Executing the Inspection Plan in Closed-Loop Manufacturing

Doing it well helps ensure the continuous production of quality products

Published: Wednesday, May 31, 2017 - 12:02

The execution of an inspection plan is critical for ensuring the continuous production of quality products. The purpose of this article is to explain how software tools can be used to maximize utilization of the inspection system within the main control loop once the inspection plan has been created.

In my previous article, "Get the Scoop on Closed-Loop Manufacturing," the essential elements of a closed-loop manufacturing process were discussed. One of those essential elements, referred to as the sensing element, is where the inspection system acquires measurement data needed for the control element in a repetitive manufacturing environment. Continuous measurement is needed for an efficient manufacturing process and therefore preferable to doing inspection planning outside of the main control loop. In this way, the inspection plan can be deployed on the inspection system with minimal interruption to the main control loop.

Introducing the execution workflow

The execution workflow involves all operator actions that are required to keep the inspection system running. The operator's software environment must therefore enable several key functions. The most important of these functions is direct control of the inspection system, which normally entails system startup procedures, such as homing the machine to reset the scales, qualification of probe tips needed for measurement, and recovery procedures. Other functions include the selection of inspection plans created during the planning phase and ad-hoc measurements made on the fly.

Repetitive manufacturing vs. batch manufacturing

Measurements made on the fly while under direct control of the operator may be required in some circumstances, though it is not desirable for repetitive manufacturing because it may cause disruption to the process. However, sometimes there are advantages to having basic measurement capabilities at the inspection system, thus incorporated within the sensing element itself. This is usually the case when the production process is not totally repetitive, but operating in a batch manufacturing mode. Batch manufacturing occurs when variations of components are manufactured in lots, or there is some degree of customization between lots. In situations like these, adaptations to the inspection plan must be made in real time by the operator. This means that the software needs to be incredibility flexible to make quick measurements without a lot of coding or testing.

PC-DMIS offers some flexibility in these situations by having all the tools in its core environment always accessible at the inspection system; however, it is not ideal for the most efficient process. Unfortunately, batch manufacturing does not lend itself to efficient closed-loop processes unless the batches themselves are repetitive. In cases where they are repetitive, inspection plans can be broken down into smaller sets of routines that can be later combined into functional inspection plans for any batch. This avoids the need to have such broad measurement capabilities in the operator environment in the first place. One of the latest solutions in PC-DMIS from Hexagon Manufacturing Intelligence addresses this need directly by offering a flexible execution interface that takes the place of the full PC-DMIS environment for a more controlled execution workflow.

Software solutions for repetitive manufacturing

Repetitive manufacturing calls for a highly-controlled execution workflow to achieve a stable and efficient process. The whole point of a closed-loop manufacturing process is to keep it going, and the best way to do this is to avoid delays due to decision making at the inspection system. If implemented properly, the only real decisions that need to be made at the inspection system after initial startup are the selection of the inspection plans. For this purpose, PC-DMIS developers have created a new standalone application, INSPECT, which is a user-friendly interface that makes the selection and organization of inspection plans intuitive and convenient for the operator. Although INSPECT was primarily made with the operator in mind, it also includes administrative tools to assist with the deployment and maintenance of those inspection plans. On the administrative level, INSPECT enables the defining of directories where inspection plans can be accessed for execution, as well as built-in version control. For example, INSPECT always checks and indicates the version of PC-DMIS it connects to and automatically runs the last version that was used by an administrator when connecting to the PC-DMIS host. INSPECT acts as a client interface to PC-DMIS, while PC-DMIS runs in the background. It is through this client-host implementation that the main interface is kept lightweight, flexible, and version safe.

INSPECT provides a user interface exclusively for the operator that is simple and intuitive to use, while clearly communicating essential results for the successful execution of the inspection system. These objectives are achieved through the modularity of the solution as a standalone application and through the simplicity of its interface. Through its modularity, it can be easily added on top of an existing PC-DMIS installation, and utilizes the operator's existing inspection plans. Through its simplicity, it can be easily used so that little or no training is required. By reducing the number of choices in its user interface, significant improvements can be made in workflow efficiency at a critical point in the manufacturing process.

Figure 1: INSPECT standalone application showing selectable routines as thumbnail images

Figure 2: INSPECT standalone application showing selectable reports and graphical report summary within the REPORT menu tab

Monitoring your measuring environment

Monitoring the execution of the measurement system is one of the most overlooked aspects of a closed-loop manufacturing process. A great deal of work goes into perfecting the plan and then setting up the machine, but what about maintaining its execution? If at any point the measurement system stops due to an environmental disturbance, then the entire closed-loop process is affected as well. The production process relies on the proper function of its sensing element, i.e., the inspection system. It is not merely enough to have a well-tested inspection plan or machine interface that is easy to operate, because disruptions will always occur.

Historically, many companies accept the notion that an operator must be present to monitor a machine, but this not an efficient use of labor resources. If the inspection system is always susceptible to interruption and needs to be watched, then remote monitoring is the answer. This is the ability to monitor and react to disturbances without physically watching the machine, and it is exactly where PULSE comes in. PULSE is a remote environmental monitoring software designed with the internet of things (IoT) in mind. The system monitors the measurement execution status along with several typical environmental causes for interruption or failure in the measurement process, including vibration, temperature, humidity, luminosity, and air pressure. Not only are these environmental conditions monitored, but they are recorded to provide the actionable information needed to keep the manufacturing loop closed and continuous.

Figure 3: Pulse dashboard used to monitor the measurement system's environment

Continuous improvements in user experience

In addition to offering a way to monitor your measurement routines away from the measuring system, Hexagon is also improving the hardware for a better user experience for the operator. Some of these improvements include status and work piece lighting. One example of this is the PC-DMIS Notification Center, which is a new solution that enables the configuration of status lighting and sound events for different inspection system warnings. Status lighting can be configured to show warnings on both monitors and external light stacks. Status lighting gives the operator a quick view of the inspection system from across the shop floor while an inspection plan is executing. This provides operators with a means to manage a greater number of inspection systems at once and to perform other value-added tasks during production. If production is interrupted and the operator needs to intervene, then improved workspace lighting enables easier diagnosis of system errors caused by probe-related errors, work piece setup, or the work piece itself.

Figure 4: PC-DMIS Notification Center enables the configuration of status lighting and sound events for different inspection system warnings.

Utilization of the inspection system asset

Although inspection planning plays an important role in implementing a closed-loop manufacturing process, having control over the assets within that loop ensures that you are staying productive. The inspection system is an expensive asset within this loop and does not have any value when it is not running. Though inspection systems can be used for research and inspection planning, they are best utilized and have the highest return on investment when they are limited to execution mode.

For more information on this topic, check out the webinar, "How to Execute Inspection Plans in Closed-Loop Manufacturing" on Tuesday, June 6, 2017, at 2 p.m. Eastern and 11 a.m. Pacific. I will be presenting the webinar and Quality Digest editor in chief Dirk Dusharme will be the host. Register here.

About The Author

Jonathan O’Hare

Jonathan O’Hare has more than 20 years of experience in manufacturing, beginning as an applications engineer at Brown & Sharpe Manufacturing Co., followed by roles in product development and product management within Hexagon Manufacturing Intelligence. O’Hare’s latest role focuses on the development of measurement software solutions for industrial computed tomography systems in cooperation with technology partner YXLON International. O’Hare holds a bachelor’s degree in mechanical engineering and a master’s degree in business administration from the University of Rhode Island.