So here’s a question I’ve recently had, how far down is the PTFE tube supposed to go? This image has the tube stopping at the heat break but I know there is tubing inside of there as well. Should it extend down into the “melt zone”? The tubing I have is supposed to be able to handle temps higher than I run so I should be able to but idk if I should or not. What are your thoughts on this? It seems like it should NOT be inside the nozzel as it would keep the plastic from melting as fast. On the other hand, maybe it causes issues with retraction? Any info is appreciated but some pros and cons would be great. Pics would be even better.
If it’s an E3D, then it’s meant for temperatures above 250C-ish where PTFE starts to off-gas and degrade, losing it’s slippery quality. The PTFE is meant to stop above the hot-zone to prevent this degradation.
If it’s another hot end, it’s typically run all the way to the nozzle because it’s cheaper and requires far less actual knowledge and mechanical knowhow to produce.
Generally this is the sign of a lower quality hot end, with the exception being the legit J-head from http://hotends.com - reifsnyderb was one of the earlier RepRap guys, and his hot end is produced to a very high standard of quality.
One of my cheap print heads tends to jam after each print if the tube doesn’t go all the way to the nozzle, as a bit of melted filament wider than the filament forms in the gap.
From what I understand, the PFTE tube should slide into the top of the heatbreak. You want an unbroken path from the motor to the nozzle tip. If something jams up a bit, the filament can kink if there’s any unsupported area along the way, causing jams. The very top of the heat break should not get hot enough to melt the PFTE, or you have cooling issues
Note: get a j-head (which a genuine one is near impossible to find) or get an E3D Lite6, which is cheaper, easier to use, easy to find, and pretty darn good.
The only issue is using 3mm filament, which Lite6 does not support.
I’m always curious about how the geniune E3D v6 all metal heatbreak does to not causing jam, especially when printing with PLA. My experience with all metal heat break was not successful.
To me I always put PTFE all the way down to the nozzle.
Maybe I should try some geniune E3Ds to find out.
@Stephen_L if there is a gap then either your tube is not seated properly or the heatbreak/coldend were not machined properly which is leaving a gap for plastic to collect in.
@Xiaojun_Liu I have a filament wiper/cleaner that has a tiny amount of oil on in. The oil keeps the pla from sticking in the heatbreak. Also you cannot have too long retract.
@Stephanie_A oilers are also preventing PLA from sticking to itself. If you layer adhesion is less important than lools, they are way to go. I can cofirm that they lower the friction but weakening part structure.
Best advice I have ever heard on how to avoid jams, is to use good quality hot ends and filaments, and most importantly NEVER turn off the HE fan befor the block is below 60C
@Alex_Skoruppa wow the page changed. Last I remembered, there was almost no inventory listed! I checked about two months ago. The only place to buy anything good was a MakerFarm clone.
I’ve been using “all metal” without problems. What it really means is that PTFE doesn’t touch the hot zone. The heat break bore does need to be smooth and the nozzle needs to be tightened to spec so it doesn’t get loose in use and that the heat sink fan is running when the block is hot. A rough bore, loosening nozzle or lack of heat sink cooling are what cause people jams with this style hot end.
It’s important to understand that all-metal hot ends use some special physics (kind of discovered by accident and not widely understood, even by hot end makers) to avoid jams. I don’t want to write pages explaining the details here, but it’s basically a matter of managing heat flows through and around the filament as it enters the hot end as a solid, and starts to melt in the temp transition zone across the heat break. For example, you MUST have a well-cooled metal-exposed section in the cold zone between the filament inlet and heat break to cool the filament and prevent heat creep. That’s why an E3Dv6 PTFE liner stops where it does.
It’s VERY easy to screw up an all-metal hot end design if you don’t understand those physics, or if you try to cut corners on some of the fabrication details that make it work. That’s why knock-offs of the E3Dv6 tend to jam – cloners don’t understand the melting mechanics and cut corners that shouldn’t be cut.
In comparison, PTFE-lined hot ends don’t jam simply because PLA doesn’t stick to PTFE very much. So it doesn’t really matter if you don’t get your thermal fluxes and transition zone profiles exactly right: the hot end is simply quite tolerant to shoddy design and construction. So if you want low cost and robust against abuse, you want a PTFE-lined hot end.
There are three big reasons why a well-designed all-metal hot end is superior for performance though:
The PTFE liner will slowly degrade (at a rate that depends on your printing temp) so it’s effectively a maintenance consumable that end-users have to deal with
PTFE has very short life over 260C and no life over 280C so it’s limited in filament selection
PTFE is an insulator, so heat flux into the filament is limited, and the PTFE liner will roughly cut in half the hot end’s top printing speed (in volumetric flow terms)
@Ryan_Carlyle well I only print plan at a temp of 200c, well below the limit. I was only considering changing it because I just ordered some new tubing to replace the stock tubing for my bowden extruded. It has an ID of 3mm and there is a lot of play in the system. The new tubing had a 2mm ID and should help with retractions. I was going to use this same tubing inside the hot end as well if it would be beneficial. I just didn’t want it to be too long or too short. Kinda sounds like the tubing should stop where the nozzel starts.
