Reverse Engineering for Improved Performance
“When working on $350,000-supercars we have to determine how we can engineer our products to outperform what the OEM produced,” says Tony Wells, product development manager at Fabspeed Motors, a shop in Ambler, PA, that specializes in working on exhaust systems for Porsche, Ferrari, Lamborghini, and Maserati owners.
The company produces several header manifolds and complete exhaust systems that can boost the performance of vehicles.
One of the challenges of creating exhaust systems is that the bends are exceedingly complex. Even though the company invested serious money in a Unison Breeze CNC tube bender that provides the capability of bending a single pipe with various tight radii rather than having to bend, cut, and weld pieces together, they discovered that given the available space under a car where the exhaust systems snake, a bend that’s off by only a few degrees results in the tube being scrapped.
So they purchased a ROMER tube inspection system consisting of a shop floor capable, Infinite 2.0 portable arm CMM and non-contact infrared tube inspection probes. The ROMER tube inspection system, with its optional Data Overlay Camera System (DOCS) software, was developed, manufactured, and is currently supported by Hexagon Metrology (hexagonmetrology.us). In addition to tubes and wires, the system also has the ability to inspect profiles such as brackets, flanges, bosses or other geometric forms aiding in the inspection of the entire exhaust assembly.
To reverse engineer an exhaust system, the team positions the ultra-lightweight, portable measuring arm under a vehicle that’s positioned on a lift and measures the existing system. The Fabspeed operator passes a tube probe over each point of bend change, in sequence, from one end of the pipe to the other. The probe’s visual guidance, via a red laser stripe, indicates where points have been taken while the infrared sensor “sees” and acquires 3D coordinates.
This under-the-car exercise might seem cumbersome, but the portable arm’s pneumatic Zero-G counterbalance offsets its weight and the device moves around easily like a human arm. The Zero-G counterbalance also helps to reduce fatigue when an operator is working high above the arm’s midline, and eliminates the tendency of the arm to flop during operation, preventing unintended crashes. Audio feedback confirms the points measured are sufficient for a given step in the part program.
Once measurement data are collected, the software compares it to the theoretical data. After adjusting the CNC bender, the next pipe produced conforms to the desired specifications. “The time saved is the key factor,” Wells says. “What used to take days now takes hours. The percentage of scrap tubing has almost been eliminated entirely.”
Fabspeed also decided to purchase traditional tactile ball probes to measure components bordering the exhaust path. This capability proves invaluable for the production team as it facilitates the inspection of surrounding features and gives them the ability to approximate the shape and orientation of the original components. Fabspeed has further reduced inspection time as non-contact tube probes can be easily exchanged with ball probes without re-calibration. Multi-sensor part programs combine data collected from the tube inspection probes or ball probes into a single inspection program to facilitate analysis of the information.
Additionally, by measuring where surrounding parts are located in 3D space, the company is able to export the results into a third-party CAD based software platform to obtain a virtual representation of the exhaust pathway. The software integration allows them to virtually test various design ideas.
Laser Scanner Provides Tactile-like Measurement Accuracy
The LC15Dx digital laser scanner for CMMs from Nikon Metrology (nikonmetrology.com) is designed for measuring high-precision parts and complex geometries. It has the capabilities to bring laser scanning in the accuracy range of tactile inspection.
With its solid-state laser scanner technology, calibration method, and Nikon lens, the LC15Dx achieves a probing accuracy of 2.5µm (0.0001 in.) and a multi-stylus test accuracy of 6µm (0.00024 in.) in tests comparable to EN/10360-2 and -5. A thermal stabilizer inside the scanner body eliminates uncertainty and delay caused when the laser scanner is used before reaching operating temperature.
When measuring the surface of a workpiece directly, probe tip compensation errors are eliminated by the use of non-contact triangulation between the laser source, workpiece, and CCD sensor. To collect data, the LC15Dx passes over the workpiece mounted on a CMM and a laser line is projected onto the surface. The line measures 70,000 points per second at intervals of 22µm (0.0008 in.). As the entire part is checked to the design-intent CAD model, any areas of concern are highlighted using color mapping. Further investigation and analysis is possible using fly-outs, sections, and a library of geometric dimensioning and tolerancing (GD&T).
The scanner is capable of measuring a range of surface materials, finishes, and colors, without manual tuning or part spraying. Unwanted reflections are neutralized by a software filter while changes in ambient light are absorbed by a high-grade daylight filter. In situations where a single-sensor technology is insufficient for measuring all features, the LC15Dx can be combined with a tactile probe and change rack to create a fully automated multi-sensor CMM.