
Ask HN: What’s the best commodity robot arm? - danecjensen
I want to play around with some robotics what’s a good robot arm I can buy?
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bradd
This is a common question. I have wanted a "good robot arm I can buy" for a
long, long time. I would like something with about 16 inches of reach and 6
degrees of freedom. The motion must be smooth with a position resolution of
around 0.01 inch.

Alas, in my opinion, such an arm does not exist for the hobbyist. Why? Mainly,
I think, leverage sucks (in this case). At 16 inches there is quite a lot of
torque required at the base to move the arm (with the mass of the arm plus
what it is grasping). And liability may be (probably is with most would-be
suppliers) an issue.

I have built a few arms myself with various hobby servos. High torque motors
where needed and smaller, light weight ones towards the wrist. * Some * of the
motions are smooth and neat. Others are simply jerky. Then there is the
problem of backlash.

There is a company (Trossen Robotics, I think) whose arms are ..., well, I
don't know what to say. Certainly, it seems, they offer cool motors that are
seemingly designed for what we want. But the videos are always disappointing.
Maybe its just me.

I assume you want something for a couple of $K. In my opinion, it does not
exist. The demand/application is not there to bring the cost down.

And, again, there is the liability issue.

Maybe some day, soon.

(I hope someone responds with something that will work for ya. I would like to
see that.)

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cr0sh
This is a very open-ended question; depending on what you want to do with such
an arm would be important to know what to recommend. Do you need fine control
and accuracy? Do you need speed, or strength, or some combination? What kind
and size of work envelope? Cartesian vs revolute vs...?

Have you considered going "old-school"?

That is, picking up a used Microbotics Teachmover can be easily done - though
you'll probably have to hack up a controller for it. Similarly, there are old
Rhino Robotics arms that can be bought fairly cheaply (though I warn you -
they are very heavy). There are several other robot arms from the 1980s that
you can find if you look, but all of them will require more than a bit of
"hacking" to get working with modern computer systems.

Have you considered building an arm using Lego or some other similar building
kit (Meccano, Fischertechnik, KNex)? Or maybe parts from Servo City, or 80/20
extrusions?

What about hacking a conversion? Like converting an old Armatron to be
computer controlled (not easy to do, but it is possible - it was done more
than once back in the 1980s, and those articles on how to do it are still able
to be found). Note that it is easier to convert the Radio Shack Armatron that
has a wheeled base, than it is to convert the joystick controlled Armatron
(the latter requires a bit of mechanical skill and knowledge, on top of the
electronics to interface it).

Another possibility (though fraught with even greater issues) would be to find
a second-hand laboratory industrial robot arm, and get that interfaced. There
are more than a few out there which were electric powered (mostly - some have
pneumatic end-effector attachments), and are small enough to play with in a
"home" setting. The downsides are lack of inexpensive replacement components
if you need them, among other issues.

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billconan
maybe this one?
[https://store.ufactory.cc/pages/kits](https://store.ufactory.cc/pages/kits)

most of them are super expensive, I would consider building one from scratch
by following
[https://www.youtube.com/watch?v=Citiq6Zfdu4](https://www.youtube.com/watch?v=Citiq6Zfdu4)

