3D Printed Piggy Bank - a Journey in Problem Solving

This is a guest post from Bethany Jones, who currently teaches a 7th grade science elective called Engineering Design in Mason, Ohio. Bethany is the mother of two tiny humans and one very energetic dog. She is a tinkerer, lover of learning and recent 3D printing enthusiast.

“If at first you don’t succeed, call it version 1.0”

This has become my motto as I have leapt headfirst into the world of 3D printing with my 7th graders. One thing I have tried to share with my students is that it’s not all about the end product, but the journey you take along the way. There is often more learning that takes place through failing than if you get it right the first time around.  

Ever since our 3D printer arrived a month ago, I have been adamant that it not just be a toy, but an avenue for creation.  I am encouraging my students to try designing something on their own that has a purpose or that solves a problem. In an attempt to show them that I was in this crazy new adventure with them, (as well as wanting to test the print size limits of the printer) I decided to make a piggy bank.

I kid you not, about an hour into the print, a group of students are hovering over the printer watching in awe and one says, “how are you going to get the money out Mrs. Jones?” Face-palm. I had forgotten to put a hole in the bottom to get the money out! 

I told my kids that we’d just have to break it open. It ended up not mattering, as this version printed with a giant mystery hole in the back. But I quickly went back to the computer and edited my model to include a money-retrieval hole in the bottom. Great teachable moment about learning from your mistakes right? 

My students and I had fun analyzing the possible causes for the other print issues and we decided to try and make the walls thicker for more support and hopefully close the mysterious hole.

The second time around, I think something went awry with the printer as everything went well until the very end. The slot on the top printed crooked and the ears  were hanging on by a thread about halfway up. Since I couldn’t find any explanation for this, I printed the same model with no edits and it worked! Third time's the charm!

I am loving the iterative process of designing, printing, redesigning and reprinting until I get something right. It is a wonderful lesson that my students are learning as well. I am finding that in a world where they may have been afraid to fail before, they are energized by the possibility that they can analyze the problem and attempt to fix it! Beyond making something cool to look at, it is something to be proud of when you can create something on your computer screen and make it come to life as a tangible object to enjoy and share with others.

Piggy Bank: http://www.thingiverse.com/thing:1533937

*Addendum: Fast forward one day past writing this post and the poor perfect piggy version 3.0 took a flying leap off my desk and met his demise as a clean break ripped through his body, splitting him in twine. I almost cried real tears in front of my students. But looking on the bright side, as one must do to remain sane, we can now analyze broken piggy from the inside out.

The real payoff of 3D Printing: Free Donuts

I've got a new side project - one that's not really in full motion yet - in fact it is hardly started - but it still needed a mascot, an icon, a persona. Isn't that the most fun part of any project, naming it and giving it personality? Yes, of course it is.

Well, for this one, we decided the personality would be a Donut - yes, with a capital D. And please accept this simpler spelling rather than the annoying and all-too-accurate Doughnut spelling.

As with any good product, it's a loser without a 3D Printed product logo - so - the quest to 3D Model and 3D Print a frosted, sprinkled, delicious Donut began.

Design Goals

What I wanted most out of this model was for the final product to actually look like a donut - unmistakably. 

For man made objects which have structure - like buildings or cars or, uh, Raspberry Pi cases, it is pretty easy to represent the object in 3D modeling. 

But for things which occur naturally in our environment - like a Donut - it's a bit harder. I wanted to capture the Donut in it's natural state - soft, sugary, harmful, yet delicious. 

Are you hungry yet?

The type of Donut I selected to model was also critical. I choose a broadly accepted favorite - the Chocolate Frosted Sprinkled Donut - knowing that done right, it would be impossible to deny.

Design Start

Let's face it - without the frosting, the Donut project would be a simple Torus - the rounded and circular shape often called a... Donut. The hard part was the frosting. I literally stared at a picture of donut for 7 hours straight (well... maybe it was 7 minutes, but you get the idea) before figuring out a strategy to achieve frosting which had both a rounded top to match the contour of the Donut and drippy sides to represent that perfectly desirable, about-to-melt look. 

First, I drew a splatter shape with the Spline tool (just random curves connected at the end into a circle. Then I drew another similar shape - smaller and inside the first - for the inside part that would fit against the Donut hole. I extruded the space between the two shapes into a donut-like splatter shape - 4mm high.

The main issue now was to give it a curve to match and sit atop the donut.

