Solved Filament jammed inside BETWEEN extruder and hot end

Okay, might give the oiler a try once I can get it up and running again to print the oiler gadget. What kind of oil you use? Canola?

 

Did you see my question about a picture? I'm curious to see what's happening

 

For me? I didn't see another question. Sorry, I did take some pics, but not after disassembly. I actually have a video review I was planning to post of the RoBo 3D, generally positive but showing a few of the issues (not this most recent one -- I recorded the footage before all this went down. Now I've been busy just trying to get it fixed)

I could take a photo for you showing the stripped heater block that wouldn't reattach to the cold-end (I tried to reassemble them cold, but there may have still been some PLA that I couldn't see gunking up the threads. I think it would have worked better if I had the heater attached and turned on, but it would have been a little bit tricky to do. )

I'm confident that the replacement hotend will solve my problem, and I will chalk this all up to a learning experience. I'm pretty new to this whole reprap FDM modeling thing, and wasn't entirely sure how it all worked and what all the parts did or how they came together. Now I know a lot more, and will be able to better troubleshoot and tweak. Hopefully RoBo can continue to make slight improvements to their design, as well (if I could see better/easier mounting of the hotend, and an elimination of the ribbing/banding artifacts, then this printer would be a hands-down winner)

One more question: what's a good way to remove the silicone boot (and heater and thermistor) for the heating block , if it's all caked over with PLA. Just keep it turned on and wear some good gloves while I work? (I've been using oven mitts, which is not great; I do have a good pair of leather welding gloves I will turn to instead when I do this next step...)

 

I'm just really confused what issue you're having getting it in. A picture would be very helpful because in my opinion swapping the nozzle on the robo is very simple

 

I was able to swap it in once... after that, there was difficulty... the screw wasn't "digging in" to the sides of the aluminum. However, I was able to get it more or less in place (secured with one screw, anyway)

The problem came when I took the hotend apart -- dismounted the heater block from the heat sink cold-end section, to remove the jam in that segment. It wouldn't go back together. Attempting to do so stripped the soft aluminum threading of the heater block, so it no longer seals tight/flush. And that seems like something unfixable outside of replacing the hotend completely.

 

The heater block is stainless steel. edit: actually it is aluminum

Are you sure you don't mean heatsink? That's held in with a set screw

This is all very confusing. Let's discuss more after you share pictures because right now I have no idea what you mean.

 

Yes, sorry... I was misstating the screw-in part as brass earlier (at first I thought that brass center channel ran all the way through -- didn't realize it was steel at the bottom until further research in the forums)

And if the heater block is stainless steel... it doesn't look like it, and it gets stripped mighty easily by the steel screw-in bolt at the bottom of the heat sink. You sure it is stainless steel? It neither looks nor feels like it... (and the threading is stripped... I will take a photo.)

 

Here's some images (sorry, just have them in Google Drive, not an easy place to embed from):

https://drive.google.com/file/d/0B2Q1ZSqb8_UaLVhadmV6U3M3cUk/view?usp=sharing

https://drive.google.com/file/d/0B2Q1ZSqb8_UaMzlLbGEtdlV5OTg/view?usp=sharing

(couldn't get any closer, unfortunately... next time I'll use my USB microscope camera, but don't have it with me at the moment)

 

I'm positive that my hexagon has a stainless heater block. Yours appears to as well judging by the color. We could weigh it to find out for certain but it's unlikely to be aluminum because it wouldn't work as well.

We need to remove the plastic that's preventing you from threading in further.

Here's what I suggest, get a helping hand or something to hold the heater block by the wires, then heat it up to around 190C or so.

With a pair of tweezers you'll want to pull out as much melted plastic as you can by hand. Remove the brass nozzle as well.

Then you want to get an M6 Machine screw or bolt. Use that and thread it all the way through the heater block while it's still hot. This should push out most of the filament left in the threads, as well as fixing any threads that may have stripped. Which, btw, it looks like there's not enough thread engagement to really secure on the heater block at the present because of the plastic.

With everything still hot you can carefully remove the black silicone shroud and clean the excess filament using something like a brass bristle brush.


