I have two Taz 6 Printers. I have the stock head on one and the Aerostruder on the other. I have been printing with PLA in my classroom. On both the printers, after I get done printing an object, after a few hours the PLA breaks close to the extruder and the last 10 inches or so is very brittle. It may even break in a few places. So, if I don’t start a print immediately after, I have to remove the broken filament and cut off about 10" until I get to a section that is no longer brittle. I assume this has something to do with that section of the filament getting warm during a print and then cooling after. Any thoughts on why this happens and is there a solution?
While generically a filament might be called a “PLA”, the PLA (polylactic acid or sometimes called polylactide) is just part of it… other things are added to give it color. And then there are variations on PLA (e.g. HTPLA). The properties of the PLA can vary a bit based on who makes it and what they actually put in it.
I have some “silk” PLA’s that have a satin luster and those filaments are very brittle … every morning I’d come back down to the printer and see the broken filament.
I don’t think it’s related to the filament getting warm (the filament that has not yet gone into the extruder wouldn’t have gotten nearly warm enough to change any of its properties. Rather it’s that at time of manufacturing, the warm PLA is extruded, cooled, and still slightly warm as it is wound onto the spool and then develops that “memory” of being coiled. As the filament unwinds to go into your extruder, it is forced to straighten out – rather than get to remain in it’s coiled state. That puts stress on it. It can handle that stress for a few minutes … but over the course of many hours it can ultimately break.
You might want to consider switching to a different PLA to avoid this.
Thanks for the reply! I’ve had this happen on Gizmodorks, and Polylight. The reason I suspected something from the printing process was because about 10 inches up the spool I can bend the filament and it will bend (though show some stress.) However, after printing, the 10 inches closest just snaps. It didn’t do that before printing. I do agree that can’t imagine enough heat would be transferred to change its properties. It could be that that last section being held straight might be developing some micro fractures or enough heat coming from the bed slightly warms it and then it gets cool in my classroom at night causing it to stiffen up.
This is actually common and is more due to the filament than anything else.
Certain brands are more prone to having the filament become brittle than others.
Esun filament will generally always do this in my experience.
A lot of the times it could be older filament, filament that has been exposed to a little moisture, or filament that has been overexposed to UV.
I think it is quite common. If I leave mine resting for more than 2 days it breaks. I think the part going into the head is under some stress and it just breaks. If I print every couple days it does not break like that.