Followup photos to my post yesterday about milling a jammed hot end in half.

Followup photos to my post yesterday about milling a jammed hot end in half.

Photo 1: Microscope shot of the chopped “Makerbot mk7 style” thermal barrier tube. (Ignore the swirly damage from where it jumped out of the hot block and jammed in the end mill.) Note the rough finish. And the internal diameter step is in the wrong place. Something went wrong with drilling.

Photo 2: Microscope shot of the actual cold zone jam. I pried this out of the cold zone from right below the misplaced step. With ridges like that, no wonder it wouldn’t move…

Photo 3: same pic as yesterday, but annotated to show where the internal diameter step is, versus where it’s supposed to be.



Are the grooves on the inside something that you did, or was it like that? It’s almost like it was threaded on the inside.

@ThantiK I did the big swirls across the heat break neck. The ridges/grooves (below the arrows pointing at the hot and cold zones) are from the manufacturer. You can see the matching surface on the filament piece picture.

This is a dualstrusion machine… I’m going to have to check the other tube and see if it’s the same way.

That step was almost" in the noise" of the original image. I wrote it off as flashing from the milling. While it’s undesirable, do you think that step made any difference? The rough bore is really sad though. Clearly worth buying an upgrade.

@Jeff_DeMaagd the misplaced step didn’t do its job to prevent cold zone jams, and made it especially difficult to unload the jam once it formed. Solid PLA of larger diameter than the inlet simply isn’t coming out through the top.

In theory, rough walls across the melt zone won’t matter much. It’s a problem across the transition zone.

Great photos Ryan. A jam forming so far above the transition zone would prove very difficult to clear. After seeing your photos I’ve a very strong suspicion this I’ve been experiencing this on one of my printers. It explains so much.

I’ve been clearing the jams by unplugging the cooling fan, pre-heating and letting the heat soak up the thermal tube to soften the plug.

Thanks for sharing your finding.

@Ryan_Carlyle The rough walls would make it harder to do cold pulls. It’s not helping the jam clearing, but the step might be causing the majority of that problem.