How to accurately and easily measure Filament Moisture Content.
 
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How to accurately and easily measure Filament Moisture Content.  

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bryn51
(@bryn51)
Estimable Member
How to accurately and easily measure Filament Moisture Content.

A lot is said about excess filament moisture.  Many folks experience its effect on printing experience and print quality.
You can buy a filament dryer on any street corner. 
- nobody know how much moisture their filament contains, only that it exhibits certain symptoms. 
- nobody publishes a list of symptoms that appear at a given moisture content. I have sought and not found any inexpensive filament moisture content measuring tool. 
I think that's because it isn't easy, since the moisture in question is mostly bound up inside the filament.
But the moisture content affects the weight of the filament. The density of the filament is an available parameter, given as grams per cubic centimetre (not exactly a handy unit of measure).
the steps seem to be:
1/. determine filament density.
2/. measure an appropriate length of the filament that should weigh x grams. (say, one gram).  We  know the diameter, of course. So its just the volume of a cylinder....
3/. weight it accurately.

From the density, work out what that length of filament should weigh, compare with what it actually weighs, difference is moisture.

Not exactly an easy pathway, especially for those challenged by science.

Has anyone discovered a simple pathway to measure water content, instead of just guessing that symptoms means its damp ?

 

Posted : 14/10/2023 8:44 am
_KaszpiR_
(@_kaszpir_)
Reputable Member
RE:

I guess the list of effects may be misleading because there may be different causes which manifests in the similar way. That's why general rule is just drying filament for few hours to factor out some of them related to it. That's why you rather find tables describing how to dry filament in given conditions, such as filament type, temperature, weight and time vs outside mousture.

The main effect of the wet filament is boiling water in the hotend trapped in the pockets between melted filament. This manifests in popping and hissing sounds from the hotend in the place where filament leaves the end. Those pressure differences cause uneven extrusion from the hot end, wich results in for example blobs of filament followed by not enough of filament extruded after that. Notice that setting wrong extrusion/retraction distances cna just manifest in similar way.

I remember reading and watching videos and general outcome was that for example PLA - which does not absorb water that much - can get water into it and it will get something like 0.6g for 470g of spool - that is something a bit over 1% of weight increase - in normal situations just hard to measure, but the effects will be noticeable.

Afair the most dramatic effects are with nylon which can really absorb to around 7% of its mass as water, people were reporting prints getting bad within minutes from opening the spool in moist rooms.

Some people use basic humidity sensors in dry boxes as rough estimators, looks.like it's cheap and works well enough.

See my GitHub and printables.com for some 3d stuff that you may like.

Posted : 14/10/2023 12:34 pm
Thejiral
(@thejiral)
Prominent Member
RE: How to accurately and easily measure Filament Moisture Content.

 

Posted by: @bryn51

A lot is said about excess filament moisture.  Many folks experience its effect on printing experience and print quality.
You can buy a filament dryer on any street corner. 
- nobody know how much moisture their filament contains, only that it exhibits certain symptoms. 
- nobody publishes a list of symptoms that appear at a given moisture content. I have sought and not found any inexpensive filament moisture content measuring tool. 
I think that's because it isn't easy, since the moisture in question is mostly bound up inside the filament.
But the moisture content affects the weight of the filament. The density of the filament is an available parameter, given as grams per cubic centimetre (not exactly a handy unit of measure).
the steps seem to be:
1/. determine filament density.
2/. measure an appropriate length of the filament that should weigh x grams. (say, one gram).  We  know the diameter, of course. So its just the volume of a cylinder....
3/. weight it accurately.

From the density, work out what that length of filament should weigh, compare with what it actually weighs, difference is moisture.

Not exactly an easy pathway, especially for those challenged by science.

A simpler yet coarser method is to weight a spool before and after drying.
To estimate the absolute moisture content you have to either have a method that ensures very low humidity levels or use these theoretical density numbers.

I would imagine that measuring the water content of a short filament piece precisely you would need proper analytical scales which can measure down to 1 mg.

Mk3s MMU2s, Voron 0.1, Voron 2.4

Posted : 14/10/2023 12:43 pm
Artur5
(@artur5)
Reputable Member
RE: How to accurately and easily measure Filament Moisture Content.

 Not only analytical scales but  a caliper accurate at least up to 0.01 mm. Diameter tolerances of most brands of filaments stay within +/-. 0.05mm. If the actual diameter was 1.80 mm instead of 1.75 it makes a difference of almost 6% in area. Another thing to consider is the real density of that specific piece of filament. For PLA the nominal value is 1.24g/cc but it may change a bit between different batches. 

Posted : 14/10/2023 1:59 pm
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