Prototype BMG based 'tall' direct drive extruder tool

Discussion in 'Tool heads & ToolChanger' started by Jai Stanley, Dec 12, 2019.

  1. Jai Stanley

    Jai Stanley Well-Known Member

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    Hi chaps,

    Thought I'd put a few pictures up of my current project: a dual geared extruder toolhead that uses existing parts to go from the bowden tool heads to direct drive cheaply and easily.

    My intent is to use as many parts I already have as possible, dock onto the existing pins without having to move them in X/Y (more solid that way and uses the excellent machined parts without the ambiguity of printed parts as an interface) and allow me to use the existing wipe/brush.

    longer term: I want to be able to quickly swap tool heads on the tool changer so having the pins in a fixed position is important to me. I will design a connector at some point.

    Anyway: first prototpye printed last night and I immediately realised a fndamental mistake! I placed the nozzle too high in the z axis! A look at a CAD of the toolchanger I downloaded; it is 3.6mm too high so I am currently banging my head against fusion to improve.

    Some pictures so far:

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  2. Jai Stanley

    Jai Stanley Well-Known Member

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    I've used a stepperonline 0.8deg pancake motor. We shall see if it has enough torque. I also have an E3D 0.8deg pancake with connector, but it is 6mm deeper and heavier so I want to give this one a go. Stepperonline also do a 1.9deg that has more torque at the same weight. I prefer this short design though as it is easier to package and wont stick out too far when docked.

    Anyone tried a BMG with this small pancake? I had it on my last printer (CR-10 based) and it was fine to be honest, but it was a slower machine.

    I'm goint to make a new tool-head wire support that covers the end-stop wires and make the extruder look better, but these will come after I proof of concept this one. I'll also print it all up in white PC-Max like the rest of my machine. I LOVE that material!

    Any feed-back appreciated!
     
  3. Greg Holloway

    Greg Holloway Administrator
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    That looks very cool. I'd be very interested to know how it performs.
     
  4. Jai Stanley

    Jai Stanley Well-Known Member

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    Ntesla66 and Greg Holloway like this.
  5. Jai Stanley

    Jai Stanley Well-Known Member

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    Next job: make a tool-head chimney and temporary harness to try it out. Then onto making a fewchanges, such as wire management and place to put zip-ties. Then it needs a cooling fan.

    Watch this space; hopefully I'll at least be able to get a print out of it later today.
     
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  6. Andy Cohen

    Andy Cohen Well-Known Member

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    Nice design!
     
  7. garethky

    garethky Well-Known Member

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    Nice job!
     
  8. Jai Stanley

    Jai Stanley Well-Known Member

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    Getting there. 6 month old, long print times and slow cad skills mean everything takes longer than I'd hope. It's rapid prototyping; minus the rapid part:

    Today I've got the third prototype (neon orange) onto the printer and printing. This tool already had a 0.25mm nozzle; so I've kept that. It's currently printing a linear advance calibration before the first test print.

    The second prototype (blue) went on and I did some test prints. This one has the pancake motor on it and is therefore very light. Trouble is I ended up running the current as high as it was specced for and it got very hot. If I reduced the current, I would hear griding and chattering noises which I assume was the motor loosing steps when the linear advance made it rapidly change direction. You might be able to get away with the 1.9 degree varient but instead I got four of the E3D small motors in their sale.

    I had to make a different toolhead wiring support to allow the longer motor to fit by the way. Not so with the pancake motor.

    Hermea printing the third prototype at 0.24mm layer height, 0.4mm extrusion width:

    Crappy fast and dirty cooling nozzle on the blue one:
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    Part off the blue prototype:
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    Third prototype:
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  9. Jai Stanley

    Jai Stanley Well-Known Member

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    More cad work to do. I'm going to enlarge the top so there is room to cable manage and hide the connectors when assembled. I need to deepen the wiring slot for the cooling fan and make more/better facility for containing the cables up the side. The top needs a neat wiring trap also.

    What do people recommend for a cooling fan? I think that a small concentrated blast at the nozzle tip is best, well it seems to make the most sense to me. I might be able to get it to blast from two angles if I get my loft on.

    So far so good.

    Is it as good a my Hemera? Well, not so far, but I've only printed a bit. I don't expect it to be, but think it'll be lighter and importantly: cheap as chips for those who already have the V6 assemblies. You'll need a few heat set inserts, various M3 and M2 screws and some BMG clone gears (full BMG clones are approx £10 each and delivered quickly from banggood).

    Let me know if you have any thoughts or ideas.

