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namibj 9 hours ago [-]
Does anyone have a link to a 6DOF version of what this does?
Like, the design principle would easily function for a hexapod (swap the dual-rod linkages for single-rod and manage to pre-load the result; add 3 more motors, change how the actuators are arranged relative to the platform they manipulate), but it'd be great to see at least predicted work volume and/or translated stiffness/precision numbers that e.g. adjust from this project using the different kinematic equations, before I'm investing a bunch of R&D into figuring out how best to orient things and whether I may want that to rely on AppliedScience's diy vacuum preloaded spherical air bearings that could probably take care of the necessary pre-loading of the mechanism; machining a graphite block into a hexapod movement stage side "platform triangle" (the floating part that moves) doesn't really need force after all, just sufficient control over where the milling tool/drill is, and obligatory effective dust collection lest the workshop gets a strong dusting of graphite powder.
Attaching ball bearings balls to the rod ends would probably be one of the hardest machining part of the entire idea.
But this 3d printed rubber band preloaded journal bearing concept is also intriguing for it's simplicity, even if it's probably more limited in usable range of motion.
That was me, I realised after I commented that I should make a post about it.
22 hours ago [-]
option_greek 1 days ago [-]
This guy is a legend. His whole series on building this along with other videos is worth watching on YouTube. It amazes me how some random guy simply drops a sub um manipulator diy on YouTube and disappears into the ether. No promotions nothing.
bahmboo 1 days ago [-]
I was surprised to see this here and was wondering if he updated anything from a year ago when I first watched it. Doesn't seem like it but I haven't dug into it. Really nice stuff and I'm hoping he got a job from it or got really busy doing stuff around it that pays the bills.
Curious how temperature and so forth are managed --- that was a notable effect back in the days when folks were doing things such as engraving The Lord's Prayer on a piece of metal type.
bahmboo 1 days ago [-]
I'm not an expert but the video is very comprehensive. There is closed loop control that is extremely precise in a relative way. In this domain it's all relative anyway because there's no GPS so to speak. It's all reference frames and 3-2-1 locality. [edit: ahhh at 21:47 in the video he says (paraphrasing) "there is offset due to thermal drift of the plastic parts as they get warmed by the motors". ]
Joel_Mckay 1 days ago [-]
In general, platforms are placed in a temperature-controlled/heated draft-guard chamber, on a vibration isolation table, and use uniform materials that do not deform much in the narrow operating temperature range (+-0.5'C).
The stage is not the primary design constraint, but rather it is the position sensors that still cost. At a certain point, some realize the pi-usa stages lofty price was actually fairly reasonable in retrospect.
Best regards, =3
namibj 9 hours ago [-]
Closed loop control is very effective (where it's available).
Of course that's not always usable and thus some tasks do necessitate the stage to provide such positioning precision as absolute accuracy not merely precision.
bahmboo 1 days ago [-]
Interesting. I researched what you referenced. This is a fantastic "hobby project" level of engineering but if one is truly tasked with this level of metrology there are still many aspects that need to be addressed and corrected for. Usually that means there is a lot of money on the line and one can't mess it up. Hence the high price tag of established industry accepted solutions. -whew- I wrote that myself.
alted 22 hours ago [-]
It's also possible to DIY piezoelectric stick-slip actuators with potentially sub-nanometer(!) resolution, albeit at greater expense (~$1k) [1].
They also have a manual, non motorized version. I am building this currently for eventual use, with modifications, in a point diffraction interferometer.
I know it's open sourced, but I'd love for the author to launch a Kickstarter product.
ikidd 1 days ago [-]
I wonder how it compares to a deltabot, since those are often used for pick-and-place which requires pretty fine resolution. Seems like a delta would have way more range of motion than this.
dubbie99 19 hours ago [-]
Wow strange to see this on here. I just spent the weekend working on my build of this.
But this 3d printed rubber band preloaded journal bearing concept is also intriguing for it's simplicity, even if it's probably more limited in usable range of motion.
edit: direct link to the video: https://www.youtube.com/watch?v=MgQbPdiuUTw
The stage is not the primary design constraint, but rather it is the position sensors that still cost. At a certain point, some realize the pi-usa stages lofty price was actually fairly reasonable in retrospect.
Best regards, =3
[1] "Low-cost, open-source XYZ nanopositioner for high-precision analytical applications", https://doi.org/10.1016/j.ohx.2022.e00317
https://youtu.be/-mgqq0qdDRM?is=nFvtZprNsjMn3D_B
https://en.wikipedia.org/wiki/There%27s_Plenty_of_Room_at_th...