Hey, I'm really looking forward to building this project, but I had one main question. You wrote on the spreadsheet bout count and amount. Which is which and what do the mean? Also, the "1mm shim, 5mm ID" had neither of those, what should I do?

 

Don't know if it helps but try one of these clips: Bowden Tube Clip by walter

Without them I have a lot of bowden tube "play".
It might turns the retraction more accurate.

 

Does this go under the flange of the push fit coupling? I noticed there is some movement there.

 

Yeah they make it so when you retract the coupling doesn't suck up into itself on the motor's side or push in on the extruder side on recover. I noticed that the fitting that came with my E3D "bowden extras" had quite a bit of travel on the retract, and the retract doesn't actually begin until the PFTE tube stops moving with the filament so those clips seem like a great idea. Of course, just this weekend I replace my extruder fitting with a BSP one that has a very small amount of movement to it. I thought it would make more of a difference but it only knocked my retraction distance down by about 1mm. Still, every bit is an improvement.

@carl I am definitely going to try your XY carriage, ordered a 40mm NEMA17 because I don't think I need a full 48mm heavy motor for extrusion, or I hope not because it saves a lot of weight.

 

Parts printed, install in progress

 

Beta direct-drive installed, and functional! Just printed a test cylinder and it looks great.
I used a modified version of @trublu832 rear bracket, so I could mount his fan shroud back there. Working well.

Thoughts on the design:

• I printed this with my rep1, the same machine used to print all the other parts for the c-bot. Maybe tolerances\settings have changed, but I had to drill out both the 1.75mm hole in the top of the gantry where the push-fitting goes just to get the filament though it. I also had to drill out the holes the lower ptfe tube goes in quite a bit to slide it in place.
• The only easy way to load the ptfe tube is when the extruder is out, and you can slide it in from the top (otherwise the shaft blocks you). I don't expect to be changing this that much, but an easier way to swap it would be nice: Maybe change the upper bracket it fits in into a two-part design like what the J-head uses below it: A couple small bolts holds the outer bit on, if you need to change the tube you just remove the outer bracket and pull the tube easily out.
• The whole thing is slightly wider that the original bracket, so I lost a few mm of print space on X: I need to redesign my x-endstop mount though, and I can recover the space that way: Would be nice if there was an option to mount the endstop on this bracket, right now there are no available mounting holes.
• May be hard since everyone's hobbed gear could be different, but it'd cool if the printed bracket directly below the hobbed gear mated super-close with it: Would allow us to print stuff like ninjaflex.
• It's... not easy loading filament actually: When the filament slides passed the hobbed gear it's no longer lined up with the ptfe tube, so you need some small needle-nose to grab it and shove it in there. Not the end of the world, but a bit clunky. If facing it, I feel the extruder could be moved from .5 to 1mm left, may help resolve this.

But as a first pass, it works pretty slick!

On a side note, I also simultaneously mounted a .6mm stainless-steel volcano nozzle on it, so I can print carbon fiber: Unfortunately it jammed on my second print and I'm unable to get any more filament though: Looks like I need to remove the nozzle and clean... I think this is just a feature of the new nozzle though, and not the overall system. Nozzle is also making a weird burning smell I've never experienced with the brass ones I normally use.

 

@Carl Feniak :

• I'll adjust these to give more clearance. How was the larger hole dimensions for the tube coupling?
  • Bit tight, I feel like it could be expanded slightly and make that push fitting thread in there easier.
• Do you think is need backing nuts or just have it thread into the plastic carriage plate?
  
  • While the backing nuts wouldn't hurt, probably not needed since there's not a lot of perpendicular stresses I see going on there. It's all mainly vertical force.
• It should be the exact same width as I used that file as a starting point. Could of been a duplicate file though, I will double check.
  • It's definitely wider, just eyeballing it, maybe a cm or so? I figured it was on purpose to make room for the stepper relative to the top wheels. I feel it could be smaller \ the original size though.
• Endstop mounts: what does yours look like now?
  
  • My X is mounted to the left side of the Y gantry. I'd rather it be mounted directly to the x-gantry. You can see an (old) pic here (my Y endstop has since been moved to the front)
  • 
    
  • Building the C-Bot 3D printer: Part 17 : Electronic & Software day 2
• What do you think of this instead: just leave the lower PTFE tube 8-10mm longer so that it extend up and supports the filament? Alternately I can provide the 3D printed support as you mention as I've though it out already
  • I had originally tried that myself: It's really, really hard to load the filament into it, since the hole is so tight: Getting the filament around the hobbed gear at that angle and immediately tucking into the ptfe would be neigh-impossible.

 

I made one too!


It is comical to me how little retraction I need now. Was 7.5mm 65mm/s, now 1.0mm 60mm/s.

