Revolutionizing Precision Automotive Technology in Metal Forming
Achieving exacting standards in manufacturing is paramount, especially in the automotive industry where safety, performance, and quality depend on incredibly tight tolerances. This demanding environment necessitates cutting-edge approaches, particularly in metal forming processes. Precision Automotive Technology is constantly evolving, and a recent advancement involving hydraulic press die cushions highlights how sophisticated control systems are pushing the boundaries of manufacturing capability to meet the stringent demands of modern vehicle production.
A key challenge faced by Spartanburg Steel Products involved upgrading an existing hydraulic press. The objective was to incorporate a new die cushion that could operate seamlessly with the press’s existing ram motion, which was already moving at high velocity upon contact. Compounding this was a distorted press bed that required rectification before any new hardware could be integrated. According to Tom Pedersen, Dayton Die Cushions manager, they meticulously reconstituted the bed using adjustable guides, achieving alignment to within 0.001 inch via a 3D laser, a testament to the required precision.
The critical hurdle was the interaction between the high-speed ram and the new cushion. Unlike traditional press operations where the ram hits the cushion before it begins to move (causing a pressure spike), this application couldn’t tolerate the collision dynamics. A method was needed to anticipate the contact and initiate hydraulic action before the ram made contact. This predictive approach is a vital component of modern precision control systems.
Furthermore, valve responsiveness was crucial. Any delay in increasing oil flow could damage the workpiece. The hydraulic oil had to move the cushion precisely as the ram prepared to contact the die. This level of synchronized action is central to achieving automotive high performance technology in manufacturing.
CAD drawing illustrating precision hydraulic die cushion with pneumatic assist cylinders for automotive manufacturing.
Dayton Die Cushions’ innovative solution leveraged a programmable motion controller capable of setting up a virtual motion axis. A physical axis could then be ‘geared’ to this virtual axis, allowing the slave (physical) axis to follow the master (virtual) axis controlled internally by the system. Pedersen notes, “We created a virtual closure of the die-cushion control loop before the ram hits the cushion, which no one had done before.” Closing this virtual loop initiated oil flow before physical contact, ensuring a smooth interaction despite the ram’s speed and kinetic energy. This approach demonstrates how advanced control strategies are key to the automotive technology industry.
To handle the high dynamics and required force (250 tons maximum holding force), the team selected a servo valve with high flow and very low mass. They also aimed to minimize oil volume, reduce the hydraulic power unit size, and lessen oil conditioning needs. Given the cushion’s large size (125 by 69 in.) and the sheer volume of oil needed, they incorporated two passive pneumatic cylinders alongside the hydraulic cylinder. These pneumatic cylinders provide the base tonnage, allowing the hydraulic cylinder to focus on providing the variable tonnage needed for precision shaping of automotive components technology.
Delta RMC75 electro-hydraulic motion controller, a key component in achieving precision automotive technology.
For implementing the hydraulic controls, Aleksandra Spiess, a Dayton Die Cushions engineer, chose a Delta Computer Systems RMC75 electro-hydraulic motion controller. Pedersen highlights the RMC75’s capability to run four separate task-execution engines simultaneously, designating one task for background computation, crucial because a PLC wouldn’t be fast enough. The controller manages two servo valves, each assigned to a separate control axis, offering simultaneous and independent control. The ability to quickly move oil to the tank allows for rapid die cushion movement when the ram first makes contact, with the cushion slowing down as compression completes. Achieving this level of control is vital for precision processes.
Correct pressure timing throughout the stroke is paramount. The new system utilizes two Balluff magnetostrictive linear displacement transducers (LDTs) and Hydac high-speed pressure sensors linked to the Delta controller. Before ram contact, the RMC75 opens valves and begins oil flow. Upon contact, it runs a pressure-control loop as the cushion descends. At the bottom of the stroke, as the ram reverses, the RMC switches to position-control mode, causing the die cushion to ascend rapidly. This precise timing is needed for the die cushion to meet a robotic arm that removes the finished part. Pedersen notes that the cushion must ascend repeatedly within a specific time window to meet the transfer arm, requiring adaptive closed-loop control that accounts for dynamic changes like hydraulic oil temperature and flow properties. This complex coordination is crucial in modern automotive collision repair technology and manufacturing.
Dayton Die Cushions successfully completed the motion-control program after three iterations, receiving significant support from Delta engineers. They learned advanced techniques like using the RMC75’s S-curve instruction for smooth acceleration/deceleration to prevent hydraulic shock and incorporating feed-forward parameters to speed up the control algorithm’s response. Delta’s RMCTools Plot Manager software was instrumental in graphically proving system functionality and optimizing control-loop gains, critical for meeting Spartanburg Steel Products’ urgent need to add tooling for a new automotive model year. Although this application focuses on stamping, the principles of precision control are also relevant to fields like automotive led lighting technology.
This project demonstrates how hydraulic control systems are becoming increasingly sophisticated and ‘smarter’ to meet the heightened demands for productivity and quality in modern automotive manufacturing. The programmable electro-hydraulic motion controller stands out as a key component enabling these advancements in Precision Automotive Technology.
