Multipress Inc., a Columbus,OH manufacturer with a 50-year history of producing custom presses for themetalworking industry, was recently contacted by a customer with a requirementfor a 50-ton deep-draw press. In this newapplication the customer specifications included:

To help with system design,Barney Raye, president of Multipress and Rick Snyder, Mulitpress' electrical engineeringmanager, worked with Advanced Industrial Products Inc. (AIP), a hydraulicsdistributor with which Multipress has worked on multiple press developmentprojects in the past.

After reviewing therequirements for the new press with the Multipress executives, hydraulicsexpert Mike Joyce of AIP and Bruce Coons, regional manager for Delta ComputerSystems, decided to use the Delta RMC75 motion controller. Multipress has usedRMC controllers manufactured by Delta Computer Systems in five previousapplications.

To connect the motioncontroller to the system components in the new press, a complete analogfeedback signal system is provided to the Delta controller for precise controland troubleshooting. Of the two motion axes supported by the RMC75, axis 0 isused for closed-loop pressure control of the hold down (clamp) cylinders, whileaxis 1 is used for position/velocity control of the main press ram. The motioncontroller uses additional analog interfaces for pressure monitoring of themain ram and open-loop joystick velocity and directional control of the mainram. Eight digital I/O interface lines were used by Multipress for handshakingwith the system PLC to coordinate overall machine operations.

Controlling pressure is acritical element of this design because variable pressure must be applied bythe clamping cylinders to avoid damage to the work piece during the presscycle. Even though the primary mode of control of the main ram is based on theposition and velocity of the ram piston, pressure monitoring of the main ramhydraulics is also needed to ensure that the correct amount of pressure isapplied through the metal forming die.

Tuning the motion axes wasfacilitated by the RMCTools software package included with Delta's motioncontroller. Using RMCTools' scale and offset Wizard and Wizard for automated positiontuning, both the closed-loop pressure control axis and the closed-loop position/velocitycontrol of the main ram were reportedly set up and tuned in two hours.

Since the AIP and Multipressengineers had never before implemented an open-loop joystick control interface,they chose to use the programming and simulation capacity of the Delta RMC75 totest the motion control program before connecting the hardware. The joystickcontrol is used to operate the main ram used in part setup and rework.

For normal automatic pressoperations, a simple one-step repeating program is provided that Multipressmachine operators can call up with an input from the human-machine interface(HMI) that is confirmed in the PLC. The PLC downloadsall pressure settings; position setpoints corresponding to hold down pressuresettings and position setpoints for closed-loop main ram position control. Themotion controller program uses variables so that different position or pressuresetpoint values can be selected via the HMI. An operator can push a single buttonon the HMI to cause a new set of hold down pressure settings and ram positionsettings to be loaded for production changeovers. Another button on theHMI enables the change between automatic and joystick modes.

To support the joystickinterface, Multipress programmed an "open loop rate" command that uses theanalog feedback of the joystick (A plus or minus 10V dc) as the rate control for the main ramwhen under joystick control. The joystick can be seen in the lower right-hand side of the press bed by the post in thephoto.

For the HMI, Multipress andAIP chose the Automation Direct C-More EA7S6C programmable touch panel. The HMI connects to the Ethernet interface providedon the RMC75E motion controller. This interface had been used on otherDelta systems by Multipress and a downloadable program example was available inthe large sample code library on Delta's website. Use of this software reducedthe engineering time necessary for screen setup and programming.

Based on the success thatwas achieved with this project, Multipress will continue to standardize on DeltaRMC controllers for future closed-loop motion control applications.