• I had no issue with the size of the 1.75mm hole to accept filament. I didn't add a push fit fitting up there because I don't think I need one.
• I unbolted the hotend from the mount, inserted the pfte tubing and estimated a generous amount, forced it up toward the extruder motor, then remounted the hotend. I then cut the PFTE tubing as close as I could to the drive gear at a bit of an angle. I would have liked to get a little more angle to it but it is kinda hard to get the scissors in there.
• My endstop is a hall sensor that I screwed into one of the spare pair of holes in the carriage plate, those aren't there any more so I had to temporarily zip tie the sensor to the block for now.
• With the test filament piece it slid right into the PFTE tubing and I was shocked. When loading it for realsies it almost lined up but all I had to do was touch it with a screwdriver in there to knock it over. I think my pfte is higher than yours so the deflection is a little less so it is easier to load? Also it would be easier if I had cut the angle a little more!
• My original single extruder carriage is 73mm and this is 80mm (roughly) so it is a little bigger. It looks like some can be shaved off the width on the right side (from my picture) of the stepper? Not a big deal for me though.
• The only thing I had that didn't seem perfect was that the nut traps in the back were a little large so if I tighten down the screws, the nuts start spinning.

 

Ha @CapnBry , sounds like we have two different print settings My nut traps were a little small: I had to use pliers to get my nuts in there (but they fit great once pressed in), and like mentioned, I had to drill out all my other holes. But this was the experience I had with all the nut traps on all the previously pieces I printed. What's interesting is, I use the same print settings (on my rep1) to make captive hinge bracelets (which obviously need really tight tolerances so as to not stick together) just fine. Meh, apples and oranges.
I did have my ptfe tube longer like yours, but (like mentioned) I had a heck of a time getting my filament in there as it passed around the hobbed gear, so I cut it lower so I could use some pliars to cram it in there. Wonder why that was such a different experience for us... hrmm...
I've not yet got a chance to tune anything since my new stainless steel extruder jammed... hopefully tonight!

 

Yeah the motor fit perfectly in the slot and it appears to rest on it. I don't think it could fit my stepper any more snugly. Carl I completely forgot to also say a big thank you for whipping up this design. I'd been trying to tackle my retraction dollops with all sorts of combinations of retraction speeds and methods and temperatures and print I've got going looks amazing and perfect. I am very interested to see the one section of this that really brings out ringing artifacts because I didn't adjust my acceleration settings at all yet.

@AK Eric yeah I printed these pieces on my C-Bot which I am still messing with the settings on. My first layer was a little high and the ABS even started to pull up a little. I'm also under-extruding by close to 10% just because I was trying to get rid of the retraction blobs so all of these might contribute to my perimeter dimensions being just a touch smaller than actual size. I printed with 0.24mm layer height, 0.6mm nozzle, 0.72mm extrusion width.

 

@Carl Feniak , to echo @CapnBry , huge thank you on this upgrade: After swapping back to my brass .6mm volcano nozzle, I printed out a dual-cylinder test with 1mm of retraction. Not a bit of stringing of blobbing. "So Happy"
To answer your question: I actually didn't use your back plate, but used it as a template to modify the one by @trublu832 : So while the steppers rests in the notch just fine, I had to sand the sides down slightly to get it to fit. But that could be my bad on the redesign.
Here's my happy cylinders: 60mm/sec:

 

Great, thanks for that design update @Carl Feniak !
FYI, I just knocked out a 3dbenchy, with really no print tuning yet other than dropping the retraction to 1mm. Man, came out soooo much better than the Bowden. Here it is with no cleanup using the .6mm volcano nozzle, 300 micron:

 

I think the motor is great where it is, but I can definitely see that AK Eric's has a bit of a bend around the drive gear. Mine does not have that but it may be just that we have slightly different diameter gears.

I've got my retraction down to 0.7mm 60mm/s and I am just starting to see some occasional stringing. The acceleration I think will have to be lowered but that's not a big deal. The top piece I printed at 3000mm/s^2 the bottom was at 2500mm/s^2 and both show some obvious ringing. I need to check the tension on my belts too because I just sort of pulled them tightish and started printing. The print time for this dropped from 3h10m to 2h52m just even with the slower acceleration just because of the retraction takes so much less time now. It is amazing how well my pieces fit together now because they're so flat on the top.



The little strings you see in this last picture are more caused by the fact that I had the print temp a little too low so there was some incomplete extrusion in the infill which stuck to the extruder tip and kinda got pushed around for the rest of the print.


I'll also need to make a different spool holder or put a brake on it. Because the head is jerking at the filament directly, it can really yank a bunch of filament as it zips across a 300mm build plate at 200mm/s. The extra just kinda falls off and starts wrapping around the spool axle which eventually is going to bind up.

 

I've been following all of the new direct drive developments and the results look good so far. I can't help but think that this design somewhat backtracks on one of the key goals of this printer to remove as much moving mass as possible.

