It's not an inspection jungle out there, any more.
Perhaps you know the story of the five technicians who were sent to the jungle to inspect an elephant. Each inspector viewed the beast in a different way. One measured the tail and proclaimed it a rope. Another scanned a leg and said it was a tree. Other data pointed to a mountain wall (the elephant's flank), a snake (the trunk), and hollow logs (tusks). The data were then sent to company engineers for analysis. They needed six weeks to compare the data to the original plans. They determined that the beast was indeed an elephant. They could not, however, identify whether it was an African elephant or an Indian elephant, so a new inspection method was immediately ordered to check the size and shape of its ears.
Manufacturers have always been faced with the elephantine task of inspecting components and assemblies with precision. In the old days, plumb lines and micrometers were the standard tools, but now there are a multitude of high tech devices and paperless electronic 3D CAD model inspection software. Today's devices shown here include laser trackers, theodolites, DCC coordinate measuring machines (CMMs), videogrammetry, photogrammetry, and the latest breakthrough using inspection probes right on the machine tool, to name only a few.
To date, however, there has been no standard for integrating these new devices into the latest electronic CAD models. The confusion is costing manufacturers thousands of hours of lost time and millions of dollars in training and testing. One of my customers in a large aircraft factory describes its procedures and needs in this way:
"We, as a large aircraft manufacturer, and the inspection device manufacturers spend millions of dollars on inspection software accreditation or mathematical algorithm testing each year. Currently, each inspection device manufacturer goes through two tests to stay accredited with us. The first is a standard mechanical inspection device calibration and the second is the device software algorithm mathematical testing.
"Both of us would be wise to be a part of a common inspection software platform that would save millions of dollars in testing. A common inspection software platform would mean that only four mathematical algorithm tests be done each year, accrediting all devices per test, rather than what we are doing now. We are using nine different devices each of which has its own inspection software. Each requires testing with every new software release. Using a common inspection platform would mean conducting only one software algorithm test per quarter rather than nine tests every quarter at a cost of millions each year. Inspection device manufacturers would also like the fact that they only need worry about a simple mechanical calibration test, rather than being caught up in lengthy software algorithm testing that delays orders."
Data sharing on a PC platform
The common inspection software platform is a software package that runs any inspection device on the shopfloor and completes on-the-spot analysis comparing inspection data to the original CAD mode. The common platform provides off-line or on-line device integration for dynamic results, real-time surface analysis and "virtual" or "gageless" detail assembly of tooling fixtures, or large structures.
Such a powerful common software package with redlining or markup and drafting ability allows inspection personnel to import 3D CAD models in various native formats (i.e. CATIA, Unigraphics, ProEngineer, etc) and standard formats such IGES, DXF, VDA, ACIS, and the like. Solids, surfaces, and even critical inspection instructions that reside in the 3D CAD model can be imported from the model comments section from engineering at will. A device of choice can be selected and complete inspection tasks performed "on" or "off-line".
With a process like this, operators need be trained to only one system. Reports are uniform, mistakes are caught on the fly, and with redline markup and drafting or graphically documenting the inspection results, a major communications gap between design and "as-is" manufacturing can be achieved.
The common inspection software platform is a simple solution to a complex training problem. With new inspection technology leaping into play in the last two years, manufacturers are struggling to train their people on all of them. Because each device has its strengths and limitations, many manufacturers choose to have multiple systems in their plants. Each system requires about a month of training and about six months of practice to master. The ideal common inspection software would run on a standard PC using Windows 95, 98, or NT, and only require about a week to learn and a month to master. Once mastered, the technician could operate every single device in the company's possession by selecting the device of choice from a menu.
A plethora of benefits
Inaccuracy and complexity are two more issues that the common platform approach addresses. Each time data are collected on a different device, one has to worry about accuracy of the coordinates, accuracy of the device, and mistakes in handling the data. The more complex the system, the less accurate the data handling. Inspectors are told to err on the conservative side, so if a part is even suspected of being out of tolerance, no matter where the error lies, that part is often scrapped.
