The Next Step

In recent years, the advancements in control hardware have made available systems that are not only more cost-effective but also more powerful.

By Joseph N. Arnold and
William R. Padin

Originally, the quality function focused on dimensional part inspection. The goal was improving the organization's profitability by preventing the inclusion of defective parts in the final product. As manufacturing technology progressed, the focus shifted away from "inspecting in" to "building in" quality through improved control of the manufacturing process.

This change was characterized by the adoption of statistical process control along with closed-loop feedback. It also brought about the widespread use of sensors in hand tools and automated data-collection equipment. With them, dimensional data can be automatically collected, analyzed and stored on a network.

Today, the trend is toward combining gaging and other quality functions with manufacturing. Gaging is a nonvalue-added operation in any manufacturing process (i.e., gaging does not add value to the product being produced.) Thus, manufacturers are looking to reduce or eliminate gaging costs. The obvious response to this is to control the process, thereby eliminating the need for gaging altogether. But until then, manufacturers will be looking for ways to combine gaging functions with manufacturing functions.

Sharing the same computers, networks and databases--making the quality system an extension of the manufacturing execution system--certainly provides one method to reduce and control costs associated with gaging. Another is adding manufacturing capabilities to the gaging system itself. Machine monitoring and control, closed-loop machine feedback, production reporting, displaying work instructions for production and/or equipment maintenance are examples of manufacturing functions being integrated with today's quality systems.

Suppliers have continued their development efforts and now provide equipment and software to further integrate the quality management function into the manufacturing process. Incorporating dimensional part inspection solutions into the manufacturing execution system promises further improvements in the bottom line by providing a better understanding and improved control of a company's manufacturing process.

Typically, when parts are inspected today, whether in manual, semi- or fully automatic inspection stations, the data-collection system includes a data logger or custom "gage box," which collects the data, calculates attribute values as well as performs simple statistical analysis on the data collected. These systems provide limited control functions--typically gage cycle start and stop.

Some higher-end systems also can send tool offset commands to PLCs or other machine controllers, while at the same time storing results on the network for later historical analysis. The new generation of data-collection and control modules and their associated human machine interfaces (HMI) use a completely open architecture and standard PC components. This enables them to seamlessly integrate the quality and manufacturing functions by providing enhanced control capability and improved real-time support for the operator.

One feature now available is a network browser imbedded into the HMI control software. When an out-of-control situation is detected, the operator can use the browser to query an expert knowledge database. This gives the operator access to the information needed to help generate the appropriate corrective action. The information stored in the expert database can be documents, such as procedures, manuals or even CAD part drawings containing relevant dimensional information.

  In addition to standard HMI program help files, user-created help files can also be made available. Fully customizable help can include both standard text and interactive multimedia files. Using readily available PC hardware and easy-to-use software, interactive help, including videos and sound, can easily be created. For example, a file can be created that intermixes video clips showing the proper loading and unloading of parts, with text and pictures providing detailed online operating or maintenance instructions. Similarly, an interactive troubleshooting procedure can be generated that uses operator responses to first identify the problem's cause and then provide details on the actions required to rectify the situation. With the HMI computer properly networked, the browser can access files stored locally, on the network or intranet, as well as the Internet.

The newest generation of HMI programs, such as Moore Measurement Solutions' Process Interface, Process Vision and Process Data Collection, which run under Windows, allow the operator access to other applications from the HMI computer. The advantage here is that, should an out-of-control condition exist, the operator can immediately send broadcast e-mail notifying all affected individuals. Likewise, using a preformatted word processing document, a trouble report can be completed right then, and forwarded or archived as required.

Multitasking also can provide the operator online access to the gage management database containing up-to-date calibration information for all masters. Using this feature, the operator can quickly verify that any master used in setting or checking the inspection fixture or tool has a valid calibration, and also its exact dimensions. In addition to reducing the paperwork involved in gage management, this eliminates the time required to retrieve the current information.

But software improvements only form part of this story. In recent years, control hardware advancements have provided systems that are not only more cost-effective but also more powerful. Intelligent data collection and control modules offer not only data collection and analysis, but also integrated control of automated gages and ancillary equipment at the same time. Designed as truly open systems utilizing readily available industry standard components, these advanced precision part-   measurement solutions reduce acquisition costs and provide a lower total cost of ownership. This vast integration between the engineering, manufacturing and quality systems can only occur when each component involved utilizes open standards. Open standards permit interoperability between applications.

