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Data Input
Reporting / Printing / OLE
Chart Analysis / Interpretation
To begin with, Newton's Telecom dictionary (7th edition,
1994, Flatiron Pub. N.Y.) defines ODBC as: "Open Database Connectivity
is Microsoft's strategic interface for accessing data in a heterogeneous
environment of relational and non-relational database management systems.
Based on work-in-progress on the Call Level Interface (CLI) specification
form the SQL Access Group, ODBC provides a vendor-neutral way of accessing
data in a variety of personal computer, minicomputer and mainframe databases.
" QA Inc.'s SPC ODBC Query Feature will allow any ODBC data source
to be accessed and data brought into the program for read-only analysis.
The "query definition" will be stored as part of a regular QDB
file, and can be subsequently re-run to obtain a current set of data.
The "query results" data will appear much like normal columns
in the SPC data set.
Dynamic Data Exchange (DDE) is a Windows feature which
allows users to create links between one application and another. With
these links, data inputted into one application is automatically "transferred"
to the other. SPC-PC IV uses these links in two ways: (1) Direct transfer
of data, and (2) Macros.
The most common use of DDE is a transfer of information
with a spreadsheet application such as Excel or Lotus. SPC-PC IV acts
as both and client and a server, meaning that you can either enter data
into SPC-PC IV and have it transferred to another DDE compliant application,
or you can enter data into the other application and have it transferred
to SPC-PC IV. You may want to create these links for a variety of reasons.
Perhaps to perform different types of analysis on your data such as pie
charts within Excel. Or, if you have data residing in another application,
and you want to use SPC-PC IV’s powerful analysis and graphics use
DDE to transfer it to SPC-PC IV
The other use of DDE within SPC-PC IV is for Macros. Macros
are customized programs which perform a wide variety of functions, namely
they are designed to perform repetitive, time consuming tasks which no
supervision. These Macros are written within another application, then
using DDE the Macro can execute features of SPC-PC IV. For example, if
a certain report needs to be generated every Friday at 4:00 PM containing
the same 10 charts, you can create a Macro which will open up SPC-PC IV,
create the necessary charts, and print them. You can even write a Macro
to open of a word processing package, import through OLE a chart from
SPC and print that report with the updated chart and accompanying statistics.
See MACRO
COMMANDS in our Online
Help system for more information.
SPC-PC IV allows you to print charts to a JPEG file. JPEG
files can easily be imported onto your web server so that Internet users
can view the charts. Your server, and the page permissions, define who
has access to view the chart.
See
PCX and JPEG File Exports PCX and JPEG File Exports in
our Online Help system
for more information.
I
open the same files all the time. Is there a way to automate this?
Worksets are a tool within SPC-PC IV that will allow you
to do this. Worksets allow you to group frequently used data sets and
charts, and open them with a click of a mouse. You can even set a default
workset which will open automatically every time you run SPC-PC IV. This
feature is very useful for new users of Windows to easily access the files
they need as well as for supervisors to easily gain access to each of
the charts which need to be monitored.
Another useful feature is the ability to create your own
layouts for future files. We often find users continuing to use the basic
variables and attributes layouts which are included in the shipped version
every time they create a new data set.
Basically, the layout is a template in which you can add
columns which may be common to multiple files. For example, the column
headings “operator”, or “part number” may be in every
file you create. So instead of editing the existing layout, and adding
these column headings every time, simply create a new layout once, and
use that layout for each subsequent file.
SPC-PC IV also has the ability to either add the time
and date automatically when you are inputting data in real-time or enter
them using only a few key strokes while inputting data manually.
To enter the time and date into your data set manually,
press Control D for date and Control T for time y When entering data in
real-time simply select which columns you want SPC-PC IV to enter the
date and time while in the Gage Cursor dialog box.
And don’t forget that within Windows if you wish
to open multiple files in a single step you can drag selected files from
the file manager to the SPC-PC IV application window.
Files
always seem to be opening in "Read Only" mode, even though
the File Open Mode option is not set that way.
With the file closed, select the Open option
from the File menu. Select the file (do not open it), then select
the Open Mode button. Choose the Normal option (even
though it may already be set to Normal) and "Set Default." This
file should now open in normal mode. This should be done on a file-by-file
basis.
The File Types defined in your Window Explorer Folder
Options are not associated with SPC-PC IV. You've installed another software
which uses the same file extension, in this case the accounting software
Quicken. Even though the file extensions are the same, the formats of
the file are quite different. It appears that Quicken corrupted the SPC-PC
IV qdb file when it tried to open it.
The Multi-Chart Print feature determines the arrangement
of the charts in the page by alphabetical order of the chart file names,
which is not necessarily the order of creation.
If you choose to use the default chart file names (ex: Chart1.qdc), the
alphabetical order will be the same as the creation order until you have
more than ten charts, when the alphabetical order results in:
Chart1, Chart10, Chart11, ...Chart19, Chart2, Chart20, etc.
The Multi-Chart Print function may cause an Error 21 Print
Overrun error on HP-IV printers when the Page Protection option is turned
OFF in the Printer Driver Setup. Typical results would be that approximately
1/8th of the page is printed with the rest of the page blank.
The Page Protection option forces the entire page to remain in printer
memory until it is ready for printing, and is only available if the printer
has at least 6 Meg of internal RAM (2 Meg is standard so you may have
to upgrade). Reference information on this can be found in the following
website document:
http://hpcc997.external.hp.com/cposupport/printers/support_doc/BPL01206.html
The customer can find out how much ram the HPIV has physically installed
by running the self test doc from the printer:
Take Printer off line
Press "Shift" and "Form Feed" simultaneously to produce
the "Test Menu" in the display
Press the "Item" button until "Self Test" appears
in the display
Press "Enter"
The printer will kick out he self test form with among other items the
amount of ram the printer has (Displayed in the middle left side of the
one page print out)
Make sure the printer driver in windows is set to the same amount of ram
the printer reports having to avoid problems.
