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I've built a custom machine based on the AM8 (Anet A8 upgrade). I've got an E3D V6 clone hotend in, seems like a decent clone. I've replaced the heat break, heat block, and nozzle several times but after a given period it seems like filament leaks up the heat break. The heat break and nozzle are "all-metal" titanium versions.

How I set it up: I insert the nozzle all the way into heat block, I unscrew it about 3/4 of a turn. I insert the heat break until it makes contact. I then tighten using pliers and spanner. I assemble onto the printer. I heat until 285 °C, give it a few minutes, tighten as much as I think I can before something would break. I let it cool down. I heat again to 285 °C, tighten again as much as I can. Cool down. Then ready for printing (mainly using PETG at 240 °C).

What am I doing wrong? What should I be doing differently?

Photo of hotend on 3D printer

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  • $\begingroup$ Maybe it is a not-so-decent clone? $\endgroup$ – Tom van der Zanden Jun 17 at 10:14
  • $\begingroup$ Possibly... but I fail to see how the extruder would cause the leak. Any info would be helpful. $\endgroup$ – BossRoss Jun 17 at 10:48
  • $\begingroup$ Not a solution, but I don’t like that the bottom fin of the heat break doesn’t get air blown on it the same as the rest, the blue air guide misses it. That’s the most important area to keep cool, lest heat creep up and the filament gets soft too high in the tube and jams. $\endgroup$ – ChinchillaWafers Jun 17 at 18:08
  • $\begingroup$ Your blue plastic fan shroud is upside down. $\endgroup$ – ChinchillaWafers Jun 18 at 19:33
  • $\begingroup$ Do you know that tightening should not be "as much as you can" but "just a bit more than hand-tight"? check one of these so you don't make mistakes again: thingiverse.com/thing:2613057 $\endgroup$ – FarO Jun 18 at 19:52
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How does this happen?

For melted filament to leak around the heat break threads, it has to first get through the metal-to-metal machined surface joint where the heat break contacts the nozzle. Given this keeps happening, the problem must be a systematic error of some kind.

Thermal Cycling

Based on your description of your installation procedure (heat to 285 °C, tighten, cool, reheat to 285 °C, retighten, cool, print at 240 °C) I see a potential issue: titanium is subject to brittle fracture. Your titanium hot end and nozzle, together, are being overstressed with the combination of heating well beyond print temperature, overtightening, and cooling (the aluminum heat block has a much high expansion coefficient than titanium).

Suggestion

What I'd recommend is to change to a brass nozzle or, if you need to print with abrasive filament, hardened steel, and a 304 or 316 stainless heat break. The steel or brass nozzles will cost less than titanium and do at least as good a job (brass is best for thermal transfer to the filament, though it has limited wear life), while stainless steel for the heat break will have similar or lower thermal conductivity and is less brittle. As a bonus, with your tightening routine, the brass nozzle material will deform when it is compressed against the stainless heat break and act as a gasket, rather than fracturing after a few heat/cool cycles.

An Additional Concern

While answering comments, I was reminded of another possible issue: the same reason aluminum wiring is no longer used for in-wall home electrical installations. Aluminum tends to deform permanently after heat expansion under constraint, rather than recovering its original shape (as copper and brass will do), and expands several times as much per degree as titanium does. Even if the heat block is an alloy rather than conductor grade pure aluminum, this will occur (though most alloys are significantly harder/stronger than pure metal) with the heat, tighten, cool process. Also, 280 °C may be hot enough for aluminum to undergo heat creep (a slow, permanent deformation under stress normally well below the yield point). The rule I recall from material science courses in college, almost forty years ago, is that creep becomes an issue when the absolute temperature is more than about half the melting point, for most metals, and pure aluminum melts at about 933 °K while you're printing at 553 °K (by comparison, 70/30 brass, as used for firearm cartridges, has a solidus -- the lower melting point of a two-component alloy -- of about 1183 °K.

This permanent deformation of the aluminum heat block at the threads may result in the threads becoming loose, thus allowing extrusion pressure to force molten filament between the heat block and heat break. That layer of filament material then acts as an insulator, increasing the temperature differential between the heat block and heat break -- and with the heat break now running cooler, the gap opens further.