Using a common platform approach simplifies the decision-making. Only one person is required to conduct a full analysis of the product with whatever device works best. The common inspection software platform makes all the tough calculations, using intuitive graphic user interfaces. A common platform works in two ways: not only must it run every inspection device in the shop, it needs to compare all the data to a master CAD model and do it quickly and painlessly.
As with any new software application, we are finding that common platform inspection software also provides a variety of side benefits. Common platform inspection systems need to have CAD capabilities to work with the CAD models, especially models that make use of "layering," "notes," and "comments" etc. In addition to organization of a 3D CAD model, the model may also require some cleanup for the inspection process i.e. reversing surface normals, creating new coordinate systems, erasing unwanted geometry, creating vector normals for programming a DCC 0MM, etc. Engineering need not be bothered about these adjustments.
Most important, alignment of the device to the 3D CAD model is critical. Using multiple methods of "best fit" allows for quick alignment "on" or "off-line" to the CAD model. With "off-line" analysis, the part has its own coordinate system in which it was inspected. The model may be given in part or aircraft coordinates or, with a fast alignment method, reports can be generated in either coordinate system.
Tooling balls are not always available and the part may be shaped like a potato chip with not a straight line to be used for alignment. Using the CAD geometry and drag and drop methods in conjunction with "best fit" reduces this task of aligning to a minimum.
Engineering costs can also be dramatically reduced by using the actual CAD model surface for alignment, rather than having to add to the design, use tooling balls or optical tooling points, or consult with manufacturing on the ideal locations of these alignment points. This progressive solution is the next step; products may now be measured where they lie, without difficult repositioning.
Assembly work, too
Common platform software is not only for inspection--it can also be used for assembly work. When two parts are mated, they need to be positioned within a specified tolerance of the original CAD model. A part or detail of an assembly may need microscopic adjustments in one direction or another. Laser trackers, mechanical arms, and videogrammetry devices provide real-time measurement. Packaged with a dynamic common inspection software platform, they create a completely "virtual" or "gageless" tool-building or part detail assembly solution.
The common platform lets assembly workers read deviations right from a nearby PC computer. This singular solution allows assembly of high precision, hard-to-maneuver parts as if they were large Tinker Toys.
The preferred common platform solution is a PC software package, a simple and compact system for operating very complex inspection devices. An inspector with a laptop computer can go anywhere on the shopfloor or even in the field, plug in the data or the available real-time device and complete the inspection process in short order. Scripting, macros, and other graphical methods of the predefined inspection process also streamlines routine inspection jobs.
Common platform software also coordinates multiple, concurrent inspection devices. As an example, a laser tracker can measure the outside of an assembly while a mechanical inspection arm is measuring the inside using one computer and one CAD model. The common platform ties all the data together into one set of data points and analyzes the full shape against the original 3D CAD model. This multiple device flexibility is of great benefit, when dealing with a complex assembly.
The concept of a common platform is not radical at all. CAD/CAM packages have had common platform solutions for a long time. There are any number of tooling, milling, and manufacturing machines, all with separate drivers, but most of the CAM software packages have integrated all of these driver interfaces. Inspection devices are no more difficult to interface. Any new device that comes along can easily be integrated with a driver interface. Once the benefits of common platform software are fully and widely understood, no doubt the makers of inspection devices will clamor to have their products included in the interface menu of a powerful common inspection software platform.
We no longer live in a jungle of complex, threatening inspection systems. A revolution is underfoot and now the end of the assembly line has caught up with the drafting tables and the machine shops. A critical juncture has been reached. The big manufacturers have sounded reveille, and software companies are finally heeding the call to charge forward.
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|Comment:||It's not an inspection jungle out there, any more.|
|Publication:||Tooling & Production|
|Date:||Jul 1, 1999|
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