Instructables
Picture of Laser Cut Sphere-O-Bot

The Sphere-O-Bot is a simple 2 axis CNC machine that can draw on most spherical surfaces. You can use it to decorate ping pong balls or eggs.This design is based on the 3D printable Sphere-O-Bot. By building your Sphere-O-Bot using a laser cutter, you can achieve a clean look while also reducing the production time of your parts. This design also features an electronics bay for your wires, micro-controller, and motor drivers.

The Sphere-O-Bot described in this tutorial was designed for a workshop in which kids get to build their own motor controllers. For more projects by the Maker Corps interns at the Children's Museum of Houston, visit our site: kidmakers.org

If you like this project, please consider voting for me in the epilog challenge. My internship at the Children's Museum of Houston will end in a couple of weeks and so will my unlimited laser cutter access. Having a laser cutter of my own will allow me to keep developing more instructables for you. Thanks.

 
Remove these adsRemove these ads by Signing Up

Step 1: Materials

You will need:

Optional:

Step 2: Laser Cut & 3D Print

Picture of Laser Cut & 3D Print
IMG_20140710_093503.jpg

Download the design file here and cut it out of the 1/4'' wood using a laser cutter.You could probably also cut these out of plexiglass except for the curved part, since it would not be flexible enough.

The 3D printable files can also be found under the same Thingiverse post. The printable files are actually borrowed from this 3D printable Sphere-O-Bot design.

Disclaimer: It's ok if the renders/pictures in this Instructable don't exactly match the design file on thingiverse. That just means that I've been doing some design changes to help things fit better.

HI! love the project.

So im planning on building this bad boy and I'm trying to figure out the software that i need to run in order to make it all work out. I was just in Arduino with the sketch and I'm getting an error telling me the 'StepperModel' does not name a type. I'm not sure what this means but it's preventing me from running the code. Could you give a bit more information on how to set up all the code with the various libraries and plugins in order to get the code on the arduino as well as implementing different designs converted to Gcode.

Thanks!

Looking forward to building this!!

pastprimitive4 months ago

So I am a bit curious how you keep the axis that your egg rotates around stable? It looks like you're using a 3d printed bearing housing that you thread an 8mm bolt through and thread a nut onto it to keep it trapped onto the bearing. It's been my experience with most precision bearings I've used that they still allow for a significant amount of "wobble" at least when it comes to the realms of precisions CNC control, plotting etc.. I really love the aesthetic of your design. Just trying to figure out how it stays stable before I commit to the build time.

Also you might think about moving the uno board so that the usb port is flush with one of the outside edges, with a port cutout so it's more seamless. But I understand that is a trivial detail.

Also perhaps shift the motor mounts, etc... up about 12-15mm to take full advantage of your z space.

The only other question I had was how do you adjust for various size objects? Or is it your intention to set it for one or two sizes? On an older model egg bot I built there was a spring loaded rod that the suction cup was on.

juanifico (author)  pastprimitive4 months ago

Thanks for your feedback. I will admit that the machine does experience some slight wobbling. Then again it is not a precision machine, just a fun little toy. Using two bearings does help a bit. I am currently working on a laser cut bearing holder that places the two bearings farther apart to make the axis more stable.

Also, I changed the placement of the UNO board so that the USB port faces the back of the machine. There are also holes in the back that allow you to route the USB and power cables through.

I do like the idea of shifting the motors up. It would allow for more Z space and it would prevent the pen from hitting the walls of the machine.

Yeah, wobble... I have a few cnc machines. it's the curse of of my solidoodle 3 3d printer. I had to do significant expensive mods to get it out of a $800 machine.


I included a picture of my old eggbot solution for bearings. I decided instead of using precision bearing I would print mine. Looks like you have printer access as well. Anyhow the rotation has practically zero runout compared to precision bearing setups, and with the proper sized print, and a bit of lubrication it rotates well under the torque capabilities of my nema 17 steppers. Another method I like to use for adjustable runout is similair to an anti-backlash nut methodology. Where as opposed to applying pressure against both thread walls you apply pressure to one side of the bearing to cause it to sit slightly out of perpendicular to the rod. Set screws, glueing them at angle, etc.... Do the same with it's counterpart bearing, and you can get runout to very acceptable tolerances with some fiddling.


Again your housing is beautiful. LOVE IT!

I'm going to be building it today, and will probably make a few minor changes to accommodate thoughts I had. I'll be sure to post pictures, etc...

