Lean Six Sigma Approach Helps Keep Costs on Track
Changes in purchasing and line practices can save big dollars.
The benefits of implementing Lean manufacturing philosophy are higher throughput and elimination of the variation that can introduce defects into a process. In a static environment, implementing Lean philosophy creates significant efficiencies that stay in place with little oversight. Most electronics manufacturing services (EMS) providers have very dynamic environments, however, where supply chain, customers, project technologies, volumes, production personnel and factory floor layout change frequently. In that environment, inefficiencies can creep in. Six Sigma training provides employees with a formalized product-solving methodology that allows these inefficiencies to be corrected. SigmaTron in Tijuana, Mexico, uses Six Sigma as a tool to keep its team focused on eliminating inefficiencies. The facility faced three major challenges over the past year: changing dynamics in the materials market; more projects moving to Mexico for tariff mitigation; and spikes in demand at existing customers for their products. This column looks at four Green Belt projects that cumulatively have eliminated nearly $300,000 in unnecessary costs in the first five months of improvement implementation.
The Green Belt teams use a DMAIC (define, measure, analyze, improve, control) methodology to identify each improvement opportunity and strategize the appropriate solution. Their facility’s Yellow Belts helped with their continuous improvement projects.
In the Define phase, teams develop a problem statement, identify critical to quality (CTQ) and defect metrics, create project objectives, determine the business case and financial impact of the desired improvement, determine customer impact, set milestones and a timeline, define the project scope and boundaries, and assign team responsibilities. In the Measure phase, the teams measure the variances they associate with the problem they’ve identified, utilizing core tools such as cause-and-effect diagrams and gage R&R measurements. In the Analyze phase, the teams analyze the data collected to determine trends and possible corrective actions.
In the Improve phase, the teams implement improvements and then utilize design of experiments (DoE) to determine if the proposed solutions correct the problem. In the Control phase, measures to ensure continued achievement of desired metrics are implemented.
The first project involved material cost reduction. The goal of the team was to analyze the most active parts in major projects to ensure that as market constraints lessened, best material pricing was achieved. The team developed a list of over 250 parts that needed to be requoted based on changing market trends. They implemented additional negotiation training for their resident purchasing team, established goals for continuing cost reduction in a list of parts targeted for additional cost reduction, and implemented a more robust management review process. They also now measure cost savings by buyer. An annual cost saving improvement goal of 25% was set, and by month five of the project the cumulative average exceeded that goal.
The second project involved quality defects on a rapidly growing project in the SMT area. The defects on that specific project were substantially higher than defects in other projects in the SMT area. The goal was to decrease the defective parts per million rate (DPPM) by 70%. Defects are measured at the individual solder joint level. The team determined four primary improvement areas: solder paste deposition height, printing process parameter, squeegee maintenance and standardization of operator inspection criteria. They looked at two failure modes: solder defects and placement defects. They also did gage R&R measurements of the accuracy of operators identifying defects. The solution involved adjusting solder paste height, replacing solder paste squeegees more frequently, recalibrating some feeders on placement machines, providing additional IPC-A-610 workmanship standard inspection training to production operators, and developing a manual to better explain the inspection process. The result achieved the defect reduction target and significant cost savings by eliminating associated rework.
The third project involved reduction in solder dross. Initial measurement and analysis of wave-solder machines indicated one machine appeared to be generating more solder dross than the others on the production floor, so the team decided to study it first. Further analysis determined variance was caused by inconsistencies in preventive maintenance and weighing of the solder and dross in the container, so a standardized weighing and maintenance process was defined. The team also looked at optimum solder pot fill levels and whether residual dross on pallets contributed to an increase in overall dross accumulation. DoEs indicated that while fixturing to ensure a uniform fill level did impact dross accumulation, solder pallet cleanliness had no impact. Solder dross accumulation was reduced by nearly 50% in the first five months of the project.
The fourth project focused improving production throughput for a customer whose project volumes were growing rapidly. The goal was to better balance the lines while improving revenue generated per employee. The entire production process was mapped to determine areas of processing inefficiency. It was determined production flow through the factory was inefficient, and the hot bar process represented a bottleneck, in part due to machine-related inefficiencies in temperature measurement. The process flow was redesigned to minimize the transport distance among work areas and to improve the layout efficiency of process lines and workstations. A faster thermometer was added to the hot bar stations to enable operators to monitor and maintain optimum temperature more efficiently.
Individually, the savings on any one of these projects in the initial stages aren't significant, but cumulatively these four projects are expected to represent nearly $750,000 per year in cost savings. More important, the three production-related projects increased standardization, which eliminates the variation that creates defect opportunities. The nature of the EMS industry creates inefficiency. Training employees in Six Sigma techniques helps ensure inefficiency is identified and eliminated on a continuing basis.
is NPI manager, is quality assurance engineer and is purchasing manager at SigmaTron International in Tijuana, Mexico; juan.morales@sigmatronintl.com, filemon.sagrero@sigmatronintl.com and erick.rios@sigmatronintl.com, respectively.
Ed: The original version of this column had an incorrect spelling for Erich Rios.
