Pinball Wizards Bank on FEA to Redesign Game

	Stern engineers modeled a drop-target assembly in ALGOR. The above image shows the target being struck by the pinball and the stresses on the arm during impact. Stern engineers then compared high-speed video with ALGOR analysis results and confirmed that the drop target needed to be strengthened before use in one of its recent games.
	After modeling the event in ALGOR, the part was redesigned. In fact, the new target assembly barely resembles the previous part. The hardware was changed, and while made of the same material, the target itself has been flattened and simplified.
	Stern Pinball, Inc. is the only manufacturer of coin-operated pinball machines in the world. Shown above is its latest pinball machine, GRAND PRIX. The main feature of GRAND PRIX is a loop that runs around the entire playfield. Energized by magnets, the loop sends pinballs racing around it like cars racing around a track. The GRAND PRIX pinball machine is available with English, Spanish, French, Italian and German voice and visual language response.

Housed in a single, 40,000-square-foot building in Melrose Park, Illinois, Stern Pinball, Inc. is the only manufacturer of coin-operated pinball machines in the world. Stern has either purchased, outlasted or excelled over all of its competitors and now enjoys an exclusive market position thanks in large part to a tradition of technological innovation. Today's pinball games are designed using sophisticated computer simulation software including ALGOR's finite element analysis (FEA).

Using 3-D modeling tools to create many of the typical game parts, Stern employs four mechanical engineers and numerous designers to create state-of-the-art pinball machines that include English, Spanish, French, Italian and German voice and visual language response. Each new game takes about a year to design. Stern employs 63 core staff members augmented by up to 200 temporary employees who produce up to 55 new games per day. Stern designers challenge themselves, employing competition among design teams, to develop innovative, exciting new games such as its recent GRAND PRIX pinball machine. Stern recently used ALGOR FEA software to analyze a mechanical assembly that was failing during use in one of its games.

Stern designers ran into problems with a part known as the “drop-target assembly,” a mechanical assembly on the pinball playfield. The assembly consists of a plastic target that retracts beneath the playfield when struck by the solid metal pinball. The idea of the game element is to strike the target and then redirect the ball up the ramp to score points. In the new game, the drop target was placed, without backing, in front of the ramp. When struck by the ball at near-maximum speeds, the testers found a high incidence of breakage in the target.

Mechanical Event Simulation (MES) and Real-World Pinball

John Rotharmel, Stern Project Engineer, designs most of the games’ unique elements. Previously, the company exclusively used Cosmos Express to model such parts. But from his experience using FEA software, Rotharmel knew that ALGOR would be necessary for the dynamic analysis of the moving target. So, he purchased a personal copy of ALGOR to evaluate the drop-target design and showed his design to Stern Pinball, Inc. President, Gary Stern.

Recognizing the value of ALGOR analysis, Stern asked Rotharmel to investigate the product more thoroughly. Convinced that Mechanical Event Simulation (MES) software was necessary, the company purchased ALGOR Professional MES, which combines large-scale motion and stress analysis and includes linear and nonlinear material models. The combination of motion and stress analysis considering full inertial effects allows engineers to see motion and its results, such as impact, buckling and permanent deformation. Having never before used MES, Rotharmel was pleasantly surprised at how easy it was. “It was simply a matter of knowing what parameters to use to set up the model, how to make sure you choose the right components for the assembly, how to test the proper criteria using comparative analysis, changing the ball velocity and so forth.” After experimenting, he quickly began to model and analyze the action of the ball against the target.

Around the same time, the company also purchased a high-speed video camera and Rotharmel recorded the action of the ball as it struck the drop target. Stern engineers then compared the high-speed video with the analysis results. After several iterations, Rotharmel realized that he had successfully modeled the event quite closely. “The event in ALGOR and the real-world event were remarkably similar,” said Rotharmel. The company was able to confirm that the drop target needed to be strengthened before use in one of its recent games.

Redesigning the Target

Using the results of the analysis, the part was entirely redesigned. In fact, the new target assembly barely resembles the previous part. The hardware was changed, and while made of the same material, the target itself was flattened and simplified. Using ALGOR, Stern engineers also cut the cost of designing and engineering the part. “We are the only game in town, but we never want to be complacent about our product. ALGOR helped us keep our commitment to quality, innovative and robust games that challenge game users but won’t break during use,” said Rotharmel.

John Rotharmel immigrated to the US from France in the 1970s after graduating from the University of Metz with a degree in Engineering. Before assuming his current position as Project Engineer at Stern Pinball, Inc., Rotharmel worked in numerous industries. He first used ALGOR six years ago to design power tools and was responsible for bringing ALGOR to Stern Pinball four years ago.