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5+ Axis Robot Arm

Building an open source robot arm for makers and small businesses

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In September of 2015, a five axis industrial robot arm able to lift a kilo started at $10,000 USD.
In October of 2015 Marginally Clever Robots, Ltd introduced the Evil Minion and brought the starting price down to $2000. Since then we've been working to improve our offer with easier manufacture, more reliability, and greater ease of assembly.

I see an opportunity for low cost arms to serve small industry, hobbyists, and schools. I want to drive the cost down even more 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.

Tell SpaceX and RocketLabUSA I need their rockets - lets put Marginally Clever Robots to work building a lunar colony.

Like what you see? Support me on Patreon.

View all 14 components

  • Study number 5

    Dan Royer10/26/2017 at 06:59 0 comments

    I was up until 4:30am last night working on the fifth attempt to design the arm.  Previous post on HAD.io were of (at best) study 4.  I reached a point in the design where I'd found enough mistakes that it was easier to restart and use the existing design files as a reference to do a better job.  I believe that - after three days of work - I've got something that solves all my previous issues and has fewer prints. 


    With lessons from the previous attempts, this time I built things in large passes:
    place all the things that can't be negotiated (bearings, motors, screws in motor faces)

    1. build the bones to hold the parts together as rough blocks
    2. plan where to cut the bones for printing
    3. add the screw holes, screws, and nuts to each block
    4. cut the bones into pieces
    5. calculate bill of materials
    6. order missing mechanical parts
    7. adjust each piece for printer tolerance and print.  <-- I am here
    8. the rest of the Gantt chart

    Speaking of BOM, here are some stats:

    • 218 fasteners
    • 34 mechanical parts off the shelf, including the drivers and the controller
    • 35 printed parts using ~1.8kg of filament at 20% infill will take 65h of continuous printing.

    Cost for raw goods and DIY printed parts is matching my expectations.  The long pole is the 8 larger bearings.  I got them from VXB.com and they're about $250+shipping.  Ugh!

    So for day to day updates, follow me on Instagram.

    Become one of my Patreon supporters today and you get early access to the Fusion360 files.  Build this yourself!  Contribute ideas!  Automate all the things.

  • shoulder printed

    Dan Royer10/22/2017 at 06:17 0 comments

  • Bicep printed

    Dan Royer10/16/2017 at 21:44 0 comments

    Bicep parts are all printed.  I have to collect a number of missing fasteners and wait for bearings to be delivered.  In the meantime I'm going to assemble the circuitry for the controller and run some tests on a rotation sensor idea that's staying under wraps for now.

  • 6 axis model progress

    Dan Royer10/14/2017 at 22:02 0 comments

    Here are some pics from the 6 axis model I'm currently working on.

    https://www.instagram.com/p/BaPQChtgkqp/?taken-by=imakerobots

    https://www.instagram.com/p/BaK56pIg09m/?taken-by=imakerobots

    https://www.instagram.com/p/BZuFjqrAWwr/?taken-by=imakerobots

    As I print and assemble each part I check it against the model.  More efficient than building an entire model in a vacuum and finding I made mistakes.  Maybe it couldn't be done without an existing, purely-vacuum model as a reference.  Hard to say from the other side!

    The design files for this version are on Patreon. https://www.patreon.com/imakerobots

    You can wait until it's for sale or chip in a little now, get the files early, and support development.  Your call.

  • Hiatus

    Dan Royer03/28/2017 at 17:59 0 comments

    I'm always thinking about building the arm and life laughs at my plans.

    I'm currently building several robots as commissions; running Marginally Clever.com; and spending a lot of coding time on Robot Overlord. I've got newly designed AS5045 sensors that work well, they now need to be integrated into an updated arm design. I may actually repurpose those sensors in another project first: A new Stewart Platform being built for a local science museum.

    https://www.instagram.com/p/BR1p9Msgd5P/

  • Rotation sensor AS5045 upgrades

    Dan Royer12/28/2016 at 17:10 0 comments

    https://www.instagram.com/p/BOim_CBjiaU

    The biggest problems with the last arm design all stemmed from poor sensor construction.

    - the wires were exposed to users where they could catch, fall off, etc.

    - the sensor and magnet have to be held in perfect alignment or the arm loses sensation and goes nuts.

    To fix that I'm working on a single sensor unit that I can test independently and use as needed in my next arm.

  • When will there be more news?

    Dan Royer09/22/2016 at 22:51 0 comments

    I'm deep into preparing for a new product launch, and then finishing the Jigsolve. My winter project is to make a new arm and integrate it with Robot Overlord, which still needs a way to record/play back every robot it supports. I'm also putting together a team to build a new game based on my design doc, which should eat ~6 months and cost ~100k.

    All of which is to say I'm really busy and I need all the help I can get. I'm looking for talent everywhere.

    There is a growing number of open source robot arms, which is super. I only build one because I can't get one at an affordable price. So if you're making an arm, please let me add Robot Overlord support and together I hope we can achieve greater things.

  • Added Andreas Hoelldorfer's arm to Robot Overlord

    Dan Royer05/03/2016 at 20:03 0 comments

    @Andreas Hoelldorfer has been building a 3D printable robot arm. It's making progress faster than mine.

    https://hackaday.io/project/3800-3d-printable-robot-arm

    His forte is hardware and mine is software. It seemed only reasonable to combine forces. So I asked him to share his Inventor model files with me, and then I imported them to Robot Overlord.

    https://github.com/marginallyclever/Robot-Overlord

    Here's a quick video of forward kinematics in action.

    https://www.instagram.com/p/BE9AE8YIfB7/

    Inverse kinematics shouldn't be too hard. Java support for joysticks is shamefully bad. Firmware to connect RO and AHRobot together is definiitely possible.