    Jai
     
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  10. Jai Stanley

    Jai Stanley Well-Known Member

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    After a bit of frustration with inconsistant extrusion this afternoon: I realised the weak fast printing PETG hinge wasn't applying goo pressure on the idler drive gear... Since reprinted in PC-max with an additional 1mm of thickness on the wall the spring presses on and annealing at 100 ish deg C for an hour.

    I'm currently printing calibration parts again (in Rigid Ink ASA atm).

    Also: at 1200mA, the motor was HOT in an ambient temperature of 60 degrees. I have reduced motor current to 1000mA to see how we go, but with the new hinge: no problems so far. I might consider fitting a heatsink and fan to each extruder if it's still bad, which will again require a re-think on the toolhead design. I might be able to fit a fan to the toolhead that the stepper motor and heatsink approaches when docked/picked up.

    After fiddling around, I've not cadded up my changes so an overnight print opportunity missed...

    All good fun!
     
  11. Greg Holloway

    Greg Holloway Administrator
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    Good to see how this is developing :)
     
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  12. Jai Stanley

    Jai Stanley Well-Known Member

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    Realised shortly after the last post that I had the nozzle and heatsink out of concentricity to the drive gears by about 0.3mm! Annoying. Took ages to re-cad it without destroying the geometry. Back to where I was now and need to re-print to see if it has improved the design. Also: I've clashed with the longer E3D motor with my Hemera head a couple of times at the edge of the print bed at the back. I'll try the pancacke motor again once I've re-printed to see if the trouble was with the path not being straight enough. Otherwise I'll have to re-think the design; possibly spinning it 90 degrees to the motor doesn't sit out too far. Oh well, this is why we try these things!
     
  13. Jai Stanley

    Jai Stanley Well-Known Member

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    Update:

    I've had real trouble getting consistant extrusion and think I've sussed out why:

    The gears were quite hard to turn by hand. First I thought I was getting too much meshing on the main drive gear so I printed a version with 0.2mm slooted motor moutns - allowing me to adjust the backlash/play in the gear. This helped but not a lot.

    Next I realised the long 'reverse bowden' (annoying term from youtube - the feed tube - had lots of friction. I have temporarily used a feed from above the machine with a much shorter feed tube. Also helped: but not a lot.

    Next I turned to the settings. I found that lowering the 'jerk' helped a LOT. even getting the 'tighter' extruders to print. I notice the under extrusion/gaps are coming after areas where the pressure advance has rapidly moved the extruder.

    Then I alos noticed that the original BMG I have here doesn't have the extruder teeth lined up perfectly in line with the 2mm feed/extrusion tube, unlike the design I cribbed from (ripped off) which has them centred. This allows the sprung arm to do the gripping, but produces much less friction on the filament and allows you to remove the filament a lot easier by releasing the spring pressure. I re-jigged the design and printed one. I put it on today and have printed some benchy's seen below. I must say though: the issue of requiring much lower jerk is still present so it might just be an inherant part of the design. I really should have somehow tried the original BMG for comparison....

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    The blue PETG one is the newest iteration; the white is a PC-max version with less mesh on teh gears. The blue one produced the following:

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  14. Jai Stanley

    Jai Stanley Well-Known Member

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    Does anyone have any experience of tuning extruder acceleration, jerk and pressure advance settings? The lower 'jerk' (instantanious speed change) setting of 200mm/min seems to produce the nicest results with no obvious detriment to the print speed (after a cursory watch of the print).
     
  15. Jai Stanley

    Jai Stanley Well-Known Member

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    Used an older prototype extruder on the volcano tool last night. Had to mix and match parts to make sure it had decent backlash and clearnace due to the issues mentioned above: the bontech have a slightly different diameter on the teeth and gearset; and the various chinesium ones also. This was useful, and also a source of the issues I suspect.

    Anyway: I reccomend getting the Triangle labs parts over other chinesium, and original bondtech over all of them: that said; I just ordered two mor £11 clone extruders from the UK warehouse of Banggood. That way I'll ahve four identical with very little lead time and for the least money. I suspect I'll end up publishing three variants of the design to allow people to match to their needs (0.1mm difference in drive shaft bearing location on each).

    I spent a couple of hours tuning pressure advance and trying different instantaneous speed change (jerk) parameters last night with this 0.6mm nozzle and volcano hot end:

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    I've settled on 200mm/min for now: the same value that seems to be best for the newest version and V6 with 0.4mm incidentally. Not sure what about the design requires this: it doesn't actually seem to be the friction. More testing and head scratching required, but even if it reduces the speed a bit, I'm not bothered. I find speeds of about 50mm/s are reasonable for quality and it doesn't seem to affect that speed at all... I prioritise accuracy and quality WAY above speed.

