How-to Forge a Skull Crushing Robotic Arm to do Your Dirty Work.

I recently was given 10 servos as a birthday present, so the question really was what to do with all of them? I started looking around at robotic websites that offered robotic arm kits. One of the sites sells robotic arms that are very cool, but they are also very expensive at prices upwards of $300. Then I came across a miracle on Lynxmotion's website, an older robotic arm known as the L6AC-KT. The whole construction was of lexan, so I thought to myself, hey, I have lexan as a resource. Now that the build is completed I hope to spread my ideas and hopefully inspire someone to build something equvilent.

Also, if you could please vote for this instructalbe in the Microcontroller contest , the Toy contest , and the Make it Move contest it would be highly appreciated ;D
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Step 1: Design and Fab

Picture of Design and Fab

For this project I used the lynxmotion arm as a large point of reference, but because the site does not actually give any CAD files or any dimensions of the older arm I was forced to make those decisions for myself. I used SolidWorks for the design of the whole arm assembly, this made everything go by so smooth since I could save the files as .STL or .Dxf and have a laser-cutter and FDM machine make the parts for me. Besides that the Items I used are:

1x 24x24 sheet of neon green lexan.
5x Hitec HS-422 servos
2x Hitec HS-645MG servos
1x box of 4-20 x 3/8 self tapping screws
1x box of 2-28 x 1/4 self tapping screws
some 8/32 x 1/4 socket cap screws

Check the next step to see what all the parts are used for...
Fitty Charles9 months ago
i need to build a robot under 11 volts and i was wondering what the voltage on this robot is
tinker2342 years ago
wow could i make this out of alliaum never can speel that sorry
that is possible, but look out that it isn´t to heavy.
but if you use springs so the arms weight is near nothing.
you would be able to make it out of alluminium with no problems
marvin T1 year ago
Hi, i'm about to start this project but might there be any chance of sharing the drawings/codes? I have solidworks so no issues there,
if so please send to
could you send me the codes please?
hello can help me , i am searching about this design to save my time i have my final project so plz if can send to me as DXF file , my email is
Very nice model.........have you used encoders?? Yes or or no, in both cases please make a tutorial on how to choose, use and connect encoders.
FlyingToaster (author)  dchakraborty2 years ago
Because servos have potentiometers already attached to the output gear, there is no need to use encoders; in fact, encoders would be much more inaccurate. Check this link out for more on how servos work:
docdavies2 years ago
Any chance you would share your CAD files?
mahsa arian2 years ago
thx FlyingToaster
Pretty cool! This neon green material looks great.
I want to make a robotic arm to play chess, but I don't know what to choose, stepper motor or servo. Stepper motors are more precise, but more expensive, heavier and i would need more mechanisms.
So my question is: do you think your robotic arm has precision enough to position pieces in a chess board?
Thanks and sorry for bad english.
FlyingToaster (author)  jcano yribarren2 years ago
The issue I had with stepper motors was with the control, you see I used an 8-bit arduino chip to control my arm, in order to control stepper motors I would need to make or buy an array of transistors, neither option was cheap. I would say servos could easily place chess pieces on a game board, plus you can easily program them to the degree. If you do take the servo route you may need to have stronger servos like the Hitec HS-645 series to have it move smoothly and precisely.
Ok. Thank you so much. I will try to create one with servos.
jwkooi3 years ago
Nice design. A video would be nice. I wonder: is it smart to have to servo's at the base in parallel? Are you sure they will move in the exact same way. Otherwise it will be a current drain, I gues, since the 2 servo's will try to rotate all the time.
But again: nice job

FlyingToaster (author)  jwkooi3 years ago
Good question(s). You are right, they the two servos at the base are going to try to fight eachother, but it can easily be fixed. First you can slot the holes where the lexan is attached to the servo, and second you can always take a servo horn off and reposition it. Both those methods should prevent the servos from fighting eachother for home position.
OK. Slot the hole will work but then only one servo will do all the work or you get a sluggy respons.
One servo will work, but you only have the strength of one.
Reposition the horn: I am curious if it works and keeps working over time.
Maybe it isn't that critical. Keep us posted wtih your experience.
FlyingToaster (author)  jwkooi3 years ago
Sorry, what I mean is you can either slot the hole in the lexan the same diameter as the original hole inorder to secure the lexan to the horn. You should not see less performance from slotting the holes because they will still keep the screws thight to the lexan. The second option was moving the horn. Lynxmotion has their lexan slotted, but I think I may set both servos to 90° and adjust the horns to match. Hope that helps. I'll Include more info in the instructable when I have some time.
OK. Seems like you know what your doing. Looking forward to see more results. I have made several project but no robots yet. Would like to but other family thing keep getting more priority. But have a look at the wooden aperture. I made a instructables for that, inspired (read:copied :-) by the cardboard aperture. Keep up the good work.
sarveshk jwkooi2 years ago
I think you can use Futaba SR10 for the precision you want.
See the link of the product
Blackice5042 years ago
nice design, how does the robotic arm sense the object it picks up?

i did not see if you used light or maybe a sensor of some sort.

i would love to make something like this but i cant cat plastic and wood work is so so, i think i will use some light steel.
vishalapr3 years ago
I was about to make an instructable on this and you made it...well...
PS1183 years ago
This is so cool!

So are you using your own original design, then?
If so, would you mind attaching it? (Please, please, please!)