Pegasus 12" Build Notes

[uncle_bob]

Hi

So, after some fiddling, the printer is back up and running.....

Seems that *somebody* (I blame the dog) didn't quite get the e3d hot end tight enough when it was hot. There was a very slow leak that piled plastic up on top of the hot end. Eventually blobs of it started dropping of into prints at various random places. That lead to a lot of "why did the software make it over extrude there?" kind of questions. Needless to say, changing software settings didn't have much impact on the issue.

Tightening the e3d involves grabbing it with two wrenches / pliers when it's hot. One grabs the top of the heatsink and the other grabs the bottom of the nozzle. Significant force is applied to get things tight. Since it's all running hot *with* the teflon tube in place (in my case) the fan is on and running. .... fan shroud gets pushed down into the hot block .... hot block wins.

The second part of this is: Print up a second fan shroud (and maybe a third and fourth) *before* the one you have melts down. Getting the hot block up to temperature with a big hole in the bottom of the shroud is not easy. It appears that the filament used to print up the shroud does not matter much. The original melted pretty fast.

Pealing back through the layers of goo on the head, I can spot the colors of each of the rolls of filament I've gone through on the machine. This isn't something that just came loose on it's own. It never was adequately tightened ever. Also putting the new fan shroud on, it fits a lot better than the old one. Hmmm..... I suspect that somewhere along the way I shut things down a bit to fast (hot end cool fans stopped to soon) and the heatsink got warm enough to soften the plastic. That may have been part of the reason the fan shroud dropped down while tightening the thing up.

Again ... it could not possibly have been my fault .. The dog is to blame. Now all I have to work out is which of the three dogs was the one I assigned that task to ...

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The basic issue here is that you assemble the hot end cold and then mount it up. After that you go through a bunch of work to get things wired up. Way late in the process you "remember" that the hot end needs to be tightened. It now has a PTFE tube in it and that mandates the use of the fan.

So, here's a suggestion:

At the point the part is first screwed together (the three metal parts plus the nozzle are mated) you do not have a PTFE tube in it. It's sitting there on your bench. Hmmmm ..... any chance you have an oven? Can it be set to 300C (maybe 250...)? If so, chuck the assembly on a cookie sheet in the hot oven. Let it sit for a half hour. Pull it out (with pliers) and tighten it down. Repeat one or two more times. Do this while you are putting the rest of the printer together.

Bob