Start by screwing the nozzle into the heater block until it touches the metal, then back it off 1/2 turn so it's no longer seated against the metal. Then take the heatsink/heatbreak and thread it in until it touches the brass part inside the threaded hole. Then taking the 4.5mm wrench in your tool kit tighten down on the flats of the heat break and the brass nozzle until it's secure.

That should fix your leaking problem.

 

Yeah, that blue PLA that is in there is because it wouldn't thread, though. What I saw (or what it appeared, anyway) when I was trying to thread is that it would jam up, then wobble loose and the threading looked stripped, and I saw metal dust/shavings grinding out of it. That's why I have concluded it was stripping.

It might not be aluminum, but is it a soft alloy? (after all, stainless steel is an alloy)... when I search for info online, I can find nothing stating the actual metal of the hotend... it just says "all metal"

 

Well give what I said a try, Threading through an M6 bolt should fix any threading issues.

I'm almost positive it's stainless. Just doesn't make sense to use an aluminum because of the thermal dynamics involved. Best way to tell is to weigh it. An aluminum heater block would weigh 5.7g while a stainless would weigh 18.6g

 

It does feel a little heavier to the touch than I would expect if it were pure aluminum. But feels (and looks) lighter than I would expect from stainless.

I'll probably be hitting up the hardware store today so will see what kind of stuff I can round up while I'm there. Propane torch and M6 bolt are now on the list. (I was considering just firing it up to 210 while plugged in, held in place with a wrench while I try to screw the cold end in, squeezing the existing PLA out. Difficult, though, because of the way they designed the attachment of the cold end)

I'll give it another go at repair, but in the meantime I have some backups on the way if I need them. My time is worth money, so it gets to a point where if it is taking me too much time to repair, it's not worth it. I got pretty frustrated and my blood pressure really went up, so I had to take a little break from dealing with it..

Do I need the rubber boot/sleeve on there? Or is that optional? (I ask for if/when I have to install the replacement unit)

 

It can be frustrating I know. I have to take a lot of breaks because sometimes I just wanna take a hammer to it. You'll get there and be much more knowledgeable in the end. It sucks learning new things, but afterwards you kinda realize it wasn't as bad as you originally thought and should something else come up you'll be more prepared.

Heating it up on a wrench will be hard because the wrench will act as a heat sink and make it difficult to heat up. That's why I suggest holding it from the wires. If you do take a blow torch to it, be sure to remove the heater cartridge and thermistor first.

It's good to have a replacement, but I think we can fix yours. You could also start a replacement part request from Robo3d to get them to ship you a replacement maybe.

The rubber sleeve is optional. I'm not sure if kits even come with it. I think it was something special Robo3d got. Primarily it's used to secure the thermistor in place. Secondary functions it keeps the nozzle cleaner. I just used kapton tape http://i.imgur.com/A8QZBL6.jpg

 

Yeah, the reason I ask about the rubber sleeve is:

a) It actually makes it MORE difficult to keep the nozzle clean at this point, because it traps the melted filament, preventing it from dripping off (until later) and preventing me from wiping it off (ever)
b) It seems unnecessary, since I believe the heater and thermistor are clamped into place with a screw to secure them (or is that only for the heater, not the thermistor?)
c) As you said, kapton tape should work and, while it might not look as nice and will need to be replaced eventually, doing so should be much easier.

 

a) I agree on this. It keeps the steel block from getting crusted with burnt filament, but at the expense of a nice collection point. It's a bit of 6 one way half dozen the other. For assembly it's the obvious choice and I understand why they did it. Also looks nicer imo
b) The heater is secured but the thermistor is not. There are alternative methods to secure the thermistor. The E3Dv6 has a nice method of doing it, and can be theoretically adapted for the hexagon. There's also screw in thermistors like this: http://www.printedsolid.com/shop/e3d/stud-thermistor/

C) Kapton tape is alright. You eventually get filament trapped up under it and it gets pretty gross looking. Depending on how well you tape it will limit that. I'd just as much not use it, but it's a proven method.

 

Mike, I'm pretty sure the heat block is aluminum. It does look like it has a Electroless Nickel plating though. That gives it the "stainless" shine. This link from e3d forum shows a full heat block meltdown. I can believe the heater melting aluminum but not stainless!

http://forum.e3d-online.com/viewtopic.php?f=7&t=267