cloudy or matte appearance on PETG and ABS
Mass loss greater than 0.5 percent after thorough drying
A working moisture control protocol
Specify the material with traceability. Source from a known supplier with batch records. The OzFDM engineering range is one example designed for this kind of use.
Inspect the spool on receipt. Weigh it, check the vacuum seal, and log batch number and date of arrival against the production plan.
Dry before first use if storage history is unknown. Typical guidance is 4 to 8 hours at 70 to 80 degrees Celsius for nylons, and 4 to 6 hours at 65 degrees Celsius for PETG and TPU.
Store working stock in sealed containers with desiccant. Use silica gel or molecular sieve with a humidity indicator to flag when the desiccant needs regeneration.
Mount in a heated dry box for printing. Long jobs over 24 hours absorb moisture mid print without active drying, so keep the dry box on for the duration of the build.
Return unused material to sealed storage at job end. Spool exposure between jobs is the single most common entry point for moisture in a busy production cell.
Weigh, do not guess
A 1 to 2 percent mass loss after drying tells you the spool was meaningfully wet.
Keep a simple log of pre and post drying mass against batch number to build evidence over time.
Why it matters for industrial work
For sustained production work, in print drying boxes that hold the spool at moderate temperature prevent re absorption mid job. Long prints are particularly susceptible to mid job moisture absorption without active drying. The cost of an in print dry box is trivial against the cost of a recalled or rejected production part.
Industrial workflows integrate drying into the production loop rather than treating it as a workshop nicety. Specify it on the drawing, log it on the build sheet, and audit it like any other process control. The customer never sees the dry box, but they always feel its absence in the final part.
Global3D runs full moisture control as standard on engineering thermoplastic work. Send your CAD package and we will quote the production ready outcome.