How to accurately and easily measure Filament Moisture Content.  

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.

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.

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. 

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

This might be an old thread, but wondering if anyone has measured filament moisture with a moisture meter?  There are several kinds intended to measure moisture of cement or wood.  There are the type with probes, but there are many without probes that are very inexpensive ($20-50). For example this one: 

https://www.amazon.com/gp/product/B0CNPH4BQQ/ref=ox_sc_act_title_1

Other than these, there are so many to measure moisture in rice, beans, grains, etc.  Long story short there many, so hard to believe none would work on filament.  

RE:

Posted by: @allen8355

... has measured filament moisture with a moisture meter?

Yes.  I've seen quite a few posts from people who tried it and always got 0% even after letting it soak in warm water overnight.  I would gather that is because even what we would consider to be "wet" filament still has a very low moisture content, well below the sensitivity of any consumer grade meter.  I did see on Hackaday a year or two ago about a guy who made a rather elaborate setup that semi-worked by sintering a tiny spot on a piece of filament with one laser while using another laser to measure specific outgasses including but not limited to steam.  The lasers tho were just better-than-average pointers and none of the other parts were too exotic.  Suppose you could build it yourself <$100.

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

I might be missing something obvious here, but a simple air-moisture-measurer in a air-tight container with the filament should be enough. A dry filament in moist air will absorb moisture, whilst a wet filament in dry air will release moisture. At some point, the moisture content of the filament will be equal to the moisture content in the air. Thus, simply measuring the air moisture in an air-tight box will equate to measuring the moisture content in the filament. 

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

Wood moisture meters do read the moisture, it's just not that repeatable. If you took 25 readings and averaged them together, it might work. Sealing it in a box and reading the air humidity might work, but it would take some time, and you have to consider the air humidity to start, but sounds like a very valid approach. Just surprising there isn't a filament moisture meter out there. 

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

In my opinion, a change of weight measurement (before and after drying) is the most repeatable method available to us non-industrial types. And even then the sample mass has to be significant enough to make the change in mass detectable on our scales. I frequently dry my filament spools  and I don't even bother weighing the spools unless there is at least 250 grams of filament left on the spool.

I leave my in use filaments in non-heated dry boxes with viable desiccant packs, and usually don't see printing problems, unless I absently leave a filament roll out of the box.  New filaments are a different story. I don't keeps records, but I estimate that at least 1 or every three new rolls of filament, fresh out the vacuum sealed bag, will give up at least 2-3% of its mass when drying the filament. This was eye opening to me and now unless I need to open up a new roll to finish an in progress print, I always dry new filament before using it.   

To compound the problem moisture is absorbed (and released when drying) from the outer layers first and inner layers acquire and release water second hand ... so if atmospheric conditions were poor you might remove a spool from dry storage and in a few hours find the filament coming off the spool too wet to use although ¾ of it, the turns of filament buried inside, was still dry.   Insufficient drying of a very wet spool might cause the reverse effect meaning a long print might start well and deteriorate later.

I dry every spool before first use.  All part spools are dried after use and stored along with freshly dried dessicant in ziplock bags.  Most filaments store this way can be used straight from the bag but Nylon, TPE and anything unused for over a year generally gets re-dried before use.

Cheerio,