Cream of the Crop 1/Cream of the Crop 1.iso/BUSINESS/SPC11.ARJ/SPC_XR.PGH

Text File | 1992-01-21 | 13KB | 499 lines

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freak_point_2
           IMPORTANT CAUSES OF FREAK POINTS

The two most important causes of freak points are:


   1. A sudden change in raw materials


   2. A measurement error

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freak_pattern_2
           CAUSES OF FREAK PATTERNS

1. Drastic changes in raw materials

2. A forgotten operation

3. A partially completed operation
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freak_pattern_3
          FREAKS AS PART OF LARGER PATTERNS

1. Freaks usually appear in a larger pattern.

2. Usually by correcting the larger out-of-control pattern,
   the freak will come into control as well.
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shift_2
               WHAT DOES A SHIFT MEAN?

1. Something new has been introduced into the process.

2. Something different from what you've been doing or using before.

3. This new element changes the whole process.  At least for awhile.

4. You have shifted the center of the distribution.
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R_shift_up
        SHIFT UP IN R CHART

1. There is too much variation in the process.

2. The process IS NOT CONSISTENT!

3. There is no telling what kind of product you
   will end up with.
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R_shift_down
      SHIFT DOWN IN R CHART

1. The process is MORE CONSISTENT!

2. Examine your process to determine the
   cause for this shift down.

3. Make the change permanent and have a
   more consistent product.
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X_shift
    COMMON CAUSES OF A SHIFT IN THE X CHART

1. A change in the incoming MATERIAL

2. SET-UP of the machines at the beginning of a shift

3. Running the machine at different SPEEDS

4. A difference in the way parts are being MEASURED
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X_shift_1
                CHANGE IN MATERIAL

A change in MATERIAL is the most common cause of a shift
in the X bar chart.  Ways to solve this problem include:

   1. Stick to one supplier.

   2. Insist that your suppliers produce a
      more consistent product for you.

   3. You could require your suppliers to
      implement an SPC program.


   The key is to find a way to make sure that your incoming
   materials are as good as possible.
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R_shift
  MOST COMMON CAUSE OF SHIFT IN R CHART

The most common cause of a shift in the R
chart is the OPERATOR.
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R_shift_up_1
  MOST COMMON CAUSE OF SHIFT IN R CHART:

             The Operator


 MOST COMMON CAUSE OF A SHIFT UP IN R CHART:

         Poorly trained worker



1. Make sure that the operators are well trained.

2. The competency of your OPERATORS has the MOST
   impact on your R charts.
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R_shift_down_1
  MOST COMMON CAUSE OF SHIFT IN R CHART:

             The Operator


 MOST COMMON CAUSE OF A SHIFT DOWN IN R CHART:


   Well trained and experienced workers



1. Make sure that the operators are well trained.

2. The competency of your OPERATORS has the MOST
   impact on your R charts.
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R_chart_1
             IMPACT OF OPERATORS

1. Make sure that the operators are well trained.

2. The competency of your OPERATORS has the MOST
   impact on your R charts.
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cyclic_1
                 CYCLIC PATTERN

A cyclic pattern is caused by the same thing happening
at the same time over and over again.  Common causes
of cyclic patterns include:

1. Defective equipment

2. Fluctuating electricity

3. Weather conditions such as humidity, temperature,
   and pressure

4. Human Factors
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R_dec_trend_1
          DECREASING TREND IN R CHART

1. You do not have a problem.

2. This tells you that things are getting better.

3. As the range decrease, your product is becoming
  more CONSISTENT.
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R_dec_trend_2
      CAUSES FOR DECREASING TREND IN R CHART

Downward trends in the R chart are probably because of:

1. Educating or training the workers

2. Improving the maintenance on the equipment

3. Operators having more experience and knowing the
   job better.

4. Better process controls in other areas of the
   operation.
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R_inc_trend_1
          INCREASING TREND IN R CHART

1. The process is getting WORSE!

2. The process is becoming LESS CONSISTENT.
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R_inc_trend_2
       CAUSES FOR INCREASING TREND IN R CHART

1. Often a result of WEARING.

2. It could be your tools.  The tools might be
   getting dull or loose.

3. It could be your operators.  The workers could
   be getting tired.
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X_trends
     CAUSES FOR TRENDS IN THE X BAR CHART

Common causes for trends in the X bar chart include:

1. Tooling wear.

2. Aging tools.  When the tools get old, they may
   not be working right.

3. Your workers may be getting tired as the day
   goes on.

4. Machines may become slowly clogged with dirt
   and dust.
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stratification_2
           CAUSES OF STRATIFICATION PATTERNS

Stratification patterns appear because of the way data are


               1. MEASURED

               2. RECORDED

                 or

               3. SAMPLED
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stratification_3
            CAUSES OF STRATIFICATION PATTERNS
          (MEASUREMENT, RECORDING, or SAMPLING)

1. Workers want to look good so they record false
   data points.

2. Workers are told to falsify records to make their superiors
   look good.

3. Often, workers measure just one part and assume that the
   other parts will have the same reading.

4. The measurement scale is inexact.
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run1
                     WHAT IS A RUN?

RUNS -  This is any sequence of points for which a large
percentage fall on the same side of the mean.  This definition is
vague since many experts and source materials disagree on what
conditions to use.  This is conventionally identified.  The
following criteria are used to identify a freak pattern:


   (a) More than 7 (some say 5 and others say 8) points in a row on
       the same side of the mean.

   (b) Ten of 12 on the same side of the mean.
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run2
                    WHY IS A RUN UNUSUAL?

