22 March, 2014

Silhouette Hack 04: Shrink plastic

The Silhouette is one of the weaker craft cutters, so it can only cut thin sheets of plastic. However, I found this Instructable that introduced a new material that I hadn't heard of before: http://www.instructables.com/id/manufacture-custom-gears-with-a-cricut-and-shrink-/ ok, it's not really a new material, it's stretched polystyrene that shrinks back to its original dimensions when heated. One common brand is Shrinky Dinks. Supposedly, in its stretched form, it's thin enough to cut with the Silhouette.

I found that Art Friend sold individual sheets of this brand called "Shrink Me". Can't find it online, though. Now, different brands have different shrink rates and temperatures. This is supposed to shrink 3x.
If the dimensions shrink by 3x in 2 directions, that's 1/9 the area, so the thickness should increase by 9x.

Ok the main problem with this material is that it can't be cut with the Silhouette, regardless of force or passes. If your designs are simple, you can partially cut them, then finish with a knife, which is what I did here.
I tried to make a planetary gear set from another Instructable: http://www.instructables.com/id/Making-a-Laser-Cut-Planetary-Gear/, which looked more interesting than individual gears.
So I spent maybe 1 hour cutting them out. The problem is I don't have an oven to shrink the plastic, so I used a hair straightener, which didn't work so well.
They tend to warp, especially if your heat isn't uniform or it's too hot.
So, sadly, this project didn't work. Another problem with this material is that it's very brittle after it's shrunk.

Heat Sources
They recommend using a kitchen oven or toaster oven, but I didn't want to put plastic in my oven. Another source is a hot-air gun (not hairdryer), which I don't have but could be useful for shrink plastic, heat-shrink tubing and embossing powder. Shrink plastic needs about 140°C to shrink so hot water won't work. I had a hair straightener so I tried it, because it's portable and flat. However I think it runs about 200°C, which is too hot. The plastic will warp if it's too hot, especially since my hair straightener is only about 2 cm wide. I'm thinking of getting a better hair straightener, one with temperature control, to use with this and heat-shrink tubing. I believe with temperature control from 120-200°C, it'll work.

I tried another type of plastic from Amazon: Graphix shrink film http://www.amazon.com/gp/product/B000KNPKIE/ This material is supposed to shrink by 2x. It can't properly be cut by the Silhouette either, but you can force the pieces out and they leave a layer behind:
I'm also having trouble getting this to shrink uniformly:

So, before I can use this type of material, I have to:
  1. Find a way to cut it (already got one)
  2. Find a good way to shrink it

Update 22 Apr 14
I bought a hot air gun, because I thought, instead of spending $50 on something that's not designed to do this and only might work (hair straightener), I might as well spend $50 on something that's designed to do this, and I can also use it for other things. It works beautifully. Better than a toaster oven would, I think:
  • Fast - finishes shrinking in about 30 seconds
  • No plastics in your oven
  • Very little curling
It's a 300W craft model that claims to run at 350°C. I think the DIY models might be a bit too powerful.
Now I have a chance to compare the 2 plastics. I made some dots 10 mm apart, and after shrinking they were about 4 mm apart. Remember, the clear Shrink Me plastic is supposed to shrink 3x and the white Graphix one is supposed to shrink by 2x, but they both actually shrink by the same amount. Graphix sheet thickens from 0.25 to 1.8 mm in the process.

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