Each year, I visit hundreds of plants to work with engineers, and they all have one common goal: to increase their throughput. I’ve found that this need is driven by the right reasons, such as dealing with a labor shortage and/or increased demand while simultaneously improving product quality. Current trends in manufacturing are also driving attention to measuring and increasing overall equipment efficiency (OEE), return on investment (ROI) and payback (time). In many cases, these three factors determine the fundamental design of the robotic welding cell.
A typical cell consists of the welding robot and a dual-station positioner. This type of design allows the robot to weld on Side A (station 1), while the operator loads and unloads on Side B (station 2). One of the most common types of positioners used in this configuration is called a "ferris wheel," which indexes the fixtures between the operator side and the robot. In other cases, a dual-station system can utilize two headstock/tailstock positioners located on each side of the robot.
I frequently see these types of robotic welding cells in production, and they have a high percentage of idle time. This means the system is waiting on the operator to complete a task (loading/unloading) before welding the next part. Assuming this dual-station cell meets the plant’s throughput and quality needs yet has a high percentage of system idle time, I suggest the system is over designed for the application.
In these cases, consider a cell with only one fixture station or single positioner, such as a headstock/tailstock where the robot sits idle while the operator tends to the fixture. If this type of cell design meets the throughput requirements, then there are many benefits of using a single-station cell over a dual-station design. Single-station cells have a smaller footprint, are easier to safeguard, and require half the maintenance and programming of dual-station cells. Operators of single-station cells also benefit from the increased reliability of having fewer working components.
So, depending on the ratio of the robot cycle time to the operator load/unload time, a single-station robotic welding cell can offer a very cost-effective solution. In fact, investing in a second robot for a single-station cell can be much more cost-effective than purchasing a dual-station cell with a single arc welding robot.
After all, if your robot is idle while the operator tends to the fixtures, and you are meeting your production requirements, haven’t you met your goal?