Rostock Extruder Maximus

by bLITzJoN Jan 8, 2016
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Just printed this and installed in anticipation of some Ninja Cheetah filament. V7, printed in PLA. Everything came out great, but I did have two small stumbles before getting it to work properly. First was 100% my fault, in not adjusting the drive roller for the new thickness. The second, may be design, but more likely just a tolerance issue. When my red release lever was installed, the bearing was pressing against the upper portion of the feed tube. The alignment of the feed roller is dead center, but the bearing seemed about 1mm to high, as if my red arm was shorter than the one designed around. This prevented the necessary friction from being applied on the filament. The fix was easy, just taking a razor blade and trimming the bearing side of the upper feed tube, enough to allow full contact.

With PLA, this extruder works great, and I'll know about the TPU filament later.


I expect some level of razor blade tweaking since the tolerances are pretty tight. Let me know how it turns out with the flexible stuff. It still takes some tweaking with retraction and flow but it's magical when you're doing the impossible - printing TPU with a Bowden setup. I will say, if the TPU binds inside the tube (it will look like a spiral swirl in the tube) then some better tubing might be in order (e.g. Capricorn tubes).

Some success and some failure. I was able to get a few test prints just fine, but on longer prints, I consistently have issues. At one point, I came back to the print, and i had a small batch of red spaghetti spilling out, the filament squeezed through, and was piling up. All my troubles stem from having a smaller drive wheel, I measured 11.X mm. I don't remember the exact number at the moment. Would you mind posting your working model? There isn't much I can do with the .STL files to fix my problem, and I have had no success with printing the v5.

glad you remixed this and did it right ! when i was making mine i just did it 'good enough' to where it was working for me and I was set. I"ll download this and try it out when the time comes. good work man !

Version 7 has been published!!

I'm close to releasing an updated model. I've modified the hob gear hole to accommodate the larger size (12.4mm), tweaked the pinch point, top has a tweaked design with larger hole for the manual gear to rest against the hob gear, built-in support for the spring nub, and screw holes are smaller for tighter fit. Anyone else have any suggestions?? I've already printed the new design but I accidentally moved a screw hole out of alignment so I need to print another.

This part fits great with all the stock hardware except I had to sand out the hobbed gear hole quite a lot to make it fit. The hand wheel doesn't slide on to the stepper shaft enough to get grip for manual feeding.
I'm Also getting the issue where the filament seems to eventually bind up in the bowden tube and then jam. I've tried all sorts of settings, nozzle sizes, speeds etc.. same issue.

What is the diameter of your gear? My hob gear is 11.8mm and humanzee's is 12.4mm (read below). I'll upload another model with some tweaks for both sizes (providing yours is the 12.4mm). As for the flex (assuming that's what you're referring to), I'll post my S3D profile settings in the description once I upload the model. I've printed several things without issues and was thinking of printing some gellies for my kiddos.

Yeh mines 12.4mm as well.
If you can increase the hole area for the hand grip wheel to fit all the way up to the hobb gear that would be great. So far this extruder mod is working great for normal filament

Sure thing, and I have a few other tweaks in mind as well before I finish a full remix into a flying extruder.

This is a great improvement for printing Ninjaflex in that it is now possible. One issue I'm running into is that tension seems to build up inside the bowden tube until it binds and under-extrudes or stops extruding at all. My current fix for this is to manually relieve the back-pressure when it starts to become a problem, and I'm messing with lowering the extrusion multiplier in an attempt to not outpace the extrusion at the hotend. The extrusion multiplier thing seems to be working to some extent, though I haven't got it dialed-in yet. Have you or anyone else experienced this? Either way, any thoughts?

Yeah, the grip of the extruder works a lil too well at times. I'm still tweaking, but this is what I've been printing with using a 0.4 nozzle. Extruder Multiplier at 1.15, Extrusion Width set at 0.35. Layer height 0.2. Retraction Distance at 6.5. Temp is at 235, bed at 50. Printing speed at 20mm/s.

