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Automated SPC Data Collection and Monitoring

PCs are rapidly displacing specialized SPC data collection terminals, for the same reason specialized labor collection terminals are being displaced by PCs. Most of the SPC data collection software suppliers are converting their software to run under DOS/Windows, and are designing their soft­ware for central monitoring of SPC chart activity of all the terminals on the network.

Almost all standard quality measurement tools such as micrometers, calipers, height gauges, and the like can be purchased with a digital output. Several manufacturers manufacture a small electronic box called a multiplexor that translates the measurement gauge reading digital output for PC input. The user calls up the right SPC chart at the terminal and with a button on the gauge sends a measurement to the computer system when ready. When all the sample readings are completed, the software calcu­lates the sample average, range (or standard deviation) for plotting the sample results on the SPC charts and checks for statistical violations.

(Software is also available for attribute data and attribute SPC charts and related analysis such as Pare to charts, etc.)

With network applications, many SPC software packages offer one or more monitoring stations that display on computer screens the status of all the active SPC charts on the PC network. A quality engineer can glance at a screen and see those SPC charts out of control, or approaching out of control conditions. Moreover, the quality control engi­neer can get a full display of any SPC chart of interest, view the original data and review any operator messages or comments about the samples taken.

The cost of the SPC data collection software and instru­mentation per terminal typically ranges from two to three thousand dollars. The software enables manufacturers to extend quickly the number of SPC control chart applica­tions, to improve the productivity of both workers and quality engineers, and avoid making parts that are scrapped or reworked. We have visited manufacturers who obtained a pay back from their investments from these systems in a few months.
Production Simulation Software

A specialized type of simulation software has emerged in recent years for modeling production operations. The newer production simulation software has built in subroutines and commands that save hours of coding time compared to using a basic simulation language. Industrial engineers are now able to quickly develop simulations of a wide variety of production problems using PC simulation soft­ware in hours that once required days and weeks of coding. We have evaluated several production simulation software packages for PCs with costs from $10,000 to $30,000.

In our factory we have set up JIT lines but we have a wide variety of products that use the same lines. Simulation provides just about the only practical way to simulate how to best balance these lines for a given mix and quantity of work.
Finite Scheduling Software

The detailed data files built for line balancing simulations are also part of the data required for finite scheduling. Capacity of production facilities is not static but also dependent on the mix and sequence of the work scheduled. Until recently the cost, the difficulty and the time to make finite scheduling runs made finite scheduling impractical. Our shop has some tricky job shop scheduling problems associated with many of our product lines, and we believe that finite scheduling will help us to more realistically assess our trade-off in meeting schedule, and/or optimizing our production costs. We believe that we can implement finite scheduling where we need it for less than $50,000 in software costs and each 1% improvement in labor utiliza­tion is worth double that amount. Our company has inves­tigated several finite scheduling applications that have improved throughput in other factories from 3 to 10%.

Bar Code Lot Traceability Data Collection

The purpose of this application is to develop computer records so that parts from any production lot can be quickly traced to the shipment lots that used the parts. We plan to use a modified version of inventory-by-lot software with bills of materials software to solve this problem. We don't need to maintain our inventory records by lot, but we plan to scan in the bar code lot trace numbers associated with each component part used in an assembly operation at the time of manufacture.

Benefits of this software application include the accuracy of bar code input and the speed at which the parts can be traced into higher and higher levels of workorders on the computer versus manually digging through boxes and boxes of closed work order documents.

Perhaps an even more important benefit of lot traceability is the ability to develop statistical correlations between quality parameters of components and final product per­formance. For example, how did the critical parameter of lot A versus lot B of a component affect the end performance of the product?

Shop Documentation Software

This software displays drawings and manufacturing in­structions on screens or can print hard copy on demand. The software can import drawings from CAD systems or transmit video frames or still video images. Users can zoom in on details for a better view. To more rapidly prepare manufacturing instructions, users can "cut and paste" these drawings or video pictures into other documents, or can "mark up" these drawing sections with arrows and labels. The advantage is the speed of preparing manufac­turing instructions with more pictures and fewer words for more rapid comprehension on the shop floor.
Sometimes associated with this software is the ability to add inspection verifications after certain steps are per­formed via the use of passwords and/or security codes. Thus we can have computer records of inspector stamps and signatures that normally are made on the shop traveler that accompanies the material.

Future Developments—The Paperless Factory?

After our company implements all of the above applica­tions, our factory will be close to a paperless shop floor. At present we feel we will still need a traveler piece of paper to attach to the physical material on the shop floor as identification. We also plan on using this work order traveler document as the source of needed bar coded part numbers, work order numbers, sequence numbers, and the like for rapid bar code data input. Nevertheless, imple­menting the previously described applications will help our factory become a "less paper" factory.

It is fun to speculate on what future computer technology holds for the factory. RF systems are beginning to replace wires to computer terminals. Voice recognition systems may replace keyboards and touch screens. The storage capacity of the CD and higher capacity systems will likely make full motion video more practical. (Today one video screen image requires a megabyte or two of data.) Manu­facturing instructions may more easily be made available with video images accompanied with spoken words in several languages. Also manufacturing instructions could soon be made interactive with computer based verbal commands based on synthesized speech and spoken com­puter input based on voice recognition software.

But we do not need to wait until tomorrow. We can find many cost effective client server and PC computer software applications today that will improve the profits and com­petitive position of our factories.