There are two classes of robot, those driven by stepper motors and those that are driven by other types of motor. For those driven by stepper motor, (LABORATORY ROBOTS; e.g. Caliper Twister range, Hamilton Microlab SWAP, Hudson Plate Crane), the robot will probably stop when it hits an object and has very little capability to do serious injury to a user. However they can cause cuts, especially to the head, that can be a distressing at the time.
The rest are driven by servo motors, these robots are less likely to stop and have the capability to cause injury (FACTORY ROBOTS; e.g. Mitsubishi, Staubli). It is this category of robots that need to be enclosed for the users safety. The main sources of injury would be facial injury, pinch points and crushing injuries.
Most instruments are safe to operate, although a great many of them have pinch points of one type or another.
Sample preparation interactions
Possibly one of the major safety areas. Most robotic procedures are handling biohazard materials and therefore best handled in isolation. The basic safety cabinet offers some protection, however some systems need laminar airflow and air filtration.
Users in the robotic areas
Ironically open access to a robotic system is often not good for the system either. Curiosity and the ability to influence a robotic installation makes the system prone to unwanted human interaction. A simple screen or enclosure can stop unwanted human interaction.