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New Gripper — Parallax Forums

New Gripper

ercoerco Posts: 20,257
edited 2014-08-21 14:12 in Robotics
This arm on Ebay shows a slick-looking new gripper in the top 2 photos: http://www.ebay.com/itm/New-6-DOF-Manipulator-Aluminum-Robot-Arm-Kits-for-Smart-Car-Base-not-assembled-/331173360823

Looks nice, but other photos below show the same heavy aluminum one we've been seeing for years, probably what actually comes in that kit.

Anybody know anything about the new gripper? Gotta be available somewhere. Might be plastic or nylon.

attachment.php?attachmentid=109196&d=1403115486
gripper.jpg
500 x 500 - 19K
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Comments

  • Bill HenningBill Henning Posts: 6,445
    edited 2014-06-18 11:53
    Nice find!

    That plastic gripper looks good - let's hope they start selling it by itself.
    erco wrote: »
    This arm on Ebay shows a slick-looking new gripper in the top 2 photos: http://www.ebay.com/itm/New-6-DOF-Manipulator-Aluminum-Robot-Arm-Kits-for-Smart-Car-Base-not-assembled-/331173360823

    Looks nice, but other photos below show the same heavy aluminum one we've been seeing for years, probably what actually comes in that kit.

    Anybody know anything about the new gripper? Gotta be available somewhere. Might be plastic or nylon.

    attachment.php?attachmentid=109196&d=1403115486
  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-06-18 13:02
    I've seen a few 3D printed grippers that kind of look similar but I don't think I've seen that one before.

    The photo below is from the link above.

    gripper2-printed.jpg
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2014-06-19 15:12
    Not a bad looking gripper. Erco could tell you how much it would cost for the dies alone if this were injection molded versus 3D printed. I imagine with a faster printer than the average hobby model, and a wall of 10 to 20 of them, you could churn out lots of these kinds of parts in low quantity and make a pretty good profit.
  • ercoerco Posts: 20,257
    edited 2014-06-26 18:35
    Then there's this "function specific" gripper. Overpriced, but scroll down the photos to determine the booty.

    http://www.ebay.com/itm/Robot-Clamp-Robotic-Hand-Kit-Form-for-robot-builders-and-projects-/221263142796?pt=LH_DefaultDomain_0&var=&hash=item33844f9f8c
  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-06-26 20:23
    I wonder if the gripper can really lift a full can of soda? (No, I don't really wonder. I'm pretty sure it can't. (At least not with an inexpensive servo))

    My cool Smart Arm with a bunch of nice Dynamixel AX-12+ servos can just barely pick up an empty soda can. I wouldn't have a chance picking up a full can.
  • Martin_HMartin_H Posts: 4,051
    edited 2014-06-27 09:26
    I think that gripper could lift a soda can if the arm was designed to do it. For example here's a video of the uArm lifting a 1/2 Kg weight fairly easily:

    It uses ordinary servos, but has good payload capacity because its design gives them a fair amount of leverage.
  • xanaduxanadu Posts: 3,347
    edited 2014-06-28 06:19
    I ordered one of these on eBay for $90 shipped with servos a few weeks ago. Couldn't resist, should have it soon. I was able to find a video on youtube of it (or something very close), and it mentioned the kit doesn't come with servo horns. Will report back when it arrives... Edit: It was actually over a month ago, could be here this week!
  • NWCCTVNWCCTV Posts: 3,629
    edited 2014-06-28 13:54
    $90 shipped with servos
    Can you post a link? I cannot find one that cheap anywhere.


    Edit: I have to wonder what they are using for air.
  • xanaduxanadu Posts: 3,347
    edited 2014-06-28 14:43
    Negative, auction is no longer available. Seller was - "elec_mall2012". Ordered over a month ago *yawn*.
  • NWCCTVNWCCTV Posts: 3,629
    edited 2014-06-28 15:42
    Oh, I thought maybe it was a China deal!!!
  • ercoerco Posts: 20,257
    edited 2014-06-29 10:13
    See http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=160998716216
  • xanaduxanadu Posts: 3,347
    edited 2014-06-30 19:57
    Interesting, the link Erco posted is the exact price I paid to the same seller. I'm positive I ordered the one with the pics of the nylon looking gripper, which I cannot find at that price now. At the time I remember wondering which gripper it came with. Not complaining, six metal gear digital servos and all the brackets were a good deal.

