3DPrinting

Plus humidity is bad for your filament.

I keep on hearing this but it does not check out for me.

I have a Prusa 3S+, self assembled. I do not do a great deal of printing and go through phases. I did a flurry of prints during the pandemic and then it rested idle in our rather cold and slightly damp study for a couple of years. When I bought it, it came with a spool of silver Prusament which worked nicely. I then bought a spool of "Sunlu" filament (Chinese firm off of Amazon) and then a box of 10 colours of the stuff.

I recently got the printer out and updated the firmware, re-calibrated it and so on. I've done several prints with filament that has been open to the environment for at least two or three years and its fine. I have done a print using some transparent filament which was unopened and that was fine too. The unopened stuff was vacuum shrunk wrapped so could not possibly be damp. The opened filament was stored in the original cardboard box in a slightly damp and unheated room.

For me the main issues for a decent print are:

• Adhesion on the plate. I actually used glue for a print for the first time recently
• First layer calibration. If the first layer is wrong, the rest is wrong. You need to get the right amount of "squashing" to get a smooth bottom
• Always clean the plate between prints - a squirt of EPA and a decent rub with tissue whilst the bed is heating up does the job
• Keep the guide rails lubricated - Mine whined that all three axes were too tight or just wrong and yet the Prusa app to check belt tightness and forum and wiki advice said it was fine. Any engineer will tell you to lube up when in doubt - do it! X, Y and Z.

I will try repeating a challenging print with filament that is way older now and see what happens. I printed a couple of tank models in red around four years ago. Both involved their turrets with the barrel facing upwards - that's a lumpy cylinder about 4cm long and 2mm wide.

I have seen some notes about PLA being hydrophylic (absorbs water) on the Prusa website's official advice but I don't personally think it is an issue and people are probably missing another factor or factors that is fucking up their prints. I think the filament dampness meme is "cargo culting".

PLA is heated to around 220C whilst being extruded so any water will steam off very quickly as water vapour - which is not even "wet", well before worrying a print job.

PLA is touted as bio-degradable and it is ... eventually. It is extremely stable, despite being derived from corn starch. It really doesn't seem to care about a bit of water hanging around. That's why I can print new hinges for a plastic garden storage thing to replace the original ones and they last through winters and summers in the UK.

So, if you think moisture is an issue for PLA filament used for 3D printing, why not do some experiments and then decide for yourself.

I'm happy to be proved wrong.