Maintaining production flexibility was also very important to the Miba Bearings team. ¡°Currently we have 18 dies that we run on the press, some for single bearing halves and some for multiple halves. In the future, we plan to have up to 40 in,¡± says Gillespie.
The Bearing Forming Process
The key machine in the new workcell grouping is a servo press that makes crankshaft bearing halves with a single press cycle involving two steps: a preform step followed by a forming step. At the start of each cycle, a robot loads the bearing blank, which can vary in dimension from 2 in. ¡Á 3 in. up to 11 in. ¡Á 3 in., into the press and a laser scanner makes sure that the blank is seated properly. If the blank is not sitting in the fixture correctly, the press will inform the operator of an incorrectly set blank and stop the auto cycle until the part is properly placed.
Two linear hydraulic motion axes are involved in the forming operation, a preform cylinder and a forming cylinder. The preform cylinder is embedded in the press platen and extends to preform and set the blank in the tooling. Both the preform and final forming cylinder extend simultaneously. Once the blank is preformed, the preform cylinder retracts, the laser sensor confirms the proper position of the preformed blank, and then the final forming cylinder completes the cycle. All of these motions and checks are controlled by an RMC75E motion controller, manufactured by Delta Computer Systems Inc.
During the preform cycle, the pressure in the preform cylinder is monitored. If it is determined that the part is too hard and not bending properly, the operation will be aborted. As the forming process continues, the preform cylinder is retracted and the main forming cylinder completes the operation under closed-loop force control. When the proper force has been exerted on the part, the forming cylinder is retracted and the cycle is complete.
Selecting a Motion Controller
As described, the forming process requires precise control and monitoring of many factors through the operating cycle. In order to accomplish this, a motion controller was needed that has digital I/O capability in addition to interfaces to proportional servo valves and pressure and position sensors attached to the cylinders. To fill this need, Multipress, working with Delta Computer Systems distributor Advanced Industrial Products, Columbus, Ohio, selected the Delta RMC75E. ¡°We¡¯ve used Delta Computer Systems electrohydraulic motion controllers on many of our press designs over the last few years,¡± says Barney Raye, president of Multipress, ¡°so selecting a Delta motion controller was a natural step for this new bearing press.¡±
