Zeiss aids General Motors in the design and manufacture of custom probe tooling.

ThermoFit Pro components do not have threads but instead are conjoined by plug-in connections and are then screwed from the backside of the cube. Source: Carl Zeiss Industrial Metrology

Designing stylus systems in the Stylus System Creator (SSC) is as easy as using building blocks. Source: Carl Zeiss Industrial Metrology

GM Casting Engine and Trans-mission Center (Pontiac, MI) had been successfully inspecting parts with Zeiss coordinate measuring machines (CMMs) for several years and was looking to accelerate and globalize the design and manufacture of the custom probe tooling to be used on the CMMs for a new project spanning across its facilities in North America. Using the Stylus System Creator and the new ThermoFit Pro components from Carl Zeiss, GM entered into the era of advanced probe tooling using flexible stylus systems and stylus simulations.

For years, offline quality inspection programming has been a well-known method of developing the launch of production processes. It frees up the CMM for existing measurements and speeds up the programming process on a dedicated offline station. But, the design and manufacture of custom probe tooling for CMM operation was still time consuming. It required CAD modeling of many new components. These custom probe tools required a CAD engineer and a significant amount of time for any last minute changes. They were also difficult to document and often came with long delivery terms.

The CMM and gage engineering group of the GM Casting Engine and Transmission Center is a centralized team of about 10 CMM programmers and engineers responsible for supporting all of the North American quality inspection labs for their next generation of 4-cylinder, V8 engines. There are nearly 150 Zeiss CMMs dedicated to this project, mostly Accuras and Prismos, at various production facilities in the United States, Mexico and Canada. This team designs CMM probe tooling and writes inspection programs for this new project and wanted more control over the reproducibility of components at all locations, reduced design and manufacturing time for tooling, and simple and quick tooling modifications for product changes.

Carl Zeiss 3-D Automation, part of the metrology division of Carl Zeiss, first visited the GM Casting Engine and Transmission Center in 2010 and introduced new probe extensions with rotary joint systems. GM liked the thermal stability and carbon tube design, but was looking for fixed machined extensions for more control at their remote inspection labs. The company also wanted some interchangeability if a probe configuration change was needed. For this next generation project, the CMMs purchased were specific to the lifecycle of a particular component. Since the lifecycle could be five or 10-plus years, depending on the product line, the company also wanted durable probe systems that would last and that could potentially be reused at the end of the project. After collaborating and testing probe tooling samples with GM, Carl Zeiss 3-D Automation completed development of and launched its next generation probe tooling, called ThermoFit Pro, in 2011.

The GM Casting Engine and Transmission Center started using its first ThermoFit Pro modules in June of 2011. The new product line enables GM to build up even the most complex stylus system using the Calypso stylus simulator without the need for typical custom designing in CAD. Generic angle blocks can be modified in the software to the desired angle by simply choosing the according angle values. The real angle blocks are then quickly manufactured from semi-finished parts. The finished angle blocks can be machined either by Carl Zeiss or if desired by their own tool shop, as the semi-finished parts are available from stock. Each piece gets a Zeiss part number for easy documentation and reordering.

No CAD engineer or drawing is needed and everything can be done by its own application engineer within the Stylus System Creator. “I’m very impressed with the development of the Calypso simulation and Stylus System Creator using ThermoFit Pro modules,” says Craig Wegienka, senior manufacturing engineer at GM Casting Engine and Transmission Center. “I was able to use the Stylus System Creator to create the entire set of block and head tooling for our project. I simulated each individual probe configuration in Calypso to verify the tooling. The simulation proved that all tooling would work correctly.”

The library of the Stylus System Creator contains more than 1,200 different styli, extensions and connecting elements, plus additional tools to create virtually every kind of custom probe tooling. With the help of different sized cubes and bars, even the most complex system can be designed and built quickly. ThermoFit Pro modules have plug-in connections instead of threads to help avoid angle distortions when exchanging worn styli. Even whole branches of the stylus systems can be exchanged without having to readjust angles. GM has about 13 sets of ThermoFit Pro tooling, each with approximately 15 different configurations. “All of these options and the ease of use reduce our probe tooling design and manufacture time by about 40%,” states Wegienka. “It saves us not only time, but also money because we don’t have to scrap probe components when there are changes.”

The task for GM to guarantee reproducibility of its products by having the same quality results-regardless if the parts come from a plant in Bangalore, Shanghai, Detroit or Sao Paolo- is a big challenge as varying employee skill levels or the availability of spare parts can cause production delays. And product design changes require program and probe tool modifications along with documentation changes. GM can now rely on the ThermoFit Pro modules and the Calypso Stylus System Creator to globalize quality control programs and reduce product launch time, while also quickly adapting to any product changes.

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