Broken teeth on gears

I was building a 3D printer and I was using this gear transmission:
Motor - 12-tooth gear driving 36-tooth gear.
On the same shaft with the 36-tooth gear, there is 12-tooth gear driving rack gear.
The teeth broke on the 12-tooth gear driving the rack gear after the carriage hits rack gear bracket. I didn’t put limit switches on the 3D printer. The clutches are on the motors. Should I put clutches on the 12-tooth gears driving rack gear?

Your building a 3d printer?

Either i miss unsterstood what you meant or you are building one hell of a robot!

You are putting to much pressure on one gear, try doubling up on the gears and if that doesn’t work increase the gear reduction.

Hope this helps