One could well say that the primary purpose of an MES system is to collect data
and to report it when, where and how it is needed. How is data collected and used
in the InSite system? How can the factory be assured that what is being produced
is what is desired? How can you tell if equipment is drifting out of spec before
units start failing? Data Collection and Statistical Process Control is the answer.
Data Collection
What exactly is a data collection? Generally data collections are used to capture
the results of parametric process data taken in the manufacturing line or as a result
of engineering tests. In the InSite system, a data collection is a set of data values
that are input by the operator, by the equipment or gathered from an interface to
an external information system. Every step in the workflow is capable of having
data collections if desired. The data collection itself is attached to a transaction
that occurs during the processing of that step, such as the move-in, track-in, track-out
or move-out. You can also gather data on demand with an ad-hoc data collection.
The data values can be of any data-type and may be a single value or a list of values.
How is Data Collected?
The main impediment to the data collection process is how to collect the data without
impacting the production line or the operators (see Automation for more detail).
For the moment it is important to realize that any of the manual data collection
processing discussed here has the possibility of being automated. It is up to the
factory to determine the best cases in which the expense of automation is justified.
In the InSite system, an engineer typically defines a set of data values that are
needed and someone in the system support group enters the data collection definition
into the InSite system once it has met the approval of the process control group.
After the data collection definition is defined, it is attached to the transaction
that represents the point in the processing where the data is needed. The most common
location is the track-out transaction. At run-time, the operator will see the data
collection screen appear after doing the track-out (or whatever transaction it may
be attached to). If the entry is manual, the operator then needs to enter the data
results by hand. If there is automation it can be gathered automatically or triggered
by operator action.
Where Does the Data Reside?
Data gathered by the InSite system is stored in the MES database. This database
is a relational database system, so any software that allows access to relational
databases can be used to evaluate or report on this information. The InSite SPC
module is already set up to read this database. See the information on LiveView to see the
methods for retrieving and reporting on this data. The most integrated way to use
this information is to use Statistical Process Control.
Statistical Process Control (SPC)
What is SPC? It is a software method for demonstrating the success or failure of
a particular manufacturing step. It is accomplished by gathering data, either from
an operator entry, automated interface, or integration with an external system.
This data is evaluated by the SPC control system. Many different chart types and
formulae may be utilized to generate the charts for each spec. In addition to displaying
charts, the SPC can initiate operator or equipment actions. The InSite solution
for SPC is a fully integrated software solution. Please reference the materials
on the optional
InSite SPC module.<
Automatic Action Procedures
When an out of control process needs to initiate an action (also sometimes called
OCAP) the SPC system can place lots on hold, send messages to operators or engineers,
and can even place the equipment into a down state. In addition to these actions,
the lot may be moved to another workflow (typically for rework). For even more actions
including time/event based alarms and corrective action procedures see the LiveAlert module.
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