The question is literally the tittle above. You're wasting your time reading this.
For context: The planet Abios is inhabited by a race of sentient robots. They're mechanical. They need infrastructure to replicate. Which means they need miners. Which means they need an entirely dedicated clade of robots to fill this niche in the assembly line... You're pretty much up to speed.
Miner bots or as I call them BOBs (boulder-obliterating-bots) are at the bottom of the supply chain. They dig around, find ores to eat, grind them in their 'stomach' with ball mills, mix it with water and excrete slurry which is then transported further along the supply chain.
They eat rocks. That's all you need to know.
These hunk pieces of metal have a simple, yet sturdy design. Stainless steel protects them from impacts and corrosion. They are powered by hydraulics and trusty lithium ion batteries (there's no fossil fuel on Abios, did I mention that). They are designed to be compact to fit through tunnels and make them more durable. They move on trails and dig using shovel-like limbs. When they sense a rock they shatter it into smaller pieces using a hydraulic hammer. They then eat the pieces, grind the pieces, turn them to powder in internal ball mills, mix the resulting powder with water to make slurry which then moves along the supply chain. They're like mechanical earthworms in a way... why are you still reading this?