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LesHall

Ivan the Robot Arm (vaporware alert!)

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Hi all,

Sorry that this is vaporware, I plan to print it soon. Ivan is my companion robot. He has taken many small and playful steps in his development into a full robot. In this version, Ivan is an industrial robot arm. Here is the GIF animation that I will discuss with you:

5a3327b25daf6_IvanArmTwo32.thumb.gif.137fa85c377a97e1f8bea0f7a6fa165e.gif

In this image Ivan is playing "touch the ball", a game in which a red ball is randomly positioned by the OpenSCAD design file for Ivan, then Ivan's motor angles are calculated according to four simple trig expressions that I developed and a touch of algebra as well. These do a good job of positioning Ivan's toolhead close to the ball as you can see. This method is simpler than forward kinematics and easier than inverse kinematics. I think, though, they are a form of forward kinematics. Anyway, that is ball tag.

Ivan's big discs contain planetary gear sets, and Ivan's connecting rods are PVC pipe. Ivan looks unstable but he has screw holes from underneath and a large enough wooden platform to keep him in position. The planetary gear sets are key to Ivan's identity. They function as plastic bearings rather than use metal bearings because, you see, Ivan is nearly all plastic. Except for motors, fasteners, and control electronics (and wooden base), Ivan is entirely plastic. The plastic consists of all 3D printed parts except the section joiners which are PVC tubing for strength and reduction of print time. Ivan will be printed in Nylon, which is ideal for gears.

Also related to the planetary gear sets is Ivan's history of Gear Toys in open source hardware. Ivan is somewhat popular, mostly I deduce from parents printing Gear Toys for their kids. So the Gear Toys have become a learning sequence from toddler to teen and above into adulthood and I thought a robot arm would be nice.

Anyway, that is Ivan.

Les

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Here in this animated GIF image (click for animation) we see the drastic evolution of Ivan the robot arm that occurred yesterday. When I realized that putting the motors in-line with belt/chain drive meant that the planetary gear joints could be reduced to simple bearing joints, this was the result.

5a3327d33ed1e_IvanArmThree17.thumb.gif.8c0486dac6f36fb8d98af3541f925df0.gif

Ivan now accurately touches the magenta ball through -60 to 120 degrees at a radius of one to three section lengths, which I find to be quite a capable result for such a small amount of algebra and trig. He's also low in part count (about a dozen parts total) and both quick (relatively) and easy in printability. I hope you like my latest Ivolution!

Les

5a3327d33ed1e_IvanArmThree17.thumb.gif.8c0486dac6f36fb8d98af3541f925df0.gif

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Hi Sander!  One "s" in "Les" please.  The hospital stay was somewhat serious, but I feel 100% better now.  I am currently making adjustments and some design changes to Ivan's planetary gearbox.  It is thinner now which will improve print times.  The tougher part will be to lower print times and improve printability of the arm pieces.  Thanks for your interest!

Les

Edited by Guest

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I'm finally able to print out Ivan's parts and if you'll reference this forum thread:

forum thread on PETG printing and heat transfer

you'll understand why the big base part has a poor surface yet the gears are fine. Anyway, I have things tuned up right now. The design is also evolving as I go, with the gears much thinner and added posts instead of hollow gear mounts, etc.

Les

5a33282d5569a_IvanGearBoxPrintError.thumb.JPG.d8934ce48dab1dc7357840d59b4f82d4.JPG

5a33282d5569a_IvanGearBoxPrintError.thumb.JPG.d8934ce48dab1dc7357840d59b4f82d4.JPG

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Seems like different nozzles made a big difference! :)Curious to see how it will continue. Did you also use PetG as that thread you refer to, or is this PLA?

If PetG, why did you choose that over PLA?

 

yes, the nozzles made all the difference. I choose PETG because of its higher temperature coefficient. I want to use a filament that won't melt in a hot car.

Les

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