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  1. #51
    Technologist
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    Oct 2016
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    184
    So got the new z-screws installed, after some reprinting of the z-screw parts. Didn't get the parts glued in at perfectly, there was a bit too large gap between the parts and motor doesn't have enough power to move through that without skipping steps. Newest parts work well as long as I don't print parts over 90mm in height.
    Changing the screws was quite easy, luckily I designed the whole bed carriage to be detachable. Also the z-motor mounts are quite easy to detach.
    https://www.dropbox.com/s/toqsp6n5ds...45.39.jpg?dl=0
    https://www.dropbox.com/s/1t6tr260ce...15.10.jpg?dl=0

    The new flex coupler works quite nicely, although the Filaflex tube is maybe even bit too flexible.
    https://www.dropbox.com/s/gc0zejm6f9...15.21.jpg?dl=0
    https://www.dropbox.com/s/81lchfvkyd...16.07.jpg?dl=0
    https://www.dropbox.com/s/1fj4uf4rft...18.23.jpg?dl=0

    Also printed part cooling fan using Taulman Nylon. Nylon had absorbed some moisture, which lead to stringing, but after cleaning the part it seems to work ok.
    https://www.dropbox.com/s/t1tkh0p50l...06.26.jpg?dl=0
    https://www.dropbox.com/s/vyxeiahun0...06.30.jpg?dl=0

    Anyways, now the bed moves more or less straight. Another stackable box, green PETG. Again, having trouble with retraction, even though I upped the retraction length from 2.5 to 3.6. Starting to think that maybe the linear advance might be doing something nasty...
    https://www.dropbox.com/s/s4vptji4l7...46.33.jpg?dl=0
    https://www.dropbox.com/s/koi9dqru4p...46.40.jpg?dl=0
    https://www.dropbox.com/s/7q3frm3hqb...46.52.jpg?dl=0

    To fix the retraction problems, I ran KISSlicer destring wizard. To get a good baseline, I disabled linear advance for this. For string-free results, 5.3mm of retraction is needed. Next I'll run the same print, but this time I replace the increasing retraction length with increasing linear advance. Once the LA is tuned in, I'll run the retraction calibration again to get the hopefully optimal retraction settings...
    https://www.dropbox.com/s/gz8as6q77e...06.13.jpg?dl=0

    One thing Dollo has problems with is printing circles. I suspect that the friction of the axis mount causes very small stalls in the movement that lead to small imperfections. Loosening the motor mount screws should ease the movement, but I think this type of rail setup will never be perfect.
    https://www.dropbox.com/s/vy2gh92k90...06.21.jpg?dl=0

  2. #52
    Technologist
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    Oct 2016
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    184
    Ok update time. Been working on few things on the new Dollo build and I guess the build could soon be said that it's "finished". As if any printer build project is ever truly finished...

    First, I made some adjustable feet for the frame. The feet are adjusted with the screw in them. There's also dampening parts under the feet, printed with Filaflex. Don't mind the gap in the top surface, using linear advance with KISSlicer seems to require upping the infill-perimeter overlap quite a lot and I haven't tuned it in yet.




    For electronics, I designed some mounts that attach the frame. The PCBs are held in place with notches on the side and for example RAMPS/Arduino can be just slid in the mount. For RAMPS, designed a 60mm fan mount that clips on the RAMPS PCB (blatantly copied this design: https://www.thingiverse.com/thing:145946). With 5V, the fan is practically silent, yet has some airflow.
    Also as I need some extra 12V and 5V outputs and a way to connect ATX PSU with PCI-E connector, I designed and connector mount and fan connector board with 12V and 5V outputs. There's also a connector with 5VSB,PS_ON and GND so I might use 5VSB line in future to power Raspi and RAMPS and control the ATX PSU from Octopi. This would get rid of the USB changer for the Raspi. For now, PSU main on/off will do fine.







    Also mounted ATX PSU under the frame, which you might just see here. There's new cable shroud, previous version was too flimsy and sagged too much. This version uses PTFE tbe as the spine, which seems to work much better.
    I need to get longer cables for the display, it's now on the back left corner of the printer.



    Printed this vase to test the ~full z-height. The result is ok-ish considering the whole z-axis uses only plastic, but the inconsistencies get worse when going higher. Not sure what's the cause, but two possibilities come to mind: the z-rail slides seemed too loose last time I checked them (PETG probably wasn't the best material for those) or the glass plate I use moves around slightly, due to how it's mounted. I'm revising the rail slide design a bit so that should tell me more.




