Using 3.0mm jhead MKV with 1.75 mm filament

Simple question. I accidentally bought several 3.0 mm hotends and I have tons of 1.75 mm filament. Do you think I'll face any problem if I try to extrude the filament with this setup

Thanks!

... the 1.7mm filament won't seal the 3mm bore, so you can't apply enough pressure to extrude the molten platsic -- it will simply oouze out at the top end of the hot-end

What you can try - inserting a tube with 3mm OD and 2mm ID ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

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You mean changing the inner ptfe tube from inside the jhead?

... if you have a bigger bore with a 3mm-ID-PTFE-tube inside, then better replacing it with a press-fitting metal tube and insert a thinner PTFE-tube fitting to the 1.75mm-filament ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

I've heard of someone simply putting a PTFE (Teflon) tube with an 3mm OD and a 2mm ID in theirs J-head, lining the inside of their entire hot end. Here's a link to a 3mm J-head easily converted to 1.75mm with a PTFE tube: 1.75mm J-head. The ptfe tube is probably fairly inexpensive, and I would think that this should work for you.

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Thingiverse Profile

I bought a 1.75mm J-head clone from reprap.me, when I received it I found that it was one of these 3mm + 1.75 PTFE tube conversions.

My experience with it was horrible, the big problem I had was that it seemed that the melt chamber was waaay to big, which meant that when starting extrusion there was some lag (as it built up pressure) before it started pushing out melted plastic and when stopping extrusion it would extrude for a bit until pressure came down.
This meant that stop/start and retract/unretractions caused really bad artifacts in the prints.

The only way I was able to print anything at all was by configuring the slicer such that the extrusion rate was as continous as possible (infill, outlines etc all the same speed), and even then I had bad artifacts whenever starting/stopping a line (moving the printhead).
I spent a lot of time tweaking (even tried experimental stuff like the marlin advance algorithm), but at the end of it the prints were still very bad.

Some may say that this was perhaps a bad clone, and not a problem with the 1.75mm conversion mod, however the first hotend I had I was also a j-head clone (came with the printer kit), though that one was actually 1.75 and it was much better and even though I was very green when I got that hotend it gave me much better prints.

I have now switched to a E3D V6 and I am never going back, it beats both the j-head clones by a large margin.

Edited 2 time(s). Last edit at 08/13/2014 04:37PM by oysteinkrog.