MODIFICATION TO GENERAL MOTORS POWER PRESS ANALYZED WITH ALGOR FEA SOFTWARE

Danly engineers built a computer-generated solid model of the press bed with added cut-outs using Solid Edge by UGS, captured the CAD model using ALGOR’s InCAD technology and performed a linear static stress analysis. The calculated von Mises stresses were within Danly’s standards for safe operation and fatigue.

Americans love their cars as much for their looks as for their performance. Automotive manufacturers create the curves and angles of car bodies with stampings produced by power presses. These presses form flat pieces of metal into the shapes we love to love. Recently, General Motors (GM) contacted the Danly Engineering Services Division of Enprotech Mechanical Services, Inc. about a modification to a Danly U4-1000-132-84 power press located at a GM stamping plant to accommodate a different type of die. Engineers at Danly used ALGOR Finite Element Analysis (FEA) software to analyze the modification to the 1,000-ton capacity machine. 

A Danly U4-1000-132-84 power press was installed in a GM stamping plant in 1955. Engineers at Danly recently used ALGOR Finite Element Analysis (FEA) software to verify that the addition of cut-outs to the bed of the power press would not compromise the structural integrity of the 1,000-ton capacity machine that is used to trim and shape automotive body parts.

Today’s manufacturing methods require more versatility in power press production systems and, in this case, the customer wanted to combine a trim function and a forming function in a single die. In order to do this, scrap removal cut-outs had to be provided in the heavy, load absorbing plates of the press bed while maintaining Danly’s strict deflection standards.

Gabe Buzas, a Danly engineer, built a computer-generated solid model of the steel bed with added cut-outs using Solid Edge by UGS. “We did a similar modification on a different press bed a few years ago, so I had an idea of approximately how big the cut-outs could be,” said Buzas. The Solid Edge model was then captured for analysis using ALGOR’s InCAD technology. An automatic, 20,000-element hybrid mesh was created consisting of bricks on the surface and tetrahedral on the inside. 

“ALGOR’s InCAD technology helped us to save a significant amount of time in acquiring geometry for FEA,” commented Danly engineer Dan Weber. “We were able to justify the cost of the InCAD software because of the time we saved on this project alone.”

Danly engineers determined that a linear static stress analysis would be sufficient to verify the structural integrity of the modified bed with cut-outs because dynamic effects are negligible compared to the 1,000 tons of load exerted by the actual stamping process, and because the stresses were expected to fall well within the linear range of behavior for steel. Forces were applied on either side of the top of the base to simulate the 1,000 tons of load. Fixed boundary conditions were applied where the press feet attach to the bed. The press feet anchor the entire machine to the plant floor. 

After the analysis completed, Danly engineers reviewed von Mises, maximum and minimum principal stress and displacement contours. “Danly has been in the power press business for decades and follows both industry standards and proprietary standards for stresses and displacements that are largely based on field experience,” explained Weber. “We design to keep the stresses quite low in order to meet deflection standards.” The analysis results for the modified machine were within Danly’s standards. 

Today, the modified power press is successfully in use at a GM stamping plant and Danly engineers have moved on to simulating motion and resulting stresses with ALGOR’s Mechanical Event Simulation (MES) software. “The analysis of the modification to the power press bed was easily solved with traditional linear static FEA,” explained Weber. “Many of our other projects are dynamic in nature and will therefore require MES, which combines kinematics and FEA to provide motion and stress results in a single process.”