Is the need for direct drive more for the Volcano nozzle users, where filament is oozing out of the larger nozzle?

Either way, it's always fun to see the design evolve.

 

Here's my opinion, take it for what you will

Volcano nozzles generally print with slower speeds, but a higher extruded volume, thus ultimately faster print times. But with the larger orifice size, the Bowden setup really contributes to stringing and blobbing: Even though the direct drive adds more moving mass, it's moving a lot slower (compared to a .4mm nozzle) with the volcano anyway, so the 'greater moving mass will cause print issues' sort of goes away. And the direct drive system (as shown) suddenly removes all the stringing and blobs the Bowden caused with the volcano, so, direct drive, IMO is a win for Volcano.

If you want to go with a standard nozzle size (.4mm) then you need to print faster to get even close to the volume rates of the volcano, and based on the smaller orifice size it's less prone to blobs and stringing using a Bowden, so using a Bowden seems far more applicable there. Bowden = less moving mass = (technically) faster print speeds.

Long story short: For me, Volcano = direct drive, normal nozzle = Bowden. But this isn't really based on any science, just what I've personally observed. And note I've never put a .4mm nozzle on my cbot, this is mainly from looking at prints done by my buddy @sheffdog and his .4mm nozzle.

 

I'm thinking the same thing: Something with a larger ID than the 1.75 ptfe used in the extruder (like what my Rep1 uses for it's guide tube, think its teflon?). I agree because, right now getting the filament routed is my new problem: I have it running through some zipties clamped to the wire-bundle going from the left-front corner of my bot to the hotend, but there's so much tension it'll pull the whole bundle down flat against the top bot: Need something more rigid (the tube) to help reduce this issue.

 

For my Pegasus, I made a spool holder based on the profile from one of Carl's designs so I didn't have to redesign the contact with the v-groove. It takes a spool holder that I modified from Thingiverse since some of the spools I have needed a larger size, but some need the smallest, so it's quite large, but works fine. I then printed a spacer that holds the spool snug to one side to keep it from unwinding too far too fast. A 1/4" bolt snaps into the top.

I like it better than the piece of plywood that was inserted through the spool in the original kit as that takes a good amount of force to pull.

 

Thanks for all the great info this forum is generating. I'm hoping to go direct drive soon as well, but I need to work out my fundamentals first. I'm hoping to benefit from some of your success in tuning your C-Bots.

I'm looking for advice on settings. Here is a coat of arms for a co-worker who's a big Harry Potter fan.
I'm using Matterhacker's Midnight Blue PLA at 200 deg. with a .6 nozzle on my dual volcano rig.
This is a single extruder print with these settings in S3D:



I started with a retraction rate of 7mm and had a clog, I backed it off to 3mm and was able to finish the print.

Here are my results.



The piece is 9.5 inches high and took about 10hrs. Printed on it's back. As you can see I'm getting lots of pips and stringing. There are areas in the middle of third image where the plastic is not filling in.
Any suggestions on changes to my settings? Vertical orientation with supports rather than horizontal?
Any input would be appreciated.

Thanks again!

P.S. Credit where credits due: Hufflepuff Coat of Arms author: Andrew Forster's Profile -

 

After loading the filament a couple of times now, I think the V1 is slightly too far to the right so this is a good move. I can see it definitely pushes the filament to the outside just a tad, which is great because you know you're going to get great grip but more often than not I am poking around at the filament to get it to align into the PTFE tubing. I haven't printed your second version yet though, things are working too well for me I don't want to take it apart again! I did up my retraction to 0.8mm 60mm/s though (from 0.7mm).

I rigged up a quick system with my remaining 2mm PTFE and a clamp and that also prevents the filament from being jerked off the spool. I've ordered some 4mm PTFE and a couple fittings to give it a little bigger tube / less friction which should be an easy swapout. I'll make a little extrusion-mount fitting holder next time I have that color filament in.

 

Off the bat, have you done a calibration cube with that PLA? Your extrusion multiplier is .9, I usually run PLA .95 -> 1.0. It feels like it's under-extruding. Also, you could try turning up the temp more: The cooler it prints, the more it looks like spaghetti and less likely it is to stick to the stuff around it. How fast are you printing? Printing too fast could contribute to that, but if you're at 60mm/sec or under, that seems like the right ballpark (based on my .6mm nozzle usages) for that sized nozzle.
Finally, I'd print it vertical if you could: Reason being, with a nozzle that size, the Z-axis has the least resolution (.24 mm per step based on your settings), while the XY has the most: If you flipped it up on end, you'd see a great reduction in all the stair-stepping you see on the face of the shield. Or you could print it at .15 micron (which would almost double your z resolution): I recently did a life-sized head at that res with my .6mm nozzle that turned out great.