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Boost process efficiency and eliminate errors
with the right data collection software.

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by Thomas Lutz and Susan Rogers

Today's companies are under constant pressure to become more efficient in their manufacturing processes by increasing productivity while keeping costs down. Accuracy is imperative as companies race to develop and maintain procedural standards to meet ISO 9000 compliance and position themselves for corporate survival in the 21st century.

 The idea behind such quality initiatives as ISO 9000 is to encourage manufacturers to develop their own standards for quality control and then implement procedures to meet these pre-established standards. The primary reason for developing standards is to offer some guarantee of consistency and quality, as well as accountability for problems, when one manufacturer purchases a product or part from another. Continual improvement of product quality should be the ultimate goal. The first step toward achieving this goal is developing methods for measuring each manufactured product for consistency and compliance with predefined standards.

 An integral part of most manufacturing quality control procedures is the simple measurement of every part produced at every stage of the manufacturing process. Statistical process control is then used to examine the measurements, analyzing trends or variations that could cause parts to be out of specification.

 A typical scenario follows: You manufacture widgets that are made up of several wire forms, and each is cut with a different machine. As the blades wear out on the cutting machines, you begin producing parts that vary in size. In addition, each cutting machine's blades wear out at different rates. By measuring each part after it has been cut, you can determine the optimal number of cuts to make before changing a blade. If you cut your parts in large batches, you can also catch problems, like a defective blade, before you produce thousands of bad parts due to an issue with your cutter. Not only does quality control help you produce products that consistently meet certain standards, it also has the added benefit of making your processes more efficient and more cost-effective.

 Manufacturing a product is a procedure. Quality control is the process of monitoring such a procedure with the goal of making it more efficient. Automating the measuring and SPC process by using computers makes the quality control procedure itself more efficient.

First steps in quality control

 Typically, when manufacturers implement a quality control procedure that involves measuring something, they start by purchasing a measuring instrument (e.g., caliper, micrometer, height gage, bore gage, force gage or coordinate measuring machine). The manufacturer might then develop a procedure for measuring parts, assigning someone the task of taking measurements, recording them on a piece of paper and then keying them into either a spreadsheet or a dedicated SPC software program for analysis. Obviously, this method has some potential pitfalls because manual data entry is slow and tedious, and people make mistakes.

Automating quality control

 A more accurate and efficient approach to data collection is to enter data from your measuring instruments directly into a spreadsheet or SPC program. Most of today's measuring tools are equipped with some form of electronic output that makes it possible to connect the instrument to data loggers, printers or computers, thereby eliminating the steps of manually writing down measurements and typing them in. Automating data collection removes all possibility of human error and allows for real-time data analysis. It's also possible to control an entire process based on the input from the tools that you use to measure the process. From our previous example, when you measure each part that comes out of your cutting machine, the measurement can be immediately fed into a computer programmed to instruct an operator to change the blade when the measurements fall outside a specific tolerance. This type of automation creates an extremely efficient process designed to maintain the manufacturer's quality control standards.

 Interestingly, the metrology industry has never settled on any one standard for the electronic interface between instruments. This is partly due simply to company rivalries. Each of the different key players in the measuring-tool industry developed its own electronic interface with the hope of making it the standard for the entire industry. But by protecting the interface standard with patents, companies lock the competition out from any customer that adopts their electronic interface standard.

 Most of the electronic interface standards were also developed long before computers were commonly found in the manufacturing environment. Because personal computers are now the dominant tool for data collection and analysis, an entire industry has grown out of the need to convert the different measuring tool interfaces to one that is PC-compatible.

The PC connection

 If you look at the back of any com-uter, you'll find many different connectors or "ports." Most of the connectors are designed to connect to a specific type of device. For example, the keyboard port is designed to connect to a keyboard, and the printer port is designed to connect to a printer.

 Fortunately, the original designers of the IBM PC had the foresight to include an additional connector called an RS-232 port. It was intended to be a general input/output port, thereby allowing data to be sent and received to and from many different types of external devices.

What exactly is RS-232?

 Recommended Standard No. 232 was originally developed by the Institute of Electrical and Electronic Engineers (IEEE) to allow a computer to be connected to a modem so that data could be transmitted over telephone lines. The standard defines the electrical characteristics (i.e., connector-pin outs, voltage levels and electrical signals) for transmitting data from one electronic device to another. The RS-232 interface is also called a "serial" interface because digital data is transmitted "serially," one bit at a time. Bytes of data are taken apart by a transmitter with each bit being transmitted in series. The receiving device collects the bits and puts them back together into the original data bytes. The content and structure of any data that is transmitted is not defined by the RS-232 standard, however; the most commonly used format for data is text and decimal numbers, that is, readable data (at least in the measuring- instrument industry).

 RS-485 and RS-422 data formats are also serial. RS-485 is also called "multi-drop" because it allows users to address multiple devices over an RS-485 cable. Both RS-485 and RS-422 are easily converted to RS-232, or you can purchase special ports for your PC.

A near-perfect standard

 There are three factors that make the RS-232 standard the ideal interface for instrumentation. First, every PC comes equipped with at least one or two serial ports (RS-232 connectors). Even laptops and hand-held machines come with at least one serial port. Additional serial ports and multiplexers are readily available and are priced very low (about $40 for each additional port).

