thank you for taking the time to experiment. Much appreciated!
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Wow, that’s really cool! I somehow missed that original post of Dan’s. I will have to give this a try—thanks!
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Thank you for sharing your file and time, I will put this on my to do list.
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Interesting. I just force the bearings into my fidget spinners with a press, and haven’t experienced any cracking yet.
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i wonder how short you can make the ‘petals’ and still get some flex.
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I’m now neck-deep in experiments trying to figure out when the sunflower works and when it doesn’t. Since I want to fasten 8mm magnets, the cuts are quite close to each other. The proximity heats adjacent cuts, which I think annoys the sunflower. What does a sunflower do when it’s annoyed? It sheds petals: they look like tiny teeth, glittering in a halo around the intruding magnet.
Petal-shedding doesn’t always happen. It depends on how tight the fit. And, I think, the age and quality of the acrylic. I had consistently frustrating results on some clear acrylic from TAP Plastic’s scrap bin (hey, it was cheap!). Better luck with fluorescent green acrylic from TAP’s regular inventory. All were cut using Proofgrade settings for green acrylic.
Today I’m going to try an 18-petal sunflower with petals in alternating colors, so I can cut them in two separate passes. I’ve also added a little loop where each petal joins its neighbor. This might help absorb the stresses, as suggested in this article.
Finally, I realized that the sunflower approach offers a way to glue magnets to acrylic. It disrupts the glossy surface sufficiently to disguise the glue and offers myriad crevices for an adhesive such as CA to leech ’n’ grab the hapless magnet.
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The 18-Petal Two-Pass Sunflower with Loops worked quite well. To put it to practical use, I designed a compact reading stand for my Kindle ebook reader. It consists of two pieces which cling to each other magnetically when they’re not supporting the Kindle.
It’s 1/8-inch acrylic, cut using settings for Proofgrade acrylic. The sunflower magnet fit is quit snug. I insert the 8mm magnets by pressing down with a flat surface, generally the other piece of the Kindle support.
Kindle Holder.svg.zip (219.8 KB)
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Super application. Great idea to split the petals into multiple different colors so you can separate the cut operations.
The stand is a good design too - sturdy and portable at the same time.
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It was in a comment on the Fiducial Alignment Ruler post:
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You should split this out to it’s own topic.
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After making a few of the Kindle stands, I found that one of the sunflowers cracked when I inserted the magnet. The good news: it cracked on the bottom edge, which suggests that the loops are deflecting the pressure away from the sunflower petals. If you decide to cut that design, I suggest increasing the outer diameter of the sunflowers by about 0.004 inches.
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Here are my best attempts at a range of sizes for the sunflower socket.
I’ve alternated colors for the petals so they can be cut in two passes, minimizing heat build up. And the interior end of each petal ends in a small loop to minimize strain from pressure. I am a flawed draftsperson so you will notice some irregularities (petal length on the 30-petal design is shorter than the others, loops are not perfect little curves, some loops are wider than others) but still… At least the shapes are consistent within each petal variant, and I used Inkscape’s node snapping feature to nail the joints between every petal.
I invite your experimentation. The 18-petal version works quite well for me, resized to hold 8mm magnets. Bigger petal counts would match to wider magnets.
Acrylic Iris.svg.zip (22.1 KB)
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Nice adaptation! The name makes it even cooler.
I think the loop should go at the base of the petals, to end each cut. Is that not where the petals break, when they do?
Before I included loops the petals consistently broke at the top, which is why I put them up there. Now when they break they break at the base, and I can use a smaller center opening for the magnet.
But there may be other, better solutions for relieving stress breakage.
As I said earlier, I invite experimentation.
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Here is an updated collection of sunflowers in petal counts from 12 to 30, including a 16-petal flower [16c] with loops at the base of each petal in addition to the inner part. I haven’t yet experimented with the extra loops version. I’ve also fussed over the other sunflowers, smoothing the loops and making them more loopy and less lumpy.
I have mostly used the 18-petal version and I’m happy with it but there may be better approaches. There are about 23 trillion variables here: petal length, loop curvature, loop size, petal count (have I reached my first trillion yet?)… And loop curvature itself is packed with variables since the curve is not an arc but a segment of a spiral. Curve experts are welcome to correct my terminology.
The many-petal versions might be useful for larger-diameter joining projects. The lower petal-count variants are intended for small joins where melting can be an issue. Also, as the diameter of the sunflower decreases, the thickness of each petal shrinks proportionally. Lower petal-counts help compensate.
Acrylic Iris.svg.zip (28.6 KB)
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At @petej’s request, I’m going to re-post the picture of a test socket I worked up. (I had it up briefly last night then decided to wait until I had a use for it, to make sure it worked consistently.)
But what the heck…it’s a work in progress. It does seem to be stable enough to not split at the base.
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@Jules inspired me to rethink my design. I initially remodeled the 24-petal version, but when I reduced it to fit 8mm magnets the inner petals were too close together and distorted during cutting. So I reduced petal count to 12.
This works quite well, and it doesn’t look like a Loop Festival. At this point I think I’m quite done with my experiments. Here is my final (I hope) version.
Acrylic Iris V2.svg.zip (3.5 KB)
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I love this idea, and think it could very easily be exported for use with things like small batteries. Great work.