Strip Design and Development—Gaining Confidence in the Process

“We use simulation software differently than other tool builders might,” begins Jason Andras, design manager at Atlantic Tool & Die Co. (ATD), when asked to describe the firm’s recent uptick in inhouse die design and development. The 650-employee automotive-stamping and assembly company works out of numerous locations, including four in Ohio; plants in Texas and Mexico; a primary design and engineering center in Costa Rica; and a die-build, stamping and assembly shop in China. ATD’s facility in China produced 70 new stamping tools for ATD and other North American customers in 2013, generating $3.5 million. In 2014 it is projected to produce 100 to 120 new progressive dies generating $5 to $7 million.

We caught up with Andras, who oversees ATD’s die-design and development process, at its headquarters facility in Strongsville (Cleveland), OH. Up for discussion: its evolving use of 3D modeling and surfacing of dies and weld fixtures, based on its use of:

• VISI PC-based CAD-CAM software; 

• Progressive-die strip simulation using the Dynaform suite of software modules; and 

• Reverse engineering of cutting sections and forming details using a portable coordinate-measuring machine —a Faro ScanArm outfitted with a laser scanner.

ATD’s Faro ScanArm portable coordinate-measuring machine, equipped with a laser scanner, captures surface data and enables reverse engineering of die surfaces—new trim edges, for example.

ATD launched its foray into 3D design and development—of stamping dies and of weld fixtures to support its secondary operations—in 2005. The goal, says Andras, was to develop expertise in stamping and assembling more complex parts and assemblies, such as large rear parcel shelves and tiny yet complex airbag housings.

“While we’ve used VISI companywide for years primarily at our design center in Costa Rica,” says Andras, “we’re ramping up its use here in Cleveland as we look to retire various other software and consolidate to VISI. To supplement the eight seats of VISI in Costa Rica (two added in June of 2013), in the last two years we’ve acquired four VISI seats in Ohio (one at its Sharon Center plant, two seats in Strongsville and one in Texas), with more coming. One of the nice features of VISI our designers really appreciate is the ability to work in 2D and 3D—they can sketch in 2D and extrude in 3D, surface and model all in one. That’s been a great benefit.”

Accurate Simulation Starts with a Robust Material-Property Database

ATD’s ongoing design-software evolution also aims to improve its ability to accurately simulate new progressive-die strip models, and also to support weld-fixture development. Enter Dynaform, with modules for estimating blank size and predict thinning and thickening; create complete die-face models, including binder and addendum, from part geometry; simulate and validate die designs and identify problem areas, as well as optimize designs to reduce wrinkling, thinning and tearing; and analyze a completed die to provide insights into stamping-production issues such as scrap shedding and material handling.

“Simulation has become an important tool for us,” shares Andras, “as we seek to control the development of our progressive dies and simulate the process during strip development. We can easily flow data back and forth between VISI and Dynaform, to avoid excessive troubleshooting in the press, which can become quite time consuming and costly. 

“The real benefit to simulation for us,” stresses Andras: “Creating a robust forming sequence and strip layout that we can pass on to our tool designer and builder with confidence that the die will run in production almost immediately.”

ATD uses its ScanArms to scan some of its more intricate stamped parts, “to capture features not easily rendered with a conventional CMM,” Andras says. “We can scan tiny features, enlarge them on the screen and run cross-sections through them for metrology and color mapping of deviations.”

Moving up the learning curve as ATD engineers zero in on the benefits of Dynaform simulations, Andras points to the need to completely understand material properties in order to ensure accurate simulations. We’re talking yield strength coefficient, k, n and r values, yield stress, precent elongation, ultimate tensile, etc.

“We are creating our own library of material properties for the alloys we stamp, by sending material samples out for testing,” he says. “These are stored within Dynaform. This practice is particularly critical to accurate simulation results when forming our more sensitive parts.”

Last but not least, engineers working in the ATD design center in Costa Rica employ Dynaform further downstream in the die-development process, to develop press and energy curves for the company. “This ensures we can run specific dies in specific presses,” says Andras. “And, Dynaform can tell us, by calculating forming pressures throughout a tool, where we might need to tweak the tool, by adding nitrogen cylinders for example.”