What happens moistured filament used?

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What happens moistured filament used?

Almost 3D printing filament takes moisture from the atmosphere. It is well known moisture affects 3D printing, but little is known about what happens when filament is moistured. When moistured filament is used, three things occur mainly. (1) Foaming, (2) Resin melt chenge, and (3) Hydrolysis.

(1) Foaming

When moistured filament melt, water inside expands at once and becomes bubbles. Bubbles are generated in the highly viscous molten resin, it will not disappear after print immediately. As it is, it will be printed with bubbles mixed.

Bed adhesion decreases

Image is raft printed with a moistured filament. You can see many crater-shaped bubbles. These bubbles are generated not only on the surface that is visible, but also on the surface that is in contact with the bed. Therefore, even if it looks well contacted, if there are bubbles, the actual contact area will be reduced. Since the adhesion of the bed decreases, problems such as peeling and warping of the prints are likely to occur.

Damp filament - Source:solidoodletips.wordpress.com

Interlayer adhesion decreases

Bubbles are generated not only in the first layer but also upperlayer. Resin does not filled the area where bubbles are formed, so interlayer adhesion will be reduced. The appearance of the prints will also becomes worse.

Moisture in new printer filament - Source:thrinter.com

Nozzle clogging occurs

The pressure inside the nozzle and barrel rises as bubbles grow. This internal pressure acts in the direction that pushes back the filament and thus becomes a resistance. Since the internal pressure gradually increases with printing time, the dispense followability gradually deteriorates. When internal pressure reaches the limit, it will not be possible to dispense and the nozzle will be clogged.

If the filament cannot be loaded even if the nozzle is replaced and the motor makes a "Dan! Dan!" sound, there is a possibility that the internal pressure is too high.

In addition, when the internal pressure rises, extra force is required for extruding, which puts a load on each 3D printer component. Problems such as wear of drive gear, plastic parts breaks, and insufficient extruding are also likely to occur.

(2) Resin melt chenge

Resin becomes difficult to melt

In order to melt the resin that has absorbed water, not only the heat energy for melting the resin, but also the heat energy for vaporizing the entrapped water is required. the amount of heat equivalent to the latent heat of vaporization is lost when moistured resin is melted, so extra heating is required.

Glass transition temperature(Tg) decreases

Generally, when the resin absorbs water, the glass transition point decreases. It is considered that water enters the resin, making it easier for the polymer chain to move. Due to the lower glass transition temperature, the softened part of the resin in the hot end becomes wider. This makes 3d prints not sharp.

(3) Hydrolysis

Stringing

Water in resin melt breaks the polymer chain. This hydrolysis causes lower molecular weight and melt viscosity. In simple words, it becomes muddy. Resin drooling from nozzle tend to be stringing when hydrolysis occurs.

3D Print Stringing - Source:all3dp.com

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