1. A chart which is in control should have points randomly scattered
   on both sides of the average.

2. A run indicates that some non-random or unnatural causes of
   variation are affecting the process.

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freak_point1
      WHAT IS A FREAK POINT (SPIKE)?


A freak point (or spike) is any point on the
control chart which lies outside of the Upper
or Lower control limits.
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freak_point2
          WHY IS A FREAK POINT UNUSUAL?


1. 99.9% of all points in a chart which is in control
   will fall within the Upper and Lower control limits.

2. A freak point indicates that some non-random or unnatural
   causes of variation are affecting the process.
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freak_point3
         WHAT DOES A FREAK POINT MEAN?


1. Freak points mean that something very unusual
   has happened in the process.

2. A freak is produced by an outside unusual cause.

3. It isn't present for very long.

4. Freaks are the easiest chart patterns to find
   the assignable cause for.
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freak_pattern1
                 WHAT IS A FREAK PATTERN?

FREAK PATTERN  -  This is any sequence of points for which a
large percentage fall more than a given amount away from the mean.
This definition is vague since many experts and source materials
disagree on what conditions to use.  The following criteria are
used in this software to identify a freak pattern:


   (a) 2 out of 3 points in a row outside of the 2 sigma limits.

   (b) 4 out of 5 points in a row outside of the 1 sigma limits.
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freak_pattern2
          WHY IS A FREAK PATTERN UNUSUAL?


1. Very few points should fall outside the Warning Limits.

2. Something in the process has drastically changed for
   a short period of time.
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shift_up1
               WHAT IS A SHIFT UP?

1. Several consequetive points tending to be below the
   average followed by several more consequetive points
   tending to be above the average.

2. Something has acted on the process and changed
   the distribution.
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shift_up2
               WHY IS A SHIFT UP UNUSUAL?

1. A chart which is in control should have points randomly scattered
   on both sides of the average.

2. A shift up indicates that some non-random or unnatural causes of
   variation are affecting the process.
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shift_up3
              WHAT DOES A SHIFT UP MEAN?

1. Something new has been introduced into the process.

2. Something different from what you've been doing or using before.

3. This new element changes the whole process.  At least for awhile.

4. You have shifted the center of the distribution.
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shift_down1
               WHAT IS A SHIFT DOWN?

1. Several consequetive points tending to be above the
   average followed by several more consequetive points
   tending to be below the average.

2. Something has acted on the process and changed
   the distribution.
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shift_down2
              WHY IS A SHIFT DOWN UNUSUAL?

1. A chart which is in control should have points randomly scattered
   on both sides of the average.

2. A shift indicates that some non-random or unnatural causes of
   variation are affecting the process.
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shift_down3
             WHAT DOES A SHIFT DOWN MEAN?


1. Something new has been introduced into the process.

2. Something different from what you've been doing or using before.

3. This new element changes the whole process.  At least for awhile.

4. You have shifted the center of the distribution.
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cyclic1
               WHAT IS A CYCLE?

1. A sequence of several consequtive points which tend
   over time to regularly rise and fall.

2. A cycle may have several deviations from this pattern;
   however, the overall tendancy is for a regular rise
   and fall pattern.
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cyclic2
               WHY IS A CYCLE UNUSUAL?

1. A chart which is in control should have points which change
   randomly with no particular tendancies.

2. A cycle indicates that some non-random or unnatural causes
   of variation are affecting the process.
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cyclic4
                 CYCLIC PATTERN

A cyclic pattern is caused by the same thing happening
at the same time over and over again.  Common causes
of cyclic patterns include:


   1. Defective equipment

   2. Fluctuating electricity

   3. Weather conditions such as humidity, temperature,
      and pressure

   4. Human Factors
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cyclic5
       CYCLIC PATTERNS & THE HUMAN FACTOR

1. The most common cause of cyclic patterns is the human
   factor.

2. Do not forget to look at the human factor when looking
   for causes.

3. Shift changes and new hires show up on the charts.

4. Being tired or unfamiliar with with job can cause some
   pretty strange chart patterns.
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stratification1
                    WHAT IS STRATIFICATION?

STRATIFICATION  -  Sometimes referred to as "hugging the center
line."  This is any sequence of points for which a large percentage
fall less than a given amount away from the mean.  This definition
is vague since many experts and source materials disagree on what
conditions to use.  This is conventionally identified.  The
following criteria are used to identify a stratification pattern:

   (a) Ten or more points in a row which are within the 1 sigma
   limits.
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stratification2
    WHY IS STRATIFICATION UNUSUAL?


1. The points are unnaturally quiet.

2. There is too little variation.

3. If the process is in control the points
   should be more spread out.
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inc_trend1
            WHAT IS AN INCREASING TREND?

1. A sequence of several consequtive points which tend
   over time to rise.

2. An increasing trend may have several downward steps;
   however, the overall tendancy is for upward steps.
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inc_trend2
           WHY IS AN INCREASING TREND UNUSUAL?

1. A chart which is in control should have points which change
   randomly on both upwards and downwards with no particular
   tendancies.

2. An increasing trend indicates that some non-random or unnatural
   causes of variation are affecting the process.
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dec_trend1
         WHAT IS A DECREASING TREND?

1. A sequence of several consequtive points which tend
   over time to fall.

2. An decreasing trend may have several upward steps;
   however, the overall tendancy is for downward steps.
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dec_trend2
            WHY IS A DECREASING TREND UNUSUAL?

1. A chart which is in control should have points which change
   randomly on both upwards and downwards with no particular
   tendancies.

2. A decreasing trend indicates that some non-random or unnatural
   causes of variation are affecting the process.
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