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Yazzo PolyBot - Cranberry Edition

by WilliamAAdams, published

Yazzo PolyBot - Cranberry Edition by WilliamAAdams Feb 1, 2011

Featured Thing!

Description

After many little pieces, I am finally able to construct a delta robot that is mostly made of printed parts.

This thing is a delta robot frame. There is the basic frame, mounted motors, arms, tool holder, and the like. The arms closest to the motors are printed plastic notched spans. The longer arms are wood dowels, with tape on their ends to enhance the friction fit into their fittings.

Steel rods in this case are 5/16". The size doesn't really matter, you can select any size as long as the vertices match.

the size is 2' on edge. that's a pretty huge build area if you decided to use this robot as a 3D printer.

It's a good platform for experimenting with various delta robot ideas. The arms will be replaced with carbon fiber. The 'bearings' will be replaced with brash, with 1/4" axles, the motors will be replaced with servos, etc.

At any rate, at least a model can be built, with not too many different types of materials. There isn't a fastener on the whole thing. Of course if it were actually moving, you'd probably find places where you'd want some fasteners, but that's the whole point of the experiment anyway.

Some interesting aspects of the design:
This is an endoskeleton. It can take a 'skin', but it's not required for structural support.
The tetrahedron is a fairly stable self supporting structure.
No threaded fasteners, other than the threaded rods themselves
Use zip ties to hold the little motor board in place. That board could be gotten rid of entirely if the motors mounted to the rod instead

UPDATE: 05022011
Changed male and female clevis part counts. They were 24 ea, and they should have been 12.

UPDATE: 06022011
Created a page on RepRap as this is more of a development project than I think is appropriate for Thingiverse
reprap.org/wiki/PolyBot

UPDATE: 27022011
There have been many parts updates. I've included a new picture with the servos and new arms, as well as the base plate in place. I've added a video on YouTube of the thing in action: youtube.com/watch?v=VzWJDWvJvqo

Recent Comments

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I had no idea what a delta robot was before googling videos of it. My mind is seriously blown, I haven't seen anything move so fast. This project is amazing.
&
amp;gt;:o

I really like the way you used three servos/motors in this design. I'm wondering if there is anything preventing this design from being flipped upside down. Raising the extruder rather than suspending it to eliminate the need for the metal bar frame. I'm trying to think of whether it would be able to cover the same area. Anyway, awesome design keep up the good work!

truncated tetrahedron... Hay, that looks pretty cool. I could model that fairly easily with the various types of connectors I have. Probably using ball/socket joints.

And don't forget to check out the latest edition: http://www.thingiverse.com/thi...

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Instructions

1) Decide how big you want your bot to be, and what diameter of rods you want to use.
2) Cut 6 threaded rods to the same size. If you pick a standard size that your supplier carries, you won't need to cut anything.
3) Print all the little bits and pieces of plastic you need.
4) Snap and slide them together
5) Put motors into motor clips
6) Put motor mounts on the triangle shaped board
== There are holes in the board so you can fasten to the rods
7) Use zip ties to fasten board to rods
8) Put arms on motors
9) Rejoice!

This is of course a very abbreviated instruction, as the actual instructions could take a while, and require some pictures. My hope is that the design is so obvious and symmetrical that you could figure it out from just looking at the picture.

Comments

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cyborg527 on Aug 7, 2011 said:

I had no idea what a delta robot was before googling videos of it. My mind is seriously blown, I haven't seen anything move so fast. This project is amazing.
&
amp;gt;:o

Anonymous on Jul 27, 2011 said:

I really like the way you used three servos/motors in this design. I'm wondering if there is anything preventing this design from being flipped upside down. Raising the extruder rather than suspending it to eliminate the need for the metal bar frame. I'm trying to think of whether it would be able to cover the same area. Anyway, awesome design keep up the good work!

Cogworkz on Jun 16, 2011 said:

Ok - after seeing what you were doing here, I had to share an alternate polyhedron for the shape:

http://en.wikipedia.org/wiki/F...

http://en.wikipedia.org/wiki/F...

integrates the servo mount into the shape of the polyhedron while giving you greater Z displacement and room for a larger print bed. And the added bonus... your existing software
will most likely work. :)

WilliamAAdams on Jun 17, 2011 said:

truncated tetrahedron... Hay, that looks pretty cool. I could model that fairly easily with the various types of connectors I have. Probably using ball/socket joints.

