Next personally challenge: figure out how to use the damn onshape spur gear generator featurescript.
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PETG attempt thread. Much more finicky than PLA.
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Gear design and printing accomplished! Sub-thread on further adventures there. Been a while since I updated this thread so you'll notice my newer prints are red rather than black. Bought the red filament to print stuff for my rover and is now default.
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Figured out how to make gears in OnShape today using their featurescript. I am now officially unstoppable. 3d printing them now. This is just a hacky test job (those spokes on the largest gear are bad... I made them with a pattern of holes rather than an equal width spoke)
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Next adventure being cued up: TPU filament was on sale on Prime Day so bought some (0.5kg for ~$8). It prints soft, rubbery parts. Goal is to see if I can print my own tire designs for rover. Stretch goal though.
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My Monoprice Mini doesn't print TPU out of the box, it needs a small mod (a feeder widget) that can be 3d printed out of PLA. Obviously others have already figured out how.
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Here is the mod somebody made, on thingiverse
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A video on TPU printing... he's using the same printer as mine, so I'm hoping I can do it too, though he seems much better at the finicky stuff than I am. I get impatient. 3d printing is like the Potions class at Hogwarts.
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First time trying to print a design with difficult overhangs: yak horns for use with yak rover
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made a 3d model of yak horns that can be 3d printed and bolted on to any of our robots... forms in onshape) #yakbot
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Auto support generated by Cura looks dubious but ok
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Nope. Support adhesion failed near end of print. I think I need a raft for this. And/or design in my own supports. The two pillars at horn tips got ripped up. Wonder why? Up-tension from horn curve?
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Not the best job but am starting to get the hand of using a dremel. The high-rpm/low-pressure way is much more fun than a drill.
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Recently remembered one of my earliest introductions to engineering thinking: my dad (a mechanical engineer) posing a classic CAD brainteaser to me when I was a teenager: what object looks like a circle in the top view, a triangle in the front view, and a square in the side view?
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Later in freshman engineering school, our engineering drawing instructor posed the same brainteaser, before proceeding to demonstrate the answer by shaping a piece of chalk into the answer (whittling a piece of chalk by rubbing it on a board is legit machining btw)
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The answer, which I just made in OnShape using the loft feature, is a thing which may have a name, I don't know, but is kinda like an oddly shaped cone frustum. Here is the drawing:
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Ignore weird lines. They are an artifact of how OnShape does lofts geometrically. A loft is when you smoothly transform one face of an object into another. In this case, the 2nd surface should actually be a 1-d edge, but OnShape needs a face, so I made a very narrow rectangle.
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Another way to pose the brainteaser is to ask: what object can plug a square, circular, or triangular hole, depending on how you orient it? So just for fun, I made a stencil of that too.
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Stay tuned... 3d printing both rn, and will have a video presently.
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I actually don't know if this is the "only" correct answer. Afaict, a 3-projection view completely determines a solid model, but maybe complex surfaces have indeterminacy. I think I'll have to sand off some edges to make it the right answer.
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Doh. Of course the solution is not unique. This one is skew symmetric. Any set of contours that fits within the 3 contours will do. I could have added a halfway loft plane with an ellipse cross section and that would have forced symmetry.
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Anything contour that stays within the bounding box defined by square and triangle projection lines will work. Blue is what OnShape generated. Red is what I’d force if I wanted.
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Also reprinting the horns from yesterday. Scaled down 50% with raft. Dunno what all that wispy stray fiber is. Too dry? From supports being printed coarse? PLA spool being not as good? Drip during travel?
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Done. Messed up a bit tried to make the triangle equilateral and the rectangle a square at the same time. Doh. No way to satisfy this template. If you have a square, triangle will be isosceles.
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The horns printed fine but that fuzz is a mess. Not sure it will clean up easy.
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After some cleanup. Not much better.
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Called on the brain trust for help.
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3d printing mavens… any tips for sanding PLA prints down to a smooth finish? @divalbanerjee @h_thoreson @chenoehart
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Much excite. Printing TPU for the first time. If it works I’ll be able to design my own tires 🥳😱
en.m.wikipedia.org/wiki/Thermopla
Just a simple rubbery washer to start with.
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Fingers crossed. Seems to be printing fine. Shiny with some stringing. Used Cura generic presets for TPU-95, whatever that is. Higher nozzle temperature (228F) but lower bed temperature (45) than PLA (205/65)
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Ok it’s ugly and messy and needs a haircut but it basically works.
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ugh broke thread... continues here
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Decent compliance, rather stiff at normal resolution printing with 60% infill. I bet I could get much wider range by messing with infill density. But clearly settings need work. But unlike PETG this feels different enough as a material, it’s worth mastering.
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