    It arrived today, and it's the traditional gripper. I heard a rumor that there was a new gripper that uses all 180 degrees of servo movement and was hoping that I had found it but I guess not. Should be easy enough to switch out...
  • ercoerco Posts: 20,257
    edited 2014-07-01 13:10
    I got one too. The no instructions part is no fun. Not digital servos afaik, just metal gear: four mg996 and two mg995 (ugh). I also ordered the metal servo horns, recommended.
  • CrazyrabbitCrazyrabbit Posts: 116
    edited 2014-07-01 14:01
    Nice. Something to think about with the Detroit Maker Faire coming up.
  • xanaduxanadu Posts: 3,347
    edited 2014-07-01 19:08
    erco wrote: »
    I got one too. The no instructions part is no fun. Not digital servos afaik, just metal gear: four mg996 and two mg995 (ugh). I also ordered the metal servo horns, recommended.

    I was under the impression the servos were digital. I booted one up and it doesn't act digital. I'm reading conflicting info online some sites say they're digital and the mfg www site doesn't mention the type.

    I hope to start building it this evening. I seem to have misplaced the metal servo horns I found on eBay. If I can't find them soon I'll just use the plastic.

    Which axis would you use the stronger servos on? I'm guessing closer to the base where more weight is on them?

    Thanks.
  • xanaduxanadu Posts: 3,347
    edited 2014-07-01 20:55
    This seems like a really good way to fry servos. This thing is heavy and I have my doubts about putting this on a robot already. I pieced it together with minimal screws for now. I used the two weaker servos on the shoulder pan and wrist rotate because they seemed to be the least torque.

    I used this pic as a guide, with the exception of the base which you can't really see. I just drilled a couple holes in it and "made it work".

    ad.JPG

    Here is the one I built

    IMG_0098.JPG
  • xanaduxanadu Posts: 3,347
    edited 2014-07-06 14:04
    I'd also like to add that the servos are rated up to 7.2v but for some reason at least two will not function properly past 5.3v. The two that will not have the most weight on them, so it's probably safe to say all of the servos wouldn't function properly with more than five volts.

    I had been using a Vin of 7vdc on a protoboard to power the servos, and they seemed to have no strength at all. I would help the elbow by taking weight off it with my hand to get it to move. I connected it to an RC rx and powered it with a five amp BEC and it worked great.

    I assumed there were a problem with my Prop setup like a code issue. I swapped out the arm for some smaller servos and they worked fine. Back to the arm itself... After an hour or so I managed to accidentally use the 5v instead of Vin to power three of the servos and they all worked well.

    I connected all six to the 5v regulator (keeping an eye on current) and it worked great. Since then I added a separate 5v supply for just the servos.

    In some cases I've managed to draw up to 3 amps (gripper closed tight while moving). In most cases resting was around .25 amps and movement with a small object was around 1 amp.

    The repeatability is as good as the frame I put it on. I left it running overnight picking up and putting down a dual relay board. Didn't seem to have any problems with that. I'd have to say for $95 it's a good deal.
  • Bill HenningBill Henning Posts: 6,445
    edited 2014-07-08 07:47
    Thanks for posting that mini-review.

    Looks like fun!

    I may have to order one. I have a couple of grippers like that, but not the base & all the brackets.
  • NWCCTVNWCCTV Posts: 3,629
    edited 2014-07-08 20:41
    Are you using standard servos or CR? I have some of each of Parallax's and I have an arm design in mind.
  • xanaduxanadu Posts: 3,347
    edited 2014-07-09 00:54
    CR could be dangerous due to the servos wires, and much less accurate for repeatability without additional sensors.

