This topic contains 21 replies, has 6 voices, and was last updated by 
Charles Jackson 1 week, 6 days ago.
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If i get chance ill do a quick video of how to do it next time i need to. In mean time see below.. obvs warranties void and hot things are close to touch so be careful..
- Retract the filaments if possible, follow the instructions under robox support for removing jammed filaments - brief summary is as follows. Power off remove head, power back on, feed filament forward (around 50mm) then cut it.
- Eject the filaments, Power off. Reattach head, feeding filaments into bowden in head carrier
- Turn on and heat the heads up to 250°C using M104 S250 T250
- Heat soak the head for 5 minutes. Power Off and remove the head and try and pull the filaments out they should come out ok.
- Now Remove the rubber nozzle cover. Take a picture of the nozzles so you remember how tight they are against the heater block. Now use a small ratchet with a 7mm socket on it and gently start to undo the brass nozzle. If it needs anything more than a bit of force (sorry not got a toque wrench and setting) then the head will have cooled too much so repeat step 4.
- The Brass nozzle should come out and expose the needle valve.
- Clean up the interior of the heater block gently.. nothing abrasive. Keep re attaching the head ,reheating (m104 S250 T250) and then removing if needed. You need to get the surface where the brass nozzle seats into the heater block absolutely clean to ensure no leaks whey you reattach the nozzle.
- Now clean up as much of the material out of the nozzle as possible using hot needle method to melt filament or Acetone if its ABS. Don’t use anything abrasive like Dremmel, drilling with small drill bits or wet&dry or sandpaper as it will wreck the nozzle and it wont ever seal again either at the head or the needle valve.
- Blow torch works well in short bursts of 4 to 5 seconds with propane blow torch just to burn away / melt and plastic.
- Put the head back on.. heat soak again for 5 minutes at 250. Remove the head and start screw the brass nozzle back into the head. Take care not to cross thread and take your time. Don’t over tighten.. and support the heater blocks by jamming screwdriver in between it and the robox casing as over tightening or too much torque will snap the titanium heat bridge and then, in the late Bill Paxtons words, “its game over man”.
- Repeat 4 - 10 for the other nozzle if necessary
This worked for me the first time i did it.. i havent had any material leaking from where the nozzle screws into the heater block or anything. If you do have this problem then you probably havent got the nozzle far enough back into the heater block and need to see why - probably some obstruction where the nozzle seats against the heater block. You might be able to use some kind of sealant that is stable to 300°C to help seal but i havent tried that.
Hope this helps
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This reply was modified 2 weeks, 5 days ago by Charles Jackson.
Aerospace Engineer with a creative itch being scratched by Robox!
Interesting to know!. Yup I can risk a 150odd quid for the greater good.. Whats more a problem is if i do FUBAR my dual head and i cant buy another!. Think Ill get a spare head before i try and mod my currently working one!
Aerospace Engineer with a creative itch being scratched by Robox!
much obliged @chazr33gtr 🙂
I am deathly afraid of needle valve seals failing and its always handy to have a DIY guide for such things. I am also waiting for the single heads to come out for hopefully under 50 quid *wink wink CEL*
Your welcome. Note this isn’t a fix for needle valve seal failure at the top of the heater blocks. Its a last ditch fix for a totally blocked nozzle.
Cheers
Aerospace Engineer with a creative itch being scratched by Robox!
Ok.. So i had another material jam using next gen flex in my Dual head. The Settings are right. It printed about 4 or five things before jamming on a longer print.
Took my head apart — goodbye warranty!. and yup exactly as expected the ngenflex had formed a ring (well square shaped ring) of material between end of bowden tube and the metal feed guide of the head. stopping the material moving backwards or forwards. I’ve videoed the whole procedure and will edit later and share a link to it.
In meantime heres a couple of pics of the problem and I’ve got some bowden tube turning up today so I will try and fit a longer piece. Note: NGen Flex is on the left and ABS is on the right. Suspect if i fed ABS into the other nozzle it <span style=”text-decoration: underline;”>wouldnt</span> have jammed.. its just when using “softer” or flexible materials that loose rigidity at lower temps.. i.e PLA starts softening at 70°c ish
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This reply was modified 2 weeks, 3 days ago by Charles Jackson.
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This reply was modified 2 weeks, 3 days ago by Charles Jackson.
Aerospace Engineer with a creative itch being scratched by Robox!
Success - so far. Replaced the bowden tube with a slightly longer one (see pics).. Infact it needed to be compressed ever so slightly along its length to get the metal housing to seal around it. The bowden now buts up tight to the end of the metal feed guide.
Am printing right now a long print.. so will see what happens..
@pete - if alls good. i might disassemble and replace the heatsink paste with a high end computer CPU paste as you suggest.. but left as is for now
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This reply was modified 2 weeks, 3 days ago by Charles Jackson.
Aerospace Engineer with a creative itch being scratched by Robox!
@chazr33gtr The lack of thermal paste may be contributing to the jamming as the tail of the head may be overheating and letting the filament soften. If the filament is getting soft that far back, the tail is getting too hot.
I operate two Betas and four Production Robox.
I am the US/Canada Technical Support engineer for the Robox.
See my 3D Hub site at https://www.3dhubs.com/phoenix/hubs/benHey Ben 🙂
Yup could be two things causing the issue. Ill dissasemble again and replace with high end CPU thermal paste and see how things go from there.
Maybe your manufacturer has changed thermal pastes, or has an assembly issue that wouldnt get picked up in normal QA testing. AS it takes a while for problem to manifest.
Equally I might just have a monday morning or friday afternoon head !
Cheers
Aerospace Engineer with a creative itch being scratched by Robox!
Things still working a treat.. have done a good few prints now. Material Ejection and swapping between PLA , ABS and PETG not had any jams, missfeeding or inability to eject material yet. Must admit had been having material eject issues quite commonly and they seem to have gone for now…!
I would say the primary problem was the short( only by a 1mm or so) bowden tube. I will belt and braces it with better thermal paste too.
@pete If CEL are getting heads returned with jammed filament etc (dunno if thats true?) maybe this is one of the causes.
Aerospace Engineer with a creative itch being scratched by Robox!
Quick Update.. Disassembled the head and cleaned off the thermal paste and replaced with some high end CPU paste.
Still had a problem printing Colorfabb PLA but now not at the head but at the exit of the head carrier into the head. So the revised tubes and thermal paste defo doing their job . Turns out i hadnt set the ambient temparature right it was at 60°C.. So the combination of ambient temp, plus nozzle temps and bed temps were causing the head carrier to get hot enough to cause the PLA to swell at and jam at that point.
So Ambient temparature being set is very imporant with materials that can deform at low ish temparatures like PLA. I will repeat for NGEn Flex as that ambient was set to 60°C as well and I reckon the problem will go away there too.
I dare say the OEM head even with the issue of bowden tubes being a little short would be fine and the problem was really with heat soak in the head/head carrier due to ambient temp being too high.
Aerospace Engineer with a creative itch being scratched by Robox!
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