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  1. #41
    Mounting Y and X axis motors.

    Vitamins:
    - 9 x 50mm M3 screws
    - 3 x stepper motors with gears assembled

    Other parts:
    - 4 x bow_tie.stl (see previous steps for print info)

    Y-axis:
    Take one motor, two motor_mount_small parts and 3 50 mm M3 screws . Assemble and screw the screws in only couple of turns:
    https://www.dropbox.com/s/y173f3t5ym...31.58.jpg?dl=0
    https://www.dropbox.com/s/isyfxwuiz7...06.17.jpg?dl=0

    Next, slip the assembly on the rack. If it doesn't fit, open the screws more:
    https://www.dropbox.com/s/x682jr7uwu...06.21.jpg?dl=0

    Tighten the screws until the mount needs considerable force to move. It's a good idea to move the mount back and forth while tightening the screws. Move the mount through whole length of the rack. Turn back the screws in small increments until the mount moves relatively easily. Don't expect it to be buttery smooth and move freely, there are no bearings here.

    Repeat the operation on the other side of the frame:
    https://www.dropbox.com/s/sxynn7bevq6b5uo/2018-02-25%2014.47.14.jpg?dl=0

    X-axis can be assembled before assembling the motor mount for it, because the motor mount can be slid in and out freely.
    To mount the x-beam on the Y-mounts, first move the Y-mounts to the end of the racks:
    https://www.dropbox.com/s/dw5t56if961lm7z/2018-02-25%2014.47.33.jpg?dl=0

    Then slide the x-beam on the tie slots on the Y-mounts:
    https://www.dropbox.com/s/5erg4vkb8fcwiih/2018-02-25%2014.47.52.jpg?dl=0

    The bottom of the rack should be approximately on the level with the Y-mount top:
    https://www.dropbox.com/s/3bii49ml4e8ngtq/2018-02-25%2014.49.44.jpg?dl=0

    Add bow_ties to the bottom of the Y-mount and x_spacer junction. Assemble motor mount for the X-axis same way as for the Y-axis.
    https://www.dropbox.com/s/rh7cfco4veirkrs/2018-02-25%2014.54.51.jpg?dl=0

    Moving the mounts might seem bit rough and that's expected. These are printed parts so there will always be some unevenness. But in this case things will get better; after a some time printing with Dollo, the parts will adjust to each other and he movement will get somewhat smoother.
    Last edited by spegelius; 02-25-2018 at 08:34 AM.

  2. #42
    Been modeling parts for bed and Z-axis. Previous version of the bed carriage was bit too flimsy, didn't use existing parts and also needed nuts and bolts for assembly. So for the new setup I'm going to be using the extention pieces which should make the carriage quite robust. Z-axis prototyping is also underway.

    Wanted to see how well my first Dollo build handles a bit more complicated model so printed a terminator skull. A 28 hour print, with two PLA colors. Enabled M600 command in Marlin so filament change was a breeze. Had some problems with the black PLA jamming. Got the base printed after cranking the speed to 150%.
    Result is actually better than I expected.
    https://www.dropbox.com/s/2o9km6rlzo...29.50.jpg?dl=0
    https://www.dropbox.com/s/3arosjqir4...25.09.jpg?dl=0
    https://www.dropbox.com/s/0q9ukgh8b6...24.43.jpg?dl=0
    https://www.dropbox.com/s/faz0n9ecsm...24.29.jpg?dl=0
    https://www.dropbox.com/s/fg88hzgrw9...23.56.jpg?dl=0
    https://www.dropbox.com/s/hnxtgugqyz...21.16.jpg?dl=0

  3. #43
    Got the first working prototype of the Z-axis screw-mechanism. It works, but turning the screw requires a bit of force. But there's no slack so that's probably a good thing. Probably need to smooth out the threads with a file bit, because it seems that the seam is also causing a bit of unevenness.


