Perhaps you have been given the job of selecting and purchasing a coordinate measuring machine (CMM) or some other geometric measurement system. Now you are comparing the various brands of equipment and trying to figure out what differentiates them, with software being a secondary consideration. If that is what you are doing, I am going to suggest that you may have the cart before the horse and would do well to reorder the decision-making process.
Consider evaluating the software first and then selecting equipment based on whether or not it is compatible with the software. Of course, the equipment must be suitable to the application. This drives everything. However, considering software first will help focus on the big picture-enterprise goals of inspection and how they can be realized more intelligently, with the highest quality results, the least effort and the lowest costs.
The idea of making measurement processes more software-centric is a core tenet of computer-aided inspection (CAI). This decade-old concept was advanced primarily within the R&D and high-tech manufacturing communities primarily because it required expensive custom measurement and analysis software to tie inspection results back to the computer-aided design (CAD) system.
Today that is changing as software developers introduce a range of off-the-shelf metrology packages with enormous amounts of built-in intelligence. These are capable of both maximizing the performance and operation of specific devices and providing a bi-directional conduit for metrology information between and amongst diverse measurement devices and CAD databases. The result is an enterprise metrology system capable of realizing the goals of inspection at speeds and efficiencies well beyond anything currently available.
Think of this new breed of measuring device software as an intelligent inspection system. As such, it is an extension of the original CAI model in that it eliminates many of the fundamental process inefficiencies associated with the traditional inspection process. Call the extended model CAIIS (pronounced case) for Computer Aided Intelligent Inspection System. This acronym provides an accurate and helpful description of the versatile inspection software tools that are becoming available from many measurement system manufacturers and third-party software providers.
A range of portable measurement systems, such as the laser tracker and measuring arm, can be programmed and operated using common CAIIS software based on the PC-DMIS CMM engine. Source: Wilcox Associates
When evaluating CAIIS alternatives, it is important to keep in mind the ultimate missions of the inspection processes-transforming raw data collected by the measurement devices into actionable information to:
- Allow customers to buy off on the manufactured goods, so the enterprise can ship them, send an invoice and make a profit.
- Monitor and adjust manufacturing processes to maximize equipment uptime while eliminating scrap and rework.
- Troubleshoot design and manufacturing problems to improve product performance, reduce recalls and warranty issues and get to market faster to gain a competitive advantage.
Note that this way of thinking about inspection intelligence gets immediately into the core issues of the measurement system’s bottom-line impact. It also helps to avoid being overly distracted by technical details, which may be important to the selection process but secondary to accomplishing these objectives better, faster and with less associated cost. Off-the-shelf CAIIS packages do this because they view the goals of inspection from the enterprise solutions level, and, as such, target the bottlenecks in all aspects of the inspection process.
Primacy of CAD
Today, more and more of the work of manufacturing happens in virtual reality. Manufacturers design, model and refine products, parts and assemblies within their CAD systems. Then, using the information embedded in the CAD model, computer-aided manufacturing (CAM) systems create the tool paths for manufacturing parts with a minimal number of setups and least possible movement of parts among computer numeric control (CNC) equipment. In the virtual world, to the greatest extent possible, data is moved instead of parts, and that drives out substantial labor cost.
CAIIS is a logical extension of the CAD/CAM progression. In all but the most rudimentary measurement systems, CAD models are the basis for programming inspection routines and reporting a wide variety of actionable information. What’s more, some advanced CAIIS software can leverage design intent information that is embedded within the CAD model to generate inspection programs for the part automatically, while optimizing the program for the device that will ultimately inspect it.
Sometimes this CAIIS software resides within the CAD station. More often, it is associated with a particular measurement device or is part of a stand-alone workstation for off-line programming multiple devices. Regardless of where it lives, the CAIIS software can eliminate a substantial amount of programming labor-75% or more.
Inspection Planner Software is CAIIS software that interprets design intent based on GD&T data embedded in the CAD model
A New 80/20 Rule
CAIIS packages should have the intelligence necessary to automatically create measurement programs for a range of measurement devices and probe technologies and leverage the best characteristics of the device at hand to accomplish its mission.
In general, about 80% of the information required for performing inspections-programming conventions, GDT requirements and the deliverable report outputs-is common for all inspection equipment. This suggests that most of what operators need to know to inspect parts is the same whether they are using a conventional CMM, a vision system, a multisensor system, a portable measuring arm, a CMM with laser, vision or white light sensing, or a CNC machine equipped with a probe.
