Week 3:  Computer Controlled Cutting

2.11.2015 - 2.17.2015


Lecture Notes:

Homework:

Resources:

Files:

Design Software:

    I utilized Inkscape software to begin my kit prototype.  Slot geometries were modified using Inkscape's cloning function. 

Material / Laser Kerf:

    To properly design sufficient joint interference, I first investigated the laser kerf for 4mm cardboard using sample shapes.  Kerf was taken from multiple measurement and found to be approximately 0.3-0.5mm using a 40W Epilog Mini 24 laser cutter with vector settings of 40% speed, 100% power, and a frequency of 2.5KHz.  Measuring the kerf was complicated in small part due to the flexibility of the freshly cut cardboard edges. 

Press-Fit Joint Experiments:

    I investigate three different press-fit joint construction systems for this assignment.

    For my first design, I created a conventional two-part slotted hub and link (disk) system. The slot-less disks permitted the hubs to curve out of plane. 

LC_Kit1_w

    For my second design I investigated using a single universal building unit utilizing tapered finger joints rather than rectangular slots.  The tapered slots allowed me to wedge and press adjoining pieces together across the plane of the cardboard rather than through it.  One objective of mine was to create a flexible building system that could create flat planes or curved structures.  The tapered finger joints allowed me to tile within a single plane, incrementally adjust the positions of adjoining tiles in one finger increments, adjust the distance between tiles, and create joints at a variety of angles in addition to 90 degrees. 

LC_Kit2_w

I varied the dimensions of the fingers and finger spacing from course to fine to explore different fits.  Finer finger spacing led to localized ignition of the cardboard. 

    My ultimate goal was to design a construction system that had the greatest variability in its joints and thus the greatest versatility to create new structures.  There is a limit to which more slots are beneficial or can be incorporated into a 2D flat pattern. 

    With my third system I returned to a hub-and-link type but made the hubs and links hinged to give them the greatest angular flexibility.  The hinges were made from the lower face sheet of the cardboard and created utilizing the color-mapping feature within the Epilog properties menu.  The parts' perimeter vectors and their hinge vectors were assigned unique RGB values within Inkscape followed by unique, color-specific laser properties within the Epilog software. 

LC_Kit3_Vector_w

    Perimeters were through cuts while hinges were partial cuts.  For 4mm cardboard I used the following vector cutting settings:

Laser Cutter Property
 Through Cuts
 		Partial Cuts
Speed
 40%
 100%
Power
 100%
 50%
Frequency
 2.5 kHz
 2.5 kHz


LC_Kit3_Comp_w

Besides hinging the 40mm hubs, I created three types of hinged links measuring 15mm x 100mm.  Link hinges permitted the links to bend up to a 90 degrees with respect to one of their body axes.  Some sample assemblies of this kit are shown below.

LC_Kit3_Assy_w

Chamfered corners were omitted for the purposes prototyping these early kits however they would be incorporated into any future iterations.

Additional features to explore could include two-sided hinges cuts, mirrored copies of angled hinges, and mixed multiple hinges on the same link for more construction versatility.  Perforated hinges using a very low laser cutter frequency could also facilitate bending.

Impromptu Testing:

I had intended to discard all of my cardboard projects once they had been tested and photographed but had left them on a lab workbench by mistake.  The following day while a lab member was working on a his own project, his three elementary school aged children found the kits and instinctively started to disassemble, experiment, and build with them.  His children continued to work with the cardboard kits until the lab was prepared to close for the evening.  They enjoyed building with them so much they asked to keep them, take them home and continue working with them.