    https://www.dropbox.com/s/b70qxbx19z...52.38.jpg?dl=0


    The screw itself is a V-shaped thread with a pitch of 3 mm, diameter 25mm. I didn't want to use simple nut, because of the wear that will happen. Wear in intself wouldn't be that big of a problem if it would happen evenly on the length of the screw, but unfortunately fost prints won't use the full z-length.
    So the nut uses side rollers matched to the screw shape and hopefully the wear will happen in the axles of the rollers and not in the screw.
    Side rollers are printed in PETG, other parts PLA. Again hoping that the different materials reduce wear. Also using some silicone grease inside the rollers.


    https://www.dropbox.com/s/jfoo0uhhnq...53.28.jpg?dl=0


    Also improved the mechanism for joining screw parts together using a keyed center part, same as I use for the z-rails. Keying makes sure that the screw parts are joined in proper way.
    https://www.dropbox.com/s/pn1jp7dbtd...52.58.jpg?dl=0
    https://www.dropbox.com/s/i69e4xfeg3...53.00.jpg?dl=0


    Source code for the screw thing: https://github.com/spegelius/Dollo/b...s/z_screw.scad


    Next, create motor screw coupler, integrate this thing to the bed carriage parts and try to print the whole thing. Who knows, maybe even get it working...
    Last edited by spegelius; 03-17-2018 at 06:18 AM. Reason: links

  4. #44
    Oh Prusa Slic3r, why you do this to me... over-extrusion and blobs and stuff. Started print the parts for the Z-rails and having a hard time to get the parts to print with decent quality. For most part Prusa Slic3r has been working ok, quality has been decent and consistent. But for some reason the rail parts are hard for the slicer. Switched to KISSlicer to see if the problems persist and lo and behold, pristine quality (Slic3r on the left, KISS on the right):

    https://www.dropbox.com/s/iuqovg1dds...20.42.jpg?dl=0
    https://www.dropbox.com/s/r89p7yanfu...21.18.jpg?dl=0
    https://www.dropbox.com/s/duyaqt57me...21.36.jpg?dl=0

    I guess the slope on the rail is the problematic are, as Slic3r tries to ensure vertical shell thickness and does it over somewhat. I haven't seen this problem this strong even though there have been some hints about Slic3r extruding more material than S3D and KISS. Also I've upgraded my Prusa MK2 with E3D Titan, which is a geared extruder (it's calibrated properly).

    Switching slicing sw mid project isn't something I like to do because it's yet another variable and might cause problems when fitting parts together. But slicer starts to misbehave, alternative is to spend extra time with post processing, which I'd like to do without as much as possible. So KISS it is, at least for these rail parts.

    Other progress: I have the z-screw - bed carriage part somewhat finished. But I'd really like to make the rail sliders replaceable, so one doesn't have to reprint the whole z-screw part when replacing them so going to do some more tweaking. Onto OpenSCAD ->

  5. #45
    Z-axis is progressing, models are finalizing, parts are printing et cetera.

    In the meantime, X and Y endstops holders. There are two varieties to choose from, both clip on the rack. Choice is yours.
    Top of rail, good if you want to have some flexibility in choosing the endstop position. Using one on my first Dollo:
    - https://github.com/spegelius/Dollo/b...op_racktop.stl

    End of rack. To adjust endstop position, whole rack needs to move:
    - https://github.com/spegelius/Dollo/b...op_rackend.stl

    Print settings:
    - material: PLA or other.
    - 2x perimeters
    - 10% infill
    - perimeter first
    - no supports

    Assembly is easy, just slide the switch in the slot and slide the whole thing either on the dovetails on the end of the rack or on top of the rack.
    https://www.dropbox.com/s/99oxk2w85f...23.26.jpg?dl=0
    https://www.dropbox.com/s/1wev33yxiq...24.30.jpg?dl=0
    https://www.dropbox.com/s/uajlvyt9jx...24.58.jpg?dl=0
    https://www.dropbox.com/s/itnjdpmg5c...51.01.jpg?dl=0

  6. #46
    Hello! Thank you a lot for the submission of this post! Once I had the same problem, and could not figure out what was the issue with!

  7. #47
    Finally got some Z-axis assembly done and it's actually looking like the damn thing could work even. Only one side done, other side will see some iterative updates.