As an example of the power now available and the accompanying benefits, consider a fully automated part-measurement solution that utilizes distributed control, one where the HMI is separated from the data-collection and control module. Before any precision measurement is made, the part must be properly cleaned and dried, and placed into the measurement fixture. Once the measurement has been made, the part must be removed and then sent on its way, depending on measurement results. The fixture will also need to be periodically remastered to assure accurate measurements. These tasks would typically use a separate controller for the part washer, dryer and material-handling equipment, as well as for the inspection fixture.  Each piece's controller would have to be separately configured and an overall scheme implemented to coordinate all individual functions.

Able to coordinate data acquisition and analysis with the supervision of multiple control modules, the HMI computer performing the part inspection can actually take over supervising the entire cell. Modern HMI configuration generators allow the control engineer to incorporate existing ladder logic into a single configuration encompassing the entire operation. Embedding automation into the part-inspection process in this manner greatly simplifies control process design and implementation. Distributed control also allows interfacing directly with PLCs and other machine controllers, enabling the HMI to extend its supervisory function even further up the process.

Manual and semi-automatic part-inspection stations can also benefit from distributed control. Often, several hand or benchtop inspections are performed in sequence or on a sampling basis. One HMI computer can supervise multiple input and control modules, each having multiple        I/O ports. In this scenario, multiple tools and fixtures can be kept simultaneously available, and switching from one to the other is as simple as selecting the desired inspection configuration from a list. An additional benefit from solutions using open architecture is that HMI computers can be networked together to allow multiple access to one fixture. This results in greater flexibility in part measurement as well as redundant control.

   While the advancements discussed up to this point concern improvements in precision part inspection, additional benefits can be provided by these advanced networked solutions. As mentioned above, the more advanced input and control modules have been designed to be more than just gage boxes. They can interface with industrial controllers and sensors other than LVDTs or half bridges. Having an infrastructure for collecting and storing inspection data already in place, manufacturers can include status or performance parameters such as temperature, pressure, fluid level or time since last service for any associated piece of equipment. Collecting data on these parameters can be accomplished for the cost of the appropriate sensor, if one is not already there, and an additional data input channel. This incremental cost could be as low as a few hundred dollars.

Once machine status and performance parameters are obtained, data tags can be used to store this information along with the part-inspection data. Thus, complete information on what was produced, when it was produced, how many were produced, who produced it on which machine and under what conditions can be automatically recorded. Should a problem arise, by querying this data, a complete root-cause analysis can be easily performed.

Additionally, the manufacturing department can use this information to perform ongoing equipment performance monitoring, allowing them to schedule preventative maintenance more effectively. Similarly, more accurate machine usage and cost information can be extracted. This allows more accurate job costing, which in turn will help generate true part costs.

With every inspection station's HMI connected to a network or intranet, the appropriate software enables viewing the status of the entire facility from any point on the network. Separate screens that can include animation and other active elements can be used to show the entire operation. It is possible to drill down, in real time, to view any single monitored attribute. Not only can each station's status and operation be monitored, but control or configuration changes may also be made remotely.

As the manufacturing industry continues to move forward, engineering, quality and production manufacturing data will continue to be more closely integrated. Engineering tools for product design have seen rapid advancement over the past 10 years. Many products are totally designed through CAD without a prototype ever being made. More and more effort is being expended to merge this "virtual" design environment with the shop floor equipment responsible for making the product. Computer-aided manufacturing programs already take 3-D part designs and directly convert them to CNC programs capable of machining the part. Similar efforts are taking shape to program coordinate measuring machines directly from a 3-D CAD part model.

Programs are also being developed that model entire production lines in this "virtual" environment and then program all the automation equipment directly from the model. Many manufacturers are moving toward product data-management systems that consist of relational databases containing all relevant information about a product. Quality systems must be able to extract data directly from these databases without the need for manual intervention.

Imagine a system in which engineering tolerances are changed on a CAD drawing and approved via a product data management system. These new tolerances are then automatically available to the manufacturing and quality system. The manufacturing execution system has complete knowledge of the work in progress and therefore knows where and when the new tolerances are to be applied in production. Because the quality system is linked to the PDM and manufacturing execution systems, the correct tolerances become automatically available during each inspection procedure--without manual intervention.

The end result of the combination of open architecture HMIs, intelligent data collection and control modules running up-to-date software with manufacturing execution systems will be an increase in total part quality and a lessening of the need and associated cost to inspect every part.

About the authors

Joseph N. Arnold is manager of New Technology for Moore Measurement Solutions; William R. Padin is marketing services coordinator. Moore Measurement Solutions is a leading manufacturer of engineered dimensional gaging solutions.

For more information, contact Moore Measurement Solutions, 1201 Sumneytown Pike, MS 535, Spring House, PA  19477, telephone (215) 646-7400, ext. 2352, , e-mail .

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