    I printed a 150% benchy (nozzle and layer height also 150% higher than my normal 0.4mm nozzle settings so seemed appropriate) but forgot to check the slow down below x layer time so the chimney and fine details of the cabin are a little off. Also: NONE of my test prints have any cooling yet: I;m just designing a fan shroud so I can....

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    Not too bad really, seeing as there's no slow down, cooling and I haven't printed with the volcano or 0.6mm on here before: no optimisation at all.

    This morning I have been printing with the 0.4mm V6 on the newest version of the extruder (again, no cooling but its not a complex part) to see how the settings are:

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  16. Jai Stanley

    Jai Stanley Well-Known Member

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    Ultimately: I'm now quite pleased with the extruders... The goal of utilising the bowden parts that I bought 4 of and giving a cheap upgrade path to direct drive is acheived. The width is less than a Hemera tool, and the weight; but not actually that much all things considered. The design did get a bit over complicated and large so there is plenty of scope for improvement; but right now I don't think I CBA. To go from a bowden setup to this you'd need to buy 4 pancake motors ideally (the pancake one is working fine now there's less friction and the jerk is reduced) or four E3D small motors, four chinese knock off BMG gearsets or extruders and some hardware (heatset inserts, square M3 nuts etc; and these are available on Amazon for a reasonable cost.

    I'll put up some STL's at some point soon. Not totally happy with the CAD work; but I've been teaching myself object oriented CAD at the same time: My CAD days were back in teh early 2000's using AutoCAD, and the training I had on inventor and Catia long forgotten. It'll do I guess! It certainly works.

    The weight: I measured a copper block volcano variant with an E3D (larger than pancake, but still small) motor last night:

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    Heavier than I expected! Certainly feels a lot lighter than the hemera in the hand though.

    Here is the pancake motor and Copper V6 with copper nozzle.. (NOTE: both are missing the fan shroud you'd need and the second photo might be skewed because the wiring is atatched to the printer, though probably more reprisentative, dunno):

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    Let me know if you have any questions or suggestions!

    Kind regards,

    Jai
     
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  17. Jai Stanley

    Jai Stanley Well-Known Member

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    Here's what they are like on the printer:

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    I have a filament feed from above as an experiment (blue teflon) so ignore that.

    Also note: the pancake motors have the benefit of sticking into the printer less. The larger E3D collide with the Hemera and other tools when the pause macro is run: No problem I just changed it to go near the home position when waiting. Neither interfere with the heads when within the bounds of the print volume, I think. Need to properly check. Some more testing on the limits will tell me if the pancake motors are really suitable. Can anyone think of a good stress test? I do know that they get effing hot when run at 1100mA with the enclosure at 50-60 degrees though!!! Dangerously, not good for long term health hot to the touch. I have an IR thermometer that will be able to shed light on how hot; but if they are performing well I might be able to drop the current and or fit heatsinks.
     
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  18. garethky

    garethky Well-Known Member

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    I'm considering doing one of these for the Mosquito. I did one in the orientation of the Hemera and its working but has a bunch of things that are creature comfort issues that this layout resolves. Not sticking into the are of other tools, being able to fully open the idler door to look for filament grinding, gear viewing port like on the i3 machines. I'm going to do a cad mockup and see what the layout looks like.

    Great work!
     
  19. Thomas Kamsker

    Thomas Kamsker Active Member

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    Hi Jaa,
    that is an great design i was about to draw and happily found yours do you share your files somewhere i would like to give it a try ,..
    garethky: i have done a mosquito design https://www.thingiverse.com/thing:3888182 maybe this is an good start for you and for sure and mixup of the BMG clone to mosquito might be cool ,..
     
  20. Jai Stanley

    Jai Stanley Well-Known Member

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    Yea: sorry guys: I've been slow to publish. I got stuck doing house chores and setting up a new main computer SSD, and a XPEnology NAS on an old computer after completely running out fo storage (8TB plus 250GB)... very annoying.

    The main reason is that I think I am going to make three varients... the BMG, Triangle Labs and random Bangood BMG style gear sets I have have different teeth profiles and mesh on the drive gears. I can only assume anyone else will have as many so will publish three (concentric, 0.1mm spaced and 0.2mm spaced) to allow differing tolerances on the drive gear to filament path. Also: I STILL haven't made a cooling nozzle I am happy with.

    On the plus side: I have had some REALLY nice results from the lower instanaious acceleration settings (jerk) and it doesn't seem to slow the print down when at sensible speeds for PETG. I will try with ABS too, which is a material that can actually print very fast. PETG needs slower speeds after all.

    I'll be back with an update and probably a thingiverse link ASAP.

    KR

    Jai
     

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