Snow Day

I ordered a copper heater block and a dual-metal heat break a while back and they finally arrived.
I disassembled the hotend to install them, and found a leak had welded my heater and thermistor into the block.
I ordered replacements, but they’re a few days away, and my printer is in pieces. And now we’re snowed in.

I realized this would be a perfect time to do some maintenance on the printer, and I found plenty to do!
I replaced wheels, adjusted all the axes, finally tucked my CR Touch cable inside the cable bundle, cleaned out the extruder, even found screws in the frame that had loosened up. I peeled off the holders I’d printed for the cables when I first got it, I think I can live without them.
It’s so clean, it looks like new. So it was nice to get a little downtime.

If you heat the hotend you likely can remove the heater and thermistor and clean them off with paper towel.

I added thermal paste around the heater when I changed my original heater block after stripping its nozzle threads some time back.
This seems to have cemented the heater into place. I do not recommend it.
I’m glad that replacement parts are available so cheap. That’s what keeps a clutz like me involved in the hobby. I don’t have to be afraid of making a mistake or two.

LOL. I’m having a heck of a time with the hardened steel nozzle on my Micro Swiss direct drive hotend coming loose. Yesterday, I had to disassemble and heat the hotend yet again to clean out all the filament that had oozed out onto the top of the heater block, where it then oozed over the edge of the block and down the sides. I’m still not positive whether its coming out the backend of the nozzle onto the top of the heater block or around the bottom of the heat break. I’ve adopted a plan to check the nozzle tightness before every print job, to see if it helps.

Never ever assemble your hotend in cold state or a leak is waiting in the near future.

Also make sure you tighten the nozzle against the heat break and not against the aluminum block.

@Geit, you know I’m well aware of hot assembly. Well, at least to tighten everything up when it’s hot, even if it was cold for the initial assembly.

I’m not quite sure what you mean by “tightening up against the heat break”. I don’t really have a choice. The heat break screws into the top of the heater block, and the nozzle screws into the bottom. They’re tightened in as far as they can go. Still, it seems the steel nozzle works its way loose after a while. I’m wondering if it’s because it is steel, not brass. I’m just going to have to keep an eye on it.

@Ender5r Different elements heat and expand at different temperatures and expansion %. I know that when changing bearings where I used to work, they used induction to heat the metal and as it got hot the bearing would loosen and come apart. The bearings were designed to do that by different grades of steel. Try over heating at least once and tighten.

Thx @Lowteck. I am pretty familiar with heat expansion for metal fittings. Heck, old time wheel wrights used to heat the metal bands for the outside of wagon wheels (i.e. the rims) by heating them in a fire pit in the ground until they would fit over the wheel, then quickly douse them with water to: tighten them to the wheel; push the wooden wheel components together more firmly; stop the rim from burning the wheel. I’ve used heat to loosen car wheel nuts so I could unfreeze them from the lugs. Still, this hotend is annoying. I can’t go much more than the 245C I used when I tightened the steel nozzle. Alas, I’ll just keep checking every so often to ensure the nozzle is still tight.

You need to tighten against the heat break. That’s why you screw the nozzle all the way into the heater block and then unscrew it by a turn. From the other end you now screw in the heat break. Naturally it will at some point touch the nozzle on the inside. When you now tighten the nozzle, you tighten it against the heat break and seal it.

Without the nozzle back’s surface tightens against the heater block leaving a gap between nozzle and heat break on the inside of the heater block. This ring of space allows filament to get stuck and burn to ashes as well as leak along the threads leaving upwards on top of the heater block, when parts separate while expanding. Resulting in filament dropping once in a while onto the print. The heater block in that case shows rinses of (partly burned) filament and is covered with plastic on top.

Too bad these new nozzles where the heat pipe is part of the nozzle (cold swap nozzles) are patented and expensive. These would save so much time and hassle getting the hotend assembled correctly.

I do not know if the heat break and nozzle actually touch inside the heater block. Obviously, I cannot see if they touch inside the heater block, and I have not measured their lengths to see if they are the right length to meet inside the block.

My hot end parts finally arrived, long delayed by the snow.
I was relieved to reassemble the printer that had been laying in pieces for four days and have everything work. (Glad I took notes!)
Leakage like Ender5r’s mostly ruined my old hot end (an inexpensive clone) so I carefully calibrated the heat break position this time.

My order included a dual metal heat break from Mello. I was amazed to find that the Boden tube still extends all the way down to the nozzle. More changes to come, I guess.

I found the key to reassembling the hotend was to measure everything! I used filament to probe, then confirmed that Bowden tube, nozzle, heat break etc. met my dimensional expectations. I would have definitely failed without this step.
I really feel that I know my way around my Ender 3 mechanically now.