Page 39 - EDM Today Winter 2025

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There is some level of convenience in having one all-encompassing NC program on the machine that contains full
oversight of the entire process. The operator or programmer will have a complete understanding of machine pro-
cess details including how and when the robot will perform its tasks. Process information including what job/part
number(s), tooling pallet numbers, and work coordinate/locations are identifi ed within the NC code that lives in the
machine, and the robot simply becomes an extension of the machine tool and its programs.
With the robot slave confi guration, the robot WAITS for all commands and instructions from the machine program/
machine control. Once the robot is instructed to perform a task (exchanging of the workpiece), the machine sits in an
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idle feed-hold state and awaits a reply from the robot confi rming that its tasks are completed and for the machine to
resume its operation. To establish this digital communication and handshake between the machine tool and robot, a
special hardware interface is required that can vary by robot and machine tool manufacturer.
The communications between the machine and robot are most commonly established through either RS232 or by
ethernet discrete I/O (input/output) signals. Depending on the capability of the robot being used, the communica-
tion signals can directly command the robot about what to do or trigger a more complex sub-routine (mini program)
of commands that resides within the robot’s control interface. There is a controlled sequence of events that occur
before, during, and after the robot automation actions, and this includes several back-and-forth communications
between the machine tool and robot.
The fi rst thing to occur is for the machine tool to position itself to a designated SAFE location within the work tank
where there is no chance for the robot movements to interfere or crash into the machine tool structure. Once the
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machine is at its SAFE location, the machine talks to the robot and gives it permission to perform its part exchang-
ing duties. As the robot moves into action, it has been given instructions to fi rst pick-up and remove the completed
workpiece within the machine and then place it back into a defi ned work pallet/work rack location. The robot will then
pick-up the new designated workpiece or pallet from its rack and transfer and load it into the machine. Once the robot
has completed its load/unload task, it communicates back to the machine tool letting it know its job is complete, and
that it is safe for the machine to resume its operation.

There is a more complex sequence of actions and data that is taking place during the robot load/unload movements.
When the robot goes to pick-up the workpiece, it is also controlling and triggering the clamp & unclamp commands of
the workpiece tooling. This series of actions is similar to what occurs when a Sinker EDM machine uses its automatic
tool changer to exchange an electrode. During all the movements and actions performed by the robot, there is also
a SAFETY signal that is being monitored. If this safety interlock signal is breached during the robot’s movement,
meaning that a person may be inside the machine/robot area, the robot will STOP and wait for an operator to clear
the safety breach and resume the operation.
manufacturing cell (see Figure 1), it is EDM Today Magazine
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Circling back to the machine master/robot slave relationship, this automation method is effective, but does place
the process and sequencing burden on the operator/programmer. This is an excellent way to extend unattended
machine operation (boost machine utilization), but the programming logic and complexity increases substantially
when processing a greater number of parts. The increasing challenge resides in the need to map out and defi ne what
NC programs, work coordinates, and workpiece pallets mate together for execution, so this requires VERY disciplined
planning and programming!
While this style of automation is most
commonly deployed with (x1) robot
servicing (x1) machine as its own
technically possible for (x1) robot to
service (x2) machines, but the level of
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diffi culty with programming becomes
even higher with there being more than
(x1) master driving the system. As a
robot begins to service (x2) or more
machines, the programming complexity
can easily lead to mistakes resulting
from an error in identifying an incorrect
workpiece pallet number, NC program
number, or work coordinate value
across the different machines being
automated.

Figure 1
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Robot Serving a Single Machine
(Continued on next page)
37
EDM Today, Winter 2025 Issue