3D printer nozzle clogs (partial in this case) and how I fix them up to get my printer working great again. Hope you enjoy. Cheers!
Wrong, wrong, wrong. I’ve seen so many nozzles break or end up with a bad seal after trying this. These steps should be considered a last resort, after using the cold-pull method: http://bukobot.com/nozzle-cleaning
Maybe I missed it, but probably worth mentioning this is for those printing with ABS and not to clear an issue with PLA.
I think this is the only guy that recommends to disassemble and assemble a nozzle cold.
Yeah, disassembling it cold is a particularly bad idea. If that’s even possible, you probably didn’t have a good enough seal beforehand.
As @Whosa_whatsis says, this is bad advice. Cold pulls are what we at E3D recommend, and we link people to the excellent guide on cold pulls on the bukobot site linked above.
Undoing your nozzle cold is asking for damage to your hotend. Not using the thermistor hole and just taping it to the side of the nozzle is going to give you crappy unresponsive readings and leave you susceptible to the thermistor detaching and causing a dangerous runaway state.
@MKme_Lab Yup, in the first part of the video, in the aluminium block there is what appears to be a hole for the thermistor.
@Sanjay_Mortimer It is too large for that hole. This is the way 1000’s of Solidoodle printers have/are shipped so unfortunately this is the only option without new parts- I realize you are trying to push the E3D but this is not one.
@MKme_Lab Not trying to push anything. I wasn’t aware that was the default situation on SD hotends, and if that is what it takes to get up and running again then so be it.
However I still maintain that just taping a bare thermistor to the outside surface of a nozzle is a terrible way to mount it and will affect performance and reliability. It looks as though SD had a whole load of blocks made up with those holes, only to find they were too small, and then went with a dirty hack to keep shipping regardless. A good option might be to open that hole on the block out to 2.5mm or similar to fit the thermistor and mount it there.
I had that same style hot end on my SD3 and had a few frustrating clogs. They did in fact tape the thermister to the outside /facepalm. Don’t unscrew the tip cold as it will very likely crack parts if it had a good seal. I solved my plugged nozzle issue with a butane torch a few times, worked great. Just do small cycles of burning it out or you will destroy it. You can permanently solve the problem like I did by throwing it away and getting the E3D hot end with a .6mm tip 
The torch method is also to be avoided. You tend to overheat and carbonize plastic in the nozzle, which leads to more clogs. Better to use the heater that’s already there and has feedback to keep it from overheating the plastic.
My cold-pull instructions above include a picture of progressive pulls trying to clean out a nozzle that had been abused in this way. If you must disassemble the hot end, but a torch used sparingly, just to keep the temperature high enough to keep the parts from seizing up can be useful, though if you get to that point you should be prepared to end up throwing it away.
@Shauki At E3D we use a two step reduction in diameter with much better results than we were getting with a single step reduction. You can see the drawings of our internal geometry here: http://files.e3d-online.com/v6/Drawings/V6-NOZZLE-175.pdf
@Sanjay_Mortimer Looks like you’re getting better results because of the shallow drill angle. The two-step reduction gets the bore wider closer to the opening. A long, very narrow-bore section will increase back pressure. The ideal solution to this is is to use a more acute bit to finish the hole to that the internal geometry more closely matches the external geometry (the first picture on my nozzle cleaning article shows some very good pulls, which show the shape of the inside of our nozzles because they’ve been molded into that shape), but if you’re stuck with standard obtuse-angle drill bits, this type of multi-step reduction is better than nothing because it more closely approximates the desired acute conical tip.
@Whosa_whatsis Yup, fully agree an acute angle bit would be more effective. It’s just a matter of making nozzles in the thousands and having drill bits available from stock without having to regrind etc. It just gives us a bit more flexibility in production and ease/consistency of production over multiple machines etc.