The equivalent to the Print Overrun error 21 for an HP-IV L printer is
a blinking amber light. This "personal edition" printer is a
no frills design w/out the display panel. It ships with 1meg and is expandable
to a total of 2 meg only. There is a page protection and an image compression
feature that are shipped default on to help deal with this problem but
the only effective way to deal with it is to install the 2nd meg of ram.
Typical result is a half competed XmR Advanced chart vs a fully complete
XmR non-Advanced chart.
You must re-register the SPC application:
Open the file spcwin.reg (registration entries) in Notepad or another
text editor. Find the text "spcwin.exe" and enter the correct
path for the spcwin.exe file immediately before the found text. Save the
spcwin.reg file
The following steps can be used to insert an SPC chart
object into MS-PowerPoint. The same procedure should work for Harvard
Graphics, provided the version of Harvard Graphics you are using supports
OLE (Object Linking and Embedding). If it does not support OLE, then charts
copied from the clipboard will be copied in a less than optimal bitmap
format (rather than the preferred metafile format used for OLE objects).
Graphical resolution may be comprised in the bitmap format.
1. Create a chart in SPC-PC IV. Select Copy from the Edit menu to copy
the chart to the Windows clipboard. (Note: You do not need to save the
chart as a chart (.qdc) file). In MS-PowerPoint, select Paste from the
Edit menu to paste the chart into the appropriate slide,
OR
1. In MS PowerPoint, select Object from the Insert menu. Create a New
object, selecting SPC-PC IV Chart as the Object Type. You may either create
the chart object from an existing data file, or create a new file, with
dialog boxes provided to accommodate the selected method. Create the chart
in the SPC application window. Changes made on the chart will be dynamically
updated in the embedded chart object in MS-PowerPoint. (Note: You may
need to maximize the chart window in the SPC application to see these
changes). Close the SPC application window to return to MS-PowerPoint.
2. The SPC chart is now imbedded into MS-PowerPoint. To change the size
of the embedded object (or any other characteristic of the chart), double-click
on the chart object. This opens the chart in a modified version of the
SPC-PC IV application. (Note: If this does not open the SPC application,
then the chart is not embedded as an object, but as a bitmap). Maximize
the chart window in the SPC application, and size the SPC application
window so that it is a convenient size for the PowerPoint slide. It may
be useful to have the PowerPoint slide visible behind the SPC application.
Note: Although you can size the chart within MS-PowerPoint, you may notice
that the graphics do not proportion well with this technique.
The process you are analyzing is certainly not uncommon
to manufacturing or service processes, nor is your approach uncommon.
However, we will need to make some accommodations to the data so that
it will meet the basic assumptions of a control chart.
As I understand it, your process data is obtained by taking three measurements
of a given 'piece' (or unit of production) at a particular point in the
process. Some time later, three more samples are available from a different
piece at the same point in the process. You are interested in determining
if the process is stable. You notice that when you group the three measurements
into a subgroup that the X-bar chart displays many out of control groups.
Refer to the SPC Concepts topics. The first section provides a description
of a control chart. Item 6 in this section is of particular interest:
"The [control] limits are determined by estimating the "short-term"
variation in the process, and defining process stability (or process control)
as when the short-term variation provides a good model (or estimate, or
prediction) of the longer-term variation."
For an X-bar / Range chart, the short-term variation is estimated by the
within group variation using the subgroup Range; an Individuals chart
uses the variation between consecutive groups (the Moving Range).
When you create a subgroup from three measurements from a single unit,
the within subgroup variation is a measure of the within unit (or piece)
variation; it does not provide an estimate of the total process variation,
which can includes other elements of variation, such as material variation
between units, variation between setups due to methods, machine repeatability,
temperature effects, etc.
This explains why so many of these groups are out of control on your X-bar
chart: the within subgroup variation that is being measured is not reflective
of the between group variation that is plotted on the X-bar chart. Other
examples of this include creating subgroups:
- across a stream of product, such as across the width of a paper roll;
the within group variation would be the variation across the roll, which
is influenced by different process factors than the variation along the
length of the roll.
- from multiple parts produced at the same time on a single fixture; the
within group variation would be the variation across the fixture.
- from dependant processes. See the examples cited in the attached Rational
Subgroups section.
What can you do with the data you have?
1. Any single observation of the three could be chosen to represent the
process location for that piece. Or preferably, you take the average of
the three observations and use that as an estimate of the process location.
Either way, the single data point could be plotted as an observation on
a chart for Individuals (such as the Run chart, the Individual-X chart
or the EWMA chart) to estimate the process location over time The Moving
Range chart would be used to estimate the short-term process variation.
2. The variation between the three observations provides an estimate of
two components of variation: the within piece portion of process variation
and the repeatability portion of measurement error. You could calculate
the variation between the three measurements and plot that as an observation
on a chart for Individuals (such as the Run chart, the Individual-X chart
or the EWMA chart).
Is
there an error in the way that fitted curves are being plotted on histograms?
Curves appeared to be drawn differently depending on the histogram scaling
(such as for different selections of cell width for the histogram). The
shape is correct but the "height" scaling factor of the curve
varies with the histogram cell width.
The curve is and SHOULD be redrawn to match the changes
in the cell widths. The labeling of the "PERCENT" axis should
be interpreted to mean "percent per cell" when applied to the
cells and to the curve as drawn on the chart. Thus, the area under the
curve remains constant as both the x and y-axis scaling changes.
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