Continuous Process Software
Graphical Software For Statistical Process Control

SPC On A Roll

 

This Windows based software may be used to analyze data from any continuous manufacturing process. In particular, it provides unique capabilities for roll product manufacturers and converters with provisions for handling data from both fixed and scanning sensors, with any number of process streams (or positions). It is a general purpose interactive statistical graphics system that features an extensive collection of statistical and graphical functions for analyzing, visualizing and controlling continuous processes.

 

The Roll SPC module is built on top of "A Graphical Statistical System" (AGSS), a system licensed from IBM and used extensively within IBM worldwide. The system contains extensive facilities for design of experiments, exploratory data analysis, 2 and 3 dimensional graphics, linear and nonlinear curve fitting, distribution fitting, reliability and accelerated life testing, quality control and time series analyses. The SPC module includes capabilities for adjusting X-Bar chart control limits to correct for autocorrelation effects, which, if present, can result in high levels of false out-of-control signals. It also provides the ability to produce mulivariate control charts, and to adjust these for autocorrelation effects as well.

 

The system may be run under DOS, Windows 3.1, Windows 95 or 98 and Windows NT. It can accept data files produced by leading spreadsheet programs.

 

 

Examples:

 

1. Process Stream Graphs: Comparisons of raw data, using common scaling, for multiple process streams.

 

 

 

2. Box Plots: Summarizes and compares empirical distributions for multiple process streams. Identifies potential outliers.

 

 

The empirical density functions shown on the previous page provide a 3-D view of the same empirical distributions. The empirical density functions may be viewed as smoothed histograms. Both types of plot show empirical distributions in the machine direction and provide comparisons in the cross web direction.

 

 

3. Autocorrelation Functions: These graphs provide plots of the correlation between successive points in the machine direction, as a function of lag. A lag 1autocorrelation is the correlation coefficient between successive points (x2 vs. x1), (x3 vs. x2), …, xn vs. xn-1) A lag 2 autocorrelation is the correlation coefficient between points separated by two time units (x3 vs. x1), (x4 vs. x2), …, (xn vs. xn-2) etc.

 

The plot shows autocorrelation functions up to lag 20, with .95 confidence bounds.

 

 

 

4. X-Bar Charts: Shows X-Bar charts for each process stream, plotted to the same scales to facilitate comparisons. Note that there are quite a few points that plot outside of the control limits. It is important to know whether these points signal an out-of-control situation. The answer is provided by the X-Bar charts which indicate that all of the apparent out-of-control signals were false, and were, in fact, an artifact of the high autocorrelations present in the data.

 

 

 

5. X-Bar Charts Adjusted For Autocorrelation: In these charts, the control limits have been automatically adjusted to account for variation caused by the autocorrelations. There are no out-of-control signals. Use of the uncorrected chart on the previous page could have led to costly and unnecessary actions.

 

 

 

Many other SPC On A Roll functions are provided, including multivariate control charts (T-Square and Chi-Square) both unadjusted and adjusted for autocorrelation effects.

 

 

 

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Produced by:
Schatzoff Statistical Consulting
Martin Schatzoff Ph. D., President
27 Brent Road
Lexington, MA 02173-1815

Tel: 781-862-6693
E-Mail: schatzoff@worldnet.att.net

 

Order Information:
PJ Associates
1001 Marina Drive
Suite 605E
N. Quincy, MA 02171
Tel. Or Fax: (617) 471-3798
E-Mail: PJAssociates@pjassociates.com
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Price:
Single Copy: $995.00 + $6.50 Shipping & Handling
*Please include Massachusetts state taxes at 5%.

 

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