Flash Forge Inventor II Spring Promotion

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  1. #31
    If you are looking for a printer to print parts with fine details and strict tolerances, and want it to be relatively hassle-free, Dollo is probably not a good choice. First, although I've gotten a relatively well working one made, it's not finalized and building one needs some figuring out (I need to clean up the git repo and do proper parts lists and instructions). The printed xy axes cause some small wobbling, which is seen as small artifacts. Also there's no real data how long this kind of printer will work reliably; I'm the only one with working Dollo as far as I know. For me the latest iteration has been working surprisingly stably and consistently, but it might break during the next print. Lot's of unknowns...

    So if you want to build Dollo, willingness to tinker is a must . For me, Dollo is more of a experimental project than a workhorse printer (although it's been working quite hard lately...).

    Saving money: maybe a bit if going with the cheapest parts and filament. But the cheapest printers from china probably come close so it boils down to what kind of tinkering you are interested: building from from plastic or fixing the cheap Chinese crap . Dollo should be easier to expand so that's one thing going for it.

    Money I've spent on Dollo:
    - electronics, motors, hotends etc. from Ebay: 100-150 euros. I haven't kept tabs on the costs and some of the parts weren't the cheapest options. Also had to buy real E3D heatbreak for E3Dv6 clone to be able to print PLA, so going with the cheapest parts is not always a good option..
    - plastic for the currently used models only: ~2 rolls of PLA/PETG = 60 eur
    - plastic for the experimental parts: probably another 2 rolls
    - hours spent tinkering: too many to count . Would I do it again? Absolutely. In fact once I get some other projects out of the way, some upgrades and new ideas to work on. And update the README...

  2. #32


    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!

  3. #33
    Been thinking about getting some better build instructions done, but haven't even started yet, always other stuff to do. But Dollo itself has been on real use and I have had plans for updates all the time in my head. To that end, I need to print another frame for testing my ideas (got a couple of ideas for printable z-axis that I need to test). So an idea struck me, why not document my build process as I go, telling how I printed the parts, what settings to use, what to consider before printing them, what material to print them from, how to assemble etc.

    So here's the target setup I'm aiming for:
    - 36cm x 36cm x 24cm cube (X and Y have 2 x 12cm extension beams + corner pieces, Z has one 12cm extension)
    - should hold ~20cm heated bed
    - same X and Y rack-pinion setup as my current Dollo
    - same hot end mount as my current Dollo
    - shitload of bow ties etc. needed to connect the parts
    - same gears as current Dollo
    - some extruder, not important for the sake of this experiment as long as it works if I ever get to actually print something
    - E3Dv6 hotend, RAMPS 1.4, endstops etc. default stuff

    What I need to design and prototype:
    - better heated bed carriage
    - Z-axis prototypes
    - ?

    So basically all stuff for making a Dollo (sans z-axis) axis and just needs printing, assembling and documenting. Z-axis is moro of a mystery at the moment how it will turn out. Bu I do have a working prototype of a printed ballscrew, just need to figure out how to make a z-axis out of it .

    As I already have some frame parts printed that were meant to be used on expanding the current Dollo build, I'll be using them. Though I need to print some more for full frame. So in next post I'll be detailing how to print the frame parts and maybe about building.

  4. #34
    So, the frame. Following parts are needed for basic cube (download here:
    - corner.stl x4
    - extention.stl (should be extension?) x 20

    For attaching the parts together, these are needed:
    - bow_tie.stl x 112 (my calculation may be off, but print a shitload )
    - long_tie_split.stl x less than bow_ties but still a shitload. Alternatively print long_tie.stl, but the split version is bit more forgiving if the dimensions are too tight

    Materials (my preferences, other materials can be used but I haven't tested):
    - corner: PLA
    - extention: PLA
    - bow_tie: PETG or PLA
    - long_tie: PETG or PLA

    I prefer PETG for the ties because it forgives bit more when part dimensions are off for some reason. On the previous frame I literally hammered couple of PLA ties to the extension grooves so tight that I had to extract them by cutting the out.

    Slicer software: I use Prusa Slic3r 1.38.6 and will use it until all parts are done. Not going to be changing things mid-project. I wanted to use KISSlicer 1.62 but it has problems with certain models with errors and don't have time to sort that out. KISS has nice adaptive layer-height feature, but it's a nice-to-have in the scope of this project.
    Printers: Prusa MK2 and FrankenCube

    Print settings. There are few things to note here, but in general nothing too fancy.
    For all parts:
    - perimeter first. In my experience the parts are more accurate dimensionally. Overhangs suffer, but meh.
    - make sure your printer prints straight. Any slanting will of course translate to the printer frame
    - have your printer extrusion, fan, retraction etc. tuned; better print quality, less problems during build
    - in general the quality doesn't have to be top notch as long as the dimensions are ok and parts are strong
    - brim depends on your bed adhesion

    - 3x perimeter
    - 3-5 bottom/top layers
    - 20% infill
    - use supports and brim, this is somewhat challenging print
    - I've printed these up to 0.3mm layer height, but the quality leaves need for post processing. 0.2mm is a safe bet.

