Brittle PLA

I find the same issue if I leave it mounted on my printer for a week or two without use, I need to cut off the part that was off the roll and re-insert to the printer, if I dont it will snap too easily. If I remove from the printer after use and pack back int he bag with silica gell then I dont have the problem

Hope this helps or at least confirm your not alone /

Peter

Hello Daniel,

The problem is not specifically related to PLA, but - in a different measure - it occurs also with ABS. Anyway PLA filament is subject to degrading almost easily than ABS. This is the reason that when you buy a new filament roll it is sealed including inside a small bag of silica get. What makes the difference is the environmental humidity (influenced by the external temperature and rainy weather too. I directly experienced that it is not related to the end of the filament roll or to a specific part. If I leave the filament inside the printer for some days, the filament for the first exposed meter (about) becomes fragile. I have limited to adopt the solution to place the unused rolls in a plastic bag, so I think that your zip bag is a better solution and the problems should never occur.

Anyway take in account that every time you reuse a filament (e.g. because you need that colour after a wile) that is not new and originally sealed, it is a best practice to test if it bends. If not, break short pieces of filament until it bend and become unbreakable by hand. Cut is with a scissor and start using it from that point.

I have experienced many filament producers / distributors of filament and at the moment the better price/quality I have found is from geeetech.com The reason is simple: they sell printers and filament so it sound strange if they sell low quality plastic having a bad return from the clients that  already bought the printers from them

This factor is also strongly influenced by the geographic place where you live. Nearby the seaside this problem occurs more frequently (I mean the degradation of the most exposed part will start early) while it occurs few in this period that I am using the 3D printer in the Netherlands.

Another detail that it is the worth to consider is the colour: one of the factors that influences in good measure the filament quality degrading is just the pigment added to the plastic base. For some colour this occur in positive, for some others the opposite. I have not personally tested a wide set of samples because I had to buy directly several colour for some small productions (black, white, red, purple, orange, yellow, blue) but the distributors that offer for a very cheap price few meters of all their colour set it is expected that provide better quality than other: with a single small investment you will see immediately the right response to temperature with every kind of pigment. Another detail that I have appreciated in the geeetech products (I suppose they just distribute a good quality product for the reasons above) is that the temperature performances are almost the same with every colour. About the temperatures, ABS works perfectly with 0.4 and 0.4 mm nozzles at 180C with a bed temperature of 90C

Enrico

It doesn't degrade that fast.  It is absorbing moisture out of the air and getting brittle.  You MUST keep PLA in a sealed container with some form of drying agent like those little packets that come with it.  Damp Rid works well.  I have a reusable version.  Don't leave it out!

I keep all my rolls is a large gasketed plastic box made by Zip Loc and I put this dehumidifier in it >>  https://smile.amazon.com/Improved-Eva-dry-E-333-Renewable-Dehumidifier/dp/B000H0XFCS/ref=sr_1_9?s=home-garden&ie=UTF8&qi…

Hi Daniel,

While this may not be the cause of your brittle filament I wanted to highlight something that you alluded to. The fluorescent light with its higher UV composition does work on plastics much as sunlight does albeit more gradually. In the industry of my vocation, dental equipment, we used to see both color and composition changes in the plastic parts of the equipment even when they were only exposed to florescent lighting.

John

Hi Daniel,

I have a follow up question for this thread; If the PLA is sensitive to becoming brittle does this also apply to the item created on the printer? Do the items created also become brittle or does the heating and cooling process cure the plastic in some manner?

John

My experience is that the tendency to become brittle is much more likely in the section of PLA that is in the printer, perhaps because of exposure to heat. Maybe the pigment material starts annealing into clumps or something. I always have at least 3 different colour reels open and awaiting use (black, white and clear). One or more colours may sit out for months without use. I have not had any problem with PLA sitting exposed on a reel for months. Maybe it is a combination of naturally low humidity and I print very regularly. However, the short section that is in the printer can definitely get very brittle and very weak if left there for a few days. I always eject the PLA if I don't expect to be printing the following day, and I cut off the section that is roughened by the feed gear teeth.

I have not had any problems with printed parts becoming brittle or weak.

The colour additives definitely alter the mechanical properties of PLA. I find white hardest to work with after printing. Black is much better, clear is probably the best.

Hi Doug,

Thanks for your insights.

John

Hi Douglas,

The colour additives definitely alter the mechanical properties of PLA.

this is the most influencing aspect.

Enrico

I regularly change the colours of the materials I use meaning that I have lots of partly used rolls.

The simple technique I use is to put each roll in a bag, pierce a small hole for the filament to pull through and a hole through either side to mount the spool.

Drop a few silica gel packs into the bottom of the bag and you're done.

When you want to change the spool for another one push the filament back into the bag, tape over the holes and you're done until next time you need it.

This also has the added advantage that dust and other contaminants are kept away from the spool.

This is interesting as I've been taking the reel off and putting it in the bag with silica gel.  We have had a contractor in who has years of experience with plastics and injection moulding who has overruled me and said it's not an issue (until now!)  Despite having no prior experience with 3D printers.  This is someone who knows that raw material has to be dried before used in an injection moulding machine but sees the printer as a simple and poor relation to injection moulding.

Interesting that he took the printer to his office as was sat next to it working and commented on the fumes. I did say that is smells and that's why I keep it in the lab area and not in the main office at work... 

Good to hear about your experience with actual printed parts being ok over time!

Dan.