    Also, disregard my comments on working voltage with my servos. One of my servos (wrist rotator) was drawing a lot of current over 5 volts causing the entire arm to be weak. Investigation is underway, will report back soon.
  • NWCCTVNWCCTV Posts: 3,629
    edited 2014-07-09 14:19
    CR could be dangerous due to the servos wires
    Yes, I have taken that into consideration. I have some slip rings I will be using. I want the wrist on my arm to turn 360. The rest will be fine using Standard Servos.
  • ercoerco Posts: 20,257
    edited 2014-07-09 15:02
    Andy: Will you use an encoder to measure wrist angle? And you'll use 3 slip rings to connect to your gripper servo? You might get a lot of noise, some servos might not like that. Eager to see what you come up with.
  • NWCCTVNWCCTV Posts: 3,629
    edited 2014-07-09 18:04
    Will you use an encoder to measure wrist angle?
    Possibly. I am not really looking for perfection.
    And you'll use 3 slip rings to connect to your gripper servo?
    No, Only one located at the wrist/gripper. I actually meant that I want the gripper to rotate 360, not the wrist.
    Eager to see what you come up with.
    Yea, me too!!!! I was hoping to get to it again this week but as usual, real work is getting in the way. ( That and the sun is shining, which up here we enjoy while we can!!!!!)
  • xanaduxanadu Posts: 3,347
    edited 2014-07-10 15:35
    You can do 360 with two standard servos, no limit switches, no encoders and no wiring issues to the gripper. I saw Duane had a link to the configuration using a Y cable.

    If you want 360+ degrees of travel, you'd want a CR servo. I don't see how a slip ring will help unless it's inside of the wrist servo output shaft, wouldn't it need to be on the axis that is rotating?
  • xanaduxanadu Posts: 3,347
    edited 2014-07-15 11:55
    The other (that's both) MG995 servo is bad now. It works fine for around 150 degrees, the last 30 or so it will go past where it is supposed to go. Still not a big deal for $90 it was expected. I'm happy with the MG996, the shoulder takes a ton of abuse.

    I'm wondering if I should get more of the MG996 to replace the bad servos. Does anyone know of some decent quality metal gear servos that might be a better choice for an arm?
  • ercoerco Posts: 20,257
    edited 2014-07-15 13:05
    Yikes, I guess this review was accurate: http://www.rcmodelreviews.com/mg995review.shtml

    Bill Henning concurs from his Hexapod thread. :(

    MG995 servo=boat anchor.
  • Bill HenningBill Henning Posts: 6,445
    edited 2014-07-15 13:19
    Yes, the MG995's suck.

    I will get them working :) I have just been distracted by life (family, work)
    erco wrote: »
    Yikes, I guess this review was accurate: http://www.rcmodelreviews.com/mg995review.shtml

    Bill Henning concurs from his Hexapod thread. :(

    MG995 servo=boat anchor.
  • ercoerco Posts: 20,257
    edited 2014-07-15 13:26
    MG996 for $5.81 shipped, I hope they're legit, I just ordered two for my arm: http://www.ebay.com/itm/MG996R-Torque-Digital-Metal-Gear-Servo-for-Helicopter-Car-Boat-Model-/181400127339?pt=Radio_Control_Parts_Accessories&hash=item2a3c4a476b
  • Bill HenningBill Henning Posts: 6,445
    edited 2014-07-15 14:10
    Let us know how they work out...
    erco wrote: »
    MG996 for $5.81 shipped, I hope they're legit, I just ordered two for my arm: http://www.ebay.com/itm/MG996R-Torque-Digital-Metal-Gear-Servo-for-Helicopter-Car-Boat-Model-/181400127339?pt=Radio_Control_Parts_Accessories&hash=item2a3c4a476b
  • xanaduxanadu Posts: 3,347
    edited 2014-07-15 14:45
    I'll order some more MG996. I think they're a good match for the mechanical design of the arm. I'd like something a bit more accurate, I suppose some mods are in order, and then maybe better servos.
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