Applying Lean Manufacturing Principles in a High-Mix Environment
Applying Lean manufacturing principles to high-mix electronics assembly can reduce changeover times, streamline production workflows and improve quality through standardized processes and automation.
Military, aerospace and space hardware often involves low- to medium-volume production and must meet rigorous standards. While applying Lean manufacturing principles to these environments may not yield the same productivity gains as high-volume manufacturing, selective use of Lean principles can improve factory cycle times and eliminate opportunities for defects. Additionally, Lean best practices share many similarities with established practices in the military and aerospace sectors. Axiom Electronics, an electronics manufacturing services (EMS) provider in Hillsboro, Oregon, incorporates Lean principles throughout its production floor.
One example of a parallel practice is foreign object debris (FOD) prevention. Something as simple as a loose screw can cause shorts or other damage if it rolls around inside aircraft hardware during flight. Consequently, most military and aerospace programs require FOD prevention programs. Our team combines FOD prevention and 5S to create a culture of daily cleaning, using checklists to verify that cabinets, workstations, racks, and carts remain clean and organized. Employees update shadow boards and account for all tools, verify their working condition, and confirm compliance with required calibration schedules. They also identify materials in refrigerators and on carts and check consumables against their expiration dates. The team validates adherence to electrostatic discharge (ESD) requirements and removes any material it identifies as FOD from the area. Auditors review the nonconformances that production personnel identify through their checklists to verify compliance.
In the SMT area, the team uses Lean practices to reduce changeover times and streamline first-article documentation. Each line has duplicate feeders, allowing the setup team to prepare feeder tables for the next job while the current job runs. As the previous job finishes, operators switch the tables and return the used tables to the setup team for preparation ahead of subsequent production runs.
The team classifies each production order as either a first-piece job or a rebuild. For first-piece jobs, inspectors must approve the first board before operators queue additional boards for production, since initial production may require process optimization. For rebuild jobs, the first piece still undergoes a full inspection, but operators can queue additional boards through the steps preceding reflow because the team has already validated the process. Once the inspector approves the first piece, the line can immediately begin running.
The company also applies Lean principles to its software choices. While the SMT line software tracks placements, misaligned parts, and dropped components, sharing that information requires additional interface licensing. The company’s manufacturing execution system (MES) can import machine data and optimize groups of SMT jobs to reduce changeover time, so the team now uses MES as its primary line optimization tool.
The MES reviews production schedules and groups jobs by customer, considering component commonality and optimizing reel placement so operators can run multiple jobs for the same customer consecutively without changeovers. The team is also validating the MES software’s ability to track component usage and reconcile available component counts within the enterprise resource planning (ERP) system by auditing returned reels with X-ray counters. Operators currently perform this process manually, but once validation is complete, the system will fully automate daily cycle counting and ERP reconciliation.
The company also uses specialized software to meet AS9102 first-article documentation requirements. This software allows the team to prefill initial information and add annotations as products move through production.
The overall factory layout also follows Lean principles. Materials enter one end of the factory and exit through the other. Secondary assembly workbenches feature standardized soldering irons, solder wire, and hand tools. In the system integration area, the company dedicates one work cell to a long-term customer with continuous demand, while other areas serve as flexible work cells with tables on wheels that operators can easily rearrange.
Together, standardized equipment, consistent practices, and appropriate automation reduce the variation that can otherwise lead to mistakes and defects in a high-mix environment. Checklists provide particular value by helping the team address all requirements consistently.End of article content
Rob Rowland is Axiom Electronics’ director of engineering operations. He can be reached at rob.rowland@axiomsmt.com.