Flexible, Accurate and Fast Measuring

Check fixtures have been around for a long, long time. And it may be time for you to get an up-to-date alternative.

Automation using standardized parts helps increase product throughput, reduce labor costs, establishes and maintains elevated quality standards and improves workplace safety. Business-case benefits include meeting more delivery dates, better utilization of capital budgets, improved material flow and a more efficient plant footprint.

Inspection and quality control remain critical, and in this area you can still see remnants of the hand-work and assembly process bottlenecks of yesteryear, particularly check fixtures. Otherwise known as “manual fixed gages,” check fixtures are often seen in use for automotive closure panels such as doors, hoods, deck lids and others. Generally, they are large and heavy, designed for single-part use, involve long lead times to obtain, and produce limited data sets. Make any engineering changes to the part or try to correct any dimensional shortcomings to the fixture, and you’re in line for the tedious but necessary process of grind, check, grind, check and repeat until satisfactory.

Data Flexibility Through Technology
If check fixtures are a part of your process, or even if you’ve graduated to more advanced laser checking or photogrammetry measurement methods, automated inspection cells are still worth investigating. Not only can one cell replace numerous traditional check fixtures, powerful software brings much more useful data in addition to merely checking dimensions. “One automated cell can accommodate every closure panel you might manufacture through straightforward reprogramming without adding hardware,” says Don Manfredi, business development integrated solutions for Hexagon Manufacturing Intelligence (hexagon.com). “Once I acquire original data, I can easily manipulate my point cloud in different ways to cover any number of alignments or views without rescanning. I can look at discrete points, entire surfaces, can go to virtual assembly exercises, or even re-engineer existing panels.”

Build up an archive of scans and the inspection data moves beyond quality control and can help improve future models. “Visual 3D color mapping analysis in a simple red-yellow-green format lets me easily share product issues with others without relying on columns and pages of dimensions and figures,” he adds. “This makes the data ideal for pre-production studies or solving production issues.

All of this can be achieved without a dedicated person standing over a fixture with a feeler gage manually recording results.”

What’s the Right Inspection Technology?
Inspection and metrology technology suppliers offer a number of technologies suitable for automotive component inspection. Coordinate measuring machine (CMM) inspection is a standard in the powertrain and automotive component manufacturing process, portable measurement systems like 3D laser trackers and articulated measuring arms take accuracy and precision to all areas of vehicle plants. Automated in-line white and blue-light scanning systems enable entire car bodies to be measured in minutes, and the resulting data-acquisition speeds are moving inspection from offline stations to near-line and even inline applications.

One size does not fit all, Manfredi says. He suggests a number of points to check off in determining what’s right for you:
  • What needs measuring and what is the right accuracy for your needs? Are there multiple or limited surface materials being measured?
  • What is the desired measurement speed for your operation?
  • Where will the system be located? Is a controlled environment necessary or will a plant-hardened solution work?
  • Will there be automatic or manual loading and unloading?

Going Cellular
In response to numerous checklists such as this, Hexagon is introducing a modular yet scalable piece of equipment called the 360° FMC (Flexible Measuring Cell). It can be configured with one, two or three rotary tables, and can mix or match optical scanning or laser scanning inputs, depending on product requirements. 

Pre-engineering a modular cell can greatly step up inspection tasks and data acquisition, Manfredi says. “I’m not limited to a single part, like a check fixture. I’m not even limited to a single material—the same cell can accommodate metals, plastics, and composites, painted or unpainted, shiny or matte.

Throughput is maximized because you can load and unload the idle inspection cell while measurement is taking place on another turntable. With up to three rotary tables per cell, measuring can even cover multiple components per table. With closure panels for example, I can check many measurements in the same image: holes, seal surfaces, hinges, cross-sections and more. Check fixtures move from physical to virtual and can easily be reprogrammed to address year-to-year or other changes.”

Pre-engineering also means that the FMC is built from largely commercial off-the-shelf components. After a cell is configured for your use, it can be delivered and set up typically within a week. No pits or foundations are required, so the cell can even be moved to pertinent areas of your production lines as needed.

Inspection data rapidly translates into improved manufacturing intelligence. “Acquiring data quickly and automatically builds in-depth digital archives that record changes over time,” Manfredi explains. “Take hemming for example. Looking at data over time can reveal how measurements change as tooling wears, making root-cause analysis and predictive maintenance faster, easier and more accurate.

As a result, I have more resources available for fixing problems as opposed to generating and collecting data.”