Photo: High-performance press-tending robots can provide robust ROI to make the leap to robot automation.

Achieve robust ROI through robotic transfer automation

February 2021 - Revitalizing production in the evolving post-COVID market is a common reality most manufacturers must face. Decision-makers are discovering that the use of high-performance press-tending robots can provide the robust ROI needed to make the leap to robot automation worthwhile.

Robot specifications

Press application robots should be mounted to ensure shop flexibility and optimal floor space. Dies will still have to be able to get in and out of the workcell with ease. Manual access to the dies for occasional manual operation also may be needed. When selecting the proper robot, it is important to consider the distance the robot must reach into the press and part weight, including the gripper. Momentum and inertia also come into play. The value of robot payload should never be underestimated.

The robot must work within press cycle times to avoid slowing down strokes per minute. Robot selection also depends on if the part must be reoriented as it is transferred. The ability to tilt a part back and forth, or rotate it between processes, often requires the dexterity of a 6-axis robot. Less complex operations may allow for less costly 4- or 5-axis robots.

End-of-arm tooling enables gripping of the part and allows a robot to be customized for specific applications. In press transfer applications, these tools are often placed on an extension, with the tool normally being the only part of the robot that reaches into the die.

Beneficial considerations

While manual die changeover can take hours, modern automatic die changeover technology allows this process to happen in minutes. It is important to note that part variety may make it difficult to store multiple grippers within the reach of the robot. In a situation like this, a robot track can be used to transfer the correct gripper into the workcell and remove the previously used end-of-arm tool, extending the robot work envelope. A selection of sensors is also available to verify tool identity for use with the robot controller or programmable logic controller (PLC). These sensors are commonly used with a functional safety unit (FSU) in the robot controller, which provides control-reliable change verification along with associated robot and gripper range limits.

Various rack or turntable designs can be used to continuously feed raw materials into a workcell. The robot controller’s high-speed search function, combined with sensing devices, enables the quick location of the tops of stacked blanks. Adjustable stack-handling equipment with fanner magnets automatically selects appropriate blank sizes and shapes when performing a press transfer application.

Parts must be disposed of correctly at the end of the line. Loading finished parts into engineered part-specific racks, bins or pallets is key. Normally, modular vacuum grippers unload parts from the final stamping process and place parts onto a rack. A part may not be placed into a stationary rack immediately. Instead, the part is ejected from the last die. As a result, the high-speed conveyor or shuttle can transport it to a racking or palletizing station where a robot will move the part onto a pallet or onto a rack.

If using a racking or palletizing station, it is important to remember the pallet or rack is most likely going to be removed by a lift truck operator, so it is a good idea to use robust locators with pallet- or rack-present sensors that are mounted to the shop floor, providing the utmost protection to the pallets or racks.

For companies that have already implemented press automation, retrofits on controls including motors, encoders, motion controls and HMIs are advised. It is common today to replace existing programmable logic controllers or existing drives with more up-to-date variable frequency drives, as well as newer servos and PLCs—all of which can be placed into a convenient electrical enclosure.

Given today’s labor shortages and throughput rates, robots are a solid option for many press-tending applications, reducing potential injuries and unnecessary downtime while lowering scrap and increasing production throughput.  FFJ