Possible New Arm Mockup

Possible New Arm Mockup

Postby Nicholas Seward » Wed Feb 26, 2014 10:35 am

NEW ARM.jpg
NEW ARM.jpg (26.8 KiB) Viewed 12622 times


I hesitate to show this for a few reasons. But I figure it could start a good discussion. I want a few things clear first. This is just a mockup. I am not abandoning the existing arms. All major edits will be pushed to a future version. Only minor edits will be applied to the existing version. Again this is just a mockup.

Features
*Longest dimension is 102.5mm. You can angle the part and print on a 100x100 with no problem.
*Symmetric loading
*Ball bearing pulleys will increase the effective mechanical advantage and can help reduce hysteresis.
*Gears are printed flat which in theory should be better for meshing.
*Spool is accessible
*Distance from spool to pulleys is larger so tracking will be better and the mechanical advantage will be better.
*Stringing won't require you to be a zen master. Look at that nice big opening.

Since this was a mockup, the limit switches, spring, and tuner are not pictured.

The only real drawback is that I have replaced 2 printed pieces with 8. There will also be a few more nuts, bolts, and bearings.
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Re: Possible New Arm Mockup

Postby NeoTheFox » Wed Feb 26, 2014 2:45 pm

It is pretty great! I mostly like it, however I cant figure out how are you going to keep string on this skinny blue rings, and it also is not going to be as rigid as the privios ones. Having 8 parts is not a big deal as long as total amount of plastic stays the same or redusing. Are kinematics stays the same? (Is it required to reprint theese in order to keep up with software? :D )
Last edited by NeoTheFox on Wed Feb 26, 2014 3:42 pm, edited 1 time in total.
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Re: Possible New Arm Mockup

Postby Dpharris » Wed Feb 26, 2014 3:22 pm

I quite like it, too. I assume the blue pulleys have grooves -- I think I can see them. Using smaller pieces means that failed prints are not as painful. It looks pretty solid to me. The motors are more distal, and will move the COG out, too. Overall, seems like an advance :-)
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Re: Possible New Arm Mockup

Postby Nicholas Seward » Wed Feb 26, 2014 4:29 pm

This change can use the software as is.
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Re: Possible New Arm Mockup

Postby Guizmo » Wed Feb 26, 2014 4:46 pm

Overall I like it too. I just don't like too much the motor on a position so high, but I believe that's no problem for the system. Looks very good, although you are getting away from that toy look you wanted and getting into industrial machine look (which I like more).

Bearing pulleys are a very good idea.

Are you going to print this in the near future?
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Re: Possible New Arm Mockup

Postby Nicholas Seward » Wed Feb 26, 2014 6:17 pm

@Guizmo: There are a lot of things I don't like about this particular implementation of the general idea so I am going to live with it for a while and go through many more refining mockups. To more directly answer your question, I am going to get the documentation of GUSv1 formalized and I am going to make sure I can document how to print dimensional usable parts before I do any physical work on GUSv2.

The biggest reason to put a hold on this is that the center hub will need to be modified to hold the 608 bearings which will prevent this design from being a drop in replacement for the arms. And if the center hub has to be changed then why not reevaluate every component. As I get closer to releasing GUSv2, I want to enlist several people to do design reviews of all the parts.

Version 2 goals/questions:
-Simplify parts
-Printable on 100x100x100
-No support structures for parts
-Simplified stringing
-Ball bearing pulleys
-Shorten bowden tube or move to an extruder on the hub.
-25-50% plastic reduction
-Design with calibration in mind (not sure what I mean here)
-etc.
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Re: Possible New Arm Mockup

Postby NeoTheFox » Wed Feb 26, 2014 6:46 pm

move to an extruder on the hub


Please dont put it ON the hub, the point of delta printers is to be fast!
Also in etc please consider the option for servo mounting (autolevel probe). :)
It would be also nece to have some kind of display controller mount on the bottom plate, I've made one in OpenScad recently, but mine is just 2 basic rectangles.
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Re: Possible New Arm Mockup

Postby Nicholas Seward » Wed Feb 26, 2014 8:06 pm

@NeoTheFox:

A z probe that is servo actuated is a great addition. I will add that to the list. We are bouncing around a lot of other ideas for calibration but that is a pretty standard addition so I think it is worth supporting.

I think I will put the filament drive opposite the arm stepper. This will keep the bowden tube fairly short but will keep all the weight off the hub.

I have attached an STL for a side panel that I threw together.
panel.jpg
panel.jpg (24.22 KiB) Viewed 12596 times
Attachments
panel.stl
(10.92 MiB) Downloaded 489 times
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Re: Possible New Arm Mockup

Postby NeoTheFox » Wed Feb 26, 2014 8:14 pm

Looks really nice, hovever considering where it is I'd make it not flat, but angled, sligtly less than 45deg to the surface.
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Re: Possible New Arm Mockup

Postby Nicholas Seward » Wed Feb 26, 2014 9:26 pm

panel2.jpg
panel2.jpg (25.73 KiB) Viewed 12589 times


How about this?
Attachments
panel2.stl
(367.86 KiB) Downloaded 493 times
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