Improving Productivity in a High-Mix Environment Utilizing Lean Manufacturing Principles

Applying Lean manufacturing principles to streamline higher-level assembly, reduce wait times and improve throughput.

The electronics manufacturing services (EMS) industry is a form of controlled chaos. EMS factories often have 30 or more customers with completely different products, varying levels of assembly complexity and highly variable demand patterns. To control this chaos, EMS providers implement systems to standardize production processes and streamline production flow. While manufacturers can often significantly automate high-volume production, higher-mix production typically involves a greater human element, particularly in higher-level assembly. Consequently, production team members must also standardize their approach to manual assembly activities. This article looks at the strategy EDM used to introduce Lean manufacturing principles to its production team and the initial results that training delivered.

Integrating Lean Principles Into Higher-Level Assembly

EDM is a full-service, employee-owned EMS provider with a facility in Lynchburg, VA. Its surface mount technology (SMT) printed circuit board assembly (PCBA) and test processes use highly automated, continuous-flow manufacturing. However, its higher-level, or box-build, assembly processes have traditionally used batch-flow work cells. Increasing product mix and volumes have necessitated a transition to continuous-flow processes in higher-level assembly.

As a result, the team has been implementing Lean manufacturing principles in conjunction with GENEDGE, a Virginia-based NIST Manufacturing Extension Partnership (MEP) center. The team has held kaizen workshops that introduced core concepts and tools, including value stream mapping and Deming’s Plan-Do-Check-Act (PDCA) cycle. The goal is to encourage team members to continually consider ways to apply Lean principles day-to-day to improve efficiency and throughput.

Team exercises reinforced these concepts. For example, teams started by analyzing a current-state process map of a mock company with significant inefficiencies against a limited set of improvement options. A subsequent exercise allowed the team to develop a future-state map with no constraints on improvement options. Combining these exercises helped team members better understand the impact of their improvement choices.

The team subsequently held kaizen events on the production floor. The first event analyzed a project for which the customer’s volumes had more than doubled in both required lot size and frequency of production builds compared with the prior year. The kaizen event aimed to optimize the process and improve throughput.

The team mapped the current state and then used the PDCA process to identify potential improvements and determine which would likely have the greatest impact. At lower volumes, one operator could produce 32-40 pieces per hour. When the team scaled the product to a one-piece-flow model, three operators produced a total of 120-140 pieces per hour. This improvement in throughput aligned with the customer’s increased volume requirements.

The team identified a list of improvements for the future-state map, including:

• Consolidating workspace from one workbench per operator to two operators per workbench. This change reduced the distance operators needed to transfer material.
• Changing the tool used to clean dust from a plastic overlay from a can of air to a benchtop-mounted air gun.
• Replacing regular screwdrivers with a screwdriver mounted on a tool balancer over the product. The team also replaced bins holding screws with screw presenters, enabling the operator to grab a screw with the screwdriver’s magnetic tip instead of reaching into a bin.

EDM’s Lean integration continued to focus on the wastes of waiting and transportation. Three cross-functional teams of eight people, including production operators, engineers and purchasing personnel, analyzed existing inventory levels, material flow and production flow product by product.

The teams initially analyzed two products. In one case, a spaghetti diagram of the complete flow showed that material and product traveled 73 miles over a six-week period. Moving to continuous-flow cells reduced the total wait time to 1.5 weeks. Converting the second product to continuous flow reduced four weeks of wait states to 3.5 days. The teams continued analyzing products adaptable to continuous flow until they had transferred all likely candidates. In conjunction with this analysis and the transition to continuous-flow processes, EDM also educated employees on 6S processes designed to improve workspace and workplace organization and safety.

The second kaizen workshop focused on a new product final assembly operation. The product had 33 part numbers and 70 parts total. During the initial production run, the team measured assembly time at 44 minutes of labor per unit. Team members then went through several improvement iterations, including changing the workstation setup and dividing the assembly work differently. They timed each operation to enable a line-balancing exercise.

The final configuration eliminated bottlenecks by dividing work among operators into equal blocks of time. Each operator became responsible for checking the material in their bins for accuracy and checking the prior operator’s work. The team also modified the toolkits. Historically, common tools were available in a work-cell toolset, while product-specific tools remained with the product kit. Now, EDM issues each workstation a common toolkit for the product. As a result of these improvement efforts, assembly time for the product dropped from 44 to 24 minutes.

Leveraging outside resources such as GENEDGE offers an effective way to introduce Lean concepts to production teams. Training exercises that encourage teams to apply continuous improvement processes beyond workshop activities can also help create a Lean culture.End of article content 

Matt Cline is EDM’s quality manager and can be reached at mcline@edmva.com. Mike Stanley is EDM’s manufacturing manager and can be reached at mstanley@edmva.com.