The 20% that is unique deals with the physical attributes of a particular device and employing best-practice conventions to leverage these attributes. The goal of a CAISS-based system is to employ the built-in intelligence of the system to create efficient programs for any of these device types with minimal operator intervention.
Here is how this 80/20 rule of CAIIS software plays out with some commonly used types of measuring devices.
- Conventional CMMs. Because of the prominence of CMMs in metrology operations, CMM software engines have evolved into the base engines for CAIIS. The best CAIIS software for CMMs works identically across a wide range of models and brands and has evolved to include the tools to realize fundamental CAIIS objectives.
- Portable arms. CAIIS software, when applied to portable arms, allows for the use of the very same programs written for CMMs. Operators can take arms anywhere in the shop or out in the field and use them to measure the parts, assemblies and tooling immediately without the need for creating new programs.
- The 20% difference in this case deals primarily with tools allowing operators to keep both hands on the arm and still interact with the computer at a short distance. Examples include the wrist mouse, magnified screens and audible signals that tell technicians when the probe is approaching the next area of interest.
- Vision systems. The CAIIS software’s programming environment for vision is largely identical to that for a CMM. Operators make measurements of all types by interacting with the CAD model, including using ultra-precision focusing algorithms to capture data from 2-D and 3-D surfaces. They can write and edit programs in any sequence and animate probe paths on-screen for fail-safe verification. Multisensor systems even incorporate traditional CMM tactile probing tools, thus using those parts of the programs requiring tactile measurements.
Here the 20% difference involves tools that allow the operator to select values related to the unique vision requirements of lighting, focus and magnification and provide help to adjust these values when a different vision system is used. The vision implementation of one CAIIS also provides unique tools that did not previously exist, such as the ability to use the vision measurement system for ad hoc measurements or to simulate measuring microscopes and optical comparators.
- On-machine probing. The programming environment for CAIIS software used to create on-machine probing routines for a wide range of CNC machines is essentially identical to the CMM version of CAIIS software. In addition, programmers can use all or parts of existing CMM programs to create on-machine probing routines directly.
In this case, the 20% difference deals with how the software vendor implements the intelligent inspection system for machine tools. The goal here is to minimize the impact on the machine’s “making chips.” Instead of driving the probe directly, programmers use the CAI intelligent software to develop and debug routines off-line. When they are happy with the results, the software translates the program into native machine code that the CNC machine can execute.
During a measurement cycle, the machine tool immediately sends the measurement data back to the CAIIS while it quickly continues on to the next cutting operation. Meanwhile, the CAIIS package performs its analytical, evaluation and reporting tasks on a separate computer. This ensures both that the measurement process has minimal impact on the manufacturing process and that it uses the best metrology tools available.
Because the goal of inspection on a CNC machine is to make fast checks to streamline setup or detect in process errors, the programs tend to be short. This allows a single CAIIS station to manage program generation, data collection and analysis for multiple machines.
Automatically generates PC-DMIS CMM inspection. This approach minimizes data input errors and reduces programming labor by as much as 75%. Source: Wilcox Associates
Leading metrology software manufacturers understand the importance of CAIIS principles and have embraced them. Because of the inherent importance of this technology, manufacturers can ensure that their CMMs and other measurement devices are able to make the most of this significant development. A checklist of actionable information can help during the decision-making process:
- Integration with CAD. Determine the extent to which the software can leverage CAD to automate device programming. Can it import models cleanly? Can it read embedded design intent? Can it interface directly with the CAD model?
- Software commonality. Evaluate the ability of the primary software engine to interface with and control a variety of measurement devices.
- Specific-device integration. Consider how well the software operates on and improves the performance of the specific device on which it will be used.
- CAIIS orientation. Ask the vendor to describe its plans to evolve its suite of measurement software to comply with the intent of Computer Aided Intelligent Inspection Software.
As with CAD and CAM, CAIIS operates predominantly in the virtual world to achieve critical inspection objectives with a minimal amount of labor input and with greater speed and efficiency than one would have thought possible even a year or two ago. It provides bidirectional communications to realize the big picture objectives of enterprise metrology. As long as it meets device specific applications requirements, a well-implemented computer aided intelligent inspection system is always a better choice.
- CAIIS software can eliminate a substantial amount of programming labor.
- CAIIS packages should have the intelligence necessary to automatically create measurement programs for a range of measurement devices and probe technologies.
- Some advanced CAIIS software can leverage design intent information that is embedded within the CAD model to generate inspection programs for the part automatically while optimizing the program for the device that will ultimately inspect it.