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What to Do with Your Robot Arm — Parallax Forums

What to Do with Your Robot Arm

ercoerco Posts: 20,256
edited 2012-03-21 21:17 in Robotics
Stack wooden robots, of course! http://www.amazon.com/Schylling-WSR-Wood-Stacking-Robots/dp/B000ELQVAI/ref=sr_1_1?ie=UTF8&qid=1312219178&sr=8-1

Towers of Hanoi has been done to death (Martin_H at least virtually, any progress there?) so it's time to move on to something more challenging and fitting. EVERYONE loves wooden robots, so get out those arms and start programming!

Comments

  • Martin_HMartin_H Posts: 4,051
    edited 2011-08-01 10:55
    Erco, I'm embarrassed to say no progress. I've gotten side tracked on a cool machine vision project involving the propeller backpack and the line scan camera. I've been planning to post some information about that to the propeller forum soon.

    Besides getting side tracked, I concluded that I needed to create a fixed work surface for the arm to keep everything aligned. So I have a bit of construction to do also.
  • ercoerco Posts: 20,256
    edited 2011-08-01 13:24
    We all have plenty of time to keep up on the Forum, but never enough time to work on our projects! :)
  • Tony B.Tony B. Posts: 356
    edited 2011-08-01 14:53
    OK Erco, I need a break from my other robotic projects and I have never built a robotic arm. So, I am going to build my own robotic arm. It will be out of WOOD of course! I will post my work and updates as I progress. I think I will do it first with a BS2 and then Propeller. Might help encourage a beginner and I know I'll be learning as well. I'll start a new post later tonight.

    Tony
  • ercoerco Posts: 20,256
    edited 2011-08-01 15:06
    @Tony B.

    Thattaboy! Arms are very cool and can be simple or complex. Here's my first, a single weekend project: http://www.youtube.com/watch?v=-Z8lTSX4PHs

    ... and I just ordered ten of these grippers: http://www.solarbotics.com/products/50855 I have big plans!
  • WhitWhit Posts: 4,191
    edited 2011-08-01 17:25
    erco,

    I saw that Solarbotics' gripper - pretty cool and a good deal too. At 10 you got the discount and the free shipping - Clever boy!
  • Martin_HMartin_H Posts: 4,051
    edited 2011-08-01 19:41
    Ten grippers! Erco are you building a robo-squid or something?

    At the moment it's not a time issue. Projects have the fun part and the slog part. My Hanoi project entered the slog phase and I found another fun project. But a wooden robot arm stacking wooden robots may shame me into finishing.
  • HumanoidoHumanoido Posts: 5,770
    edited 2011-08-01 21:44
    erco wrote: »
    ... and I just ordered ten of these grippers: http://www.solarbotics.com/products/50855 I have big plans!
    Oh no! Erco! I'm simply shocked that you've decided to opt out for the dark side of the spidy force and build one of these! OMG! http://img.wallpaperstock.net:81/spiderman-evil-guy-wallpapers_1741_1152.jpg
    :)
  • ercoerco Posts: 20,256
    edited 2011-08-01 22:52
    You boyz miss NOTHING!

    @Whit: EXACTLY! I may have a few extras, but you know how I love a good bulk discount, no tax & free shipping.

    @Humanoido: You DO recall my Doc Oc post, and I HAVE been working on them. You'll see! :)
  • ercoerco Posts: 20,256
    edited 2011-08-04 00:01
    Got my Solarbotics grippers in today. Look good. Only problem is that they only fit a certain servo (that I don't have, naturally). Solarbotics calls it a "medium" servo, which is smaller than a standard servo, and it only has 2 screw holes along its centerline (most servos have 4 holes, off centerline). Looks to be something like an 18g servo from what I can gather.

    Just in case anybody else is ordering a gripper, avoid the wait and order a servo too!
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2011-08-04 03:54
    erco wrote: »
    Just in case anybody else is ordering a gripper, avoid the wait and order a servo too!

    Sparkfun sells the gripper and this "medium" servo http://www.sparkfun.com/products/10333
  • Tony B.Tony B. Posts: 356
    edited 2011-08-04 04:51
    Erco,

    How much would you say the gripper weighs?
  • ercoerco Posts: 20,256
    edited 2011-08-04 08:24
    @Ron: That's the servo, all right! Kind of an oddball size, not immediately found on Ebay (I need 10, I want 'em cheap). I may first make an adapter plate and slam on one of my umpteen disposable $2 9-gram servos just to play.

    @Tony: 65.3 grams without servo or any mounting hardware. A tad heavy, but nice. The servo will strip gears long before this thing yields.

    Edit: You could drop a few grams of weight by removing two small mounting flanges and the pair of nuts/bolts holding them on, if you can use the 2 resulting holes in the main plate to attach to. Visible in the pic at http://www.sparkfun.com/products/10332
  • ercoerco Posts: 20,256
    edited 2011-08-04 11:16
    There are a surprising number of complaints on that gripper in the comments at http://www.sparkfun.com/products/10332 The recommended servo they sell doesn't fit properly either, some aluminum grinding is necessary. I had to do some grinding to mount a smaller 9-gram servo, but I like the results. 2-56 screws are a good fit in the holes in the claw gear. The tricky thing is that proper claw function is 100% dependent on exact, critical servo mounting location. I saw that coming and just tacked the servo on with CA glue instead of fiddling endlessly making an adapter plate. Will make a video later.
  • Tony B.Tony B. Posts: 356
    edited 2011-08-04 20:45
    I will be watching to see your results. From your comments seems like more R&D was needed.

