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6DOF Robot Arm

Building an open source robot arm for schools and DIYers

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This project was created on 04/28/2014 and last updated 13 days ago.

Description
I want to put robots on the moon to build my base. An industrial arm starts at $10k and go up from there. I figure I can make some money to pay for the space ticket by building and selling the robots myself. I'd like to drive the cost down by making an arm that others can tinker with, improve on, and build community around. I'd like to see two arms assemble a third.

So far I've built a 3DOF arm that I brought to the 2014 San Mateo Maker Faire. I've taught it to write so it can sign pictures and print your message here. I've also built a 5DOF prototype (pictured).

I need all the help I can get. Please share with your friends!

Thanks for reading,
Dan
Details

I don't know what to write here that isn't covered elsewhere.   Ask questions?

You can get the full part list or support me by buying a copy of the current design here:

http://marginallyclever.com/shop/robot-arms/

Components

Project logs
  • UBC robot arm Thingiverse files

    13 days ago • 0 comments

    Here you go!

    http://www.thingiverse.com/thing:767796

  • UBC student prototype

    14 days ago • 0 comments


    This picture shows my first metal arm (three years old?, center left), two of my wood robot arms (from a year ago), and the prototype UBC student engineers just delivered. It runs a beaglebone black and has two identical sections. The idea is that three sections put together would make a 6DOF arm.

    The bad

    The third section would have required very expensive Dynamixel motors that were out of budget for this prototype.

    The servos are normally 270 degrees, then geared down for power, leaving a range on each joint round about 30 degrees. Not enough to satisfy!

    If I were to mass produce this 3D printing would be a total no-no. Cable routing is a mess.

    The good

    I really like the modular design because I'm always thinking about how to make 1000s more. The math says this arm would be long enough and lift enough weight for my specs. It is surprisingly stiff! I wouldn't have expected the 3D printing to take those kinds of forces. Speaking of which, the 3D printing is gorgeous at 60% infill.

    Next

    I've been working in parallel on a plan B, so we'll see how that goes and compare the two on the far side.

    Also posted on http://www.reddit.com/r/robotics/comments/325bsh/i_asked_ubc_students_to_build_a_robot_arm_for_me/

  • Gearbox 3 Attempt 2

    24 days ago • 0 comments


    Down to the wire! A year ago I said at the Bay Area maker faire I would have my new arm at next year's event. Now here I am waiting for the design of the second version and I'm really feeling the pressure. I want to deliver so badly!

    In the meantime I've been working on the software. I have enough robots now that I can see how their programs overlap. I'm bringing them all together into a single framework so that they can work together and share a common core.

    It occurs to me that I've made three different hypocycloidal boxes and this is my second attempt at the latest. That means I've learned... six ways to not make a gearbox.

View all 27 project logs

Build instructions
  • 1

    Instructions so far:

    http://learn.marginallyclever.com/index.php/Arm3_v1

See all instructions

Discussions

Andrew Becker wrote 10 months ago point
Hi Dan, sorry for the long delay, I took my family on holiday and decided to leave the hobbies behind. I have already had a good look at your project and it looks great, I would be more than happy to share my work with you, I'm also very curious as to what control system you're using.

Are you sure? [yes] / [no]

Dan Royer wrote 10 months ago point
The software is home-grown. The electronics are a RUMBA controller - think an Arduino MEGA and a super sized RAMPS board put together.

Are you sure? [yes] / [no]

Andrew Becker wrote 10 months ago point
So you are doing all of the forward and inverse kinematics from first principles? I've managed to logic out the geometric relationships for my arm because the axis pairs intersect which simplifies the maths. I've then moved all of that into excel to visualise it and plan on using that to implement it in Linux CNC. It works out fairly simple because the alpha, beta and gamma angles fix the position of the 3rd link in space, thereafter it's a matter of working back through each joint position. Because of the geometry I chose there is only one solution to the set of equations and it's not necessary to use matrices to solve. How are you handling it?

I have a Reprap Ormerod and initially I had some trouble with the software. It turned out that the PSU supplied was not supplying a stable voltage to the controller and when the heated bed switched on it would freeze. I went for an industrial PSU with a much higher rated amperage and the problem disappeared. It did however put me off using an arduino based controller considering how easily my first Linux CNC set-up went.

Are you sure? [yes] / [no]

mad.hephaestus wrote 11 months ago 1 point
I had a random thought:
If you take that whole arm section and put it in a 2 axis gambol, centered around the elbow joint (with the elbow being the outside joint), you could get a true R-R-R spherical wrist, without twisting the belts. The entire section you have now would rotate around the center axis. With a circular track around the edge the track race could then form the elbow joint on the out side. You could actuate it with a third counterbalance motor and a gear interface to the outer track.

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Dan Royer wrote 11 months ago point
That's the first thought I had. I've skipped it for now to ... Work my way up? Also as the gimbal turns the wrist motors could collide with the shoulder assembly. I'm looking for a method closer to what existing arms do where the ulna rotation is between the elbow and wrist. I have some drawings and I'm saving them for later.

Are you sure? [yes] / [no]

Dan Royer wrote 11 months ago point
One of the things that drives my business most is customer feedback. You asked for it and I can do it, so I'll start posting here more. Given how busy I am it will probably be a copy/paste from my website, which may hurt my SEO.

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zakqwy wrote 11 months ago point
Thanks Dan. Great work so far, it's been fun to watch your progress as you develop the 4th and 5th axes.

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zakqwy wrote 11 months ago 1 point
What are your thoughts on putting more info on HaD.io? I'm less likely to click through for project logs or other updates, it's easier to read everything in one place (and comment on it here, too).

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