SPC, Cp and Cpk Explained: How to Calculate and Interpret Process Capability
SPC, Cp and Cpk explained: control charts, capability formulas, a worked example and what a Cpk of 1.33 really means for defect rates on your production line.
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Quality Management System
Quality Management Software That Catches Bad Batches on the Line
Quality management software brings control plans, measurement records, SPC control charts, nonconformances, 8D investigations and calibration tracking into one system. Each measurement is checked against tolerance and control limits as it is taken, and the right person is alerted when a process drifts, so bad batches are caught on the line rather than at the customer.
In many plants, measurements still go onto paper check sheets that end up in a binder. The data is there when the auditor asks, but nobody looks at it while the line is running. By the time a drifting process is noticed, the batch is finished and the problem surfaces at the customer's goods-in inspection. Then the 8D starts, and days go into chasing forms, emails and spreadsheets.
We build quality management software that evaluates every measurement the moment it is taken. Your control plan lives in the system; operators enter readings on a tablet, or a connected digital gauge sends them directly. When a value falls outside tolerance or a control chart starts to drift, the right person is alerted straight away. Nonconformances, quarantine, 8D and calibration records sit in the same system and link to each other, so audit preparation stops being a separate project.
What the Quality Management Software Covers
Control Plans & Work Instructions
Define which characteristic is checked on which part, how often and with which gauge. Operators see the next check and its tolerance on screen, and a skipped check is logged.
SPC & Process Capability
X-bar/R charts and Cp/Cpk update automatically with every reading. You are warned as the process approaches its limits, so you can act before a bad part is made.
Nonconformance & Quarantine
Nonconforming product is quarantined in the system and blocked from dispatch. Scrap, rework or concession decisions are recorded with who made them and when.
8D & Root Cause Analysis
Open an 8D for a customer complaint or an internal defect. Fishbone and 5 Whys analyses run in the system, and every action has an owner and a due date.
Traceability & Recall
Trace forward and backward which raw material, machine and operator went into each batch. When an issue arises, the affected batches are listed within minutes.
Gauges & Calibration
Calibration due dates for callipers, micrometers and test equipment are tracked. Readings cannot be entered from a gauge that is out of calibration.
Who It Is For
- Automotive suppliers (IATF 16949)
- Food manufacturers (ISO 22000, HACCP)
- Medical device manufacturers
- Metalworking and foundries
- Plastics and rubber
- Electrical and electronics assembly
- Packaging and print
- Defence industry suppliers
How We Work
01
Review Your Current Process
We go through your control plans, check sheets and nonconformance flow, and list what your standard and your customers require.
02
Move the Control Plan Into the System
We set up the part, characteristic and tolerance structure, and agree inspection points, frequencies and owners.
03
Connect Gauges & Design Screens
We connect digital callipers and test equipment and design operator screens for real shop-floor conditions.
04
Pilot Line, Then Rollout
We start on one line, settle control limits with real data, then extend the system to the rest of the plant.
Let a Camera Handle Visual Checks
For visual checks such as scratches, missing components or label errors, we connect our AI-based computer vision systems to the quality software. When the camera spots a defect, a nonconformance record is opened without operator intervention. For deeper batch and material tracking, see our production traceability solution; to see quality data alongside downtime and scrap, see our MES production tracking software.
Questions we hear most often
Frequently Asked Questions
What does quality management software do?
Quality management software brings control plans, measurement records, SPC control charts, nonconformances, 8D investigations and calibration tracking into one system. Each measurement is checked against tolerance and control limits as it is taken, and the right person is alerted when a process drifts. Bad batches are caught on the line rather than at the customer's goods-in inspection, and audit records build up as you work.
Are SPC charts and Cp/Cpk calculated automatically?
Yes. X-bar/R control charts and Cp and Cpk values update automatically with every new measurement. Operators enter readings on a tablet, or a connected digital gauge sends them directly. When a process starts drifting towards its control limits the system raises a warning, so action can be taken before defective parts are made. Control limits are set from real data on a pilot line.
How are nonconforming products stopped from shipping?
A nonconforming product is placed in quarantine in the system and its shipment is blocked. The scrap, rework or concession decision is recorded with the name of the person who made it and the date. If visual checks are connected to our AI-based computer vision, a nonconformance record is opened automatically, without operator intervention, when the camera detects a defect.
Can 8D and root cause analysis be run in the system?
Yes. An 8D can be opened for a customer complaint or an internal defect, with fishbone and 5 Whys analysis carried out in the same record. Every action has an owner and a due date that are tracked. Because nonconformance, quarantine and traceability records are linked to the 8D, no one spends days collecting forms, emails and spreadsheets.
What happens if an instrument is overdue for calibration?
Calibration dates for callipers, micrometers and test equipment are tracked in the system. Measurements cannot be entered with an instrument that is overdue for calibration, so readings from an invalid instrument never reach your quality records. These records sit in the same system as measurements, nonconformances and 8Ds, so audit preparation stops being a separate project.
How does the move to quality management software work?
We first review your control plans, forms and nonconformance flow, and list the requirements of your standard and your customers. We then set up the product, characteristic and tolerance structure, connect digital gauges and design operator screens. The system runs on one line first, control limits are set from real data, and it is then rolled out to the other lines.
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