    So to finalize this build:
    - try to improve the z-quality. Not mandatory, the quality is still passable
    - design parts for mounting the heated bed I bought
    - raise Z height with one set (12cm) so total print height would be ~24cm
    - maybe design a mount for the display (and get longer cables...)
    Last edited by spegelius; 08-22-2018 at 12:55 PM.

  3. #53
    Technologist
    Join Date
    Oct 2016
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    184
    For printing parts for Dollo, I mostly use my trusty Prusa MK2 (now upgraded to MK2.5). It produces quality parts with good tolerances and does it reliably. My other printers are bowden setups and although they can produce quality prints, they are more prone to filament jams with certain PLA brands. I've noticed that even the Prusa suffers from this in extreme cases, but the direct drive extruder setup minimises the problems caused by filament not moving freely. With bowden, the pressure builds in the long tube and causes quality problems.

    Since the Prusa is the only printer capable of printing all the parts for Dollo and other projects that require certain level of quality, it is quite busy and tied up most of the time. Getting another printer that can print with the same quality and reliability has been on my mind for a while. Since I upgraded the MK2 to MK2.5, I ended with some extra parts:
    - bed
    - extruder
    - smooth rods for X,Y and Z
    - bearings
    - other bits and bobs

    So I got the idea to put the parts in good use and build another Prusa. For frame, I'm going to use Dollo extension parts, I think it'll be robust enough. If not, I can always make it stronger with metal rods inside the extension parts.
    As I have the MK2 heated bed (MK42), I'm planning on using Prusa fw so I have full MK2 calibration features. As I don't have the Minirambo board, I'm going to try to port the fw to RAMPS. If that doesn't work, then just buy the Minirambo. Also I'm planning to use DRV8825 or Trinamics stepper drivers, so that should improve on the already great printer.

    I started the design work on the frame parts, I forked the Prusa repository. Thankfully the parts are designed with OpenSCAD, so modifications are easy to do: https://github.com/spegelius/Origina...tree/MK2_Dollo. Did a mockup of the original frame so I can re-create the part positioning accurately. Frame design is progressing quite nicely.
    prusadollo.jpg

  4. #54
    Technologist
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    Oct 2016
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    184
    Ok I got bit carried away with the Dollo Z-axis upgrade, it will be 2x120mm which means that the max z height is about 35cm. one z-screw and z-rail glued together, other z-screw in jig waiting for the glue to cure. I'm pleased how straight those parts are, seems that the jigs help a lot.
    More parts to be printed and assembled. Also need to redesign the z-motor mount, current solution is not very stable.



    Prusa/Dollo hybrid design is also progressing well. Most of the frame parts are designed and started printing them. Using grey and white PolyMax PLA for most of the parts, along with black PETG for the motor mounts and X-carriage parts. Quality filament does have it's good points; it's easy to print, no jams even on all-metal hotends. With same exact gcode, cheap PLA's cause problems.

    Screenshot_2018-08-31_17-39-34.jpg


  5. #55
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    Oct 2016
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    Got the Dollo3D.2 z-axis upgrade done and printing. Full z-height is now ~36cm and the bed moves that full range seemingly without too much fuss. Designed new z motor mounts, which are much more stable than the previous solution.
    Also found out few things that I need to tweak:
    - bed carriage needs to be properly tightened to the z screw parts. Noticed that it's not level because it can tilt a bit. Used some screws to fasten it properly for now
    - the larger frame is now bit wobbly, as was expected. So need to design some parts to make the frame more rigid.
    - the z screws aren't perfectly straight, which might cause problems. Need to do couple test prints with ~full height to see how it goes
    - there's no top support for the z screws and when bed lowers down, the screws wobble around a bit, maybe causing problems. Probably need to design something to keep the screws in check






    Printed benchy and the same vase as before, this time with white PLA as I had it loaded. There's some inconsistencies in layers, not sure how much of it is due to the current z-setup or the filament (which is bit uneven on other printers also). Z wobble maybe, but seems that there isn't a consistent pattern...








