Electric lawn mower blade Insulator

thingiverse

**Warning:** _Considering the inherent danger of a spinning steel blade in a lawnmower, if you decide to try this, it's all on you. If you decide to trust some rando on the internet (read: me) with your health and well being... have fun!_ I've got an electric lawnmower that has this fancy little thing in between the blade and the motor shaft which acts as a fuse in case the blade hits something. This thing is called an "insulator" and if the blade runs into something, the insulator breaks and the motor can continue spinning without getting damaged. Well, I hit something in the lawn and mine broke. Looked at it and thought "that's printable" and for once decided to search first, and found [the original thing](https://www.thingiverse.com/thing:2408199). Saw the issues that [BrandonPiper](https://www.thingiverse.com/BrandonPiper) had run into with his failing, and expected the same. Printed it, sure enough, as soon as I tried to start the lawnmower, it shattered and the motor spun freely. I tried several other things but unfortunately had no consistent luck getting the printed thing to be strong enough, even printed in PETG or ABS. The weak point was always the adhesion between the layers. So, I tried redesigning it, and came up with this design. Printed it in PETG, tried it out, and it completely shattered. Fail. One last try - I printed in ABS, and finally did something that I've been wanting to do for a while - I annealed it in the oven. * Put it in the center of the oven on an old baking tray * Set the oven to pure convection at 195 degrees F (around 90C) * Put in a digital thermometer probe to verify * Once it hits temperature (oven was within 1-2 degrees of the setpoint!) leave it for 20-30 minutes * Turn off the oven and let it cool. When I pulled the part out, it had warped a little bit, pulling up at the edges, but it looked like it would still work. Just like I had read, it also shrunk, so I had to do a bit of filing to get the parts to fit, but once I did and I installed it on the mower, I was finally able to get the mower to start without shards of plastic flying out. It held! Next was the test to see if it could mow the lawn. We've got a really small lawn, but it held. Mind you I had also sharpened the blade and the grass wasn't really high, but it worked. Now that it's annealed and stronger - I'm wondering if it's way too big and might need to be printed smaller so it's not _too_ strong. I've got zero idea what the breakaway force should be, and don't feel like hitting things with the lawnmower in order to test it. This is not a quick print-it-and-use-it fix, annealing takes a bit of time, but it could buy you some time while you wait for the replacement parts to be shipped.