This time, the bad print isn't mine

I got new printed parts for the extruder from electronic-things.de, though I am not exactly impressed with the print quality. The hole for the hotend and for the hobbed bolt are both rather stringy and will need some bits removed to work, let alone work in the long run:

The holes for various screws aren't all great, either. Disappointing. I'm inclined to send them back.

Compatibility, schompatibility

I've been pretty busy with work, but I'm taking some time this weekend to put together the E3D hotend.

Getting the thermistor in was rather fiddly, making sure the sleeving didn't slip out. My first attempt didn't go so well - you can see one of the bare wires:

I retried and got this, which looks acceptable:

Assembling the rest of the E3D was pretty easy, but mounting it showed a bigger problem: The E3D mount is a lot bigger than the J-head: 16mm wide with 12mm groove width, where the J-head is 10mm wide with 8.5mm groove. The hole in the extruder is 10.5mm.

I thought I had done my research properly, and indeed everything I find says you can mount an E3D on a Wade's Extruder. The reprap.org Wade's extruder page makes it sound like it's a 16mm hole, so why is mine different? Is mine a weird mutation on Wade's? I got it from reprap-fab.org, but when I go there now, a) my order is no longer visible, and b) the item with the same name is entirely different - it has a similar-looking hotend, though. I don't think this is an early J-head after all, but some other piece

Regardless of how this came to be, I now have a crappy hotend that fits my extruder and a shiny new hotend that doesn't. This leaves me with three choices:

1) Try to get/make an adapter (but that could make the assembly too long for the fan duct +Thomas Riedl so nicely printed for me).
2) Get (or have someone print) a new extruder (part).
3) Get a hotend that fits the existing extruder.

Incoming

One E3D hotend coming in from RepRapUniverse. I was tempted by the Volcano powerpack from e3d-online, but until I know it an e3d even works for me, that's overkill.

A couple of thoughts on what makes jam

And not the nice kind of jam you spread on bread.

I would really like to know why my extruder jams. Otherwise I'll just go on replacing things and having more trouble - and I've sure had enough trouble already.

I had a stripping back when I used the old bolt. At around the same time, I left the extruder at 220 for 20 minutes without extruding, moved the printer to a less stable surface, added the fan, and eventually changed the bolt.

I've been able to clean it enough to get a half-way decent print, but it slowly extrudes less and less again.

I had to relevel the bed, it has become almost a full millimeter "higher" - or the extruder head lower/longer. I did one successful print after the overheating incident without having to relevel, though, so at least it didn't immediately become longer.

One possibility is that there is now a little gap between the top of the hotend and the extruder. When doing prints with backpressure, this gap gets filled slowly either with stripped-off dust or squeezed-in filament.

Alternatively, there's something further down that causes slow filament buildup. I can atomic out the buildup, but not whatever is causing it.

I would get a newer hotend, but they're all so much shorter that I'd need a different fan shroud, which I can't just print. Obviously I need a printer to make parts for my printer.

I don't get why hotends are being made shorter at the cost of increased complexity. Having 1cm more extrusion height doesn't help much if you can't print because your hotend overheats. A long-necked hotend ought to have an easier time keeping the hot end hot and the cool end cool, but instead it's all cooling ribs and extra fans and fancy materials, just to get a little extra vertical space that 99% of people won't ever need.

This One Weird Trick will stop jams forever... or will it?

I've been looking at getting the E3D hotend (maybe even the Volcano, since I tend to print larger items rather than fine detail), but from a number of sources, including most importantly +nop head , heard that it's not so good for PLA. Plus I'd be unable to use my fan until such time as I may be able to print another.

On the other hand, I got a few tips, in particular a number of people had luck adding a bit of canola oil to the filament to grease the inside of the hotend slightly. Also, guitar strings are supposedly helpful, as is a bit of string with metal cleaner. I'm skeptical of the last one, as I don't know what it might leave behind.

Nop head suggests a 0.4mm (or probably 0.5mm in my case, as that's my nozzle diameter) drill shank while doing the atomic, I should get one. There's also the toothpick holder method, but I can't print the holder until my printer works:) Then there's "Korneel's Method" of carefully burning it with a kitchen torch and dipping it in alcohol. Not trying that one just yet.