    And Prusa/Dollo hybrid is partly in assembly stage. Most of the parts are designed and being printed out. RAMPS enclosure, PSU cover and display cover need to be modified and need to redesign the bed carriage a bit.
    Also modified the y-idler to be adjustable, fixed a small Prusa z-rod positioning error and planing to modify the x-idler to adjustable too. If my calculations aren't off, total usable z-height for this build would be around 23cm so 3cm extra compared to default Prusa MK2


  6. #56
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    Oct 2016
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    Tried printing something taller, a vase from here: https://www.thingiverse.com/thing:570288. Scaled 2x so 30cm total height. Print time ~24h. Filament ran out @24.7cm so I edited the file to continue from ~correct layer with blue PLA. Sadly the blue part came off, not sure why because the rest of the blue part holds together fine, even though the print quality is quite bad at the top.
    Also seem to having some problems with the extruder, had to disable linear advance because the motor was skipping steps with low print speeds... again not sure what is going on, the motor is a quite beefy thing and driven by DRV8825 driver. Maybe try switching to A4988 as the other Dollo runs fine with one, with same motor and extruder design.

    File is sliced with KISS, which leaves ugly gaps in the print. Probably didn't have proper settings for hollow print or something...

    It's obvious that the frame wobbling around starts to cause visible problems when the parts get taller. So need to get the frame rigid.






  7. #57
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    Oct 2016
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    Ok two things:
    - the blue filament is not PLA, its PETG . Explains why it didn't bond to the white... note to self, next time actually check the filament instead of 'remembering' where I left certain rolls....
    - swapped the DRV8825 driver to A4988 and no more skipped steps. I think the problem is this: http://cabristor.blogspot.com/2015/0...steps.html?m=1. Missing steps with low speeds... and the problems were evident with low perimeter speeds. Wonder how much this affects the surface quality... must print another benchy.

    This DRV8825 problem might affect my plans about PrusaDollo if I can't trust the drivers. I have those diodes mentioned in above blog so maybe I'll try if that works.

  8. #58
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    Oct 2016
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    Reprinted the vase and benchy after changing the stepper driver. Results do seem bit smoother, although the material is different color and brand PLA.

    Had a look at Aliexpress, tl smoothers that are attached between the board and stepper driver look like what I want. But first I'm going to build one myself to see if it works. BTW, buying stuff from Aliexpress is almost too easy with the mobile app.




  9. #59
    Super Moderator curious aardvark's Avatar
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    Jul 2014
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    okay - wow !
    you've made your own extrusion and screws :-)
    Damned impressive.

    Discounting your time and the print time - what sort of cost would you say the two printers will come to - individually ?
    filament, plus electronics.

  10. #60
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    Oct 2016
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    Well the original Dollo design and extrusions are by @benengel94, I've just gotten into this hobby of trying to make good enough 3D printed 3D printer . The z-screw idea has been forming in my mind slowly and still mutating to perhaps something actually useful. Well see. Current version works but might wear out quite fast.

    For the first Dollo, I'd say ~2 rolls of PLA + some odd bits of PETG, ABS, Filaflex and small amount of Nylon for the part cooling fan thingy. So depending how cheap you can get the filament, something like 40 euros.
    Bit less for the new build since it's not finished yet, doesn't have those frame stabilizer parts which I need to redesign somewhat.

    For the electronics (had a quick look at Aliexpress):
    - RAMPS + display ~25 eur
    - 6 motors ~35eur
    - 12V PSU ~20 eur
    - some ?3Dv6 clone hotend ~10 eur
    - PTFE tube ~60cm few euros
    - endstop switches, extruder gear, few M3 screws and grub screws, M3 nuts, wire... ~10 eur?

    So something like 100 eur. With the filament, not the cheapest printer out there, but I'd say much more fun .
    Personally I have bad experience with clone E3D hotends so I would opt for genuine part.
    Of course the design doesn't demand RAMPS or need a display. That's just what I've been using and configure Marlin for. I'm planning to install Megatronics 3.1 to the 1st Dollo, bought a DuetWifi for one of my other printers and Megatronics is without printer now. It has option for 3 extruder motors, so my plasn for IDEX setup on Dollo should work with that board (probably).

    For the discarded Dollo parts, I think something like 15 rolls, mostly PLA. That's prototyping... I still have most of the old parts, maybe someday I can recycle them somehow.

    Also, PrusaDolloMK2 build is progressing, bottom of the frame is mostly assembled. Printing some bow ties so I can get the Z frame parts assembled. Modified the X parts so that they accept the brass tr nut and added possibility for belt tension adjustment, need to print these.




    Box of parts waiting for assembly:

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