    Rail holders top and bottom:
    https://www.dropbox.com/s/gwk1kdnkff...32.19.jpg?dl=0

    Frame rail/slide setup. Also supports the Y-beam. Rail slides are replaceable, printed from PETG. Used PTFE spray on the rails to improve the movement, still bit siff:
    https://www.dropbox.com/s/i6j2e5o8au...25.27.jpg?dl=0
    https://www.dropbox.com/s/7jpn0lxaxu...51.12.jpg?dl=0
    https://www.dropbox.com/s/e292po68uz...51.36.mp4?dl=0

    Motor coupler, Z-screw and motor mount/leg:
    https://www.dropbox.com/s/dihvkjfkyd...07.23.jpg?dl=0
    https://www.dropbox.com/s/0rqnvq8r0r...01.41.jpg?dl=0
    https://www.dropbox.com/s/zac7e1regd...07.37.jpg?dl=0
    https://www.dropbox.com/s/ytivc70i4b...07.52.jpg?dl=0

    Assembled on the frame:
    https://www.dropbox.com/s/mcikaqyjnw...18.02.jpg?dl=0
    https://www.dropbox.com/s/xnab5e5kmy...18.07.jpg?dl=0

    Rest of the legs on the frame:
    https://www.dropbox.com/s/ihju3xijtc...29.40.jpg?dl=0
    https://www.dropbox.com/s/6vhhh7jfzf...48.22.jpg?dl=0
    https://www.dropbox.com/s/3idy1yzqzc...48.31.jpg?dl=0

    Not detailing the print settings etc. yet, because there will some adjustments.
    Things to improve:
    - all z-screw side rolls aren't turning, which is bad thing in long term: the roll will wear unevenly and probably cause problems at some point. So to force the rolls to roll, I'll add some teeth on the rolls and z-screw.
    - z-screw sections joining: currently using glue to glue the center part, but maybe think something mechanical
    - z-endstop placement; probably add a dovetail slot on the z-screw carriage where the endstop or endstop arm can be mounted
    - not perfectly happy with the rail frame mount pieces, frame needs some disassembly when installing the rails. Probably good for now though...

    I might connect some electronics to see how things work.

  8. #48
    Slow progress for few weeks, but progress nevertheless. Got things wired up and another side of the z-axis printed with even z-endstop made. New z-screw has gearing so side rolls are definitely turning. Had some hard time with OpenSCAD as rendering took few hours for the new z-screw. Actually did some optimization using render() and looping rendered pieces to get the full height which sped things up quite a lot.
    And everything seems to more or less work. A short video of homing and moving z-axis:

    https://www.dropbox.com/s/ykfw4axmky...37.19.mp4?dl=0

    Still, even though things seem to move ok, there's small wobble going on. This is caused by the rigid stepper motor coupler and a slight curve on the first s-screw, due to gluing the pieces without putting them in a jig. I already designed a screw jig and redesigned the coupler to use similar flexible system I use on the first Dollo, but haven't installed it yet. I think I'll finish this version just to see how bad the wobble is and upgrade the z-screws after that.
    I have more parts printed so assembly is needed: bed frame and couplers for attaching the bed frame to z-axis and hot end mount. Need to design parts for mounting the actual bed and decide about what kind of extruder to use. Actually not that much to go before printing can be attempted.

  9. #49
    Long time since last update, been busy with other things. But now it's my vacation and been finalizing stuff like extruder and bed attachment and doing cable management (which I don't like that much for some reason).

    Springy things for attaching bed. Not pictured here, but bed level adjustment is built in with screws.

    https://www.dropbox.com/s/woe22jzxff...26.33.jpg?dl=0
    https://www.dropbox.com/s/w4og5d38px...26.39.jpg?dl=0

    Did not take pictures of the extruder, but it's a remix of this: https://www.thingiverse.com/thing:2243325. Modified to work with E3D Hob Goblin.