Now, I duplicated the donut and sat the splatter shape on top of it - sinking it almost all the way down into the top of the donut. I then sized the splatter so that the ends barely touched the outer part of the donut.

Donut Design Magic

The magic was about to happen. 

I used the "Combine" / "Intersect" tool - with a copy of the Donut as the source - and the splatter as the target - to get a perfectly contoured splatter shape which could be fit on top of the donut! I simply enlarged it slightly and raised it to sit on top of the Donut.

The sprinkles were easy-ish - they are each just small cylinders (approx 2-3mm long and 1mm diameter) with rounded ends. I placed each individually atop, and slightly sunken into, the chocolate frosting.  I also gave each a slightly random tilt and turn - giving that "dropped onto the frosting in a carefree manner" look. (I've lost you, haven't I)

Additional Details

To make the Donut lay better on the printer bed, I added a 3mm wide flat cylinder to the bottom aligned perfectly to the tangent points that were touching the bed. Of course, I also added a key ring loop so the Donut could be conveniently displayed to make all around you jealous.

Some resizing steps were taken - harder that I had hoped - to make the Donut small enough to print fast, but big enough to notice the detail. And - as I have done before - I used Sharpies (tm) to color the donut quickly.

The model

The MkrClub Delicious Donut model can be found here - where it will attract the most hungry, sweet-toothed 3D Print enthusiasts.

CodeBug Gets a 3D Printed Box with Personality

If you've never seen CodeBug - let me introduce you.
CodeBug is "a cute, programmable and wearable device designed to introduce simple programming and electronic concepts to anyone". I first saw it at the BETT Educational Technology conference in London, where I met one of the founders, Tom Macpherson-Pope. As soon as I saw CodeBug, I new I must create a 3D Printed enclosure for it.

Design Goals

When I met CodeBug, I had just finished making my Raspberry Pi box, and brought some to the conference to show the Pi people. Now I had a similar target in the CodegBug - but what really excited me was the small size! I knew I could experiment and make variations without waiting 6 hours for the thing to print, as was the case with the Pi box.

What I really wanted in this first attempt, was just something that maintained some of the "cute" character of the CodeBug microprocessor board, but also made it easy to access the connectors (plugs and conductive "legs").

I also wanted the 5 x 5 led array to be exposed in a way which made it more fun to program - something like the mouth of a creature or a face of a robot or something similar.

Of course, I also wanted to have it stand up so it could be proudly displayed once it had a program loaded up.

Design Details

I decided that keeping with the original design meant that the buttons would be modeled to look like eyes and the 5 x 5 LED array to look like a mouth. While the CodeBug is called a bug, I saw more of a frog, so I called this first design the "CodeFrog".

I used a two-part design and gave it a clear shape to match the original board, but without every detail on each conductive leg. I also gave it clear eye-shaped sockets and gave it feet which both added to it's ability to stand up and helped to hold the two-part design together with the CodeBug board sandwiched in-between.

For design effect, I used parts of my prior 3D BitBot robot design to add a flexible arm - using the sockets attached to the body and then just using previously printed arms and hands to make it look cool.

Design Process

The most important thing was to make sure the face plate fit over the 5 x 5 LED array and the protruding buttons really well so that there was little movement and a strong connection. I measured and experimented with probably 5 or 6 prints before getting that right.

The base was also important to have a strong fit, and while the CodeBug board doesn't have screw holes to match, there is a battery protrusion on the back that was critical to fit into the base. I again played with that design until getting it just right, starting with a simple square base, and eventually shaping the base to match the face plate once I had the general position of the battery receptacle right.

I added a slit in the top of the feet to accept the bottom of the face plate and added small nubs inside the eye sockets to allow the face plate to click in and lock into the base. I only needed slight adjustments to make the face plate, CodeBug board and base work as a snap-together set.

Design Results

While this is really just a first attempt, I'm overall very satisfied with the result! My measure, of course, is whether this design inspires kids to want to code things on CodeBug which make this 3D Printed CodeFrog come to life. So far, I've gotten great reactions from my own kids, and I'll post follow ups once we have some programs to show beyond my own "mouth which opens and closes" program ;)

The Model

Look back here soon for the model - as I'll post it as soon as I do a bit of clean up on it.

A Fancy 3D Printed Raspberry Pi Enclosure

The Raspberry Pi helps make learning about computers fun and accessible for many people - and has given the maker community a powerful computing platform in a tiny package. Actually - it's a small integrated circuit board without a  "package" - it doesn't always even come with a case.

