Dereck Moore
Growth mandates periodic analysis of operational strategy efficiency.

One of the big differences in implementation of Lean manufacturing practices between OEMs and EMS providers is control of product design and the optimization of that design for production. From a production standpoint an OEM can create a Lean manufacturing strategy and then ensure future products are designed to conform to that strategy. Conversely, contract manufacturers make far more tradeoffs in Lean implementation to conform to customer preferences. As a business grows, tradeoffs that made sense on a smaller scale create constraints, and inefficiency creeps in. Here are three of the most common areas where issues can be found:

Capacity planning. For most companies, the first noticeable constraint as growth occurs is available SMT line capacity. This drives several questions. Is the best solution to reconfigure the line for increased throughput or to purchase another line? Will an improvement in changeover time help address capacity issues? Are lines standardized enough to balance production over the entire SMT area, or are constraints being created due to unique line configurations?
Addressing these questions requires a capacity model capable of supporting “what if” analyses over multiple variables. For example, the internally developed capacity model in SigmaTron’s Elk Grove Village, IL, facility includes the ability to change variables such as maintenance, holiday schedules or demand variations. The model’s “what if” capabilities also make it easy to understand the impact of line configuration changes on throughput.

Production line configuration and processes. Line configuration choices are typically dictated by product complexity, typical lot sizes and overall volume. From a Lean perspective, standardized equipment that permits production to shift among all lines provides better throughput than a production area with lines uniquely configured for different types of product, since eliminating variation increases schedule flexibility. The challenge for contractors that see a change in business mix and/or volumes is determining the best line balancing strategy. For example, the Elk Grove Village facility has found the optimum configuration for its business mix is two high-speed SMT chipshooters, followed by a machine capable of placing fine pitch and/or larger parts. That said, a contractor with lower volumes might not find the added placement speed has a significant enough effect on overall throughput to justify the cost of the second chipshooter. Conversely, at some point, adding to placement capacity moves the constraint to reflow, making adding a line the preferred solution.
Another area that should be analyzed carefully when production constraints are present is whether changeover time can be optimized. This contractor kits to an extra set of feeders and loads the next job on the line as soon as the prior job clears the machine. This practice eliminates a step in the kitting process and is approximately 40% faster than a process utilizing only a single set of feeders.

Automation strategy. The final area to evaluate is automation strategy. One of the biggest challenges contractors engaged in lower-volume production face is justifying tooling and/or design changes needed to implement DfM changes on lower-volume products. Customers don’t perceive a payback on tooling or redesign costs, and see manual soldering as way to save on nonrecurring engineering charges (NRE). From a Lean perspective, this is false economy for two reasons: First, manual processes have greater variability, which creates the opportunity for defects and the concomitant non-value-added cost. Second, manual soldering is typically more costly than automated assembly, and over the life of the project, the customer will likely end up paying more than the NRE cost in this added assembly cost, particularly if project volumes increase over time.

This contractor’s approach is to utilize selective solder in addition to wave solder to give customers an option that won’t involve tooling for lower-volume products.  The printed circuit board assembly layout does need to accommodate automated handling, but pallets are unnecessary. Palletized wave soldering is recommended for higher-volume products. A switch from manual soldering to an automated soldering process can improve throughput by more than 150% and typically improves first-pass yield and delivery performance. Contractor with engineering support centers can provide customers with DfM recommendations and PCB layout. When customers are doing their own layout, it is recommended the EMS team performs a DfM review prior to any tooling being ordered to ensure the design is optimized for automation and manufacturability.

One option for companies trying to reduce manual soldering within their existing customer base is to start by analyzing the 10 highest-volume assemblies  to determine whether automated soldering would be justified and continue that “top 10” process either monthly or quarterly until all boards have been analyzed. Such an approach can free skilled production operators for deployment in other production operations. At a time when many companies are experiencing skilled labor shortages, this provides an added capacity “force multiplying” benefit.

The customer-driven nature of the EMS business model can generate tradeoffs and inefficiencies. The challenge for EMS providers is to implement continuous improvement initiatives that periodically analyze the efficiency of the operational strategy against current business trends. The result: increased productivity at far less cost than simply replicating existing production resources.

DERECK MOORE is director of operations at SigmaTron in Elk Grove Village, IL (sigmatronintl.com); dereck.moore@sigmatronintl.com.

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