Where CAE meets inspection devices: size and distance pose no problem.
The business realities of today's manufacturing industry-tough competition and the race to consistently maintain quality in their end product - has accelerated the need for faster, more efficient methods in verification. The evolution of such technologies has reached dramatic crossroads.
Software and hardware device developers working in tandem have responded to the challenge by identifying the obstacles in production processes and by developing state-of-the-art solutions. These new-generation quality verification tools deliver accurate "decision-making" information that enables the engineer to make confident tooling corrections and design modifications. By streamlining fit and function part evaluation and eliminating rework and production line shut downs, manufacturers today can truly add value to their product lines while protecting their bottom line.
Ultimate verification world
Ideally, the ultimate verification solution is one where cost-effective software products support a variety of inspection devices. Ease of use must be one of the main features of the system, giving all pertinent shopfloor and Quality Control personnel the ability to perform "on-demand" analysis. The verification system must operate on both desktop and laptop computers, and interface with every portable or standalone CMM inspection device. It would quickly connect to a company's internal network and bidirectionally share CAD file formats.
The system must integrate well in the shopfloor environment, QC departments, and even in the field with source inspectors. It would cover the entire range of verification applications, such as point-to-point analysis for part tools, jigs or assemblies, and perform real-time analysis. Point-to-surface and surface-to-surface analysis would also be accomplished using single files or performed dynamically.
The CMM operator would use the software program to create vectors on the CAD model, select CMM formats on the fly, program, and simulate each move. After programming, the operator could perform all of the required analysis tasks and generate reports. The text reports would provide point numbers, labels, surface descriptions, and could be customized. Graphical reports would display point numbers, labels, alignment datums, and deviations in 3D color, providing complete documentation on any inspection project. "Best-fit" analysis of the part would allow for better alignment of the coordinate systems, and in many cases salvage a job that was originally tagged as out-of-tolerance.
Built-in CAD features are also very important for a verification system. CAD capability allows the operator to visualize, manipulate, and clean up 3D CAD models of the inspected part, jig, tool, or assembly. Tasks such as reversing surface vector normals, masking or moving isolated geometry to layers, deleting unwanted entities, generating vectors, or even adding or extending surfaces could be performed right on the shop floor.
Next generation inspection
A coordinate measuring machine (CMM) is a device which collects 3D coordinate point data from a machined part and converts the information into CAD-usable data. The surface capacity of a traditional CMM may be several inches to many feet, with tolerances ranging from 0.001" and up. In the past few years, a whole new generation of inspection devices - Laser trackers, motor-driven Theodolites, and Videogrammetry systems - have entered the marketplace offering dynamic or noncontact inspection capabilities. Surface areas for these systems may be up to hundreds of feet and can target large scale products such as aircraft, ships, and building structures.
A manual 3D CMM, such as digitizers from FARO, Romer, Immersion, and Brown and Sharpe, allows the user to freely define the setup for gathering point data and cross-sections from a model. A basic input device could be a hand-held Microscribe, which turns a digitizer into a 3D mouse or a stationary device such as a CMM. At the high end of the CMM price range, these devices will automatically gather point data; scan the profile of a physical model; and generate "a cloud of points" or series of cross-sections. The user can control the number of "slices or cut planes," the distance between intersections, and tolerance factors.
At the high end, Leica's new generation of laser tracker, the LTD500, is a precise (to 0.001[inches]), portable, 3D coordinate measuring system for close-tolerance, largescale inspection. The LTD500 allows a single operator to accurately measure single points or scan entire surfaces. In addition to a laser interferometer and angle encoders, the LTD500 features a patented Absolute Distance Meter, which enables both automated inspection and point-and-shoot measurement. Shooting to a range of spherical retroreflective targets, some as small as standard tooling balls, the device can continuously measure at a rate up to 1000 points per second, based on user-defined time, distance, or grid measurement criteria. The reflector can be mounted on machine tools or robotic arms to record continuous movement and provide a real-time machine interface with laser accuracy.
