What Is Statistical Process Control?

Taking the guesswork out of quality control, Statistical Process Control (SPC) is a scientific, data-driven methodology for quality analysis and improvement.

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• What is SPC?
• SPC Benefits
• SPC Features
• SPC Resources
• Mastering Quality Management
• Quality Manufacturing
• SPC 101 for Manufacturing
• SPC Glossary: Quality Management Reference
• Definitive Guide to SPC Charts

What is Statistical Process Control (SPC)?

Statistical Process Control (SPC) is an industry-standard methodology for measuring and controlling quality during the manufacturing process. Quality data in the form of Product or Process measurements are obtained in real-time during manufacturing. This data is then plotted on a graph with pre-determined control limits. Control limits are determined by the capability of the process, whereas specification limits are determined by the client’s needs.

Data that falls within the control limits indicates that everything is operating as expected. Any variation within the control limits is likely due to a common cause—the natural variation that is expected as part of the process. If data falls outside of the control limits, this indicates that an assignable cause is likely the source of the product variation, and something within the process should be changed to fix the issue before defects occur.

With real-time SPC you can:

• Dramatically reduce variability and scrap
• Scientifically improve productivity
• Reduce costs
• Uncover hidden process personalities
• Instantly react to process changes
• Make real-time decisions on the shop floor

Visit our Case Studies page to learn how top manufacturers are using SPC.

Measuring the ROI of a Real-Time SPC Solution

To quantify the return on your SPC software investment, start by identifying the main areas of waste and inefficiency at your facility. Common areas of waste include scrap, rework, over inspection, inefficient data collection, incapable machines and/or processes, paper-based quality systems and inefficient lines. You can start to quantify the value of an SPC solution by asking the following questions:

• Are your quality costs really known?
• Can current data be used to improve your processes, or is it just data for the sake of data?
• Are the right kinds of data being collected in the right areas?
• Are decisions being made based on true data?
• Can you easily determine the cause of quality issues?
• Do you know when to perform preventative maintenance on machines?
• Can you accurately predict yields and output results?

For more detailed information about SPC and SPC software.

Learn more about Statistical Quality Control.

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Additional reference material

Additional sections from legacy six-sigma:

What is SPC?

Trusted by hundreds of manufacturing companies around the world:

SPC DEMO

Minimize Production Costs, Quickly Detect Issues, and Optimize Your Product Quality

Don’t miss out! Book a demo of our specialized SPC software and unlock immediate improvements in your processes.

Book a Demo

If you are implementing Six Sigma to improve quality and eliminate defects, InfinityQS plays a critical role in the DMAIC project cycle.

Our software and services help you Define your objectives, Measure your products, Analyze your data, Improve your processes, and Control your quality.

Define

InfinityQS Consulting Services will help you define your goals and business case, create a project scope and roadmap and determine a timeline.

Measure

InfinityQS Data Collection and Integration features allow you to input any type of measurement data into your system for analysis. InfinityQS Metrology tools help you ensure that your measurement devices are calibrated for accuracy and that your gages are functioning properly and yielding reliable data.

Analyze

ProFicient employs highly sophisticated analytical tools and statistical equations that allow you to sort, slice and dice data in millions of ways, allowing extensive comparative analyses.

Improve

The data and analytics provided by ProFicient empower you to make real-time process improvement decisions. The software sends you instant alerts when your processes are out of control (or are approaching limits), allowing you to immediately fix your process before defects occur.

Control

All of InfinityQS products and services are based on the principles of a controlled manufacturing environment for maximum quality and minimal defects. When your processes are in control, so are your products and your costs.

InfinityQS software plays a key role in implementing Six Sigma. Supported Six Sigma requirements include:

• Control charts for both variable, defects and defectives data.
• Advanced Pareto Analysis to support defect management, analysis, defect weighting analysis, cumulative defect counts through several process operations.
• Million-way sorting of defects (by part, by process, by operator, by operation, by supplier, by anything tagged to the data).
• Easily import and export between 3rd party applications (e.g. Excel, Minitab, JMP, Statistica).
• InfinityQS is widely used by major corporations that have adopted the Six Sigma philosophy – Honeywell (formally AlliedSignal), Johnson & Johnson (Ethicon Endo Surgery, Cordis), Solectron

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What to Expect

• Free 20-minute call with a product expert
• Explore which solutions best suit your needs
• No-pressure conversation
• Get a live, personalized demo

Speak to a Distribution Industry Expert

What to Expect

• Free 20-minute call with a product expert
• Explore which solutions best suit your needs
• No-pressure conversation
• Get a live, personalized demo

Take the first step from quality to excellence

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Take the first step from quality to excellence

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Additional sections from legacy spc-tools:

Looking for convenient SPC tools? Take a look at our SPC Pocket Card which contains additional resources, including empirical rule chart and Ppk fallout rates, and keep it handy for future reference.