Update: I had landed very near to the settings you describe, so I thought maybe I had been a little aggressive in deburring the hole just downstream from the hob gear and/or enlarging the hole for the hob gear. So, I printed the part again and was more conservative in my modification/cleanup, and it appears to be working beautifully now.

So two notes: One, I don't know if it's be design, slightly different print settings, or if the hob gears are slightly different on my very recent model, but i had to sand about .5mm from the diameter of the passage for the hob gear for it to fit without binding.

Two, to anyone in the future, don't go crazy cleaning up in the area of the filament inlet from the hob gear and go slow if you need to enlarge the gear hole.

Update number two: Nope, still the same problem of it binding and stripping the filament at the hob, and apparently nothing to do with slack in the extruder. I guess I'll just stick to semi-flex.

I just posted something I made today using the real deal. The examples I shared actually used semi-flex.

Mini Octopus

Very interesting. Maybe your bowden tube is a little shorter, maybe my thermistor reads a little cool (I don't want to push into the 240s without an all-metal hotend)... maybe the Vudon priest who blessed my machine was a fraud.

I think I'll use this as an excuse to convert to a flying or flex-shaft extruder. Your design is still pretty ideal at the hob-to-tube interface.

LOL! Be on the lookout for a flying struder. It has been something in the works for me along with a different effector.

Did you print this in ABS? Taulman 910 doesn't suffer from shrinkage like ABS. I'm still running the same setup I posted without issues. I'm testing some ABS filament so maybe I'll print this as my test [for the filament and the extruder]. You are not the only one mentioning the hob gear being tight. I am running some close tolerances for that much needed grip; perhaps I need to include an additional stl for ABS unless SeeMeCNC hob gears are not consistent.

Interesting. My hob gear is 11.8mm. What's yours?

Mine's 12.4, so yeah I guess SeeMeCNC was sourcing them differently at different times or something.

I should mention the ooze is where I need to still dial things in as pieces can end up "hairy" when doing cross pieces. The fruit tree and cat brush are the last ninjaflex items I've printed.

Fruit Tree (Modular)
Pet Brush, for dog or cat

working great !!! thank you for sharing

My pleasure. Very happy to hear it's working for ya!

Maybe the broken ez studer was the problem, but the print didnt work. It seemed to be too small, nothing fit. I still plan on printing this, once i get my printer back together.

This print is too small?

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May be my printer. Parts didnt fit. I printed it in abs, may have shrank. Will try again in pla, once i get the printer back together. Someone is printing this again for me.

I published an updated model (v7) you may want to take a look at. You may have the larger hob gear.

Possible. I might print one in ABS to see for myself. Someone else mentioned it was tight fit. I used Taulman 910 which doesn't suffer from shrinkage like ABS.

Great design! Printing with ninja-flex flawlessly now!

How did you get the gear that grips the filament off the motor so you can flip it over?
I think mine has thread lock in there. The screw came out fine, but I can't pull or pry the gear off the shaft and I don't want to break it.

You had to flip it? I just moved it back a bit.

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Did you put thread lock on the shaft during installation? Once I loosened the set screw it easily slid for me. In your case, if you have access to a shop with a jaw puller you can break it free easily. Another option would be to slide two pieces of wood wedged between the gear and the motor while bridging across a vice or a gap that you can tap the shaft with a hammer. Wish you luck, keep us posted on your progress.

OK, the hammer works, but maybe start with a rubber or plastic hammer. I got it loose with a small clamp and regular hammer, but I distorted the end of the shaft just enough that the drive gear would not come all the way off.
I had to push it back down and grind the edges of the last 2mm of the shaft to remove the damage I caused.
I posted a "I Made One" with some other comments, but it's working great. Thanks!!

thank you thank you thank you..... I wish I could show you the failed attempts at making one f my own

Very welcome!

I had just finished well over 20 hours printing with this upgrade. Coincidentally, over 15 hours has been using ebony wood PLA. Very pleased with the feeding. The only gripe I have is the grip is so well that I can't really retract the filament manually (except Ninjaflex). I've been writing a macro to retract and feed. I'll share once I get it right unless someone else has one handy. (learning raw gcode, I can get short distances but not in great lengths)