3D Printed Rainbow Suncatcher

This 3D printed window decoration celebrates rainbows and the magical material called diffraction grating.

Diffraction grating is a plastic film that is able to act like a prism which separates the wavelengths of light being emitted from a white light source (like the sun or very bright incandescent lightbulbs). There's actually a pretty good chance you played with this stuff in a grade school science class when you were learning about the physics of how light travels. For this project, it gets used to create a geometric sun-catcher that can hang in a window or on a porch with spotted shade.

Supplies

Tools

• 3D printer - I use a heavily modded Monoprice Maker Select Plus. One day maybe I'll make an Instructable about all the work I've put into it, next time I'll just buy a nicer printer.
• Desktop cutting machine - I use a Silhouette Curio, but wish it had a slightly larger cutting bed sometimes.
• Binder clips or small A-clamps - for holding glue-ups.

Consumables

• 3D printing filament - I used clear, but also liked the way it looked with black and 'marble'.
• Diffraction grating - I didn't know much about how to buy diffraction grating but after some outreach to friends, I was directed to the folks over at Rainbow Symphony. They worked with me a lot to answer my heap of annoying questions and when I said I'd be publishing this project on Instructables, they said I graciously included this promo code for others who may want play with diffraction grating - AUDREY15 - I used their 13500 line film.
• Fast tack flexible bond glue - I used Beacon's Quick Grip - skip ahead to step 3 to learn more about why I used this glue.
• Glue syringes- a necessary item for precision glue application.

This does include some affiliate links, but know that every dollar I get through the program goes right back into buying tools and materials for my next project that I share on Instructables. Your support means the world to me.

Step 1: Designing the Star

About a year and a half ago, I took a class at my local community college to learn more about solid parts modeling. I went to school for photo/video/design and had been working in the Adobe Creative Suite for most of my professional life then taught myself coding basics and electronics over time. I figured I could probably get the hang of modeling software if I just was able to get a primer first. (Tell me what the buttons do!)

My modeling software of choice is Fusion 360, it's free for students, teachers, and hobbyists and incredibly capable.

I wanted my design to be parametric, meaning I could make tweaks to the design based on a stored set of values. I could change the number of points the star has, or the length of each star strut, or even the offset of each frame with a quick edit in the parametric control box.

Step 2: 3D Printing

It took me a lot of different iterations to get the design right. (AND my 3D printer broke which was an unexpected timely setback) I settled on a design that would print flat to the bed and be assembled with glue with minimal sanding.

I printed the file attached to this step at a layer height of .2mm, and mirrored the shape in my slicer, Simplify3D.

Only 6 triangles fit on the bed at once, so I ended up running the job 3 times.

The part .stl is attached to this step, but if you import it on to the bed, be sure to mirror the part along the longest axis.

Step 3: Getting Ready to Glue

I tested a LOT of adhesives while iterating on this project and finally found one that had a flexible hold, a quick tack time, as well as a fast bond time, Beacon's Quick Grip. A lot of other industrial craft adhesives had a much longer set-up time which was hard to be patient for when working with the nimbly little spines that could slide around too much while curing.

One thing to note is that, before gluing, I made sure I had sanded all the 3D printed surfaces that were about to be bonded with the adhesive would grip better.

Step 4: Gluing Up the Pieces

I like using craft glue syringes because it allows you to have itty-bitty thin lines which reduce the amount of glue that squeezes out of the sides of the bond. Loading the syringe can be tricky, but I go over how it's done in the Industrial Adhesive section of my FREE Glue Class.

Each spine of the 3D printed triangle had a slightly slanted angle that created the dimensions of the star. When the two sloped sides were bonded, the parts became dimensional.

Step 5: Setting Time

Each triangle pair had to set for 5 minutes before it could be handled again. I found the best way to keep these pieces together was to use these little A-clamps. I could nest them right in the lip of the offset to keep the pressure on the center of the bond.

Step 6: Gluing Triangles Together

Once I had all the triangles glued up, I went about gluing up the short sides of the 4-sided polygons. These pieces also had tapered edges that would give the star a zig-zag dimensionality.

Step 7: The Last Triagle

Gluing the last triangle, quite frankly, sucked.

This step was when I came face to face with the slight discrepancies in part accuracy of my 3D printer.

There ended up being a small gap between the last two triangles I needed to connect, but since I used a semi-flexible adhesive, I was in a position where I could flex the whole star to close the gap.

Step 8: Cutting the Diffraction Grating

For the diffraction grating, I tried cutting it by hand and it was a pain to get precise shapes. While I was building this project, I decided to get the Silhouette Curio, but wish I would have shelled out a few extra bucks for their Cameo with a bigger cutting bed.

I was able to generate the cutting tool path from Fusion 360 by going into my initial sketch profile and exporting it as a .DXF, I've attached this path to this step.

Step 9: Gluing in the Film

Gluing the cut pieces of film into the windowpanes of the suncatcher took a delicate touch. I ended up using gloves to handle it because the film was so susceptible to collecting oil from fingerprints.

I used the same Quick Grip glue in a syringe with a very small tip and then pressed down the edges with a set of tweezers - you can see more how this was achieved in the video in the first step

Step 10: Finished!

If you care to dip your toes even further into the math and science of diffraction, I found some excellent articles on wikipedia and quora that talk about how exactly white light is expanded to its prismatic potential. However, for brevity's sake, I didn't go into it in this Instructable - just know this stuff is awesome to play with for art-making. 🌈

🌟Check out this star on etsy if you'd like one of your own. 🌟