SPC Tools

Monitor your quality control process with advanced SPC tools. Use an empirical rule chart, Pp and Ppk Fallout Rates tables and more control charts. InfinityQS Proficient delivers many SPC tools for businesses in need of process optimization and quality control. The following charts serve as additional SPC tools and resources, including Pp and Ppk fallout rates, control chart constants, empirical rule chart, capability study and capability formulas.

Download our SPC Pocket Card

Pp and Ppk Fallout Rates

Calculated Capability Ratio

Pp Fallout
(both sides combined)

Ppk Fallout
(one side only)

0.50
0.60
0.70
0.80
0.90
1.00
1.10
1.20
1.30
1.40
1.50
1.60
1.70
1.80
1.90
2.00

133,620
71,860
35,730
16,396
6,934
2,700
966
318
96
26
7
2
0.340
0.060
0.012
0.002

66,810
35,930
17,865
8,198
3,467
1,350
483
159
48
13
3
1
0.170
0.030
0.006
0.001

Control Chart Constants

X and R Control Charts

X and S Control Charts

n

A2

D3

D4

d2

1
2
3
4
5
6
7
8
9
10
11
12

2.660
1.880
1.023
0.729
0.577
0.483
0.419
0.373
0.337
0.308
0.285
0.266

–
0
0
0
0
0
0.076
0.136
0.184
0.223
0.256
0.283

–
3.267
2.574
2.282
2.114
2.004
1.924
1.864
1.816
1.777
1.744
1.717

–
1.128
1.693
2.059
2.326
2.534
2.704
2.847
2.970
3.078
3.173
3.258

n

A3

B3

B4

C4

10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

0.975
0.927
0.886
0.850
0.817
0.789
0.763
0.739
0.718
0.698
0.680
0.663
0.647
0.633
0.619
0.606

0.284
0.321
0.354
0.382
0.406
0.428
0.448
0.466
0.482
0.497
0.510
0.523
0.534
0.545
0.555
0.565

1.716
1.679
1.646
1.618
1.594
1.572
1.552
1.534
1.518
1.503
1.490
1.477
1.466
1.455
1.445
1.435

0.9727
0.9754
0.9776
0.9794
0.9810
0.9823
0.9835
0.9845
0.9854
0.9862
0.9869
0.9876
0.9882
0.9887
0.9892
0.9896

Special Cause Rules

Pp and Ppk Fallout Rates

Calculated Capability Ratio

Pp Fallout
(both sides combined)

Ppk Fallout
(one side only)

0.50
0.60
0.70
0.80
0.90
1.00
1.10
1.20
1.30
1.40
1.50
1.60
1.70
1.80
1.90
2.00

133,620
71,860
35,730
16,396
6,934
2,700
966
318
96
26
7
2
0.340
0.060
0.012
0.002

66,810
35,930
17,865
8,198
3,467
1,350
483
159
48
13
3
1
0.170
0.030
0.006
0.001

Control Chart Constants

X and R Control Charts

X and S Control Charts

n

A2

D3

D4

d2

1
2
3
4
5
6
7
8
9
10
11
12

2.660
1.880
1.023
0.729
0.577
0.483
0.419
0.373
0.337
0.308
0.285
0.266

–
0
0
0
0
0
0.076
0.136
0.184
0.223
0.256
0.283

–
3.267
2.574
2.282
2.114
2.004
1.924
1.864
1.816
1.777
1.744
1.717

–
1.128
1.693
2.059
2.326
2.534
2.704
2.847
2.970
3.078
3.173
3.258

n

A3

B3

B4

C4

10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

0.975
0.927
0.886
0.850
0.817
0.789
0.763
0.739
0.718
0.698
0.680
0.663
0.647
0.633
0.619
0.606

0.284
0.321
0.354
0.382
0.406
0.428
0.448
0.466
0.482
0.497
0.510
0.523
0.534
0.545
0.555
0.565

1.716
1.679
1.646
1.618
1.594
1.572
1.552
1.534
1.518
1.503
1.490
1.477
1.466
1.455
1.445
1.435

0.9727
0.9754
0.9776
0.9794
0.9810
0.9823
0.9835
0.9845
0.9854
0.9862
0.9869
0.9876
0.9882
0.9887
0.9892
0.9896

Special Cause Rules

Empirical Rule

Empirical Rule

Capability Study

Capability Study

Download our SPC Pocket Card

ProFicient™, the leading real-time Quality Management solution, goes beyond typical site-based quality applications by offering an enterprise-ready architecture and statistical process control. Still have questions or need help with SPC tools? Contact us today for more information about our SPC software. It’s time to re-imagine your quality control process.

Speak to a Distribution Industry Expert

What to Expect

• Free 20-minute call with a product expert
• Explore which solutions best suit your needs
• No-pressure conversation
• Get a live, personalized demo