The Dream ... a Home Hobby Dual Arm Industrial Robot ...

I decided I needed to build myself a "DAIR" ... or at least a "SAIR" robot ... so I began designing parts based on using hobby servo motors ... they're everywhere and it is easy to program a Parallax BOE or HomeWork board or BS2 Stamp 2 module ... so I came up with a few ideas.

http://www.OPECoftheWest.com/DAIR-10.html

Step 1: A Better Design ...

After puttsing around looking at different 3D Plastic printers I got a 3D Touch ... it's pretty neat but quickly I found that designs for injection mold don't work so well for 3D plastic printing and so I had to begin redesigning my DAIR robot parts for 3D printing.  During this task I began to redesign the robot itself, simplifying the design and reducing the number of parts needed to build a Home Hobby Dual Arm Industrial Robot. 

Now I"m saving material and that means I'm saving cash! 

Step 2: Designing to Stick Together ...

After a few truly failed attempts to get some parts printed I found I had to add "fillets" between surfaces ... fillets are the smooth rounded surfaces that look like weld lines but are just filled-in material to create a stronger joint.  In the case of 3D printing it helps to hold perpendicular surfaces ... such as horizontal to vertical.  It also makes the robot look more professional anyway.

Step 3: Complex Geometries ...

Complex geometries was the next issue and the next bunch of images show the failures and the compromises it takes to get a robot part printed.

These images show my compromised choice ... the extra threads inside can be cut out of the way but the part will function as needed because the exterior shape fits the robot design. 

Step 4: More on Complex Geometries ...

Here you can see the CAD design ... and as you can see one side of this part has a rounded extension while the other side is cut flat.  The flat surface is the bottom of the build so that it all starts from the "raft" on the build table.  The inner cavern is the shallower of the two sides ... this is so that the threads that droop don't droop as far ... the servo horn will be glued 'n screwed to the plastic on the top smooth surface so all that ragged stuff is no problem to the DAIR robots operation. 

Step 5: And More Complex Geometries ...

In these images you can see that just printing the part sometimes is the best solution ... I gave it a try ... I wasn't sure if the printer would choke on this part or not ... I thought it had a better chance of failure but that might clue me into how to design for a better print.  After the part printed I was impressed at how good it was ... I had printed it on the left side down so the shoulders lower mount would be sticking out the side of the print.  As you can see in the far right image the innards of that mount are very complex.  I can't believe how lucky I was to get such a nice print.  But then I goofed and started over thinking ... cut the part into two pieces to see if I could make it even better (that the middle two pieces ... and you can see the base mount is junk ... not nearly as nice as having one total piece. 

Step 6: Moving on to More Complex Geometries ...

Okay, Now I'm getting brave so I printed the upper arm shoulder joint ... and viola!  It worked great!  the mess is not an issue other than cutting some away to string the motor cabling through the part. 

Step 7: Last Thing About Complexity ...

I had tried this part a few different ways ... and as before it's so much easier to just give in to the little mess on the flat surface and get a nice usable round shape ... as you can see in the printed images below the left prints are cutting the piece into two prints but the flat surfaces still have some warping ... so I just printed the part starting from the widest outer surface and let the drooping happen .. cutting it out of the way my worst case assembly is to just add a little stiffness to the flat surface where the hobby servo mounts in the middle.  This can be done with a piece cut out from a cereal box with a pen knife or laser cutter.  After all, this is a hobby machine and won't be picking up very heavy objects anyway. 

Step 8: Now I'm Starting to Feel Lucky!

I almost have all my pieces printed for one arm now ... I'll update this page if I get the robot essentially assembled before the contest ends ... I do have other things I need to be working on all the time. 

Anyway, I was happy to see how nice the arm extension printed.  That's a straight vertical print of a 24mm diameter tube ... there was a slightly rough end is where it connected to the build raft but that will get buried into one of the arm-joint pieces anyway ... However, I did have to make it 1mm thinner than the original design of 25mm ...

The first extender I printed would not fit into the hole ... rather than sand a 2mm thick piece I decided to just reduce the outer diameter and print it again.  This is hopefully the weakest part of the robot arm ... weak enough to break away before breaking any of the larger more expensive and longer printing parts ... and weaker than the servo motors so none of the motors gets burned-out from trying to lift something too heavy.

Step 9: Next Step ... Coloring ...

I've seen a few different attempts to color printed plastic.  Solid paints work.  I used some cheap nail polish to get really vibrant colors ... I highly recommend cheap nail polish ... you get the brush with the paint and it adds strength to the structure. 

I also spread a thin film of "White Glue" around the insides of some of the larger smooth surfaces and even to the fillets on the base piece fillets and nearby outer surfaces to give it more strength since I only used a 3mm thick design. 

I can't hardly wait to get the µController and battery dropped down into the top shoulder and programmed to start picking up things in one spot and moving them to another.  I guess the next project will be to build a small toy for the DAIR to assemble ...

http://www.youtube.com/watch?v=5IkjL9ApJbQ&feature=player_embedded

BTW, you can find this video and a couple of others at the bottom of my t-shirt page;
http://www.brainless.org/RoboToons/T-Shirts&Totes.html

I also have tons of demo videos on YouTube ... as the "SolidWorksMagi" ...

Step 10: Assembling Begins ...

I think the photos tell the general story ... the first servo motor connecting the shoulders to the stand is a Futaba/Parallax continuous rotating servo to give the robot 360° rotation about the stand.  The arms have MG9995 metal gear servos to give the arms a little more than average strength ... the final servo at the end of the arm is the wrist servo and would be another Futaba/Parallax continuous rotating servo to give the robot 360° rotation about the end of the arm ... Drilling, Screwing etc ... But if you do that, then the gripper assembly has to be a self-contained and under wireless control ... easy enough but requires a small battery pack and radio added to the gripper.  If you just use a standard servo at the end of the arm for the wrist control then the gripper can be wired into the same µController as the robots other servos. 

If you look close you can see the rough oddities left by the printing ... but none of it hinders the robot operations. 

Step 11: Combining Two Projects Into One!

Yes, taking my BallBot1 Robot ... adding a neck adapter it can be the Head/Brains for the DAIR!  Ain't that cute? 

The BallBot1 uses a BS2 µController chip that is perfect for controlling the D.A.I.R. robot. 

This is just one of the many "hacks" of the BallBot1 Robot ...