The precise, yet portable LTD500 Laser Tracker can be wheeled into position and quickly tied into the coordinate system of the object to be measured. With minimum production downtime, even large tools, jigs, and fixtures can be quickly inspected and compared to nominal values or CAD models. Laser tracking systems are used for inspection, building, reverse engineering, and machine control applications in various industries - aerospace, automotive, railway construction, telecommunications, and more.
V-STARS from Geodetic Services Inc is a product line of digital photogrammetric (also known as videogrammetry) systems used for a variety of industrial applications from tool and part inspection to surface measurements. To obtain dimensional information about a part, the object is photographed from at least two viewing directions with digital cameras. The digital images are processed by powerful image processing software, and a photogrammetric-bundle-triangulation provides the 3D coordinates and statistical information for each measured point.
In V-STARS' off-line mode, targets are placed on the object or at a relative position to the points of interest. A single camera is used to photograph the object sequentially from several viewpoints. The camera can be directly connected with a laptop or notebook computer, which is useful in remote control applications. V-STARS also has an on-line mode where the object is photographed simultaneously with two or more cameras from different viewing locations. The images are processed immediately after the images are shot, and the measurement results will be provided within seconds. Using a small, wireless, hand-held probe that is targeted and has a standard CMM tip attached, it is possible to measure objects without targeting them. From calibrated locations of the targets on the probe, one can readily derive the location of the probe tip.
Software for inspection, analysis
VERISURF "ANALYSIS" (Verisurf Software Inc, Anaheim, CA) is a good example of a Windows-based multisurface inspection and analysis software program that aids in manufacturing quality control. Using data collected from a wide variety of supported inspection devices, the software accurately compares a machined part with a 3D CAD model of the part, while drastically reducing the need for a fully dimensioned 2D drawing. CAD models can be imported from virtually any CAD system, or if a CAD model is unavailable, the quality control staff can quickly create a 3D model from blueprints using 2D and 3D CAD drawing tools.
Once the part has been measured and the deviation between the 3D CAD model and its corresponding inspection data has been analyzed, easy-to-interpret topographical color and text reports show which points on the part are in or out of tolerance. A Color Legend shows the amount of deviation in different shades. For example, shades of red represent Negative (out of tolerance) deviations; shades of blue represent Positive (out of tolerance) deviations; while points within the set tolerance limits are displayed in green.
A unique "Bestfit" feature included in VERISURF "ANALYSIS" helps align the coordinates of the inspection data to the CAD model with up to six degrees of freedom. The software program will continuously rotate the point cloud data from the inspection device over the CAD model until the "bestfit" is achieved. This feature enables manufacturers to save parts they may have previously scrapped by assuming the parts were out of tolerance. Companies can document or verify that a part is within tolerance, helping them certify ISO9000 compliance. "Bestfit" has dozens of options, including the ability to lock any axis or combination of axes during the operation while allowing the remaining axes to move freely.
Multiple surface vector control
To streamline the verification process, assistance from the engineering department is no longer required to create vectors on the 3D model for programming a CMM. The "teach" method allows the operator to collect random points with the inspection device and bring them into VERISURF "ANALYSIS" to automatically create the vector normals which are required for vector approach programming.
The program also supports a "CAD" method where inspection points can be created on the CAD model in many ways. For example, the operator can dynamically link to the surfaces using a mouse and select the points for measurement; or the user can create a grid of points on the surfaces. After the points are designated, the software will generate a vector file that can be formatted for DCC programming.
On the horizon
With the cooperation of inspection device manufacturers in providing open architecture and other methods of integration, software developers have made tremendous strides in verification technology to meet the multifaceted needs of the manufacturing industry. It is now possible to have an unlimited number of different inspection devices dynamically integrated even in a multiple, simultaneous use situation.
The future of verification technology depends on communication, commonality and compatibility in inspection departments throughout the manufacturing environment. Like mediators, software and hardware companies relay what we have learned in each department, share our problem solving techniques, expose overlapping efforts, and present new ideas. By pulling all of this process together, the uniformity and ease of use can only streamline the entire verification procedure making any manufacturing company more efficient and profitable.
For more information from Verisurf Software, Anaheim, CA, circle 431; http://www.verisurf.com
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|Title Annotation:||computer-aided engineering|
|Publication:||Tooling & Production|
|Date:||Jul 1, 1998|
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