When my daughter opened up her new Kano Raspberry Pi kit that she got as a gift, the "package" - the enclosure for the electronics - was one of the things that made the kit approachable and easy. Then, within hours of that insight, a good friend and blogger asked me if I had designed a Raspberry Pi enclosure for 3D Printing. My response was a fast "Not yet, but it's on the way".

Design Goals

I wanted my Raspberry Pi enclosure design to be more than just a box with holes for the wires. I wanted it to be good looking and inviting. I decided I would use the Raspberry Pi logo itself as the design for the box. Of course the box had to also be functional. The Pi had to fit in there easily and have a way to secure it and, of course, all the wire ports need to be accessible. Of course, like so many designs I do, I wanted it to be easily printable without supports - and I expected it to be two parts - a bottom to hold the board, and a fitted top, preferably one which held securely without screws.

Summary of This Design Journey

There were a few forks in this design road - so I figured I should just summarize them first so readers get a sense of how I ended up with the current design.

1) I started with the Raspberry Pi version 1 Model B (Two USB ports) - which has a specific size and layout of interface ports - implying layout of the holes in the sides of the case. Then I realized (after I got the general sizing all correct and printed) that most people, including my daughter, now have the version 2 design. (more info on Pi Models)

2) I moved to the Raspberry Pi 2 layout - using my daughter's Kano board as my basis for measurement. That got me designing in the right direction,  and I completed a box design with the right layout to fit that Pi 2 board. But it seemed boring.

3) I added a Raspberry Pi Logo-shaped bottom to the box, then created a custom top which was also in the shape and design of the Raspberry Pi logo. This looked really good - and had plenty of challenge creating the fitted top.

4) The shape of the Raspberry Pi logo was so nice, that I decided to make the whole box that shape - with adjustments to fit the board within it. I was finally satisfied after some adjustments to the top to make the Raspberry-ness really show, some strengthening of the walls, better fittings to make the top snap in place and addition of optional screw holes. 

This is where I am with my current design, but I'll fill in the details now for those who want to know more.

Basic Design Of The Box

I started with a box - figuring I would add the design elements as shapes on top and bottom of the box to give the whole package the appearance of the Raspberry Pi logo. So the focus to start was the alignment of the wire holes and screw holes and the general fit of the IC board.

After measuring the Pi board (approx 85mm x 56mm), I created a basic rectangle with those outer dimensions plus an additional 3mm extra space on all sides - that's 2mm walls with 1mm space on each side. The rectangle is now 91mm x 62mm - and I use the "Shell" command and define 2mm walls to get the hollowed out box where the Pi will fit.

Useful Trick for Early Design Testing

Drawing with all measurements

The placement of the seven (7!) port holes was critical to the success of the design, and no amount of measurement makes for a fool proof design or print. So, when I thought I had the whole bottom box design ready to go, I didn't want to print the whole thing until I was sure I hadn't messed something up. So, I came up with a method for testing a smaller version of my print to test that the placement of screw holes and wire port holes was correct.

It's worth mentioning that I created a Google Drawing which documented all the measurements in once place visually.

bottom portion only as a test

I only needed to test the bottom half inch of height - about 20% of the total printed object - to see if the mounting holes and wire port holes were positioned correctly. To isolate that portion of the object, I created a big rectangle which was slightly larger than the whole box and positioned it over a copy of the box,  specifically positioning it over the portion of the box I did NOT want to print.

Then I did a "Combine" / "Subtract" to remove the whole top of the copy of the box. That left me with the bottom portion. I printed that - which took about 45 minutes rather than the 3 hours the whole box would have taken, checked that it worked out, made adjustments and repeated. Two tries and it was done.

The subtraction shapes used to cut the wire ports and SD slot

Making Wire and Port Holes

I had to make 7 holes in the sides of this basic box. It seemed the best way to do this to allow for a few later adjustments would be to create and position 7 rectangles which would be used to subtract material from the box. Any later adjustments I made, even to the box itself, would allow me to re-subtract these same boxes, in their correct positions, from the adjusted box. This turned out to be an insightful move, as I made many box adjustments that otherwise would have been hard to maintain the holes if they were pre-made in the box itself. Once the boxes were positioned correctly, I did the "combine"/"subtract" command - with all 7 rectangles as the source - and voila, the box had 7 holes in it.

