Realizing the Value of SPC

Simplified, integrated statistical process control automates mold inspection planning and reporting in real time.

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Mold builders can monitor and control their manufacturing processes, ensure operations are at full potential, produce conforming products, and minimize or eliminate waste by using statistical process control (SPC). A method of quality control that uses statistical methods, SPC focuses on early detection and prevention of problems caused by unseen variations in the critical manufacturing processes being monitored. For example, tool wear or a gradual drift of an operation that can result in out-of-spec parts. 

SPC identifies manufacturing issues before they impact quality by highlighting changes to these critical processes over time. Identifying a quality issue after the production of an out-of-spec part can often result in additional labor and unplanned costs from scrap, waste, rework and rush shipping. For example, using raw materials that may have longer restock lead times can disrupt overall production throughput, or redirecting staff to rework parts can put stress on the manufacturing process. Even worse, sending a key customer nonconforming parts can delay that customer’s own manufacturing process, damage that customer’s brand and jeopardize key contracts. 

While SPC is a widely known quality management tool, it also has generally been regarded as a fragmented inspection process based on its use of a mix of labor-intensive manuals, paper-based processes, and multiple software programs and systems. Traditionally, SPC requires installing various software applications and measuring tools, setting up the data collection and analysis process, and collecting the data from the various stages of the manufacturing process, including data from machines and hand gages. Also, the expertise required to develop, analyze and report on the details of SPC may not be readily available in house and are costly to acquire. 

Because of these inherent characteristics and limitations, traditional SPC has been most beneficial to manufacturers with low-mix/high-volume operations, meaning a single product is being made in high volumes. In these environments, production jobs run for long periods of time, so the time and labor required to set up a typical SPC project is a justifiable cost that can be amortized across a single manufacturing line producing a high volume of products.

For mold builders who have high-mix/low-volume operations, such as making a single mold or just a few molds per production run, the time, labor and cost of implementing an SPC process typically has not been as easy to justify. The costs of most SPC software and the associated time and labor necessary to implement an SPC program can be hard to recover when the manufacturing processes require more rapid setup and change-over.

Real-Time SPC
Simplified, integrated SPC available today has advanced the quality-control process, because it is faster to implement, easier to use and includes all the needed capabilities in one solution. This type of advanced SPC option employs a cloud-based quality management system that can automatically and electronically implement inspection, planning and reporting of the entire mold manufacturing operation in real time. It makes use of 2D drawings, 3D models and graphical shopfloor data input from any browser-based device, as well as out-of-spec alerts, gage management and real-time control charting. 

Instead of the manually created inspection plans that begin the process of implementing traditional SPC, advanced SPC solutions automate the extraction of key dimensions from 2D drawings and 3D models and create an electronic inspection plan. Such advanced SPC also eliminates the manual ballooning of dimensional characteristics or key dimensions and features, and error-prone, manual entry of data into inspection plans by making use of automated applications with optical character recognition. This allows the dimensional characteristics from the 2D drawings and 3D models to be quickly extracted and published in required inspection planning documents. Then, as revisions occur, users can rapidly compare versions, visually identify changes and publish them automatically to real-time inspection applications that include the 2D drawings or 3D models integrated with the inspection plan. 

In addition to time savings and improvement in accuracy, use of electronic inspection plans allow in-process inspection data to be collected and analyzed on low-cost tablets at each workstation directly on the shop floor in real time. This helps streamline the operation, from design to manufacturing, increasing accuracy and providing a standardized process for managing revisions that ensures configuration control.

In addition to electronic inspection plans, advanced SPC uses standardized, uniform electronic flow down from the 2D drawings or 3D images to the inspection plans, giving mold builders instant access to manufacturing and inspection data. This replaces the manual creation of paper-based spreadsheets, forms, final drawings, work instructions and non-conformance procedures. All of this information can be quickly mapped to the manufacturing process using a simplified graphical dashboard that supports user entry of manufacturing equipment, gages, and job or purchase order numbers. This provides full traceability from inspection planning to shopfloor inspection. 

To illustrate: from a browser-based device, a moldmaker can view a 2D drawing or 3D image of the mold, manipulate it with the touchscreen and view point by point the inspection that needs to be performed. As he takes each measurement, he can also see the charting in real time, which alerts him to the quality conformance of each measurement. Basically, such a system graphically tracks, updates and communicates as the moldmaker measures. Manufacturing process data is now collected, aggregated and analyzed in real time. Operators receive real-time feedback on every measurement, and management can spot emerging trends and issues, such as fixture drift and tool wear. 

Integrated SPC solutions also create process control charts. Quality managers can review SPC data that has been automatically organized and presented in real-time control charts that allow for identification, investigation and correction of manufacturing process issues before they become quality issues. Conditions such as fluctuation in temperature, mold wear and surface finish variation can also be flagged, and then the quality manager can be automatically alerted in real time. 

For example, with advanced SPC solutions, quality managers can zero in on critical areas and monitor a mold to see if it is drifting (meaning humidity or temperature is affecting the surface quality). It allows them to see the beginning of process-control drift and take action immediately, rather than have to rely on the manual data collection of traditional SPC and then use mathematical formulas to create control charts to determine process inefficiencies days later, often too late for truly effective root-cause analysis.

Additional capabilities of advanced SPC include automated gage management and CMM data integrated into the SPC process, providing additional simplification and a higher level of process control. This means every measurement gage and tool, from hand tools and electronic probes to portable scanners and other wireless gage devices and machine sensors, can be tracked, including their calibration requirements and history. 

The savings associated with the reduction or elimination of many direct and indirect costs of implementing traditional SPC solutions and the potential for improvements in quality should be enough for all mold manufacturers to take a look at advanced SPC.

To see a video of SPC in action, click HERE.

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