SPC is important to you because you want to give your customers good quality products and services.

Inspection cannot build Quality into a product or a service. The process producing it needs to be capable to deliver good quality.

Quality is thus built into a product or a service through Process Assurance. Statistical Process Control (SPC ) brings you a well defined method of assuring Quality of a Process and monitoring the stability of a good process over a period of time.

SPC helps you bring about Process Assurance and in turn a good Quality in what you do.

SPC WorkBench software from SymphonyTech takes you through the scientific workflow of SPC, and firmly guides your efforts towards delivering good quality in all that you make and do.

SPC WorkBench addresses both, Variable as well as Attribute SPC.

Variable Quality parameters are the ones that you measure and assign a numerical value to. Fill Weight, Part length, Voltage produced by a circuit are examples of Variable type parameters.

Attribute parameters are ones that count defects or classify a product as defective or non-defective.

Under Variable SPC, SPC WorkBench addresses the following:

• Process Capability: Histograms, Normal Probability Plot, Process Capability indices Cp/ Cpk, Pp/ Ppk, CR and PR and calculation of PPM based on the Process Capability indices.
• Control Charts: X-bar/ Range, X/ Moving Range, X-bar/ Sigma charts, with Out-of-Control warnings and Western Electric rules for trend detection.

Under Attribute SPC, SPC WorkBench addresses the following:

• p Chart for fraction defectives
• Np Chart for number of defectives
• c chart for number of defects
• u chart for number of defects per unit.

All charts come with a feature of defect classification. In case defect classification is reported, a Pareto Chart for defect classification and action prioritization is also displayed.

Variable Control Charts supported by SPC WorkBench are:

• X-bar/ Range Chart: typically used where the sub-group size is between 2 to 6
• X-bar/ Sigma Chart: typically used where the sub-group size is 7 or above
• X/ Moving Range Chart: used when the sub-group size in 1

Control Charts are indicators of stability. Once a process is established and runs under a steady state, Control Limits should be applied on the Control Chart. These are limits of natural variation for the Control Chart. So long as the subsequent points plotted on the Control Chart lie within the Control Limits, the process can be assumed to be running in a stable manner.

If the X or X-bar Chart shows a point out of control limits, you need to investigate reasons for the drift of the process aim, correct it and then resume the process.

If the Range or Sigma Chart shows a point out of control limits, you need to investigate reasons for excessive variation that may have crept into the process.

Control Charts tell you when you need to investigate the process and tweak it, and when to leave it alone.

Control Charts help to monitor stability of a process over a period of time. Typical workflow of using a Control Chart is as follows:

1. Collect data in sub-groups and start plotting a Control Chart.
2. When you believe that the process under monitoring has attained stability, apply Control Limits. This should be done typically after plotting at least initial 25 sub-groups of data. We call these the Process Study sub-groups.
3. Control Limits are established based on the variation that is seen in these initial Process Study subgroups.
4. To assure yourself that the Process is Stable and is working satisfactorily, verify that:
   • All the Process Study points on the Control Chart fall within the Control Limits.
   • The Process Capability Index Ppk for the Process Study data collected is satisfactory.
5. These Control Limits applied should be carried forward. Continued stability of the process should be verified against these Control Limits.

In course of running the process, there will be instances where a process improvement is made. The improved process will now run with a better repeatability. It would be prudent in such cases to re-apply control limits on the Control Charts based on the improved process horizon. The Control Chart will now monitor the process stability correctly for the improved process.

A Pareto Chart is a pictorial representation of Vital few v/s Trivial many. SPC WorkBench plots a Pareto Chart for Attribute parameters where defect classification has been reported.

A Pareto Chart makes the defects that occur more frequently stand out, and channels your attention to these. You know from Pareto Analysis which defects need your attention the most. This way your problem solving efforts are channelized to the vital few defects that occur many times as against the trivial many that occur infrequently.

Variable SPC is performed when the quality parameter under monitoring is a measure that you can assign a numerical value to.

