There are 3 levers in the cave, which can disable the robot's main weapon for a turn.
The robot is vulnerable to electricity, but any kind of air damage (including air damage reflection on equipment) will charge the Sparkmaster's main weapon.
You can use equipment bonuses or potions to boost the air resistance of whoever gets close enough to trigger combat.
Using the remote to vent steam, or otherwise surround the robot in a steam cloud, can get it to stun itself trying to use the ultrabolt attack. If you can keep it knocked down, that would help, as well.
If it is still too tough, check for equipment/skill upgrades, etc, or do other things and come back for it later. It is also possible to sneak or use invisibility to get through the cave without triggering the fight.
