2 CNC machines, 1 robot, no profits

Over the years, many machine shop owners have asked if it is a good idea to automate two CNC machines with a single robot system. Although at first glance it appears to make sense, there are several reasons why it is not a profitable proposition for small and medium production runs:

Flexibility and safety. When you want to load two machines with one robot, you need to crowd the machines and robot together so the robot can reach both CNC machines, as well as install a safety fence around the entire cell to meet OSHA requirements. This arrangement makes it difficult for a machinist to have easy, adequate access to the CNC for setup, programming and adjustments. One other option is to use a larger, more expensive robot with a longer reach, but this robot will take up more room inside the CNC machine and may interfere with the spindle or tools.

Cycle times. To be efficient, cycle times of the CNC machines must be timed perfectly. Otherwise, there is a risk that the robot and a CNC could wait for one part operation to be completed before loading the other CNC, and at most job shops these processes vary significantly.

For maximum safety and efficiency, ideally each CNC machine is governed by a dedicated robot. Image courtesy of C. Zoberis

Accessibility. Ideally, machine-tending robots are mounted on an incline to allow the machine opening to stay clear for the machinist to operate manually for first articles and enable tool changing. The angle of the robot is defined in a specific way to easily access the machine clamping device without mounting directly in front of the machine. The consequence is that it is not possible for the robot to reach a second CNC because it is out of the robot’s mechanical limits. This means that if the robot wants to reach two machines, it must be placed right in front of the doors of the machines — thus you will lose operator access to both machines.