WELD SENTRY 2
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COLLECTING WELD DATA
The objective in using the Weld Sentry is to obtain a measured value from weld voltage and weld current
which will alert the user to a change in the weld process. If the process is stable, or "in control", the weld
quality will be consistent and repeatable, with consistent and repeatable measurement results. A variation in
the process which causes unacceptable weld quality should also cause the Sentry measurement results to
change. The Weld Sentry is used in four different stages:
1)
Evaluation:
determine if the process is stable, use SPC tools.
2) Setup:
establish a measurement range for acceptable welds, set Upper/Lower Limits.
3) Verification: document that the process remains stable, save results using Data Collection.
4) Monitor:
signal when results fall outside the acceptable range, use Alarms and Relays.
An important point in the evaluation and setup process is that only "good" welds should be included
initially. Each weld process is unique and there is no pre-defined range for the Sentry measurement values.
Unlike quality criteria such as pull strength or shear strength, there are no specification limits for the Sentry.
The limits must be developed during the evaluation stage by correlating a range of Sentry results with a
range of "good" welds. After an acceptable range is established, identify the variables which cause
problems in your process. Simulate the specific conditions which are causing problems and collect data on
"bad" welds. The measurement values for "bad" welds should fall outside the range set by "good" welds.
Then, you can program trial Upper and Lower reject limits.
EVALUATING DATA USING THE SPC FEATURE
Whenever the Sentry is ON, the measurement results are automatically saved in memory. The data saved in
memory is referred to as "SPC Program History". The data for each individual program can be analyzed
using the Weld Sentry SPC data evaluation tools. Select SPC from the Main Menu to access the menu
shown below.
STATISTICS, RUN CHART & HISTOGRAM - Select this feature to display and/or print:
Average
Maximum
Value Run
chart
Standard Deviation
Minimum Value
Histogram
To define the data to be evaluated, the following screen is displayed first:
After entering the desired schedule number, the "Welds Available in History" will display the number of
welds which are currently in memory. Enter the number of welds to be included in the statistical
calculations and graphs. The count begins with the most recent. In the example above, there are 1000 weld
results saved in memory, only the most recent 500 welds will be evaluated, the first 500 will not be
considered. Press [ENTER] to continue to the summary screen.
Summary of Contents for WELD SENTRY 2
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