SPC · part of Process Quality

SPC Software See the drift before it becomes scrap.

Operators enter a subgroup at the machine and get OK or a clear instruction in seconds. Engineers approve control limits, run capability studies and see every unstable, incapable or overdue characteristic on one dashboard.

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The basics

What is SPC, and what does SPC software do?

SPC, statistical process control, uses control charts to tell normal process variation from a real change, so you can act before parts go out of tolerance. SPC software collects the measurements, calculates control limits, checks every point against run rules, and works out capability indices such as Cp and Cpk.

In most plants SPC means a check sheet filled in at the end of the shift and typed into Excel the next day. By the time anyone sees the trend, the scrap bin is full. Control limits get recalculated until the chart looks fine, and the Cpk in the PPAP came from 30 hand-picked points.

Features

Statistical process control software for the line and the lab

Real-time SPC entry at the machine

A tablet-sized screen per workstation, with Enter moving to the next value so USB gauges work as they are. Typos outside reasonable limits are refused, and readings near the spec limit are flagged.

X̄-R, X̄-S and I-MR control charts

Chart a part characteristic or a process parameter such as oven temperature. Each reading records the part, shift and your own context fields, such as cavity, nozzle or supplier lot.

Run rules with a reaction for every signal

Choose Basic, Western Electric, Nelson, AIAG or Wheeler rules, or edit your own. A signal names what happened in plain words, shows the reaction plan and records the cause and action.

Control limits that never drift on their own

Limits start as trial, then a baseline of 25 subgroups is proposed, approved and frozen. A revision needs a reason, and old points stay judged against the limits in force when they were taken.

Cp, Cpk, Pp and Ppk studies with honest warnings

Save a study as a signed-off snapshot with a histogram, normality test and probability plot. It warns when the process is unstable, the data is too thin or not normal, and targets are set per special characteristic class.

Timed checks, grades and the SPC dashboard

Checks fall due on a clock that runs only in shift time, and missed ones are recorded. The dashboard puts out-of-spec and out-of-control streams first, with stream grades, a capability league table and a cause Pareto.

Connected

SPC doesn't live alone

Each subgroup can name a gauge from the calibration register, and an overdue gauge is blocked or warned at entry. Charts use the FMEA special characteristic classes, and approved capability studies become evidence on the PPAP initial process studies element.

Standards and industries

Online SPC software for automotive and aerospace suppliers

Capability targets, rule sets and approvers are settings, so customer-specific requirements win.

IndustryStandardWhat you get
AutomotiveIATF 16949, AIAG SPC manualStatistical studies on special characteristics, defaults of Ppk 1.67 for initial and Cpk 1.33 for ongoing studies
AutomotiveAIAG PPAPApproved capability studies as initial process study evidence
Aerospace and defenceAS9100, AS9145Process monitoring with a full audit trail, capability evidence for production approval
General manufacturingISO 9001Monitoring and measurement of processes, with recorded reactions to signals
FAQ

SPC questions people ask

Still unsure? Ask our team.

What is SPC in manufacturing?

Statistical process control is the practice of measuring a characteristic at set intervals, plotting it on a control chart and reacting when the chart shows a change. It moves quality from sorting good parts from bad to keeping the process stable so bad parts are not made.

What is a control chart?

A time-ordered plot of a measurement with a centre line and upper and lower control limits calculated from the process itself. Points outside the limits, or patterns such as a run of points on one side, signal that something in the process has changed.

What is Cpk?

Cpk is a capability index showing how well a stable process fits within its specification, taking account of where the process is centred. It is the distance from the process mean to the nearest spec limit, divided by three standard deviations of within-subgroup variation. A Cpk of 1.33 is a common minimum.

What is the difference between Cp and Cpk?

Cp compares the spec width with the process spread and ignores centring. Cpk also accounts for where the mean sits, so an off-centre process has a lower Cpk than Cp. If Cp is good and Cpk is poor, recentre the process before trying to reduce variation.

How do you calculate Cpk?

Estimate sigma within from the chart: average range divided by d2, average standard deviation divided by c4, or average moving range divided by 1.128. Then Cpk is the smaller of (USL minus mean) and (mean minus LSL), divided by three sigma. YourBrand does this for you and warns when the result cannot be trusted.

Can we chart process parameters, not only part dimensions?

Yes. A chart can be tagged to a part, a workstation, or both, so you can chart oven temperature, bath concentration or spindle load. Operators can record which part was running when they take a process reading.

What should the best SPC software do?

At minimum: fast entry at the machine, correct control limits that are approved and versioned, run rules with a recorded reaction, capability studies that warn on unstable or non-normal data, overdue check tracking, and a trail an auditor can follow from any point to who measured it.

Catch your next process shift while the parts are still good

We walk through it with your own parts and documents. It takes about 30 minutes.

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Related: Process Quality suiteGauge calibration and MSAPPAP softwareIATF 16949Automotive