After reassembling, when trying to center X/Y, I got "Printer stopped due to errors. Fix the error and use M999 to restart!.". Thank you for the informative error message. I tried turning it off and on again, as per IT Crowd. Worked. Sigh.

When extruding 5cm, it underextrudes quite a bit, but getting closer to the right amount, up to 3.7cm, then 4.5, then 4.725, then 4.7, then 4.8, then 4.4 (!), then 4.5. At this point I figured the difference might be due to too little tension on the extruder idler, so I tightened that. Results: 4.8, 5.1, 5.0. That's within my margin of error on this crude measurement, so I'm claiming it has gotten its problems out of the system.

An attempt at printing the test piece crashed into the bed, stripping up the kapton. Fortunately, I acquired some blue tape, which is a lot easier to apply. I did some proper levelling and calibration of extrusion (consistently extrudes 6% too little). After adjusting for that, I finally got correct extrusion. That was a lot of wasted filament there. The whole recycling filament idea seems more and more appealing. As part of testing, I extruded at 195C, at that temperature the PLA was drooling.

First test print (done without fan due to a short - I was lucky I didn't blow something) looked OK at the bottom but became increasingly stringy at the top. A sure sign of a jam coming on.

Maybe when I accidentally left it one high heat for a while I melted some of the interior and now it slowly builds up filament until it jams.

My coworker +Tom Riedl pointed out that the new hobbed bolt, being curved in its teeth, would move said teeth at different speeds, thus effectively carving out filament. My guess is that it doesn't carve enough to actually tear it off.

End of the hot-end

After last weekend's failed print I ordered some blue tape, but in the meanwhile (it's been four days, and it's still not here. FTW, Trijexx?) I happened to poke at the bed, and it turned out the corner that the print head starts in was loose. Now I should recalibrate, just to be sure. And since the backpressure was high enough that no filament got pulled for a while, check for stripping.

But first, clean. Atom. Clean. Atomic. Clean... I'm coming to the conclusion that indeed this hotend is also pretty crappy quality. Here's what it produces when I press filament through:

Very uneven. And the atomics are black and dirty. I admit defeat, and now need to find a quality hot-end for a Wade's Extruder on a Mendel90. It would appear my current hotend is a J-Head Mk II. RepRapSource has Mk V's available, but I'm not sure the shorter length is a good thing given the fan shroud. On the other hand, they look pre-glued, which is good, as gluing was a pain. Not sure if e3d or hexagon are compatible with my (2013) Wade's while being not much shorter than 71.5mm. More research is needed.

Pop! Goes the Hotend

Coming back after a week of "how on Earth am I going to get the nozzle properly cleared", I was surprised when I homed Z and the right side got stuck when I tried to move down to take out the bolt. Not sure what had happened, but the right side had gone higher than the left and was wedged, unable to move by motor power. Turned the motors off and manually screwing it down again helped, and after re-levelling it seems to work. But now I'll have to keep an eye on whether the right-hand threaded rod mount has gotten loose/worn.

With that repaired (for now), I got out the hobbed bolt and cleaned the stripped PLA off it. (Mistyped that as "striped PLA", doesn't look like anybody has tried that:) Also used a trimmed-down Q-tip and then an appropriately-sized hex screw to attempt to clear any flakes and bits out of the holes. Then I heated the loose hotend up to 230C, lifting one end to prevent backflow, and did a "hanging atomic". Without the extruder gears in the way, this one did indeed make that satisfying "plop" and showed dirt on the end:

The second one was nicer, didn't show any signs of dirt:

After that, I used the metal wire to try to push stuck dirt out, again at 230C and did one more atomic. There's a little bit of metal visible in there, so more cleaning is needed:

At the next one, I could see something black coming out with the filament I pressed through.

I rather like the sheer photographic look of these. They're very odd.

I noticed the jump up in temperature just before getting down to 90C, so that's apparently a thing the firmware does, not a result of me jiggling the wires.

Probably sticking the wire in from the tip was counter-productive, coming from the top and eventually pulling it out through the tip would prevent dirt from being pushed back into the tube.

After this showed nothing, I put everything together again and did a test cube - now on shiny new Kapton tape. Which didn't stick at all. I should have checked beforehand, Kapton is apparently not that useful for PLA.

It occurs to me that if, as Tim Hatch commented, the hobbed bolt was really poor quality, then maybe the hotend is as well. In which case, attempts at cleaning it are probably rather futile.