    Other pictures:
    https://www.dropbox.com/s/vae3yywead...26.26.jpg?dl=0
    https://www.dropbox.com/s/2awbx1j8h5...26.49.jpg?dl=0
    https://www.dropbox.com/s/wthpr7h9ex...26.53.jpg?dl=0

    And it does print, even though I had some problems with bed leveling. Currently don't have heated bed, only a glass so bed adhesion isn't the best possible.
    https://www.dropbox.com/s/93vma6n5dd...42.45.mp4?dl=0

    First prints. Need some tuning but the cable clips are very usable (https://www.thingiverse.com/thing:585580).
    https://www.dropbox.com/s/fb8pr6tep0...36.47.jpg?dl=0

    Currently printing a bit larger box: https://www.dropbox.com/s/ikk0vk5soc...36.53.jpg?dl=0. Uneven bed and Dollo's bit wobbly movement shows a bit here. X and Y axis need some time to get honed in so just need to print more stuff.

  10. #50
    Enabled mesh bed leveling which does help with the bed adhesion. As I have no sensors, I use the manual leveling, which actually works very well, just takes bit more time.
    Using Marlin's linear advance, currently testing value K150 (~60cm bowden tube). Does reduce the need for retraction, usually with this long bowden I need to use something like 5mm retraction. With LA enabled, even 2.5mm is enough.
    Replaced A4988 stepper drivers with DRV8825 for X and extruder. Does make the printer bit quieter. Will swap Y driver to DRV8825 later, need to test it properly because in past I have had some bad experience with driving to parallel motors with DRV8825.

    Some prints that I got done today on the new Dollo:

    Stackable box, looks like crap for a couple of reasons: retractions for PETG and linear advance not tuned in, warping and inconsistent bed movement (bed does not stay level in Y-axis due to bent z-screws). I actually printed this the see how much effect the last problem has and it can be seen that on 3mm intervals (z-screw pitch) there's some banding happening. Other than that, z seems to work fine and the dimensions are very good.
    https://www.dropbox.com/s/ihoysq5yej...21.34.jpg?dl=0
    https://www.dropbox.com/s/ihl0e1l26o...21.44.jpg?dl=0
    https://www.dropbox.com/s/6f0emx127p...21.55.jpg?dl=0

    Of course 3DBenchy is one test model that just needs to be printed. PETG and 0.2mm layers, S3D. Turned out quite good actually. The z-banding can be seen here too, and again retractions need a bit of tuning. Also no part cooling yet, even though PETG isn't that dependent of it.
    https://www.dropbox.com/s/j3duq4flso...39.13.jpg?dl=0
    https://www.dropbox.com/s/fy2v3o0jeg...39.23.jpg?dl=0
    https://www.dropbox.com/s/bl45m8jeir...39.34.jpg?dl=0
    https://www.dropbox.com/s/o53t6btgxk...39.45.jpg?dl=0
    https://www.dropbox.com/s/xgmrev0mak...57.40.mp4?dl=0

    Printing parts for the cable shroud. Most of the parts were printed on Prusa MK2, but now I can use Dollo to print them. PLA, KISSlicer, 0.25 layers (KISS dynamic layers). Also tuned linear advance from 125 to 150 for these parts.
    Also when positioning the models in line with the z-screws, the bed rocking motion is minimal.
    https://www.dropbox.com/s/61o1tyvt4y...33.15.jpg?dl=0
    https://www.dropbox.com/s/jcy8o5edm2...33.26.jpg?dl=0
    https://www.dropbox.com/s/h3zb8qno5h...58.48.jpg?dl=0

    To fix the bed rocking motion, I'm printing new z-screws that use flexible coupling to the motors. Also because the z-screw consist of multiple parts, connecting them together is prone to result in bend screws. I designed a jig to keep the parts straight when the glue sets:
    https://www.dropbox.com/s/srcf56s4bj...04.19.jpg?dl=0
    https://www.dropbox.com/s/qvdz1sxgry...04.34.jpg?dl=0
    https://www.dropbox.com/s/6qpp88pce8...04.38.jpg?dl=0
    https://www.dropbox.com/s/6rck3jrbsxba5h9/2018-07-05%2012.12.58.jpg?dl=0

    Next:
    - install new z-screws
    - order a heated bed
    - mounts for RAMPS and Raspi
    - mount for ATX power supply
    - design some parts for cable management
    - part cooling

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