Why does this happen? Print randomly jams and i have to cut off the end of the filament and restart the print. The end of the filament is a little bigger than it should be when it gets jammed… What fixes that?
Which printer? You’re getting heat creep and the filament is starting to soften prior to getting to the hotend chamber. Some hotends (like the E3Dv6) have a fan on the cooling fins. I had this problem also with my direct drive extruder motor running hot and it was pre-heating the filament a bit as well. I put a fan on the extruder and jamming went away.
I have an extruder fan going on auto… Im guessing its not enough?
Could be inconsistencies in the filament diameter. I’ve had that happen on a few random spools occasionally.
The fan I’m talking about isn’t the one used to cool the part but is attached directly to my extruder stepper and is blowing right onto the front of the motor where the gear is to drive the filament. I wired mine up with a separate power supply and turn it on when ever I start to print.
This is with mostly all of the pla i have
The magic of the hot end is to melt the plastic just as it leaves the tip. Unfortunately, that gremlin named reality gets in side the hot end and carries some heat up the tube, melting and softening the pla as it climbs. The soft pla is not as stiff, and tends to bulge out as more is pushed into the end. Eventually the tube is warm enough, and the bulge big enough that the pla jams against the side walls and prevents more from being fed in.
The solution is to actively cool the hot end above the heating block. Some hot ends (like the ubis on the printrbot simple) don’t have cooling fins and can be tricky to cool.
@Tim_Sills is most likely correct - you will need an extra, dedicated, always on fan cooling the top of the hot end (and possibly the extruder as well).
My fan is dedicated to my extruder…
Which printer/hotend? My Simple, with the Ubis, also developed this problem over time and I ended up getting a replacement hotend.
I’m not sure if it was a problem with the cartridge developing a problem where it began to propagate heat up the barrel or if it was a thermistor problem that meant it was running hotter than I thought. But either way a new hotend solved that particular problem.
OTOH, my E3Dv6 on my home built I3 is the bomb. So far no issues to speak of.
It is a davinci 1.0
I had that problem. Solved it by increasing hot end temperature by 5 degrees C. In my case it probably was due to plastic not being melted enough, which caused the extruder to “bite” the filament. As a bonus, my print quality got a lot better. I have RepRap Mendel with wade’s accessible extruder. Good luck
The end is always a little bigger for me when I pull it out. There’s always a part I have to snip off so it loads nicely next time.
@Alex_Wiebe is correct 100% this happens all the time on most hot ends. Fan or not.
Reduce retraction length to lessen this happening. To fix it get a teflon lined barrel.
Our new Ubis metal (on pause to retool) has some changes to accommodate for this problem. Almost 0 retraction. Essentially, many hotends are not terribly efficient, making more heat than is needed. Almost all hotends have a pretty tight envelope of optimal performance for a specific speed and material. Breaking out of that optimal envelope can work but is more likely to yield soars tic results. No one talks about it since so many variables are in play, but it’s true. Lots of testing can help you find that sweet spot. Once you do, these type of problems can be conquered. But sometimes it’s a long way to get their. If everyone used the same filament from the same manufacturer in the same room with the same temperature on the same printer model with the same settings and same cooling… That would really make my life a lot easier 
Brook
The problem was that the bigger part was jamming while it was printing. I lowered the temp a little and it’s helping
@Brook_Drumm is right…try a big, sacrificial, print with no retraction and see if the problem goes away. If it does, tune retraction (or move away from ABS, which opens up a whole host of other issues)
What is this? ?? Photograph. …
Its a tip of the plastic when pulled from an extruder
Ok