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  1. #1
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    Grounded Delta (Name in Progress)

    So, a while ago I posted about a grounded (inverted) delta project of mine, promising stupidly optimistic completion dates and seemingly giving up on the project. For those of you unaware, it is a redesign of the original GUS Simpson reprap with some basic improvements and some design changes.

    Fear not! I didn't give up, only procrastinated (and life got in the way). The project is nearing completion, I'm just finishing off the shoulder, which took a surprisingly long time to get the geometry right to accommodate the new stringing and figuring out how to arrange everything on the base of the printer. After that, I just need to knock together an effector which shouldn't take more than half an hour (famous last words). In this finalizing stage, I'd like to ask if anyone is interested in building one and helping me debug and improve the design in the coming year? Any features you want to see?

    If interest builds around the printer I'll put together assembly guides and FAQs. I'll also be posting some STLs of the parts that are ready, and eventually the OpenSCAD code once all the parts are modeled (and the clutter is cleaned up.... yeeesh....). There are 3 parts of this printer that aren't off the shelf/3d printable and will need to be machined (frame, oddly shaped print bed and an optional removable print surface). I'll be putting together a CNC in the coming months to machine these for myself and would be happy to machine a set for someone else. Worst comes to worst, the frame could be 3d printed and the bed either replaced by an off the shelf shape (no automatic steps/mm calibration ).

    So far, it looks cool if I do say so myself.

    EDIT: Also, suggestions for the name are very welcome. So far I've gone through several names. Spyder, because the way it prints reminds me of how a spider spins a web and spelling it correctly would be boring. DeltaGear, because its a delta driven with gears. Geared Up Delta, as a nod to the GUS (Geared Up Simpson).

  2. #2
    Super Moderator Roxy's Avatar
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    EDIT: Also, suggestions for the name are very welcome.
    Pictures of the printer with some nice prints it did on the bed would go a long way to generating some interest. Is your printer running Marlin?

  3. #3
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    The printer is still in the design phase, hence no pictures. You can check out pictures of the original GUS and a revision done a while ago by jfriessen to get an idea of what it'll look like. I'm doing a redesign to move the motors off the arms and have them stationary in the base, and some other minor tweaks. I should be putting together the mill I need to make the frame and bed in the next two months or so, once that's done I can build the printer itself.

    The firmware is TBD. No firmware (as far as I'm aware) supports the GUS Simpson kinematics, and I have an auto calibration routine in mind to help compensate for any inaccuracies from the printed parts used for the printer which I'll probably need to code myself. The controller will be 8 bit for cost reasons and I'm tossing up between Marlin and Repetier. Marlin seems to support a lot more new features, but I hear the code base has gotten a bit less beginner friendly due to all the different people who have contributed. I hear repetier has a cleaner code base. That aside, I've also heard some people have had better luck (less stutter/pauses) with repetier on deltas than with marlin. I've also heard some say there is no difference, but I haven't heard people say they've had better luck with marlin so I'm inclined to think there is something to it.

  4. #4
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    A slight update, I'm running into a design hiccup of trying to get a thick enough arm using bolts of reasonable length (i.e. not 150mm long) and have considered two options. Either splitting the gear in half, which will allow me to nest some parts to make the assembly more compact, or print upright. I've been avoiding these two outcomes because the first one introduces more opportunities for misalignment when the gear arm is in two pieces, and the second results in teeth that have a stepped surface rather than a smooth contour. I thought the stepped surface on the gears contributed to the original gus's inaccuracy but now I'm not sure.

    Any thoughts on the viability?

  5. #5
    Super Moderator curious aardvark's Avatar
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    none whatsoever - it's all greek to me :-)

    But you could call it 'Hamish'
    No reason, other than I like the name 'Hamish' lol

  6. #6
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    Haha, I'll add hamish to the list. I've managed to get the bolt sizes down to something reasonable (ish). I think the first model will have a print volume around 100mm diameter and 100mm tall. The scad file will be completely parametric of course so you could change that to whatever but that's where I'll start. I've decided to add an option for how to define the machine, instead of giving it a bed diameter for the base of what is roughly a triangular base pyramid, I'm adding support for the user to define a cylinder that they want to be able to print. I figure it'll be easier to visualize and people will be more used to this from linear deltas (plus it means I don't need to find a way to incorporate the funky pyramidal print envelope into a slicer).

  7. #7
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    https://www.thingiverse.com/thing:2552984

    Ain't she purrdy? Finally finished the shoulder. Getting that thing right so everything lines up, fits and doesn't get in the way of anything else was surprisingly hard. The gear arm STL on there is old, and the design has changed a bit. I'm hoping to have the finished files out in the next month or two.

  8. #8
    Super Moderator curious aardvark's Avatar
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    looks good - but why the low poly stl ?
    I know it doesn't make any practical difference - just looks better with more roundness :-)

  9. #9
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    Because I'm on a netbook and it has a heart attack and a half when it has to preview, let alone render, high resolution models :P

    The resolution can be easily adjusted in the file from a "res" parameter I've created that controls the length of the segments that make up the polygons. I believe it's set to 3mm in the render.

  10. #10
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    It's really coming along. Just ordered the non printed parts (I'm probably a bit short on cash now but Uni will be starting soon so I won't have much time...). They should arrive within the next month or two, then I'll start a build thread. The last part left to design is the base/frame (and a hotend mount, but that WILL be easy, I hope), that should be fairly straightforward and easy (famous last words, each time I said that it's been wrong).

    I'll upload an STL of the effector pieces soon. The effector/shoulder offsets ended up a bit bigger than I'd like because of some collisions I hadn't anticipated when I started, but that's that. The machine looks a bit clunky and disproportionate because things like the bearings, nuts and pulleys take up a lot more of the machine at smaller scales. If you build a 250mm+ machine it starts to take on some nicer proportions.

    For anyone curious, V0.0 will be a 50mm radius, 100mm height cylinder build volume. Of course, due to the nature of the printer it can actually print bigger but no slicer supports this shape of build volume so I made it use some more relatable dimensions and shapes.

    By the way, don't use the STLs on thingiverse to build one of these, they were all generated with different settings so I can't guarantee it will make a usable machine. I can almost guarantee it wont.

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