Extruder Motor "jumping" / Nozzle clogged? / won't extrude

Using better tools i only managed to unscrew the whole "screw" thing + nozzle. (see picture)

I guess I will put it in a glass of acetone over night. It also looks like there might still be some white ABS (the tiny bit the printer shipped with) in it.

The J-Head is really good - www.hotends.com.  The dimensions of the mounting groove are slightly different, so the MK4 might take a bit of sanding to get it to fit.

Just the hot end.  It would be best to use it with the printed MK4 which doesn't need the plate.  I don't think you would be able to get it to work with the stock acrylic extruder.

I just noticed something is wrong with the plexi of my extruder. What's going on there? (see picture)

I really hope having the nozzle + brass rod thing in acetone over night solves the clog and i can at least print the mk4 extruder before the plexi breaks.

So, it turns out my hotend was clogged from the white ABS that was delivered in the printer. After removing the filament I only used PLA and it seems it only started to clog yesterday.

The acetone helped a bit. But what really helped was drill bit with a diameter that fitted. I carefully drilled out quite a lot of white plastic from the sides and from the nozzle end. I'm not sure if I got 100% out but after several baths in acetone and more cleaning there was no plastic coming out of it. I still couldn't remove the nozzle from the threaded rod/pipe thingy though. So, who knows.

Right now I'm printing something and it seems to work fine.

Thanks for all your help!

What I learned: I will definitely need another hot end for ABS. I just don't know if it's better to buy a second one from Solidoodle or to buy two new J-Head hotends.

Also: Will the MK4 extruder work if I print it in PLA? with it's lower melting point and all.

I checked out their website, and I like that extruder, but it is out of stock.  Anyone know where I can find something equivalent?  Or when they might get new ones?  I have Lawsy's MK4 mount, so preferably, it would be something that works in that.

I am having the same issue with clogging and skipping these days.  It all started with a stringy print when I was using Octave's Black filament, and soon the extruder motor was skipping.  I unclogged the hot end, but the problem seemed to persist.

One thing I noticed is that the extruder works decently well if it is just hovering freely above the platform, but if it is printing the second layer, it almost instantly skips and clogs up. 

In my case, there are a few issues that might be to blame:

1. I didn't screw the brass fully into the PEEK since it wasn't hot at the time (maybe the filament doesn't properly enter the brass tube?

2. I accidentally drilled out a bit of the PTFE liner at a small angle, so the filament might get stuck on the walls

3. The nozzle might not have been fully unclogged.

Clearly, I made quite a mess of it, so it seems that replacing the extruder and/or the PEEK is going to be necessary in the end.

There seems to be quite a few MK IV's on ebay. As it is a relatively open design anyone can produce it as far as I am aware.

I have just printed lawsy's MK4 mount. So will be test fitting the MKIV extruder when it arrives and will  modifiy this mount if necessary.

nothing is "wrong" persay with the plexi.

those cracks are just what happens.

it's because they guys as solidoodle chose to make the extruder from acrylic rather than something less brittle, (say lexon, or ABS) as a result, the clear acrylic tends to start to fracture, eventually it cracks.

There isn't a lot that can be done.
short of buying a new head from Solidoodle, or printing one of the jigsaw replacement heads that are uploaded to these forums.

I finally found out more about the connectors. The are called IDC MTA-100 and they are blue and red because that's the color code for 22 AWG (red, for the resistor) and 26 AWG (blue, for thermistor) wire.

If like me you just need the blue and red connector for the hot-end you need these part numbers:

3-640440-2 the red one for the resistor
3-647002-2 the blue one for the thermistor

Just google the part numbers and you will find them on digikey or elsewhere (I'm ordering them from RS-Components).

Great find, I dislike how rs-electronics have a minimum order of 10. And Digikey charge a flat $34 shipping :s