Feeding Issue

Well if you are getting to the point where you can push filament through the hotend then the but on the PTFE tube is not the issue neither is filament with a slight curve in it the motors will pull through filaments with slight curves easily enough. It sound like you have a are partial jam when the filament gets chewed up as you say it is because something is prevent it from going downward. and as the motor turns it simply grinds away but I have not seen this because of slight bends in the filament. Now if the filament is locked down or snagged on something so it can move or unroll from the spool then maybe but most of the time it is from a blockage of some type below that prevents it from going downward. Some people including myself have seen the filament sometimes start coming out of the side of the extruder through gaps(not the hotend ) but the extruder assembly parts.

The PTFE tube is still a thing to look at though you have to be careful of the temps you are using and since you did not tell us that, this may or may not be relative. but the PTFE tube can itself crack or become lined with material depending on whats been going on. Things you can try areusing a different filament of a different color and then with the hot end already hot load the new filament as quickly pull it back out as soon as you feel resistance and see if the is residue from the previous color if you find thier is or maybe even a brown or black film you may have to clean out the hot end. if it is clean then it could be something a little bit closer to the nozzle. so check that out and let us know what you find and also gives us the temp ranges you have been using it could help reule out or in a PTFE issue.

 

the bad part is that cleaning them out is a bit tricky without taking it off the extruder now if you the newest setup it is a bit easier since it is simply plugged into a connector and it can be removed fairly easily.

If that is the case I would unplug it and then remove it and then plug it back in so that you can heat it up it cleans best when hot. it would help if you had some nylon filament as well as it has a much higher melting point you can try the same thing with some other PLA but it won't be that easy as you have to be very quick basically while it is hot and the inside is soften you stick new filament in and then pull it back out very quickly before it can melt. nylon won't melt at PLA temps so it much easier to use what you are trying to do is to get any loose material that is stuck to the inside of the PTFE tube to stick more to the cool new filament and then you can pull it out when you remove it quickly. This may or may not work with just different PLA unless you are REALLY FAST and it will only grab a small amount each time.

The main thing is that this will only help to clean out the upper part of the Hotend you still need to clean out the lower part and that means going through the nozzle and the best thing for that is, I heard, I think it was an "A"string for a guitar it is small enough to stick through a .4 mm nozzle and on the stiff side so it should be able to knock anything loose that could be building up.

One thing to think about is replacing the stock nozzle with an all metal hot end that does not have the PTFE tube so small drill bits can be used to clean things out.

 

Well the location of the screws is simple when looking from the front of the printer they are on the left side of the extruder assembly. If you look at the filament as it is going into the hot end you will see there is a screw on each side of the filament low on the left side of the extruder. Those two screws go into the collar on the hot end and hold it in place removing those to screws and unplugging the connector and the hot end should drop straight down. Once it is out you can plug it back in so it can get hot enough to start trying to use other filaments to insert and quickly remove hopefully dragging anything that could clog it, out with the filament.

It is hard to describe the actual action but here is what you are trying to do

The residue inside the PTFE tube will be soft because of the heat the filament you are probing with is cool you insert it and when the the cool filament contacts anything molten or soft it cools that stuff hardening it to the filament you are using but you need to pull it out quickly so it does not melt as well so it ends up being several quick insertions to try and remove and residue left behind.

I hope that makes sense.

 

Have you checked to see if there is any dust around the hobbed bolt it could be the hobbed area is not directly lined up with the filament hole. Make sure the are has no filament dust and that the teeth on the hobbed bolt are nice and clean and clear from buildup