Also thumbs up on it being a toy... Totally get that.

IMG_0408.JPG
juanifico (author)  pastprimitive4 months ago

I really like the 3D printed bushings that you used. I am trying to minimize the amount of parts that absolutely have to be printed. It looks like these could work for folks that don't have 3D printers:

http://www.mcmaster.com/#5448t2/=sxs8vh

So after lots of finagling with the sag file to get it to work with my size laser cutter I have a design I like. My bed is only 12" x 10". Slightly smaller in length than the biggest piece is. So I simply shrunk the machine size just a little bit. I also added accommodations for my double bushing bearing mount. which I think turned out really nicely, and mirrors the stepper motor symmetrically for aesthetic.. Not quite as streamlined. But I think very acceptable. Also had to customize with my logo, etc... I'll make sure to credit you wherever I post online.

Also as you might be able to tell I used 3/16" plywood. Why? Because my local hardware store sold me 3/16" as 1/4" and I didn't notice till I got home, and didn't really want to deal with taking it back.

I changed the side that the power switch was on, and added a lit up version.... Oooooo;)

For the electronics I used an Arduino Pro Micro and the A4988 stepper drivers with some 47uf caps in parallel with the motor supplies (per Pololou recommendation). I have handfuls of both of them on hand. I buy Chinese cloned versions of the micro for about $4 a piece off ebay. For convenience I used two mini self adhesive solderless breadboards that I pick up for a little under a $1 a piece off ebay. Perfect for when I am feeling to lazy to be carefully planned out, and solder a perf board together for the project.

As you can tell I haven't finished yet.

My plan for the stepper motor side of the Y is to add a 3d printed spring loaded telescoping suction cup apparatus that would use the same size spring as the other side so as to keep the object perfectly centered regardless of size, or to use a telescoping suction cup that uses a threading inner tube and a jam nut to lock it into place. We'll see what the days work brings. For the pen arm, I have not clue what i'll do yet. Something not to dissimilar from your design probably.

IMG_0421.JPGIMG_0419.jpgIMG_0423.JPGIMG_0412.jpg
juanifico (author)  pastprimitive4 months ago

It looks amazing! I like how you spaced out the bushings to make it more stable. As for the pen gantry, check out the file titled holderV2 in the Thingiverse post. I also included an animation of how it works in this instructable post.

Thanks. I should have waited a little bit I suppose. I already redesigned the pen holder, and used a laser cut adjustable "egg-chuck."

I'm satisfied with the results. I'm upgrading from my 9 volt 1 amp power supply to a 12 volt 2 amp supply. Not quite enough oomph to run the system. And I need to probably add some more cooling vents on the floor below the egg. Nothing fire hazardous, but the a4988 start misbehaving after a few minutes of running.

I'll check out your Thingiverse v2 pen holder.

Thanks again for the inspiration.

IMG_0428.JPGIMG_0429.jpgIMG_0431.jpgIMG_0428.JPGIMG_0432.jpg

Also be sure to add a 470uf Cap in in parallel with the servo, it misbehaves badly without it. At least with my pro micro.

Momable4 months ago

Very cool. We have an Egg-bot and find it can print on golf balls, as well. The thing we have trouble with is finding exact center. As for your internship privileges soon expiring, check out TXRX in Houston. It's a maker-shop and may have what you need for future cool projects. All the best to you.

dmason124 months ago

Is there a specific NEMA 17 Stepper Motor required for this project?

gada8884 months ago

is it possible to use it to draw a picture on a flat surface rather than a sphere?

juanifico (author)  gada8884 months ago

It can only do spherical surfaces. You would need something like a XY plotter or a polargraph for flat surfaces.

Also, please provide links to the various stepper motors and controllers that you used (are going to use) for the project. I'm a bit of a noob when it comes to those things and want to make sure I'm not buying the wrong things.

Well now, that would be awesome for kid events!

juanifico (author)  JoshuaZimmerman4 months ago
Thanks! That is precisely what I have used it for. Here is a fun workshop you can do with it:
http://www.instructables.com/id/Motor-Control-With-DIY-Tangible-Interfaces/

Oh, cool beans! I love how you wired in the Makey Makey. (Time to dust off mine!)

brmarcum4 months ago

very nice

ivver4 months ago
Great idea, love it :-)
Aleator7774 months ago

This is a great mini CNC. I'd love to make a mini orrery with ping pong planets!