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The main objective for this week was to create a pressfit construction kit out of cardboard. In other words to design a series of cardboard components that could be assembled in multiple ways. I decided to make servo brackets that could be clipped into each other to build little walking robots.

I started off with a simple girder design to house the servo. The tolerances were ok but the joint could slip, even when under tension. Which was a fairly significant issues for components that were supposed to move.

The girder based design had a number of issues but he key one was how fiddely the assemble was. It relied on a series of panels to slot into one another and cross bracing pegs to hold them in place. This ment that the whole assembly could eventually vibrate lose. In addition the system to mount the servo arm was rather flimsy.

Armed with these discoveries I set out in a different direction. The assignment was to build our system out of card board, so why not take advantage of the properties of corrugated cardboard that make it unique. I traded out the laser cutter for some scissors and a craft knife and started playing around with the way the cardboard behaves when it’s folded or its corrugations are ruptured.

The spacing of the corrugations in the card I was working with meant that it would fold nicely around the servo motor and also had quite a bit of spring in it.

The basis of my new system was to cut slots in the card and fold it tightly around the servo. This created a much more snug fit that was resistant to shaking loose. In addition I created some folded sections to act like springs and hold the whole assembly under tension. This tension was critical for holding the servo arm joint in pace which slots in between the corrugations, partially collapsing some to form a tight fit. For this to be successful its critical that the corrigations in the cardboard are orentatied along the fold lines otherwise the cardboard wont bend or spring nicely.

The set of components allows for servos to be attached to each other in a number of different ways depending on the kind of motion that is desired. The servos can be attached to each other at 90 or 180 offsets. The arms can be attached to each other at 180 degree offsets or to a foot.

These building blocks provide a number of different assembly possibilities. The main constraint is the strain the weight and torque the servos put on the card over distances longer than 3 attachments.

One of the may perks of prototyping with card is it’s totally guilt free. After I was finished iteration on the design for the evening all the scraps could be put in our worm farm to become yummy plant food.

And of cause I couldn’t help but try and make a walking robot with my little legs.

With no chassis design to hold the arduino and support the breadboard the weight and strain from the USB lead crushed the legs almost immediately so it became a bit of a seal. Maybe the next iteration will have a chassis system.

Tools used this week:

Hardware:
GX-24
ILS12

Software:
inksacpe
illustrator

Materials:
Cardboard!

Tutorials links or references used
Files Produced
Archived files

To kick of the week we were challenged to make a sticker with the vinyl cutter. Our lab has two Roland GX-24s and they are by far the fastest machines in the whole lab. Due to their speed and easy to use we often use them as a way to quickly introduce the concept of digital fabrication.

Our stickers each had some predefined locators on the side of them that we had to keep in the design. When finished they will all connect together.

I started off by once again taking the road less traveled and chose to use inkscape for my design rather than Illistrator that im more fimular with. After having a play there are alot of simularities between the two.

Straight away I ran into issues, Ubuntu uses Alt + Left mouse to drag windows around but inkscape wants to use this key combination to adjust anchor points. The fix is to install dconf-tools which allows the rebinding of native hotkeys. sudo apt-get install dconf-tools
Running dconf-tools brings up this screen where we can rebind the key from <alt> to something else.
Dont leave it blank or every left click will drag windows around and just generally make the mouse useless.

Actually drawing stuff in inkscape is really easy, just use the pen or free pen tools to create paths between anchor points (or nodes as inkscape calls them).

By default inkscape hides the handles to adjust each node. To turn them on can toggle the “Show Bezier handles” option. From their you can then set the properties of how each node behaves. symmetrical, fixed length, etc.

Other handy tools that are hiding in menu options include:
Dynamic and linked Offset to resize images.

Trace Bitmap to convert bitmaps to paths.

Break and Combine tools, basically groups to manage.

Our cuts came out as seen below (mine is the one on the right). Once the rest of the class finishes their sticks i’ll update this week with the final arrangement. Cant wait to see what it is!

And after much suspense its done!