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It’s one thing to hack away in CAD software, rendering the idea of a model.  It’s another thing entirely to pull it off the print bed and pop it all together.

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Last night before going to sleep I started the 2+ hour print job that became the center body piece for the CuttleBot.  When I woke up in the middle of the night, I plucked it off the build platform, started the tail section printing (a 90 minute print job), and passed out again.  This morning I printed 15 connector pins while getting ready for work.

Just before leaving for work, I yanked out the support structures using some needle nose pliers and popped it all together with the connector pins, and took some pictures to share with you, dear reader.

This was an incredibly satisfying result.  Sometimes the work spent on something like the little pins and sockets feels so removed from the design of the main object – so very far from the goals.  It feels similar to the work that goes into painting a house – you spend all this time NOT painting before you actually paint.  Moving and covering furniture and decorations, taping and masking areas off, removing cabinets and doors.  But, as long as I was able to keep my eye on the vision of the final model, laying that ground work on these components meant that I really could assemble a foot long plastic CuttleBot body in a few seconds.

Sigh.  At this point, it kinda resembles a CyberMat more than a robotic cuttle fish.

I enjoy sketching out my ideas, so here’s one in case you like looking at them.

It’s NOT a CyberMat! It’s a robotic cuttlefish!

So, what’s left to do?  A whole lot.  I need to:

1. Design newer, thinner tentacles, so I can fit more into the CuttleBot’s head.
2. Hollow out the robot’s head or at least create channels for wiring for LED’s inside the eyes.
3. There needs to be some mounting areas inside the robot to secure one or two micro servo motors, a small circuit board, a battery, and possibly a few additional components.
4. Possibly create a door allow easy access to the interior of the robot.  Once I start adding electronics, it might be great to have an on/off switch and nice to be able to connect a USB cable to it to recharge an internal battery or reprogram the behavior.
5. Add the electronics and program them.
   1. This is probably two servos, several chained NeoPixel LED’s, a LiPo battery, an Adafruit Trinket, and possibly a LiPo charger (if I have one lying around).
   2. If I’m already working towards building a new version anyhow, I might want to drop a few dollars on an OSHPark Board to help make the power from the LiPo easier to route to the servos, LED’s, and board.

However, I don’t think I’m going to be able to finish the robot before Friday.

I think I could probably manage blinking LED eyes by Friday.

Maybe.

1. Cephalopod Robot Friend, the story so far
2. Cephalopod Robot Friend Progress
3. CuttleBot Body and OpenSCAD Design Tips
4. An Assembled CuttleBot Body
5. Building the Monocle Top Hat Cat for #MicrobitVirtualConcert
6. Companion Robots and Maker Faire Season!

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I really like 3D printing – but really dislike post-processing.  This means I’ll make extra efforts to design things that can just be plucked off the build platform and hand assembled without tools.  With my limited build volume, this also means larger objects need to be printed in sections.

I’m very proud of a particular design method in the CuttleBot.  I designed the organic and non-angular design of the CuttleBot body by using the “hull” function and several carefully deformed and positioned spheres.  However, it would be very difficult to hollow out the interior – since it would mean designing another entire structure to be subtracted out.  Instead of creating the outside shape I wanted and using difference to hollow the interior, I designed the interior shape and used that to create the exterior with the “minkowski” function.

Here’s an OpenSCAD code example:

difference()
    {
    //  Traces sphere around exterior of cube
    minkowski()
        {
        //  Main object
        cube(50, center=true);
        //  Object to trace around main object
        sphere(r=5);
        }
    //  Removing center of object
    cube(50, center=true);
    // Arbitrarily large cutout
    cube(10000, center=false);
    }

Minkowski sample

Although, now that I think about it, there’s probably an even cooler way to do this!  Since the above code needs to refer to the “target” object twice, that code can be simplified by using the “children” function.  The below code creates an identical shape.

hollowObject(5) cube(50, center=true);

module hollowObject(thickness)
    {
    difference()
        {
        minkowski()
            {
            children();
            sphere(r=thickness);
            }
        children();
        //  Arbitrarily large cutout
        cube(10000, center=false);
        }
    }

The great thing about a modeling process like this is it allows  you to maintain an even thickness all the way around the model.  This would be increasingly difficult as the complexity of the underlying model increases.

Lastly, to return to the model, after hollowing out the interior of the CuttleBot, I added areas for the pins to connect the sections together.  The body of the robot is in three sections – the head, the mid-body, and the tail sections.

There’s still more to do on the model.  Ideally, I’d create a way to open the robot without having to completely take it apart each time.  A hinged door would work fine.  Also, I should probably add an area where one or more micro servos could be zip-tied or otherwise secured in place.  Also, I’ll need to modify the robot’s head later on to allow for multiple (smaller) tentacles and channels for adding wiring for LED’s to the eyes.

There’s also the whole “adding electronics” thing.  You know, to make this less a puppet and more a robot.

1. Cephalopod Robot Friend, the story so far
2. Cephalopod Robot Friend Progress
3. CuttleBot Body and OpenSCAD Design Tips
4. An Assembled CuttleBot Body
5. Building the Monocle Top Hat Cat for #MicrobitVirtualConcert
6. Companion Robots and Maker Faire Season!