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Data Exchange Speeds Inspection

 

Technology is taking dimensional measurement, data collection, and analysis in a new direction


        
By Ken Woodbine
Vice President
Wilcox Associates Inc.
Danville, CA

        

What if designers could embed their intent into a CAD master model with little additional effort? What if CMM software packages could use these models to write their own programs? What if the same software could automatically clean up after itself by optimizing probe movements? What if these automatically generated programs worked with other types of measurement equipment, such as vision systems? What if the same programs could be called down to CNC machines to help streamline machine setup and automate in-process checks? And what if all the dimensional data and analyses generated were readily available both upstream and downstream of the manufacturing process?

We will know the answer to these "what-ifs" soon enough, because many of these futuristic-sounding capabilities already exist in current versions of some measurement, data capture, and analysis software, and more are on the way. They represent a major break away from the old order, in which sharing data among the design, engineering, metalcutting, and inspection departments of just a single company was difficult at best.

The new order, which our company has named Enterprise Metrology, relies on advanced computer hardware, metrology software, and networking technology to penetrate the barriers that block the flow of data both within and external to an organization. It allows manufacturers to realize system-wide workflow improvement, productivity enhancement, and scrap reduction by:
   
  • Integrating the development and use of measurement programs to improve the productivity of diverse measurement systems.       
  • Detecting and truing up dimensional discrepancies wherever they occur throughout manufacturing organizations and their supply chains.

One of the first successes in getting electronic information to flow across departmental boundaries was the creation of the Dimensional Measurement Interchange Standard (DMIS), which defines the protocol for bidirectional exchange of measurement routines and data between CAD systems and measurement devices, most notably CMMs. DMIS made it possible for users to develop, test, and debug part programs off-line on their CAD systems, convert them into a standard format and then run them on a suitably equipped CMM. The CMM executes the DMIS program, and produces a DMIS output file, which, again, conforms to a standard.

 

A basic Enterprise Metrology System (EMS) uses advanced computer hardware, metrology software, and networking technology to move data effectively throughout manufacturing organizations.

 
   

Recently, more powerful computers and broadband networks made it practical to send the CAD model itself to the CMM. Users now automatically generate large portions of their inspection programs directly from their models. Because the software extracts a great deal of information about the part directly from these models, manual data-input errors are becoming rare. Applications engineers also find it advantageous to work in a graphical environment, because they can prove part programs using the CMM software without actually having to run the machine.

If it's so easy and beneficial to exchange complex dimensional information and even 3-D geometric models between CAD systems and CMMs, there is no reason why other complex data structures should not be made interchangeable among all types of manufacturing systems. Manufacturers understand this, and they are demanding enterprise-wide metrology solutions that integrate dimensional-data collection and analysis, and provide feedback and feed-forward of information across every phase of operations, including design, manufacturing engineering, manufacturing, assembly, quality assurance, and corporate planning.

Today's emerging enterprise metrology systems have, at the very least, the following capabilities:

  • Control and operation of all sorts of measurement equipment and devices.
  • Development of inspection routines for their use.
  • Collection, storage, and analysis of measurement data.
  • Generation of information about manufacturing operations.
  • Publication of this information in diverse formats for different uses. Output can include things like detailed reports to management, visual or auditory alarms to operators to warn them of problems, and the electronic feedback of offsets to CNC machines.

Not all of these are required for every task, but they must be available if a manufacturer intends to implement a fully capable enterprise-wide metrology system. In addition, the system should be flexible enough so that the user can configure and reconfigure it to meet changing needs.

Products compatible with this sort of metrology are beginning to appear on many fronts. Some are already on the market and others will become commercially available this year. Here are a few examples.

I have referred to CMM software and metrology software interchangeably because some of the latest measurement software is usable on almost any kind of measurement device, including CMMs, articulating arms, vision systems, integrated hand-tool gaging stations, and other equipment. What's more, software available from several manufacturers makes it possible to create sophisticated probing routines for CNC machine tools within a CMM or CMM-like programming environment.

Typically, this software resides on a dedicated workstation that can generate these inspection/probing routines, as well as collecting and analyzing data generated by multiple CNC machines. This system supports automatic feedback to the machine to adjust offsets for tooling wear.

