Welcome! Log In Create A New Profile


Strange hot end design flaw

Posted by JanJans 
Strange hot end design flaw
October 01, 2016 07:43AM
I wrecked my hot end this week. I think it is due to a design flaw in my hot end. Most hot ends are cooled. There is a fan on the hot end that prevents the heat for reaching to far up the supply line of the filament. Something like this

My hot end doesn't have any cooling. The PTFE (is it PTFE?) tube goes directly into the hot end. There are really small cooling fins attached to it with no fan anywhere near the hot end.

The heat has widened the tube creating space for the filament to flow back into the tube. This filament cools down a little creating drag on the filament. The drag slowly increased until the nozzle clogged up. I can clear the nozzle but it immediately clogged up again.

Is this indeed a design flaw of this nozzle? I can repair it by putting a new PTFE tube on it, but I'm afraid this will be a temporary solution.
Re: Strange hot end design flaw
October 01, 2016 08:49AM
I don't recon this hotend. It seems to have a PEEK heatbrake. I'm not sure, if it is supposed to touch the hotend? Maybe an airgap between the heater block and the PEEK part would help?
Re: Strange hot end design flaw
October 01, 2016 09:01AM
It is supposed to touch the hot end. Nothing wrong with that part of the design.
The brass part screws directly into the hot end.

Here is a picture of the multicolor printhead. Here you can see the brass part more clearly. The single color printhead uses the same brass connection part as the multicolor printhead.

I removed the multicolor printhead a long time ago. That thing fails miserably.

Edited 1 time(s). Last edit at 10/01/2016 09:03AM by JanJans.
Re: Strange hot end design flaw
October 02, 2016 04:07AM
There is more information available on 3D printheads design than I thought. I spend yesterday night reading about printheads. What I learned was that a normal has three zones.
- Cold end
- Transition zone
- Melt zone

My strange printhead has only one zone. The melt zone. The cooling fins without any air flow aren't nearly enough cooling to create a transition zone. Therefore the transition and cold zone will be in inside the PTFE tube connecting the extruder to the printhead. No wonder my printhead is clogged. sad smiley

I definitely need a new printhead. I will be looking in to this the upcoming weeks. smiling smiley
Re: Strange hot end design flaw
October 02, 2016 10:30AM
Maybe it was designed for high temp filament like nylon etc.?
AFAIK, PLA is the most problematic filament when it comes to clogging issues, ABS already is less critical. It needs a cold end, but no fan.
Re: Strange hot end design flaw
October 02, 2016 10:50AM
The manufacture designed its own printhead for this printer. The printer used PLA and was ABS ready according to the specifications. ABS ready is more or less a lie. The print bed is barely capable of reaching the temperature needed to print PLA. So overall it is safe to say that it is a PLA printer.

Higher temperatures increases the problems even further. The whole print head is useless without a cold end. Adding a cold end to the hot end is a bit of a risk. I think it is better to buy a complete print head.
Re: Strange hot end design flaw
October 05, 2016 10:51PM
you have a hotend which isnt working right and you need to mod something to get it working,
I think O lampe has a valid point, maybe you should try to move things around,
if it where me I'd move the peak to above the metal bracket, (i know you probably have a hole designed to fit the peek bung)
I would have the metal bracket attached to the throat above the heater block, then the peek,
maybe some steel nuts & washers could help position it, then add a fan to cool the metal bracket.
Re: Strange hot end design flaw
October 06, 2016 11:11AM
I'm afraid you misunderstand how the nozzle is assembled. The peek part has only one function. That is to keep the heat away from the bracket. If it didn't encircle the filament supply line (the peek part isn't part of the supply line) and was placed several centimetres away it would have had the exact same function as it currently has. Putting the peek on top of the metal bracket renders it useless because it loses that one function.

I did some more research on nozzle design. This nozzle is absolute not a high temperature nozzle. This because the PTFE tube goes straight into the meld zone.

It is perhaps possible to salvage this nozzle. I will have to design and build a whole cold end with intermediate zone. I think will buy myself a new print head. That will save me a huge amount of time and money.
Re: Strange hot end design flaw
October 06, 2016 08:45PM
yes & no I was suggesting assembling it an alternate way for an alternate result,
heatblock, gap/throat, bracket, peek....so the bracket can take some heat from the bottom of throat before it gets to the peek protecting the top of the throat from heat...
so if there is a big hole for the peek to go through the bracket you would have to add parts to get it to sit partially in the bracket
but the bottom part you would use some material with a faster heat transfer to take the heat into the bracket
but as you said the origonal design wanted to keep heat from the bracket(maybe incase of warping something & binding something)
but maybe that wont happen, I'm only going by what you said there is a design flaw,
the peek bung looks like it could sit higher leaving a gap so its not touching heat block.
maybe the bracket can then cool the bung, but its not going to cool it well if its touching the heater block,
and where is the fan to help?
Re: Strange hot end design flaw
October 08, 2016 02:27PM
Well, there never was a fan. That's another design fault.
Your suggestions how to improve the nozzle definitely are interesting. However, this is not the time for me to experiment with nozzle designs. I'm afraid I'm stil going to replace it. I'm going to buy a compleet E3D all metal hotend smiling smiley That should solve the issues. This gives me time to work on all the other design faults on the machine. Yes there are dozens of design faults on this printer! I'm currently busy replacing all bearing rods (they are all aluminium!), relocating the extruder, making filament spool mounting positions, making a plate to guide the wiring so that the Y axis doesn't jam, redesigning the power distribution, replacing the heating elements in the bed, replacing the power supply, adding a SD card reader..... That is about it for the bigger issues I think...... You get picture tongue sticking out smiley

Edited 1 time(s). Last edit at 10/08/2016 02:28PM by JanJans.
Re: Strange hot end design flaw
October 08, 2016 10:51PM
Yeah I get the picture but still the suggestions I made wouldnt take much time at all...and if its coming off anyway why not have a little fiddle...the design flaw maybe just an assembly issue, some people just put things together wrong, loose a washer or whatever, you must have posted for a reason. The multi head is offset from the bracket, the single one isnt, so a variation of setup is allowed, and could possibly be enhanced, but you already have your solution based on your experience with it so who am i to argue with that.

Edited 1 time(s). Last edit at 10/09/2016 02:07AM by MechaBits.
Re: Strange hot end design flaw
October 09, 2016 03:18AM
Perhaps sometime in the future smiling smiley
Re: Strange hot end design flaw
October 09, 2016 04:35AM
Well my cheap china clone is performing quite well so your probably right, get rid save time, it aint worth the effort.
Sorry, only registered users may post in this forum.

Click here to login