When I started the process of building my 3D printer, my overall goal was to primarily print in PLA due to it’s lower temperatures, less toxicity and biodegradability. Thus far my hotend has been nothing but trouble for this material. It can extrude ABS at higher temperatures with little issue, however with PLA it tends to get stuck quite often, and I have been working with the kind folks on the #reprap IRC chat to try to resolve it.
I was able to determine that this design is called a G1 from MixShop, although it was merely listed as a generic hotend from the supplier, A2APrinter. Most people have trouble with these hotends and eventually get frustrated and swap them out for a better design, such as the jhead. I suspected there would be issues from my initial testing of the hotend and have spent a bit of time researching the state of current hotend designs. Although there are several out there that would be suitable replacements, I have ordered two 0.4mm jheads for 1.75mm filament, one from Hong Kong and one from a more local reputable supplier, hot-ends.com.
My testing with the PLA filament that I have on hand is that it seems to flow alright through the hotend at about 175C, however letting it sit for approximately for a minute seems to cause something to go wrong and creates a jam in the filament path. At a higher temperature, the jam will happen in the PTFE rod leading down to the brass tubing, at about 175C the jam will happen inside the brass tube, particularly if the cooling fan is running. More testing will need to be done to see if this hotend can be made to even work with the filament. I have received suggestions that with a G1 design I may need to really increase the heat, into the range of 210C or so, but I have some reservations about doing this since it always seems to cause melted filament all the way up into the PTFE rod when using PLA. Strangely, this does not happen with ABS even though it is a much higher temperature.
For reference, below is the hotend I currently have installed, this design should be avoided at all costs.
The basics of the design is a brass nut ground down to a point with a .34mm hole through the center to make a nozzle. It is attached at one end of a threaded hollow brass tube. Upwards from the nozzle, the tube threads through a brass heading block with two resistors and a thermistor to provide heating and temperature readings. Above that is a gap, followed by an aluminum brace threaded to the brass and bolted to the extruder and x-carriage above. This holds things in place, and was intended to dissipate heat from the top of the mechanism but I suspect it is not operating as expected in this sense. Finally, the top end of the brass tube is threaded into a PTFE rod. The top of the PTFE rod meets with the bottom of the extruder.
