First of all, I crafted the inactive robot, after gaining full steel armor, a fast spear, and a gun, and I really didn't need the gun, as it turned out. Earlier, I had dug a hole down a bit in search of ores, but I quickly abandoned it. I fought the active robot, mostly in extreme close quarters, occasionally using a bandage, when I fell down the hole. The hole was slightly misshapen, so I pushed myself into the wall just as the robot came after me. I attacked it but noticed that it was doing no damage to me. There was a slight ridge above me keeping the robot from touching me, but it was still close enough that it was attempting to charge at me. If the robot is unable to deal melee damage, I suggest that it switch to the flamethrower, regardless of distance.