While testing the cats prior to animating, I came across a major issue. The shoulder joints offered far too much mobility, and easily slid around. If I were designing a toy, this wouldn't be a problem. However to animated these kittens in stop-motion, I needed the legs to move a little at a time and hold in place. Yes, I could rig each leg to hold it steady, but I wanted to nip this problem in the bud, and keep the cats functional.
This was definitely a challenge. How could I give the cats more stability without sacrificing mobility? I considered scrapping the entire shoulder design, and replacing everything with ball joints. Unfortunately, I realized the ball joints would create the same problem as the shoulder joints. After some thought, I came to the conclusion that if my pieces were made of metal, they wouldn't have this problem, as they would hold the balls tight without sliding. Because I decided to complete this project using 3D printed parts, the plastic didn't have enough grip or friction to hold onto the balls.
*Me trying to keep it together after realizing my armature is falling apart*
Rather than trying to salvage my work, I decided to start anew from the problem areas. I re-analyzed the type of movement I needed my cats to do. Realistically, they only needed to move forward and backwards, not outwards.
Out of all the pieces I had tested, the knee joints had been the most effective. If only I could use the knee joints as the shoulders...hey! Wait! I could! I remodeled versions of chest and pelvis to have knee joints fused to them. This would keep the legs stable, and provide me greater control and precision while animating.
I tested out my hypothesis and printed the new pieces. To my relief, it worked! The cats could now stand without support! I also put in only one back joint. Finally, I coated each foot piece and back ball joint piece with a rubber coating called Plasti Dip. I gave each piece a spray every hour for a few hours, and left them to dry overnight. The rubber coating gave the pieces friction, and strengthened their hold on the balls. Below you can see the black Plastic Dip on the red and grey PLA pieces.
Everything feels more secure, and easier to animate! Success! I'm beyond excited to animate them!
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