Another Grounded Delta- Krak3n

Another Grounded Delta- Krak3n

Postby GrahamHolt » Mon Feb 23, 2015 12:03 am

Has anyone taken a look at the [url]krak3n3d.com[/url]?

The base looks similar to GUS, but the arms are much simpler and it does without the spool issue. Could such a design actually work? What do you think?
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Re: Another Grounded Delta- Krak3n

Postby Nicholas Seward » Mon Feb 23, 2015 12:30 am

Can it work? Absolutely.

Pros: Simpler linkages, hidden steppers, static steppers, certainty of belt pitch

Cons: Nothing is pretty about the math to drive this, Calibration still needs to be automated, Secret?


Impression: It is very elegant. Depending on firmware, software, autocalibration, and price this could be a contender. Rapidelta has already proven this is possible. Krak3n is just flipping it upside. Can't wait to see it in action.
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Re: Another Grounded Delta- Krak3n

Postby GrahamHolt » Tue Feb 24, 2015 5:31 pm

I hadn't seen Rapidelta before, but I see that it uses the same sort of linkages. One thing I noticed was that the arms don't appear to have any swivel to them like GUS. My brain seems to think that this is going to create a machine with a smaller overall volume compared to GUS 1.0.

Is the math any different than what GUS uses? Admittedly I haven't gotten mine to work yet as I was a bit perplexed by the calibration step, segmentization and all of that. I've got a major project wrapping up this week, so I hope to be able to spend more of my lunch hours with GUS.

The build looks fairly straight forward from a hardware perspective, so it could be an interesting option once it's up and running. Cost would definitely be a factor, but unless there is something under the hood that I'm missing then it could theoretically be priced reasonably.
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Re: Another Grounded Delta- Krak3n

Postby Nicholas Seward » Tue Feb 24, 2015 6:03 pm

The envelope will be very similar. However, I think this one's resolution map is less well behaved. I suspect you would need geared steppers plus belt redution plus a torsion spring on the shoulder to get the mechanical advantage you need without the backlash.
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Re: Another Grounded Delta- Krak3n

Postby GrahamHolt » Tue Feb 24, 2015 8:44 pm

Ah, in that case all of the fancy stuff is under the hood. It will be interesting to find out more details on this one as time goes by. I like that GUS has everything out in the open so that you can see what's going on.

I could totally see people going for the Krak3n because it has a clean look; not the way I lean, but I could totally picture it on the desk of an executive or something.
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Re: Another Grounded Delta- Krak3n

Postby see3d » Wed Feb 25, 2015 10:59 pm

Looking at the picture, it would guess that it is a worm gear setup.
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Re: Another Grounded Delta- Krak3n

Postby Nicholas Seward » Wed Feb 25, 2015 11:23 pm

It definelty drives the shoulder with a belt. It would be too much to have a compound worm and belt reduction.
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Re: Another Grounded Delta- Krak3n

Postby see3d » Thu Feb 26, 2015 2:35 am

It looked to me like the shoulder wheels had only a rotational movement, like a linear vertical delta printer. It should not matter if the wheel is turned by a geared down belt drive, or a worm gear. I thought the worm drive would be simpler, but it would depend on the ratio required to get good resolution. However, after looking at their blog of the second prototype, I can see that they have belt terminations on the wheels. Too bad they did not have a video of it running. They may not be as far along as their slick web site would indicate.
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Re: Another Grounded Delta- Krak3n

Postby Nicholas Seward » Thu Feb 26, 2015 3:28 am

I have an email out to them because I wanted to make sure they knew I was supportive. I hope I find out more.
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Re: Another Grounded Delta- Krak3n

Postby timrwilliams » Thu Feb 26, 2015 12:58 pm

If my memory (and YouTube) serves me, The original (metal) RappiDelta, which as you comment Nicholas, looks like the Krak3n upsidedown, drove by a worm gear to a 38 tooth gear on the arm. This certainly printed parts for the RappiDelta Junior which was launched on Kickstarter. I think that the Junior drove the arm via a gearbox (? ratio) and certainly printed well.
It was a pity that the project was not funded as it had a high percentage of printed parts (most of the frame/arms). I also seem to remember that David Akers incorporated the Inverse Kinematics into Marlin to run Rappidelta directly. That would have been interesting to try.
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