Unlike the carpenter’s dictum of measure twice, cut once, metalworking requires constant attention to dimensions, surface finish and other specifications, often in-process, in high volumes and in less than pristine environments. Chances are, there’s no second chance.
“We’re working with a high-volume Tier 2 supplier where we have to inspect every single part, make the measurements, and pass it along or fail it,” says George Schuetz, director of Precision Gages at Mahr Inc.. “The trend is more and more OEMs are making less and less components, passing along the responsibility to the tiers.” This makes designing and delivering a measuring system that can address custom requirements, along with ever-present cost concerns, the issues of the day.
One way Mahr approaches system design is through modular components in a product group it calls “MarSolution.” Schuetz recommends thinking of the process like working with an Erector Set. Whether the tasks require outside measurements, inside measurements or length measurements, even in inaccessible workpiece geometries, standard elements of gages, probes, indicators and transfer mechanisms can be adapted to a wide variety of testing requirements.
Measuring tasks on shaft elements, for example, can include cylinder form, straightness, parallelism, roundness, perpendicularity, and total radial and axial runout.
Options exist of creating your testing device yourself by purchasing the standard elements out of the catalog or having Mahr realize a turnkey solution. Given the talent and knowledge, maximum economy favors assembling your solution from standard elements. Factors include:
• Choosing from various techniques for guiding the movable part of the measuring inserts, depending on accuracy requirements (optimal price-performance
• Shortened times for project planning and realization.
• Component availability.
• Reusability. If production of one type of workpiece is discontinued, all standard elements can be reused to create a new testing device for another.
Example 1: Shaft Measurements
Consider the need for a system that measures multiple diameters and lengths on a gear shaft, along with form characteristics, concentricity and runout. The system must also be adaptable to part variations and operate at the machine tool in a tough, high-volume environment.
One MarSolutions response could consist of the following: a custom two-station gage built from standard Mahr length gages (station one) and a motorized gage for diameters and form (station two). Add a PC for control and data collection and the system is ready to be integrated into process automation for loading and unloading, no operator required.
“Such a solution measures and qualifies shafts in seconds at the point of manufacture,” Schuetz says. “And because the gage was built entirely from off-the-shelf components, the custom solution met the customer’s requirements for reliability, accuracy, and quick pay-back.”
Example Two: Turbocharger Compressor
Another customer needed to measure critical bearing diameters in a turbocharger during machining. The gage had to be loaded automatically by robot on the production floor and provide process control information to the workcell’s PLC.
Mahr configured an automatic measuring gage dedicated to the turbocharger compressor using standard elements and LVDTs (linear variable differential transformers). The gaging computer was programmed to interface with the workcell PLC for control and qualification in process. A robot places the part into the loading station and the gage takes over, moving the part into the gage station for measurement.
The result is a robust, 100 percent automated system inspecting thousands of parts per day in a very dirty environment, Schuetz says. Gage results are documented and monitored daily.
Attention to quality details will only grow with automobile sophistication, Schuetz confirms. “Years ago, we interfaced with a gage guy. Then it was a quality control person. More and more we’re working with process engineers interested in electric motors, for example, with higher-revolution parts and much less noise. Gaging can be one of the last things process people may consider. Having a wide base of standard elements helps us approach each question with a custom solution.”
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