Screw mounts added where needed

Securing the Pi Board (screw holes)

To offer a way to secure the Pi board to the case seemed easy enough - since the Pi 1 has two screw holes and the Pi 2 has 4. But now that I had all my port and wire holes positioned, I realized that I needed to lift the board up a bit from the bottom of the case to give room for screws. This was luckily easier than it may have been, given the method I used to subtract the holes from the box. I just lifted all the subtraction shapes up 3mm and re-subtracted them from the box. I then placed small 3mm high rectangles (about 5mm square each) in the areas where the screw holes were needed and carefully measured as many angles as possible to get the holes positioned relative to the box sides and to each other. I used 1.25mm Radius cylinders to subtract holes from those shapes and aligned them to sit on the bottom of the box. Theses would also serve to hold the Pi board away from the bottom of the case with enough room for the bottom-mounted SD card and the small soldering nubs that stick out the bottom.

The Raspberry Shape - from Simple to Complex

To get the Raspberry Pi logo turned into a 3D object, I used an old trick that I've written about a couple of times. I pulled an image of the logo into Google Drawings and traced over it with the Polyline tool to create the Scalable Vector Graphics version that my 3D Modeling software can understand. With some foresight, I actually traced the outline of the raspberry separately from the inner designs of the raspberry, so that I would have some flexibility with the final objects.

I went through several iterations of using this design. As mentioned earlier, first I created a base with the outer shape - and this definitely made the plain old box look more interesting. Then I created the top with all the inner designs subtracted out. This was also a huge improvement to the plain old box.

Ultimately, after printing a very successful box shaped container with a top and bottom raspberry shape, I decided that the whole box should be raspberry shaped. The start was easy. I created the box with the raspberry outline extruded to 27mm, then hollowed out using the "Shell" tool in 123D Design. I then moved over the original box and started combining shapes - removing walls where they overlapped in areas which would be in the way of the Pi board, and combining walls where more support was needed.

Then, my original idea to save the subtraction shapes for the 7 side holes came in super handy. I moved them over, in their relative positions, to the raspberry shaped box, and subtracted them again. This worked wonderfully! The Pi Board screw holes were also moved in their original positions after adding another 1mm of height to the mounts to give the board more breathing room and the screw holes more depth.

Securing the Removable Box Top

Making the top snap into place in a way which did not require top screws was one of my design goals, and became the toughest part of this design. I experimented with a few methods before settling on opposing and offset half-round, 1mm deep rim pieces. I originally added too many of these sets of snap-together parts, and the fit was too tight - but with four of these sets, the fit was just right.

Even with the snap-togetherness of the top, I decided to add screw holes and mounts for people who want an ultra-secure enclosure. This was easy-ish - using tall 6x6mm towers on the inside of the box, and subtracting 2.5mm diameter screw holes 15mm deep into them, and through the top at the same time (to get perfect alignment).

The Final Model

There were lots of last minute adjustments, and overall, if I'm really honest about how much time I spent creating this model, I would estimate 10 hours of work not including printing time. I really obsessed over the design of the top, the combination of etched designs and full-through holes, which are functional in a case for something that might heat up like the Pi.

The final model is now available on PinShape. Please post pictures of your print on PinShape or on Twitter and include @MkrClub !

Creative Building with 3D Bot Bits

I've done lots of experimenting with connecting parts for both functional and fun purposes. The fun creative-building goal is admittedly more fun sometimes - and this latest experiment seems to have finally produced a reliable, creativity-inducing design that I'll keep enhancing.

I call these "3D Bot Bits", since most of the resulting creations are robot-looking.

Design Goals

There were a few things I knew I wanted to achieve in this design:

1 - Give the joints as much range of motion as possible

2 - Make the joints tight enough to have friction to hold specific positions (not collapse with gravity)

3 - Allow the joints to flex a bit without breaking

4 - Allow for customization - so new parts could easily be designed and added to kits

Basic Design Principle

The premise of this design is a simple ball-joint. One side is a round ball, and the other is a socket with the inside diameter just big enough to firmly hold the ball, with enough clearance to let it move around.

While it's pretty easy to make these two parts, what added to the challenge was making them in a way that gave them a flat enough base to print reliably (I don't like using rafts and supports) and let them snap together and apart without too much effort.

Detailed Design Process

With these design goals and principles in mind, here's a general description of how I went about the modeling:

1 - Created a sphere of around 10mm radius then duplicated it and scaled up the duplicate to a 12mm radius. The smaller sphere is now inside and centered with the larger sphere.