SPC WorkBench maintains the workflow such that it enables the correct effective practice of SPC. Typical workflow of a Variable SPC is as follows:

1. Collect data in sub-groups and start plotting a Control Chart. A sub-group is a collection of readings for multiple individual samples. Plot the X-Bar chart and the Range Chart subgroup wise. A rational subgroup size is selected such that the readings in a single subgroup are representatives of the variation in the process at the instant the sub-group is sampled.
2. When you believe that the process under monitoring has attained stability, apply Control Limits. This should be done typically after plotting at least initial 25 sub-groups of data. We call these the Process Study sub-groups.
3. Control Limits are established based on the variation that is seen in these initial Process Study subgroups.
4. To assure yourself that the Process is Stable and is working satisfactorily, verify that:
   • All the Process Study points on the Control Chart fall within the Control Limits.
   • The Process Capability Index Ppk for the Process Study data collected is satisfactory.
5. These Control Limits applied should be carried forward. Continued stability of the process should be verified against these Control Limits.
6. In course of running the process, there will be instances where a process improvement is made. The improved process will now run with a better repeatability. It would be prudent in such cases to re-apply control limits on the Control Charts based on the improved process horizon. The Control Chart will now monitor the process stability correctly for the improved process.
7. As the process continues running, monitor the Histogram and the Process Capability parameters over a horizon window of your choice.
8. The X-bar or X control chart being under control indicates that the process has maintained its center or location. The Range/ sigma chart being under control indicates that the process variation has remained consistent over the period of monitoring. Any out of control situations must be investigated and corrected before the process is allowed to resume.
9. SPC WorkBench also captures trends in the data, and issues appropriate warnings. Such trends of drift must also be acted upon.

Attribute SPC is performed when the quality parameter under monitoring is a Count of defectives or defects based on which you can classify output as good or not-good.

Attribute SPC is based on plotting p, Np, c or u charts. These charts being under control are indicators of stability of the process. Attribute charts are used as stated below:

• p Chart for fraction defectives
• Np Chart for number of defectives
• c chart for number of defects
• u chart for number of defects per unit.

A typical workflow for Attribute SPC is as follows:

1. Collect samples of data for defectives or defects and plot a Control Chart. The sample size for attribute parameters is usually above 25.
2. When you believe that the process under monitoring has attained stability, apply Control Limits. This should be done typically after plotting at least initial 25 sub-groups of data. We call these the Process Study sub-groups.
3. Control Limits are established based on the variation that is seen in these initial Process Study subgroups.
4. Continue monitoring the process based on the established mean of the control charts.
5. A control chart being under control are indicators of stability of the process.
6. Where defect classification is reported, SPC WorkBench will also display a Pareto Chart over the selected horizon window along the chart. A Pareto Chart makes the defects that occur more frequently stand out, and channels your attention to these. You know from Pareto Analysis which defects need your attention the most. This way your problem solving efforts are channelized to the vital few defects that occur many times as against the trivial many that occur infrequently.

Traceability information is allied information about related aspects like toolings, fixtures, methods that may be relevant to the process. Each subgroup can be assigned with traceability information. It is organized as traceability category and traceability values for each category. SPC WorkBench automatically carries forward all traceability values of the last subgroup in a newly created subgroup. Traceability needs to be manually reassigned only when you want to change it.

SPC WorkBench gives you the facility of performing a filtered analysis. You can filter out data based on the combination of traceability values that you desire and draw out reports from it. This enables you establish possible cause and effects relationships on what works for you and what doesn't.

You could for example determine whether the Capability of a Process is better with a certain fixture, method or at a certain time of the day.

Measuring instruments with digital output can communicate with computers. Such digital instruments output the measured readings on a Serial or USB interface. Instrument manufacturers also supply a data capturing software with such interface enabled instruments.

Such data capture software sits resident in the computer memory. When a reading is sent over the Serial or USB interface, the data capture software captures the reading and types it at the cursor location of whichever software is currently active on the computer. Data can be thus captured in virtually any application software including SPC WorkBench.

To capture data into SPC WorkBench specify the data entry mode as 'Manual Data Entry Mode'. All you need to do to capture data from a measuring instrument is to place the cursor in SPC Workbench data window where you want the reading to be. The capture software will seamlessly emulate the keyboard and place the captured reading at your cursor.

SPC WorkBench data is stored in files with .spcx extension. These files can be stored and used over a network just like spreadsheets or document files. These files can be opened and used by SPC WorkBench running anywhere on the network.

SPC WorkBench can be licensed as a concurrent use floating license, where the number of computers running SPC WorkBench simultaneously are controlled.

With this licensing scheme SPC WorkBench can potentially be installed on every computer on the network and run without restrictions subject to the number of simultaneous computers allowed by the license.