These Straw Connectors can be used to link together straws into big structures. For fun with kids, but also as a frame to wrap in rice-paper and use as lamp-shade, or any other application that needs a light-weight structure.
The files contain a few sample STL files for some possible connectors, but the main source is the OpenSCAD file, which makes it easy to create any size and type you want. See Parameters for details.
The sample files and default parameters are tweaked for use with the big IKEA straws (Sötvatten). Other brands of straws might work just fine.
Because the connectors require a press-fit and straws don't stretch much, an exact size of the connector is quite critical. Different straws and different printers and printer settings may lead to slightly different fit. Print a single XYZ connector first to test-fit, before printing a grid of multiples connectors.
Full disclosure: This is not my own original idea. The concept exists (or has existed) commercially, and there are plenty people tinkering with this on Thingiverse. See my collection of related things here: https://www.thingiverse.com/erie/collections/straw-connectors.
I created my own version, because I wanted to be able to easily tweak the sizes and shapes, and create new types when needed. Also, I discovered that not all straws are created equal. Even the straws from IKEA that I use (Sötvatten), have slightly different diameters for each color straw. This creates the need for very fine tuned sizing, for one connector to work with all color straws.
You probably need a whole lot of connectors to make an interesting structure. To reduce the post-processing time, the model aims to require no support structures and no build plate adhesion (brim/raft/etc). See Print Settings for details.
No support required
These connectors can be printed without support structures (at normal straw sizes anyway). A straw diameter of 8mm (e.g. IKEA Sötvatten) works great.
No build-plate adhesion required
The model already contains build-plate adhesion structures, that lead to as little as possible post-processing. I added that to the model because the default options in Cura leave to many artifacts that take too long to remove. There is very little play to have a snug fit with the straws.
So, in your slicer you should select "no build plate adhesion". If you have trouble with adhesion, you can add a bit of extra brim. I typically do that for single connectors. If you print multiple connectors at once, in a grid, they are interconnected and have plenty of build-surface area.
Enabling retraction is wise, as you want as little artifacts as possible.
I print these in PLA, but I see no reason why ABS woudn't work just as well. You might need to retweak the sizes.
These are the most important parameters in the OpenSCAD file, with some explanation what they do. See the OpenSCAD source file for more detailed documentation.
// Sizes of each tube
radiusTip = 3.85; // Outside part of each tube.
radiusMid = 4.0; // Middel part of each tube. This should be slightly bigger than the straw inner radius, and bigger/equal to the raduisTip
radiusBase = 3.95; // Base/Center part, where they connect together
lengthTip = 5.0; //
lengthMid = 5.0; //
wallThickness= 0.8; // Bigger is stronger, but slower print.
// tubeEndHoleRadius sets the size of the hole in the end of the tube. Choose 0 for completely closed, or "radiusTip-wallThickness" for completely open. Partially closing up the ends helps with keeping the round shape of the tube without having support structures.
tubeEndHoleRadius = 1.2; // in mm
// holeTroughBack can be used to string a fishing-wire trough the connector if your construction needs extra tensile strength to stay together (e.g long horizontal spans).
holeTroughBack = true; // true|false
// FlattenedSides make it easier and cleaner to print without support structures and create beter print bed adhesion. If true, the circomference of the tube will be slightly smaller, you might have to tweak the radii.
flattenSides = true; // true|false
// buildPlateAdhesionGrid creates a "1 layer" thick grid of strips underneath the connectors, connection them together and creating a larger surface area to stick to the buildPlate. If you enable this option, you should turn of adhesion in your slicing software.
buildPlateAdhesionGrid = true; // true|false
I enabled Customizer, but my file doesn't seem completely compatible. I might restructure the source code later, for beter compatibility.