2 - Flattened both spheres by taking away approximately 4mm from the bottom and 4mm from the top (to make them more like bulging puck shapes).

3 - Subtract the smaller sphere from the larger, so that the larger sphere becomes a shell.

4 - Create some gap between the outer surface of the inner smaller sphere and the inner surface of the outer shell - I used about 0.3mm radius here by pushing the inner surface of the outer shell to be bigger, but you could also just scale the X/Y of the outer shell object too.

5 - Create a break in that outer shell object so that it can stretch to allow the inner sphere to be snapped in and snapped out in the finished object.

6 - Add a connector "axel" between the parts which is 1-2mm smaller than that break in the outer shell so that it fits into the break easily for connecting parts.

Strength and Stretch

The position of the part during printing is actually quite important - which is why I designed it this way. The part that grabs onto the ball - the "Gripper" - is where most of the stress will be. As the ball is snapped in and out when the parts are put together and taken apart, the Gripper will stretch. If that stretch was done along the Z-axis part of the built part (the up-and-down axis), the prt would break quite quickly given that is the weakest part of 3D Printed parts. But with the Gripper part printed laying down, it makes it much stronger and actually allows it to flex quite a bit without breaking.

A Custom Bot Bit: Robot Hand

Customizing Bot Bits

Once I had a simple ball and gripper pair working well, I started creating some alternative parts with different configurations and shapes.

One technique I use when building models like this is to never permanently merge the component parts of an object - or to keep copies of the component parts so they can be re-used.

This made it super simple to make new connecting Bot Bits which were shaped like a "T" or with two grippers on either end, or an "X" shape to allow more complex builds.

Since my initial creations looked like Robots (hence the name Bot Bits), I decided to make some super-custom parts too - like hands and sneakers and face parts. This is where I see the most interesting potential of this design - allowing others to create their own Bits to make specific types of Bots.

The Bot Bit Kit

With a good feeling about the most simple "complete" robot that can be built with these Bot Bits, I created a simple Bot Bit Kit - which contains all the parts needed to make the basic Bot. This can be printed in one shot on my Lulzbot TAZ4 in 2.5 hours very reliably.

The basic parts in this kit can also be put together in different ways to make many other creatures or designs - take a look at the pictures at the end of this post for some ideas.

Here is a link to the Bot Bit Kit model. If you print it, please comment back here with some pictures of the creation you made with this kit!

3D Printed "House of Cards" Stackers

With all the travel I do, I have lots of leftover hotel room keys - the credit card looking type.
I thought it would be fun to design a 3D printed connector which let my kids build stuff using those cards - basically, a house of cards which doesn't fall when you breathe on it ;)

Design Testing First

I started with the simplest, but most important part of the design - the holder which connects to the card.

This is basically a simple slot - a gap between two plastic parts which needed to be just the right tightness to hold the card firmly, while not being too tight or so narrow that the 3D printer has a hard time leaving the space during the printing process.

The simplest test part was step 1 - just creating a block with different sized gaps along the z-axis (vertically upward from the print bed). I didn't bother trying to create gaps on the horizontal plane, assuming that the slightest sag in the filament during printing would fill the gap and make it useless.

Tweaking the design to actually work

After a bit of experimentation, it seemed my Polar3D provided a firm hold on a card with a 1.0mm gap. On my LulzBot TAZ4, the gap was slightly smaller but also didn't give me as consistent a fit with the squashed first layer closing the gap too often. I could have fixed this with re-calibration I assume, but didn't try.

Once I had a simple block that worked, I tried out a few on some key cards, and found that they were simply too easily popped off as I was building. I adjusted the design as a solution to this - basically putting two blocks at opposite ends of a stick with the gaps facing inward so the holder fit over the card like a strap. This worked incredibly well.

Final design and Printing

Once I had that basic "strap" design working, I added an whole set of additional gripper slots facing in all 4 directions as well as on top of the end blocks. This combination proved to be the best and I stopped there and printed a dozen or so of these to test the building.

Building Fun!

I was able to easily build a single column square block of cards about 8 cards high which was very sturdy. The card-grippers print very quickly, as they are made of very little material - probably taking about 8 minutes each at a resolution of 0.2mm. I have yet to break one either since most of the connectors are along the horizontal plane, giving it more strength.

The Model

I've uploaded the basic model to PinShape so
you can try these yourself. It's actually really fun to try printing them in different configurations to meet the specific needs of a house of cards you want to design.