Help! Extruder won't jam. Not having problems with heatbreak. Mk3 is too reliable.  

RE: Help! Extruder won't jam. Not having problems with heatbreak. Mk3 is too reliable.

As I have a skelestruder I have dropped my retractions slightly; FWIW I tried out the slicer build from SuperMerill that has "ironing" a while back... using that is guaranteed to exacerbate the issue because with a non-continuous top surface you get both retractions and a suuuper low flow rate. Prime recipe for molten plastic to squeeze back up the heat break and jam. Those were my first and only heat-creep jams. 

RE: Help! Extruder won't jam. Not having problems with heatbreak. Mk3 is too reliable.

My try at a stress test for the HB issue as I have experienced it ... and no ... there is no such thing as a sure-fire short test.

HB_Jam_Test

RE: Help! Extruder won't jam. Not having problems with heatbreak. Mk3 is too reliable.

Posted by: vintagepc

As I have a skelestruder I have dropped my retractions slightly; FWIW I tried out the slicer build from SuperMerill that has "ironing" a while back... using that is guaranteed to exacerbate the issue because with a non-continuous top surface you get both retractions and a suuuper low flow rate. Prime recipe for molten plastic to squeeze back up the heat break and jam. Those were my first and only heat-creep jams. 

I'm pretty sure this isn't a heat creep issue, at least I can't divine any way heat creep would influence the problem.  If anything, heat moving up the heat break would reduce the chance of a jam.  

RE: Help! Extruder won't jam. Not having problems with heatbreak. Mk3 is too reliable.

Posted by: Tim

I'm pretty sure this isn't a heat creep issue, at least I can't divine any way heat creep would influence the problem.  If anything, heat moving up the heat break would reduce the chance of a jam.  

If it's not a heat creep issue, it should manifest with printing non-PLA materials, no? Or am I misunderstanding what you mean?

RE: Help! Extruder won't jam. Not having problems with heatbreak. Mk3 is too reliable.

Polycarbonate:

RE: Help! Extruder won't jam. Not having problems with heatbreak. Mk3 is too reliable.

Another problem with English: define "heat creep" and what or how it would affect what is happening to cause the step to become a stopper.

The heater cartridge is biased to the nozzle, but aluminum is a fair thermal conductor.  If we assume the heater block is a solid 210c, and the heat break threaded into the heater block has fair thermal contact and conduction, the 2.0 mm section of the heat break is pretty close to 210c - and something less as filament is being extruded.  We can also agree there is a thermal gradient in the heat break metal between the heater block and the heat sink.    

The heat break neck is 2.1 mm.  The bore step starts 1.4 mm down, ends 1.57 mm, the step is about 0.5 mm above the heater block mass. 

Even using my smallest platinum sensor I have significant measurement error due to poor mechanical contact.  But if I assume a linear error, and educated guesswork, I come up with the lowest fin of the heat sink being 55c; and by calculation of the gradient at the step being around 160c, just below the common PLA melt point of 170c+. 

Also, most assembly instructions place the neck bottom above the heater block; and since stainless steel is less conductive than aluminum, we can confidently deduce the actual temperature at the neck is somewhat less than the approximation given.  This fits with observations of unmelted PLA at the step, even with elevated print temperatures as high as 230c.  If we consider the E3D blog for the V6 design, it becomes clear the designed melt point is somewhere below the neck because it is only that last part of the heat break is finished for gummy flow. 

https://e3d-online.com/blog/2014/05/15/v6-blog-announcement/

In the end, I can hypothesize a few ways I damaged my printer that lead to jamming.  Abrasive filament scarred the hot end; wood and metal filled filaments left particulate matter that lingered; etc.  But I don't really care because I've fixed my jam issues by installing the stock E3D-V6 heat break and so far the jams have not returned. 

Will I go back and reprint some of the filaments I know caused problems?  No thank you on one: I really do not need glow-in-the-dark anything and the 200g or so remaining on that spool is a reminder of stupid pet tricks.  But wood and metal filled has been in my printer since the jams, without issue.  

All said and done, the new E3D-V6 titanium heat break with a 2.2 mm full bore makes a lot of sense for prospective MMU users.

RE: Help! Extruder won't jam. Not having problems with heatbreak. Mk3 is too reliable.

My genuine E3d titanium heatbreak has a bore of exactly 2.0 mm, not 2.2.

Only bought it last week as well.

RE: Help! Extruder won't jam. Not having problems with heatbreak. Mk3 is too reliable.

I'll need to go back to that video then - came away with the notion the titanium heat break he was holding was an E3D; maybe it was the MicroSwiss, which steps, but from the opposite end.  But he says it's an E3D-V6 titanium and the image at 53:12 shows it is larger diameter than the stock heat break.

RE: Help! Extruder won't jam. Not having problems with heatbreak. Mk3 is too reliable.

It definitely looks larger in the video, I've got an unused brand new PRUSA heatbreak with the step, I'll take a picture of both so we can compare them.

I have multimeter leads which are exactly 2mm diameter and they fit snuggly in the titanium heatbreak, I've measured the leads ends and they are 2mm diameter.

The left is a PRUSA heatbreak and the right an E3d Titanium heatbreak.

RE: Help! Extruder won't jam. Not having problems with heatbreak. Mk3 is too reliable.

E3D says nothing about the titanium difference in size, so I wouldn't expect any.  Not sure what the video was showing, maybe an early prototype, or maybe not an E3D.  Or, heck, maybe glare plus optical delusion :~)