    ----

    Meanwhile I've been spending a lot of my free time working on my own design. It's very slow going. I have the wrist designed to satisfaction and the elbow is working-but-ugly. The shoulder and the pistons to drive the arm backhoe-style is where I'm currently struggling. I wish I had more time!

  • Folded Arm3 into Robot Overlord

    Dan Royer04/01/2016 at 15:48 0 comments

    instagram doesn't embed, boo hiss. https://www.instagram.com/p/BDoEmVzIfO7

    Yesterday I moved the software for controlling the arm from http://github.com/i-make-robots/Evil-Overlord to https://github.com/marginallyclever/Robot-Overlord. I, for one, welcome this move.

    I also completed the merge of the older Arm3 into Robot Overlord, along side the Evil Minion (5 axis), the Delta Robot, the Stewart Platform, and Spidee (crab robot). The only robot that isn't merged is the Makelangelo, which has been eating all my time by being very very popular.

    Also last week I was looking at https://hackaday.io/project/3800-3d-printable-robot-arm and I see @Andreas Hoelldorfer has used a camera quick-connect for his tool changer. Great minds think alike!

  • Second Evil Minion

    Dan Royer11/16/2015 at 15:09 0 comments

    Going from zero to one of something is challenging.

    Going from 1 to 2 is still challenging, even if you're planning ahead for it. The bill of materials was wrong, the assembly instructions weren't written down, and there were design choices that didn't matter for "just getting it done" that made doing it again a pain in the ass. Already I'm thinking "all this here, this over here, and those bits should be changed for easier manufacturing".

    I've ordered enough parts for five machines, and I've begun assembling them. The documentation will be smoothed out by then.

    Because of the high difficulty assembling the machine I'm only offering to ship fully assembled arms: http://www.marginallyclever.com/product/evil-minion-5-axis-arm/

    I've only had one robot go to >1000 units. I look forward to having an arm do the same.

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Discussions

trevorjtclarke wrote 10/26/2017 at 17:16 point

Hey dan! Like the iterations in this! Curious about angular measurement, are you using any encoders? Or using steppers with encoders? And yes, printing iterations for tolerance is definitely annoying. I've just added it as a variable in my fusion360 designs :)

  Are you sure? yes | no

Dan Royer wrote 10/26/2017 at 17:17 point

in my current iterations the robot is totally blind.  once I've proven the basic mechanics I plan to add first some limit switches, then some encoders.  One problem at a time :)

I also use a printerMargin value.  I'm not in love with it.  I'd love a CAM option to add tweaks after design and before printing, so it can be better tailored per-machine.

  Are you sure? yes | no

trevorjtclarke wrote 10/26/2017 at 17:24 point

Right on :) Also, it looks like if you could cnc some of the bigger sections out of hdpe or something for quicker testing?

  Are you sure? yes | no

Florian Festi wrote 09/26/2017 at 13:25 point

Nice Project! But I wonder if you are giving a way much strength and stiffness by using open cross section profiles (H and C) for the arm. In my experience constructions made out of plywood and with finger joints are much stiffer if they are closed all around. Holes in the walls are often not a big problem but missing walls weaken the parts notably - especially wrt (lateral) torsion.
It is a bit difficult to judge just from the pictures but it also seems that the different axis of the arm have different strengths - limiting the capabilities to the weak ones. Especially the NEMA17 motor for the first axis looks much weaker than the linear actuators for axis two and three, given that is also has to deal with the full length of the arm as a leaver.

It's a bit of a pity that you do not have a video with the arm under load or fast movement, so the strength and stiffness is more visible.

  Are you sure? yes | no

DontStalkME wrote 04/05/2017 at 08:57 point

If you want it to be cheap use 3d printed pneumatics. Or just home built pneumatics from pvc pipe etc.

Counter-weights will get you more strength / $

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George I Fomitchev wrote 08/15/2016 at 06:37 point

maybe smaller hand to mount to a DIY SelfieBot 

endurancerobots.com/en/robots/diy-selfiebot/

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Peter wrote 09/25/2015 at 19:12 point

Do you have any STL or STP files for this Project? 

  Are you sure? yes | no

Dan Royer wrote 09/26/2015 at 02:27 point

they're in a zip in the Evil Overlord project so the arm can the rendered in 3D

  Are you sure? yes | no

chetan wrote 09/02/2015 at 12:11 point

Nice project dan. I am regular visitor to your marginally clever website to learn CNC basics and when i was looking for DIY robotic arm then i found you again here.. :) 

  Are you sure? yes | no

Dan Royer wrote 09/02/2015 at 15:31 point

Do you think I should post this stuff to the MC blog?

  Are you sure? yes | no

chetan wrote 09/03/2015 at 11:41 point

Yes, It would be great if you post it to MC blog and link it to MC tutorials page. 

  Are you sure? yes | no

Andrew Becker wrote 06/17/2014 at 10:50 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 06/17/2014 at 15:57 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 06/17/2014 at 21:02 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.

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Kevin Harrington wrote 06/05/2014 at 04:51 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 06/05/2014 at 05:30 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 06/03/2014 at 14:35 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 06/03/2014 at 18:15 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 06/03/2014 at 12:11 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).

  Are you sure? yes | no

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