He was working in the bin to replace skirt liners under a diversion plate. Another worker was replacing the rollers on the conveyor above the bin.
The second worker caused the roller to fall into the bin and crash onto the diversion plate above.
The roller ended up falling about 11m.
The NSW Resources Regulator said the risk of falling objects hitting a person was an easily identifiable risk, with controls needing to be put in place before any work begins.
Work groups should also communicate with other work groups in the area, to determine if there are interactions or risks between the groups.
The regulator said supervisors should also ensure controls were in place and communicated to all workers involved in the tasks.