Getting Lean

The Visual Factory and Legacy Equipment and Processes

MES upgrades capture kanban inventory levels, allowing electronic replenishment pulls.

The visual factory has come a long way since the concept was introduced, moving from production status viewable by walking the factory floor to a comprehensive collection of real-time data viewable from any interconnected computer. That evolution isn’t seamless for many electronics manufacturing services (EMS) providers, however. While newer equipment platforms are designed to integrate with manufacturing execution systems (MES) easily, legacy equipment platforms may require specialized programming or other workarounds to achieve desired interoperability. Equipment communication incompatibilities often lead to multiple shop floor control systems being utilized among work areas, which is inherently inefficient.

SigmaTron International’s Chihuahua, Mexico, facility recently dealt with these issues when the facility began transitioning to the company’s proprietary Tango MES. The company’s corporate IT and operations teams have worked together to define enhanced shop floor capabilities in production and are upgrading system capabilities across facilities. The challenge for facilities implementing the latest enhancements is creating efficient equipment interfaces and integrating or replacing legacy processes.

The team started planning the transition in October 2022. One of the first issues identified involved bar code scans. The equipment and the MES each required a scan and that was slowing changeover time. The team was able to resolve the issue and create a single-scan process for its newest SMT equipment platform after discussing the issue with the equipment manufacturer. The company is standardizing on an SMT platform that integrates with the MES easily via an API and a software tool development kit. The facility also has legacy equipment that doesn’t integrate well, however, and that requires a platform-by-platform reverse engineering effort. In the case of older equipment with no software interfaces for interoperability, local programmers may be hired to create the interface.

The goal once the MES is fully integrated with all equipment platforms is to have one system capable of providing traceability at the lot, unit and component level accessible from any computer that integrates shop floor control and includes enforced routing. The MES will also enable the team to view what is being produced and what inventory is in place in every step of the process from their desktop computer or a tablet.

Incoming quality control (IQC) labels materials as they are received and then associates that bar code with each printed circuit board assembly (PCBA). SMT machines verify correct feeder/table loading based on material bar code information compared to programming data, and the enhancements integrate this activity with the MES.

Following full implementation, production lines will transition from use of physical kanban cards to electronic kanban cards based on shop orders. Monitors mounted in each production area will show what is planned for production that day. Finished unit count versus daily goals are also visible on monitors on the production floor.

The facility does both PCBA and higher-level assembly (HLA) work. There are no dedicated PCBA production lines so work can be moved among lines based on available capacity. PCBA production goes into a supermarket kanban. As PCBAs are pulled from the supermarket to support HLA demand, replenishment orders go back to SMT or through-hole lines to restock the supermarket. Currently, the supermarket uses a manual visual system of physical kanban cards and works on a first in, first out (FIFO) inventory management philosophy. Personnel need to visit the area to see what is in it. Once the MES is fully implemented, kanban inventory levels will be visible in the system and replenishment pulls will be done electronically. Since the information associated with each assembly includes date manufactured, FIFO discipline will be easier to maintain.

The system will also be used in continuous improvement efforts. The facility tracks the cycle time of each product and sets targets for improvement every five to seven months.

The ME implementation in the SMT area is scheduled to be completed in the third quarter this year.

The primary benefit of a holistic approach to automating the visible factory is the ability to have critical data where it is needed, when it is needed for appropriate management decision making at all levels of the organization. A secondary benefit is that it forces operations personnel to look at the current state of the factory floor and streamline the system and process workarounds that pop up over time due to equipment and system interoperability incompatibilities. While this automation process takes time to implement, the result is greater efficiency and better ability to address variations in demand or component availability. On a positive note, newer manufacturing equipment platforms take this need for interoperability into account, so achieving this goal will become easier over time. Article ending bug

Alvaro Grado is manufacturing engineering & quality manager at SigmaTron International ( in Chihuahua, Mexico; Michael Schillaci is vice president IT at Sigmatron International;