A Suggested Solution

One solution to this would be to switch to a brass or copper heat block. Not only do these metals have a higher melting point than most aluminum alloys, making them less prone to creep at printing temperatures, but they have much more tendency to return to original dimension after a heat/cool cycle when constrained (which is why copper house wires don't become loose over time the way aluminum ones do). The change in mass and conductivity might make it desirable to recalibrate the temperature control PID, if present, but this is a one-time operation, compared to having to disassemble and clean the heat block and heat break periodically due to leaks.

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  • $\begingroup$ I had similar issues initially when heating and tightening at a lower temperature, around 250°C, I read some forums where E3D recommended 285°C. I have cleaned and inspected old heat breaks and nozzles and could not find any defects with the naked eye. Titanium all metal heat breaks are readily available but I will see if I can source an all steel one (the micro swiss seems very expensive) and revert back if this resolves the issue $\endgroup$ – BossRoss Jun 18 at 9:40
  • $\begingroup$ I see stainless ones all over AliExpress, but if you're in a hurry I'd start by checking Amazon or the E3D home site. $\endgroup$ – Zeiss Ikon Jun 18 at 11:01
  • $\begingroup$ Titanium may be subject to stress cracks but... 280 °C for titanium is nothing, we are not talking about tin! Second, those cracks are not expected before hundreds (at least) of cycles unless he got a defective part to begin with. $\endgroup$ – FarO Jun 18 at 19:51
  • $\begingroup$ @FarO Brittle failure of titanium isn't the same as fatigue -- and the relevant material for the heat cycling is the aluminum heat block, which expands several times as much with temperature as the titanium heat break and nozzle. $\endgroup$ – Zeiss Ikon Jun 20 at 11:48
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  1. Verification: When you tighten the nozzle against the heat break, the nozzle is not tightened completely against the heater block. If the nozzle tightens completely against the heater block, it will not finish tightening against the heat break.

Note: the heat break is thin between the heater block and heat sink to minimize conduction of heat. Over-tightening the heat break into the heat sink with break the heat break.

  1. Verification: your heat break is all metal (no Teflon tube in the filament path). If it's not all metal, 285 °C may be damaging the Teflon tube. If not all metal, tighten the nozzle to the heat break at 250 °C, which is the limiting temperature for an extuder that isn't all metal.

  2. The titanium heat break has higher thermal resistance, which helps to isolate the heat break from the heater block. However, higher thermal resistance is a disadvantage for the nozzle, where you want the heat. For non-abrasive filaments, such as PETG, a brass nozzle is easier to get a good seal as well was better heat conduction. PETG is particularly sensitive to jamming from not adequately heating up when printing too fast. While the nozzle heats the filament, the filament cools the tip. Thus, you will need to print slower with a titanium nozzle.

  3. From the information so far, it appears to be difficulty get a seal between to titanium pieces. It seams like they could use a different titanium alloy. Titanium glasses frames are flexible, not brittle. However, brittle alloys are usually harder, but the heat break doesn't need to be hard like the nozzle. Of course, brass is easier to get a seal because it actually deforms to fit shape of heat break.

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  • $\begingroup$ "When you tighten the nozzle against the heat break, the nozzle is not tightened completely against the heater block." In the process of forcing the nozzle against the heat break, it does so by engaging the threads of the heater block. The same applies to the heat break. All three components are tightened against each other, but the key factor is that the nozzle upper surface is flush and properly engaged with the flush heat break surface. $\endgroup$ – fred_dot_u Jun 17 at 20:43
  • $\begingroup$ Do you see any sign of cracking as Zeiss mentioned? $\endgroup$ – Perry Webb Jun 17 at 22:15
  • $\begingroup$ The nozzle is initially inserted all the way into the heat block, then about 3/4 turn outwards before inserting the heat break. This gives enough space for nozzle to be tightened at temperature. Heat break is all metal. $\endgroup$ – BossRoss Jun 18 at 9:44
  • $\begingroup$ @PerryWebb no cracks I can see with the naked eye $\endgroup$ – BossRoss Jun 18 at 9:44
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    $\begingroup$ I'm wondering if the aluminum heater block is strong enough to crack the titanium. The aluminum alloy of the heater blocks tends to give, especially at elevated temperatures. $\endgroup$ – Perry Webb Jun 18 at 13:39

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