And don't forget to check out the latest edition: http://www.thingiverse.com/thi...

bstott on Jun 14, 2011 said:

OK - we are watching. Your silent audience is in suspense. When is the next iteration on the evolution for the Polybot?

WilliamAAdams on Jun 14, 2011 said:

Oh, you mean like this thing: http://www.thingiverse.com/thi... =-O

ScribbleJ on Mar 2, 2011 said:

I wonder how difficult it would be to make one of these:

http://home.novint.com/product...

It seems like it would make a fine input device for 3d modeling...

WilliamAAdams on Mar 2, 2011 said:

another possibility is that you put a tool on the effector, like a laser line pointer, and scan your model that way.

WilliamAAdams on Mar 2, 2011 said:

I think it would be fairly straight forward. For positioning the PolyBot, I'm just using inverse kinematics. To do it the other way, you'd just use forward kinematics. I think a key though would be having fairly decent encoders, whether they are part of the servo/motors, or separate. If you want to pay $50/encode, the MakerBot guys have those new magnetic encoders. Otherwise, you could pay $40-$50 and get something like the Dynamixel servos, or HiTec, and get some decent encoders embedded in the servo.

Totally doable. I'm sure those magnetic encoders will come down in price over the coming year.

Keavon on Mar 1, 2011 said:

Please don't tell me that this is going to be an other design for a RepRap. I mean who thought that an A-Frame would work for a 3D printer after a box. But now there's a pyramid out! 8-)

WilliamAAdams on Mar 1, 2011 said:

I think of it more as my experimental personal manufacturing robot tool base. you could probably put a pick and place vacuum attachment as an end effector as easily (if not more easily) as a plastic extruder. A dremel flexi shaft might even be possible with servos strong enough to handle the lateral forces.

My hope is that people will riff on the design and come out with cool things.

WilliamAAdams on Feb 28, 2011 said:

I've been making a lot of minor changes to the beast, and I finally got servos attached with some properly sized arms. The video can be found here: http://www.youtube.com/watch?v...

I have not updated the parts list. I'll do that as a derivative as there are enough differences.

Anonymous on Feb 23, 2011 said:

Are you going post files to print this? This is sweet.

WilliamAAdams on Feb 23, 2011 said:

The parts list below are all the files needed to construct this thing. I've been working on new parts that reduce the parts count, but haven't released the next version as yet.

If you use the parts listed below, it's mostly plastic parts which will allow you to experiment. Then you can replace different parts one by one as you want to improve your bot.

pensive on Feb 15, 2011 said:

You may find some existing code useful, specifically the genhexkins (general hex kinematics ) module of EMC2 (http://linuxcnc.org/)

http://www.imac.unavarra.es/~c... or in english:
http://translate.google.com/tr...
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amp;u=http%3A%2F%2Fwww.imac.unavarra.es%2F~cnc%2F

Not EXACTLY the same appication, but perhaps a starting point.

ccotter247 on Feb 21, 2011 said:

Bad ass...

WilliamAAdams on Feb 16, 2011 said:

All pointers are appreciated.

Glasswalker on Feb 9, 2011 said:

Hey, this design looks good! I was startled to find someone building a nearly identical design to my own. I'm not quite as far along in the build as you are as I hit a couple months of a rough patch. But I designed an almost identical concept for my own Gada Prize entry... Perhaps we could collaborate and work together?

Check out the FabPod page in the Gada Prize page on the reprap wiki. (http://www.reprap.org/wiki/Fab...

Feel free to contact me if you wish to discuss further. There is a link to my blog site on the FabPod page on the reprap wiki, and from there you can contact me. (don't want to post my email h
ere to help minimize spam lol)

And good job! The robot looks awesome!

jstkatz on Feb 6, 2011 said:

This:

http://www.festo.com/cms/en_co...

is a very cool related rapid prototyper, festo also has a bunch of other cool videos in their bionic learning network section

Its a pretty rudimentary FDM machine, looks like it has a double stack nema23 sitting on top of the effector to drive the extruder which is a bit counterproductive.

