Experimenting with Flex
The pieces at Scribbled Squirrel are made using photosensitive resins - a substance which turns from liquid to solid when exposed to UV light. Thicker pieces are pretty strong but working with the fine detail typical in handwriting and drawings presents more of a challenge for durability, especially for jewellery which can be put under significant strain. Luckily I've got a good stress-tester to carry out quality control, in the form of my 9-month old daughter who can put up a surprisingly strong effort when attempting to wrench a necklace from your neck.
Using the latest 'baby grip' research I've found that the weak point of a piece is pretty easy to predict - for example, it'll be the tail of a 'y' or the connecting line between two words. Under normal wear they stand up fine but if you apply pressure to the weakest area it is possible to bend and eventually snap the resin. I had been trying to overcome this through the design of the pieces by adding small linking elements between weak points to stabilise the design and increasing the thickness of the pieces. This wasn't really a satisfactory solution in many cases as it could detract from the source image. In the case of my eldest's stick figure drawings there just wasn't a practical way to strengthen their skinny limbs.
So this week I've been experimenting with additives to adjust the flex of the resin. I've been using MonoCure 3D Rapid Flex100. If used straight from the bottle it gives a flexible, compressible rubber-type finish which would be too malleable. I've set about finding the right proportions which balances durability against cost (the Flex100 is double the cost of my typical resin).
Using the 'love you' print above I started with a ratio of roughly 9:1 standard resin to Flex 100. I say roughly as I discovered I need to invest in some more precise scales! The weak point on here is the join between the 'e' and 'y'. Being in the middle of the print it is easy to compress and bend. At the 9:1 ratio I was able to bend the piece in half without it fracturing, however a curve was apparent for a few minutes before it returned to the original form. I'd like it to return to shape more quickly so, as soon as I've got some scales that weigh with decent precision, I will repeat with an 8:1 ratio. In the meantime, these are off to my sister-in-law for some real-life testing - we'll see how they get on.