    The weight seems a little high to me as well. I'm really trying to watch the weight. Don't want the servos having to use most of their power just to lift itself.
  • ercoerco Posts: 20,256
    edited 2011-08-05 08:56
    Video of gripper test at http://www.youtube.com/watch?v=Qcw1CEbeV-o Per my comments there, the gripper pivots were loosey-goosey and can be improved with some careful tightening of the screws & nuts.

    @Tony: I hear you, and your concerns are valid and justified. I've seen more than one robot arm built that could barely move itself, and had virtually no payload lift capacity. Suitable for weightless ISS operation only! Countersprings at each joint make sense in a case like this, to negate the weight of the arm itself. Maybe even over-springing, so the the unloaded arm needs to work some to lower towards the ground, in order to increase payload capacity.
  • Tony B.Tony B. Posts: 356
    edited 2011-08-05 20:17
    @Erco: Good idea on the springs. I hadn't thought of that. I will put that idea in my bag of tricks & solutions. My design for my arm is not a conventional set up that I hope will allow for a stable and heavy lifting arm. Can't say much more here you'll have to wait for the reveal on my post for my wooden arm.
  • al1970al1970 Posts: 64
    edited 2011-08-05 22:58
    Hi Erco:

    Here is one I made mostly from wood about 2 years ago.

    http://diyrobots.webng.com/VideoP/VideoP.htm
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2011-08-06 10:40
    And here is mine:

    http://www.budgetrobotics.com/shop/?cat=159

    SHAMELESS, I know. But I couldn't resist! I designed it for myself, then decided may others would find it practical.

    Yeah, it's more than the others, but it'll actually lift and hold something. I usually put drip irrigation rubber tubing over the fingers for extra grip.

    Anywho, I know the guys who designed and sell the cast aluminum gripper that Solarbotics and Sparkfun offers. I got one in to test and wasn't too happy with the mechanism, but it IS inexpensive. Like Erco sez, it's not too hard to adjust the nuts and screws for a better fit. Nylon locking nuts always need a bit of finesse.

    The Sparkfun/Solarbotics/Robotshop claw ("That's CRAW, not craw!") likely was designed for either a GWS Mini servo (the one I used, which fit perfectly), or an HXT.

    -- Gordon
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2011-08-06 10:45
    erco wrote: »
    I've seen more than one robot arm built that could barely move itself, and had virtually no payload lift capacity. Suitable for weightless ISS operation only! Countersprings at each joint make sense in a case like this, to negate the weight of the arm itself. Maybe even over-springing, so the the unloaded arm needs to work some to lower towards the ground, in order to increase payload capacity.

    This is where a good local hardware store comes in handy. Home Depot and Lowe's just don't cut it. I went in to my local Tru Value, asked to see their spring drawer, and hand tested a bunch of 'em. I came away with five or six contenders, and tried several that will work.

    Yes to over-springing. Along with the lilies of the field, consider the lowly garage door (the old kind, not the newfangled rollup).

    -- Gordon
  • ercoerco Posts: 20,256
    edited 2011-08-08 19:29
    Oh yes, by all means, the old WOODEN garage doors! :)
  • ercoerco Posts: 20,256
    edited 2011-09-03 09:55
    @TonyB: Once your new arm can stack those robots, you can go on to open & close & re-nest these nesting robots!

    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250773594217
    nesting.jpg
    280 x 280 - 8K
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-09-03 10:19
    I have one of CrustCrawler's AX-12 Smart Robotic Arms.

    I've been trying to figure out how to get it to lift cuvettes (small test tubes) from a rack, place them in a spectrometer and then return the cuvettes to the rack. I'm realizing this is going to be no small task.
    GordonMcComb wrote: »
    consider the lowly garage door (the old kind, not the newfangled rollup).
    The guy who just replaced the huge springs in our newfangled rollup garage door told me the the springs do most of the work. The motor isn't strong enough to lift the door without the springs.

    I think springs could really help the AX-12 arm. Heck even rubber bands might be helpful (and probably quieter).

    Duane
  • Tony B.Tony B. Posts: 356
    edited 2011-09-06 15:16
    @Erco,

    I'm still trying to come up with a good gripper design that doesn't weigh a ton, is steady, and I know the orientation of the robots in the gripper. This is a great challenge and I love it! I've had to rest on this project a while as I finish up work before harvest starts next week. Progress may be slow the next two months but be assured I'll be working on it every chance I can.

    As for the nested robots I thank that might just be a great use for the soft gripper made from coffee and a latex balloon. But again, known orientation of the pieces in the gripper is a big issue.

    Tony
  • ercoerco Posts: 20,256
    edited 2012-03-21 21:17
    Time to de-hoard at Expo! Among other things, I have 7 extra Solarbotics grippers I'll bring to the Expo. I'll sell for my bulk price of $9 if anyone wants one. Heavier than I like for a 5-6 axis arm, but good for 2-3 axis (grab & lift) arm. I'm keeping 3 for my own evil purposes. Currently $9.95 at http://www.solarbotics.com/product/50855 BYO servo!

    http://www.youtube.com/watch?v=Qcw1CEbeV-o

    I'm guessing there's a swap meet element to the Expo. I'll also bring some things for the freebie table.
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