 Second, a great deal of inexpensive PC software is available for transmitting and receiving data through the serial port. This is perhaps the most important aspect of any data communications standard. If there's no software available to support an interface standard, the hardware that uses the standard is practically useless.

 Finally, the RS-232 standard is extremely easy and inexpensive to implement. Although not all of the manufacturers of measuring instruments have adopted RS-232 as their standard interface, it's highly likely that they eventually will. Those that have not yet adopted RS-232 at the instrument level sell additional hardware that will convert their output to RS-232.

 The entire Fowler/Sylvac and L.S. Starrett lines of measuring instruments, including calipers, micrometers, height gages and bore gages, have built-in RS-232 interfaces. Although most companies have RS-232 output on their "high end" instruments, Mitutoyo, Mahr Federal and Brown & Sharpe don't have direct RS-232 output on their calipers and small measuring instruments. However, a number of converters are available that will convert the output from these instruments to RS-232. Converters can cost anywhere from $159 to $600; therefore you sometimes pay a penalty for using instruments without direct RS-232 output. In fact, the cost of a caliper with direct RS-232 output is less than the cost of a typical converter.

What about USB?

 USB is unlikely to ever be a popular option for manufacturers of measuring instruments because it requires the instrument company to provide custom software drivers for each instrument. For this reason, many converters are available to convert your USB port to one or more serial ports.

Choosing the right software

 It's both easy and inexpensive to connect almost any measuring instrument to a PC, but, unfortunately, you can't simply plug a measuring instrument into the serial port on your PC and expect the data from the instrument to magically appear in your favorite spreadsheet or SPC program -- at least not without the right software.

 Which software to use depends greatly on what you want to do with your data. If you simply want to capture data and save it to a disk file or print it out, then terminal programs are an option. You can also purchase specialized SPC software that supports direct data input from the most common RS-232 instruments (or from the devices that convert instrument data to RS-232). Another option is TALtech's WinWedge software, which allows you to input data from any measuring instrument directly into any PC program that you want, including your favorite spreadsheet or database (e.g., Microsoft Excel).

Terminal programs

 A terminal program allows you to send and receive data to and from the PC's serial port. Most terminal programs are designed for transferring files from one PC to another over phone lines using a modem; however, almost all can be used to capture and display data from measuring instruments.

    Microsoft Windows, in fact, comes with an excellent terminal program called "Terminal" in Windows 3.1 and "HyperTerminal" in 32-bit Windows versions. With either of these programs, you can input data from a measuring instrument and, at a minimum, save the data to a disk file that can be imported into a spreadsheet, database, SPC package, etc. However, terminal programs don't parse or filter your data, and the importing process can be slow and tedious. Nevertheless, if all you want to do is capture and save measurements, a terminal program is an option.

 Additionally, commercial terminal programs such as ProComm from DataStorm Technologies and DynaCom from FutureSoft have many advanced features, including script languages, and are available at most software outlets for less than $200. They are, however, more difficult to use because they can require custom programming to implement a data collection application.

Specialized SPC software with RS-232 data input capabilities

 If your goal is to perform statistical analysis of measurement data, there are a number of specialized software packages available designed to provide the most common statistical functions, including X-bar and R-chart functions, trend analysis and just plain graphing and reporting of data. Many of the latest programs support data input directly from instruments connected to your PC's serial port. Programs such as SQCpack from PQ Systems, SPC Express from Fred V. Fowler Corp., NWA Quality Monitor from Northwest Analytical, Gainseeker SPC from Hertzler Systems Inc., Visual SPC from Cimworks and QI Analyst from SPSS are all good statistical packages with built-in support for some data from a few specific RS-232 devices. Most of these products are priced from $400 and are all very helpful if you need to perform more sophisticated statistical analysis of your data.

Spreadsheet compatibility

 What if your statistical program does not support direct data collection from all of your RS-232 measuring instruments? What do you do if you want to use your spreadsheet for data analysis? For many applications, a good spreadsheet (such as Microsoft Excel) may have all of the features you need, including basic statistical functions and graphing and charting capabilities. The only problem with spreadsheets is that they don't support data input from the serial port.

 WinWedge software overcomes these limitations and, thus, makes it possible to use a standard spreadsheet with serial instruments. It can feed serial data from any measuring instrument into any Windows program, including statistical applications.

 WinWedge is essentially a fully configurable serial device driver that allows you to input data from any instrument with an RS-232 interface directly into any Windows application program. It works by tricking your computer into treating the serial port as a second keyboard, allowing you to input measurements directly into any PC program, including your favorite spreadsheet, database or SPC program. It also parses and filters your data and executes additional keystrokes, so you collect only the data you want in an appropriate format for your application. WinWedge also allows you to input data using Dynamic Data Exchange for complete data collection in the background. DDE is very powerful and allows the user to simultaneously collect data from many different serial ports. Hence, you can input data from many measuring devices all connected to the same computer.

Don't wait -- automate!

 Automating quality control processes improves productivity and ensures accurate and precise product manufacturing. So if you haven't already automated your quality control procedures, don't hesitate. Doing so is a simple and inexpensive solution to improve your products and your company's reputation.

About the authors

 Thomas Lutz is president of TAL Technologies Inc. Lutz manages all software development and manages the technical support staff. Susan Rogers is vice president of marketing at TAL Technologies Inc. E-mail the authors at tlutz@qualitydigest.com .