Advancements in Statistical Process Control (SPC)
The definition of SPC has expanded to include real-time data aggregation, analysis, and reports, all housed in the Cloud.
For nearly 85 years, quality professionals have used SPC to monitor, control, and improve their manufacturing processes. Using statistical tools to detect variability before a sub-standard part can be produced—and thus, reduce scrap, downtime, and rework costs—began in the mid-1920s with handwritten control charts. Several decades later, those charts became spreadsheets, and the tools turned digital with the invention of SPC software.
Today, SPC has broadened its scope to encompass many elements driving Industry 4.0, such as real-time data collection, analysis, and reporting.
Cost-Effectiveness in the Cloud
Perhaps the biggest trend to rock the SPC world in recent years is Software as a Service (SaaS): a software licensing and deployment model in which the software is centrally hosted, usually accessed via web browser, and licensed on a subscription basis.
One company touting this new model is InfinityQS, a longtime SPC software provider that introduced their SaaS offering, Enact, a couple of years ago. Doug Fair, chief operating officer at InfinityQS, says that Enact and other Cloud-based, real-time SPC platforms are the way of the future for in-process quality control, though SaaS has been somewhat slow to catch on.
“Our engineers will go out and work with clients who still have Windows XP or even Windows 95, because it’s expensive to upgrade to newer software,” Fair says. “But now, you don’t even need a computer; you can have an operator running our software on a cellphone. And there’s nothing to install; it’s not an app. It’s just a link to a web page, which you can access from any browser and from any device.”
Companies that access their SPC software in the Cloud, rather than on computers overseen by expensive, in-house IT teams, save money on hardware —many companies have switched to tablets and smartphones only, Fair notes— as well as on maintenance, deployment, upgrades, and IT, usually outsourcing the latter on an as-needed basis.
“With on-premises software, if you have 300 plants, then you have to do 300 separate deployments; and by the time you finish deploying all of those on-premises systems, you’ve got to go back to the first one to begin updating, because there’re always updates to the software coming out from companies like ours,” Fair continues. “But with SaaS, companies can very quickly deploy a standardized system across hundreds of plants with minimal IT support required, and without having to purchase a single server.”
The InfinityQS Enact SPC Platform was developed as a SaaS solution so quality professionals can monitor production from any device and management can review dashboards and compare quality KPIs across operations. Source: InfinityQS
Enhanced Data Collection, Visibility, and Insights
Another cost-effective benefit of SaaS is the ability to aggregate and analyze data—and not just across one plant, Fair points out, but also across multiple plants, an entire region, or even an entire enterprise.
“Control charts on the shop floor now equal about 10 to 20 percent of the benefit of SPC,” Fair says. “The remaining 80 to 90 percent of the value is to allow the quality professionals—managers, directors, and Six Sigma project teams—to access that data so that large-scale improvements can be made.”
Having that broad visibility across an entire organization means that companies can see “where their issues are, where they can make streamlined improvements, and where they can dramatically reduce costs,” Fair explains. And even when underlying statistics, specification limits, or products differ from plant to plant, new versions of SPC software enable quality teams to view fair statistical comparisons from one plant, one production line, one product code, one feature, and one region to the next.
“SaaS is awesome just for reducing costs, for the infrastructure that’s not needed and the purchases that aren’t required,” Fair says. “But the real value, the real returns on investment that we’re seeing—the multi-million dollar ROIs—are from leveraging the structure of SaaS to provide reporting and analysis across the entirety of the organization, so that these pockets of problems and areas where they need to focus can be quickly identified and prioritized for action.”
Fair points to one of InfinityQS’ clients as an example: a large North American packaging organization with 24 plants in operation at the time.
“They were going to shut one of their plants down, because their quality problems were so bad,” Fair says. “We worked very closely with the management team, in particular with the plant manager; and in less than three months, we had eliminated all of the customer complaints. Within six months, this plant had gone from the worst quality plant to the best quality plant across their entire enterprise. And the way they did it was by working with the quality data: aggregating it, summarizing it, looking at the bigger picture, and then taking specific actions.”
The new F900 Production 3D Printer is factory-floor ready with MTConnect interface and composite material compatibility. Source: Stratasys
Potential for Additive Parts
Modernizing SPC for the shop floor also includes adapting to new modes of production, like the additive manufacturing of aircraft interior parts.
Certifying such parts for aircraft installation became easier in 2018, when 3D printing company Stratasys announced its own solution: the Aircraft Interiors Configuration Fortus 900mc Production System in tandem with design allowables for ULTEM 9085 resin material, approved by the National Center for Advanced Materials Performance (NCAMP). But research into SPC is ongoing, says Scott Sevcik, vice president of manufacturing solutions at Stratasys.
“Moving towards SPC live on the manufacturing floor—understanding when you have a good part while you’re printing it, or knowing when you’re outside of your controls and you need to stop your process and understand what’s going on—that’s something that the additive manufacturing industry, as a rapid protyping industry, really hasn’t addressed, up until some of the work that we’ve been doing this year,” Sevcik says.
For instance, the latest generation of the Fortus 900 3D printing system includes MTConnect: a free and open standard for retrieving data.
“Whatever we’re collecting data on for the operation of the system, we now have the ability to bring that off the system through an MTConnect interface, so that your MES or ERP system—whatever you’re using to collect that data—then has the ability to implement pretty traditional SPC,” Sevcik says. “Historically, that hasn’t been available [in additive manufacturing], and that’s what we’re changing with the new system.”
Additionally, Sevcik notes that a strong focus on repeatability and part quality is helping Stratasys move more quickly toward additive manufacturing standards for the aerospace and automotive industries.
“We’ve spent a good deal of time looking at what drives variability in the process, and then driving that variability out: identifying the defects, identifying root causes of the kinds of defects that can occur, and then making changes to the technology in order to address that,” Sevcik says. “And by doing so, we’ve been able to take the F900 system and the ULTEM 9085 material and go from a rapid prototyping level of quality down to a very low coefficient of variation—so, very consistent part properties build after build after build, regardless of the part’s geometry or the part itself.” Q