    - 2x perimeter
    - 3-5 bottom/top layers
    - 0.3mm layer, no
    - 10-15% infill
    - no supports, assuming your printer does good bridging
    - these are quite sturdy pieces even when printing at moderate settings

    - 2x perimeter
    - 4-5 bottom/top layers
    - x infill. The parts are too small to have any infill, so in essence they'll be printed 100%

    Printing order; first print couple of extentions. Then print one bow_tie and long_tie. See how well the ties fit inside the extention groove. It'll probably be too tight, so got back to the slicer SW and scale the ties in X-direction to 95%. Reprint the scaled ties and testa again. Repeat until the ties are almost possible to insert by hand. Personally I leave them tight enough to need small rubber mallet to help them along.
    Now you have the scaling factor for the ties, so it is a good idea to print a coupe of shitloads of them. At least. It's nice to have multiple printers for this .

    Post printing:
    - remove brim and supports if any
    - remove any blobs or other print artifacts if any
    - if there's some deformations like buildup on seam, use file to even those out. Especially around the tie grooves
    - beweling the edges of the tie grooves helps during assembly

    Assembly: this should be quite self explanatory, but I'll leave some pics here for now. If needed, I can provide some explanation later.

    Pictures in Dropbox for now, seem I cannot upload pics here:

  5. #35
    Got the parts printed for the frame and also got the frame built:

    Had some issued with the extension parts, the black PLA I have (brand is bq) was oozing quite a lot and the prints weren't that clean. Haven't had that kind of problems before so going to blame this particular roll/brand of filament. Had to spend some time cleaning them, which could have been avoided by switching to another brand. Sadly don't have any other black PLA at the moment and didn't want to mix colors... need to order more.

    Next, Y-axis parts. Ordered some stepper motors from Aliexpress, those probably take few weeks to arrive. Got some random leftover motors that I can use for test fitting, but I want a matched pair for the final setup.

  6. #36
    Racks (i.e. the rails) for Y and X are done. Took a bit more time than expected, had some problems with the models and had to do some ad hoc improvements.

    Again, forum doesn't seem to work so only links available:

    Models to print:
    - 6 x rack_5.stl (or 3 x rack_4 if not enough print area):
    - 6 or 12 x rack_dove_pin.stl (optional):

    Material: PETG. Can be printed in PLA, but I prefer having the racks = PETG and motor mounts = PLA, seems to be a good combination regards wear. PLA vs. PLA seems to wear down faster and PETG vs. PETG sticks too much.

    Print settings:
    - perimeter first
    - brim if needed
    - 3x perimeter
    - 3-5 bottom/top layers
    - 20% infill
    - no supports. There's some bridging, but shouldn't be hard to get good results. Using supports with PETG is challenging to remove
    - 0.2mm layers. Haven't tried higher, 0.3mm might work fine too

    - for the frame size of this build, more than one rack part is needed. To connect the rack parts together, dovetails are used:

    The parts should be tight but still fit together. Use file/knife to remove material if needed, but be careful not to remove too much.
    For proper positioning, the herringbone rack on both of the parts should be level. Also the grooves on the sides should also be on same level.

    If the parts seem to be too loose, they can be locked together using the rack dove pins. I used small hammer to force the pins in the slots in the dovetail parts:

    The default size should be very tight, but use slicer scaling if they seem too loose.
    Alternatively, soldering iron can be used to weld the parts together, but that's more permanent solution.

    After the rack parts are connected, the side grooves need to be sanded so the motor mount will slide properly. Especially where to rack parts are joined needs cleanup. Use something like 180 grit sandpaper wrapped around a rectangular piece and work along the groove with long strokes until the whole length is smooth. There will be a small gap at the junction of the rack parts, but that's ok as long as there's no protrusions along the way.

    Next, mounting the racks to the frame (Y axis)

    Edit: forgot to mention the experimental rack alignment parts I designed for making sure that the racks are in proper distance from each other. No real need for these as the current dovetail joint seems to be working as it should.
    Last edited by spegelius; 02-17-2018 at 08:39 AM. Reason: Grammar

  7. #37
    Although the rack assembly is pretty straightforward, there are few things to consider.

    First, for this size of frame and number of rack parts, 3 long bow ties are needed.
    or, but this will be more difficult to get to proper size.