Either style is a good candidate for a bowden extruder or perhaps a 1.75mm filament extruder that could be driven by a nema 14

I t
hink the big challenges will be to get a host software/firmware combination that will work. Then getting good joints that are accurate, smooth moving, lite weight.

It might be possible to get the host software to generate gcode that is just joint angles and then you could have pretty standard fir
mware. If we had arbitrarily small segment lengths that would work perfectly. I know people have figured out some of the speeds for minimum segment length because of the throughput of the firmware side. Somebody who knows some math could probably figure out how linear the movement would be with segm
ents corresponding to those lengths. That would tell us if we can use standard firmware that just linearly interpolated between fixed positions or if that wouldn't allow sufficient accuracy with current controllers.

trebuchet03 on Feb 6, 2011 said:

Not sure what a "double stack" NEMA 23 is... NEMA just deisgnates the bolt pattern (not length). Torque can be increased roughly linearly with an increase in motor length... Since this was probably a one off machine, the designers may have just went for broke, got a high torque motor to ensure results... Existing Open source hardware was no doubt off the table for them :p

WilliamAAdams on Feb 6, 2011 said:

I like the Festo. When I first saw that video a few months back, I thought "wow, very sleek". Of course the music probably helps.

You're right. It's all about the math, weight, and tolerances in joints. I think having a platform like this helps you experiment with all of these aspects, assuming you've got the software part of it nailed.

At the moment I'm playing with some carbon fiber, bronze bushings, smooth axles, and g
enerally making things lighter, simpler, and more accurate.

I think a reasonably accurate and repeatable machine can be constructed at this level, and the nice thing is you can focus on any aspect of the design you care to improve, without having to change the whole design.

langfordw on Feb 2, 2011 said:

very cool! I actually just did a whole project on one of these delta arms for my numerical methods class. Have you figured out how you're going to control it yet? I suspect there must be some good closed form models for the inverse kinematics somewhere.

You can see my report/code here: https://docs.google.com/viewer...
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WilliamAAdams on Feb 3, 2011 said:

For me it's exploratory. I don't have a fixed model as yet. I was looking at some of the considerations of other designs on RepRap, and around the net. I have some reverse kinematics code from doing graphics, and I was going to apply that. I'd like to get a better physical model than the idealized model of the graphics world though.

This is obviously one of the more interesting areas of hard work to be done.

I do want to go with servos though, which should make a certain amount of ease in terms of programming (vs steppers). At least that's my current thinking.

I'll make it a RepRap Wiki thing so people can experiment as th
ey see fit and not be constrained by what I'm doing.

The basic bot is a good platform to start with I think.

jnfischer on Feb 2, 2011 said:

This looks really exciting, I can't wait to see more

Spacexula on Feb 2, 2011 said:

Please Document that over at the RepRap Wiki, I know a lot of us would love to help in this dev.

Need help just pm me :)

WilliamAAdams on Feb 7, 2011 said:

I went and created a RepRap page, and entered for the Gada Prize while I was at it.

WilliamAAdams on Feb 2, 2011 said:

that sounds great! When I get a chance I'll pester you for help and get it going.

Batist on Feb 2, 2011 said:

Nice! Do you have a video?

WilliamAAdams on Feb 28, 2011 said:

The video can be found here: http://www.youtube.com/watch?v...

WilliamAAdams on Feb 2, 2011 said:

No video. There's no automated movement yet, so that exciting piece will have to wait until my servos arrive. Probably next week. I could do a video of me moving the mechanism by hand.

This weekend I'm going to have a couple of friends assemble them from scratch to see how long it takes them and what to improve. I can video some of that.

WilliamAAdams on Feb 2, 2011 said:

I have actually ordered some more bearings and carbon fiber tubing, and Dynamixel servos. I won't really work on the motion until I have the servos because that makes a huge difference in the electronics. The bushings and tubing will make a much smother movement.

the challenge continues. It is a fun project.

vik on Feb 3, 2011 said:

Would you mind trying bamboo as a form of tubing? It's lightweight, cheap and available widely (occasionally in the form of skewers and chopsticks).

Jolijar on Feb 2, 2011 said:

This looks great... I would love to see a youtube video of it in action. I am curious how it figures out the z axis.

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