Failed prints after replacing the hotend  

It was too low in relation to the nozzle, normally a sign of sagging, it might just have been loosely fitted and perhaps it will go back straight when you rebuild or perhaps the wrongly fitted nozzle just made it look bad... Otoh it never hurts to have a spare.

Cheerio,

RE: Failed prints after replacing the hotend

I just went through something that might be similar. I wanted to start printing with CF Nylon and needed a hardened steel nozzle. I bought a cheap 11 pack from Amazon and had terrible results. After taking the E3D V6 back out I saw the threads were much too short for the nozzle and heat break tube to mate. It left a mess on top of the heat block (like I see in your picture) that was a pain to clean off. Purchased an E3D hardened nozzle (with the proper length threads) and everything is perfect again.

Hardened chinesium nozzles aren't always what they proclaim to be. Check the thread depth to your old nozzle.

RE: Failed prints after replacing the hotend

Whelp I took it all apart, put a new nozzle on it, cranked out a benchy and everything was looking great until my next print and it globbed AGAIN! At this point I just flat out don't know what to de besides replace the whole hot end, this is really REALLY annoying. I didnt use thermal paste to reassemble it could that be the problem? I am about to take it apart a fourth time and tighten the absolute balls out of the nozzle and then back it off a little bit. Guess I have to buy a gauge to actually determine if its 0.2mm off the block? So much money to chase down this problem this is getting ridiculous! 

RE:

I am about to take it apart a fourth time and tighten the absolute balls out of the nozzle and then back it off a little bit. Guess I have to buy a gauge to actually determine if its 0.2mm off the block? So much money to chase down this problem this is getting ridiculous! 

Sorry mate I don´t have time today to get into details, but from your post I take it that you may still need to better understand the system per se first instead of tightening things like crazy, just to thereafter turning the nozzle back. This will get you nowhere other than to a damaged system and doing it correctly is neither costly nor very time-consuming, but it does require to learn the mechanics behind it. This is absolutely not about .2 or .5 mm distance between the nozzle and the heatblock, this is about the nozzle top connecting to the heatbreak *instead* of touching the heatblock first which will prevent the nozzle top to connect to the heatbreak, i.e. this is about *any* gap whatsoever. See Joan´s post here. To me it sounds like you have a loose nozzle.

Cheers

Chris

RE: Failed prints after replacing the hotend

I concur.  There has to be a gap causing a leak.  

RE: Failed prints after replacing the hotend

Posted by: @robin

Your original post: 

My printer has been printing fine for 3 years. A few months ago, a long print detached from the bed and caused such a big mess around the hotend that I had to replace it.

I took a spare hotend from a friend, it's an E3D v6 clone (24V) and replaced my dead one.

It’s pretty safe (in my opinion), that it is your hot end causing the problems. If a printer works fine, then you change the hot end and then it shows problems that where not there before, this is not something you can fix by changing slicer settings. It’s a hardware problem of the hardware you changed. Not the idler tension, not the gears -they worked fine before, why should that have changed? Open the extruder, take out the hot end and check everything is like it should. You wrote it’s a clone, maybe it’s a crappy one. Maybe it’s slightly misaligned, maybe the PTFE is to short or to long or not inserted correctly and held correctly by the collet…

Do you still have the old hot end? Can you salvage parts? Compare them to the new one, are they exactly alike? Especially the PTFE?

Kudos Robin - your answer was right on the spot.

I took out the replacement hotend and compared parts with the previous (demaged) one:

Left: the new extruder, right: the old extruder. Everything is the same (I didn't take a picture of all the parts), but the PTFE tube is shorter. Probably because it is shorter for the MK3S (what my friend has) vs. the MK3 (what I have). I reused the old PTFE tube with the new hotend, and the results were "a little" better:

On the left - the result after replacing the PTFE tube...

I still have some issues with the printer, but they probably worth a different post. Thanks for all the replies.

RE: Failed prints after replacing the hotend

Your nozzle looks to be right against the heat block.  I think there might be a gap between your nozzle and heat break.  That gap could cause problems with leaks and clogs.  

RE: Failed prints after replacing the hotend

Posted by: @cwbullet

Your nozzle looks to be right against the heat block.  I think there might be a gap between your nozzle and heat break.  That gap could cause problems with leaks and clogs.  

Where do you see this? Maybe before I used the longer PFTE tube? Here's how it looks now (removed the fan shroud for better visibility):

Do you think that's not enough?

RE: Failed prints after replacing the hotend

I am fairly certain that I stripped the heat block threads by trying to replace the nozzle without removing the whole hot end assembly first. I am going to just replace the whole hot end and hope that I dont have the same issues that OP had. I will stop posting on this and create my own thread if I continue to have problems, cheers.

RE: Failed prints after replacing the hotend

Looks good to me.