Some of the most promising uses envisioned for this technology include streamlining part setup, automatic in-process checking to catch problems before they result in scrap generation, and eliminating the need to move large parts and components for off-machine in-process measurement on large CMMs.

One metrology software package now offers an option that will automatically generate as much as 30% of a part program directly from a CAD file without any programmer interaction. This program generator automatically creates a set of hits on each part feature according to user-defined rules, defines probe paths between those features, and optimizes the probe paths. This package applies not only to CMMs, but also to any other type of measurement system or probe-capable CNC machine the software can run on. When used in combination with a CAD-resident inspection planner (see below), this option will nearly eliminate on-machine programming while providing many other productivity and QA benefits.

A new single-touch interface package makes it easier to create simple interfaces that allow CMMs to be more readily used on the shop floor as flexible gages. With it, a CMM applications engineer can design a custom GUI, seamlessly integrating inspection programs, utilities, and custom reports into a single system. This approach eliminates the need to do any computer programming, which historically has been a requirement in building this type of application. Now, an engineer without any sophisticated software skills can weave together a single-touch system using nothing more complicated than a slide-show editor.

With one of these systems in place, an operator who has completed a machining operation simply selects a representation of his part on a touch-screen computer. The screen then shows him which fixture to use, and how to set it up. Next, it shows how to place the part on the fixture. This achieved, the operator pushes the next button and the software checks that the right fixture was chosen, measures the part, and, if all is well, flashes up a GO screen. If something's wrong, it displays a screen showing a drawing of the part and annotating the features outside of the desired limits.

A new dimensional information reporting tool takes advantage of inter and intranet technologies to publish dimensional information both within a manufacturing organization, and to authorized outside users. The location of the readers does not matter. They can be next door, or they can be on the next continent. Users work in a standard browser environment (i.e., Internet Explorer) to generate and access reports, or to distribute them quickly. This browser environment makes critical dimensional information readily available to those who need it.

A large part of the process of creating inspection programs consists of a CMM programmer poring over part drawings to determine the designer's intent, and then translating that intent into a measurement language. New, CAD-resident software eliminates this step and the potential for misinterpretation it entails by allowing the designer to embed his intent into the electronic model. This inspection-planning software allows the design engineer to select geometries to be measured, and then the necessary dimensional relationships among them. It effectively creates a virtual marked-up blueprint of the part that tells the CMM software how to inspect the part, and how to report the results. These results are achieved by using a set of integrated tools tailored for the specific CAD system. Versions are currently available for SolidWorks and Unigraphics, with several others in development.

At a very minimum, this ensures that the most critical features to the design are inspected appropriately throughout manufacturing, and that changes in design are automatically reflected in the inspection plan. But there's more. If there is a direct link between the CAD system and the CMM, the software will automatically notify the inspector that the drawing has changed, and then offer the opportunity to automatically update the inspection program with the new information.

If a CAD model includes an embedded inspection plan, the automated program generator mentioned earlier will not just build the skeleton of an inspection program, it will also automatically write most of it. These programs are not only efficient to develop and execute, they also accurately reflect design intent and minimize errors.

At our company, we believe that this approach can reduce CMM programming labor by as much as 90%. The industry assumption is that part programming costs about $35 per feature measured. With that conservative estimate, many manufacturers can anticipate enormous cost savings from an integrated solution for automatic measurement device programming.

 

With the latest release of Wilcox Associates' PC-DMIS 3-D measurement software, users can set up parts on modular fixturing within the graphic programming environment.

 

The metrology solutions summarized above represent the first of many waves of products coming from the measurement and quality assurance software industry. The solutions will leverage open-systems architecture and advanced networking technology to make measurement programs, data, and analyses shareable throughout all phases of manufacturing. For manufacturers, this next wave of software represents both a problem and an opportunity.

The problem is one of raising awareness. The reality of what our company calls enterprise metrology will require manufacturers to develop an understanding of how local metrology software operations are not just local, and that they have a global effect on quality and productivity throughout their organizations and supply chains. With this new insight, they will begin thinking in different terms, and begin to use these new tools in building efficient, responsive, metrology-based manufacturing systems. They'll use metrology to develop true insight into how their processes work and to better understand their strengths and weaknesses.



This article was first published in the August 2005 edition of Manufacturing Engineering magazine.  


Published Date : 8/1/2005

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