    Print settings:
    - use same settings and instructions as detailed for long ties. Perimeters first, use slicer scaling if needed etc.

    Preparing the frame: First, select the two opposite sides where the racks parts are to be installed. If there's long ties on the top side of the extension parts, remove them.
    The frame should look like this:

    Next, to get the racks lay flush on top of the frame, it is a good idea to use a file to smooth out the possible rough spots from the top of the frame:

    Next, slide a long bow tie to the slot at the end of the extension and then the rack on top of it. Make sure that the herringbone gearing is on the outer side. Use hammer to ease the parts to their place if needed:

    Check that the rack sits flush on top of the frame:

    From the other end of the rack, slide another long bow tie to the slot and use a long stick and hammer to move the tie to the middle of the rack. Use the length of the stick to determine how deep the tie should be moved:

    Repeat on the other side. That's basically it:

    The position of the racks is not very strict, as they can be moved if needed. With hammer. If you can move the racks by hand, they might be too loose and cause problems during printing.

    If the racks aren't sitting flush on top of the frame, this might be due to the overhangs on the racks: if there's too much droop, the ties won't be deep enough in the groove and they push the racks up. One solution is to use a knife to remove some material from the ties so they fit better. And for this the split version of the tie works better, because it's easier to modify. Of course scaling the tie in slicer works also so best to print one tie and check the installation before printing the rest.

  8. #38
    X-beam parts and assembly.

    - 2 x extention.stl:
    - 2 x x_spacer.stl:
    - 9 x long_tie_split.stl:
    - 12 x bow_tie.stl:
    - 3 x long_bow_tie.split:
    - assembled 2x rack from previous step

    Print settings:
    - for extention, long ties and bow ties, see previous posts
    - x_spacer:
    - material: PLA
    - perimeters first
    - 3 x perimeters
    - 10% infill
    - supports needed

    - connect the two extentions together with 3 long ties and 4 bow ties. Then add the x_spacers to the ends of the extentions, 3 long ties and 4 bowties per spacer. Make sure the long_ties don't protrude from the x_spacer part. If they do, they will obstruct X-beam installation in next steps.

    - make sure that the top tie groove is empty

    - use the instructions in the post detailing rack installation to install the rack on top of the x-beam

    As with the Y-axis racks, the position of the rack isn't critical, the rack can be moved.

  9. #39
    Motor mount parts for X and Y:

    6 x motor_mount_small:

    Print settings:
    - material: PLA. PETG works too, but it will not slide as easily as PLA does (assuming the racks are printed from PETG)
    - perimeters first
    - 0.2-0.3mm layers
    - 3x perimeters
    - 25% infill
    - supports optional, I don't use them

    After printing, use 3mm drill bit to open the bolt holes. They have 1 layer closed to make the hole overhang cleaner and that needs to be opened

    Example of quality when printing PLA that has tendency to jam:

    The part looks bad, but after cleaning and removing excess material from the holes, it works fine. Funny thing is that it's printed from same g-code and on same printer as the clear ones are. The black just wants to jam. Go figure...

  10. #40
    Motor gears.

    - 3 x motor_gear.stl:

    Print settings:
    - material: PLA. I haven't tried this in PETG so cannot comment on that
    - perimeter first
    - 3-4 perimeters. This one should be tough
    - 60% infill
    - 0.2mm layers
    - maybe use bit higher print temp than normally, if you can get a clean print

    Now we get to the vitamins, first time for non-printed parts on this build.
    - 3 stepper motors. I ordered these from Aliexpress for 35 euros. No idea how good they are... make sure the motors have a flat part on the shaft.
    - 3x M3 nuts (optional)
    - 3x short M3 grub screws (optional)

    - if you want to use the grub screws, insert the M3 nut into the slot in the gear, use pliers to force it in until it's in line with the hole in the gear and then insert the grub screw and screw it in but not too deep so that it won't obstruct the motor shaft

    - next, try to slide the gear onto motor shaft. The flat part and the screw should align with the motor shaft flat.
    * Important! If the gear is too tight, don't use excessive force, like hammer unless the motor shaft is supported from the motors back. I hammered away and the motor shaft moved out of position which might not be a good thing. I've yet to test the motor, so I cannot tell if it's broken, but rotating the shaft by hand feels different comapred to other motors.
    * instead of force, better us small file to open up the hole enough for the gear to slide in position. Make sure to use the file evenly on the hole so that the shaft is in the center.
    - proper position for the gear is about 2.2mm from the motor body:

    - you can check the position with the motor mount part. No need to screw the mount on at this point, just hold it by hand and see how well the gear centers on the rack:

    - when the gear is in position, tighten the grub screw if you use these

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