Composites Manufacturer Produces More Parts with Verisurf

"“The traditional method works, but it’s slow and not very accurate. The FaroArm offers accuracy comparable to fixed CMMs and software that is fully programmable for repetitive measurement so it greatly increases both the speed and accuracy of the inspection process. The result is that we are able to get more parts out the door with the same people while maintaining higher standards of quality.”

Unitech Composites and Structures, a division of the AGC Aerospace & Defense Composites and Structures Group, designs and manufactures composite structures in commercial and military aerospace markets. Most of these parts have critical dimensional and structural requirements so an exacting 100% inspection process is required. In the past, the company used traditional inspection methods which involved using hand tools for measurements and manual calculations to determine deviation from true position.

Now, the company uses a FaroArm®, a portable coordinate measuring machine (CMM), to capture points while Verisurf software uses best fit algorithms to instantaneously compute true position deviation. “We are in a business where everything we make needs to be carefully measured to ensure it meets our customers’ critical specifications,” said Alan L. Haase, President & CEO, AGC Aerospace & Defense Composites and Structures Group. “By using the FaroArm we are getting significantly more parts out the door with the same staffing.”

Traditional Methods Too Slow

“The parts and assemblies we produce are installed in high performance aircraft and there is little room for error,” Haase said. “Making sure these parts and assemblies meet and exceed customer specifications can quite literally be the difference in a successful flight or mission for our armed forces.” One of the most critical challenges is measuring geometry design and tolerancing (GD&T) features including the deviation from true position of features. The manual methods used in the past were time-consuming and subject to potential errors. Calipers, height gauges, micrometers and other hand tools were used with an inspection plate to make measurements and compare feature position to three datums. The first step, in the case of a hole, for example, was to measure its diameter. Next measurements were taken of the hole’s closest and further positions to the x and y axes in order to determine its Cartesian coordinates. The deviation D of the true position from the position called out in the drawing was then calculated using the equation D = 2√(∆x)2+(∆y)2 where ∆ equals the measured deviation in each axis. This cumbersome procedure took about 20 minutes even for very simple measurements.

Another problem with the traditional approach is that it requires someone with both math and blueprint interpretation skills that are often difficult to find in today’s workforce. “I am old school so I still know how to manually calculate true position based on manual measurements,” said Tom Van Der Griend, Director of Quality for United Composites. “But workers with these skills are becoming harder and harder to find.”

Many of Unitech Composite’s customers have moved to a model based design (MBD) or digital product definition (DPD) approach in which the dimensions, GD&T, annotations and parts lists are inserted directly into the solid model, eliminating the need for drawings. The live 3D model with a prescribed series of annotated and dimensioned views is provided to United Composites instead of blueprints. In order to support MBD using traditional methods, it was necessary to get multiple layers of the organization involved to read the model, convert the model to 2D drawings and then inspect to the 2D conversion.

FARO Arm and Verisurf Software Speeds Process

“It became obvious that we needed to find an inspection method based on MBD and DPD,” Van Der Griend said. “We looked at laser scanners and CMMs. Laser scanners are powerful tools but they require a considerable amount of manual effort to perform a true position inspection. On the other hand, the FaroArm and Verisurf software provide a truly seamless solution that can be programmed to dramatically reduce the time involved in inspection while also reducing the potential for error.” In the case mentioned above of determining the true position of a hole, the operator clamps the part in place using simple tools because the part does not need to be accurately positioned. The operator captures data points by using the device’s probe. The FaroArm determines and records the location of the probe in 2D space and reports the results through software. The rotational angle of each joint and the length of each segment in the arm is determined using optical encoders that count rotations incrementally via detection of accurately spaced lines on a glass grating disc. Software converts the counts into angle changes and determines the position of the probe. The device’s laptop computer simultaneously illustrates the 3D measurements on-screen and records all of the data.

The operator begins by taking several points along the datums to accurately establish the position of the part. The process is repeated for the hole. The software then dimensions the position of the hole. When all of the points are taken, the user pulls away from the part. The entire process takes less than five minutes.