Lean and Lean Sigma Print E-mail
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Written by Carlos Rodriguez   
Monday, 01 February 2010 00:00

  

There is a practical way to sequentially implement the two efficiency systems.

There is no debate that correctly applied Lean manufacturing philosophies can increase production efficiency. However, there are variations in Lean tools. The fundamental difference between Lean and Lean Sigma is that while Lean manufacturing focuses on the elimination of waste by removing steps in processes, Six Sigma fine-tunes processes by focusing on specific process improvement activities.

Implement core Lean philosophy first. EPIC chose to implement Lean manufacturing principles first. Major points of focus included:

Process flexibility. A critical first step was developing a production process that could handle small lot sizes over a wide range of customers and product types. This included working with suppliers capable of modifying their equipment to support rapid changeovers.

Operator cross-training. Operators are cross-trained in several production processes and certified to a range of skills in a training matrix. Compensation is tied to certification levels achieved. A core group of operators is deployed in a range of critical production processes and moved throughout the factory based on areas of highest demand.

Visible/frequent communication. Visible scheduling tools are used to ensure that scheduling data are in the hands of those charged with producing products. EPIC uses a three-zone system for production staging and a two-bin system for material planning. There are no production schedulers. Operators are empowered to prioritize the production sequences for each line based on color-coded pull signals. Material use is coordinated electronically between facilities via a bar-coded “virtual” Kanban planning system that mirrors the “visual” card system on the factory floor.

Visible metrics. A Plant Operating Review (POR) system drives the monitoring of approximately 50 metrics company-wide down to the floor level. These metrics are reviewed on a daily/weekly basis by the customer focus teams, monthly by the plant managers and directors of operations, and quarterly by the senior management team.

Mutually beneficial supplier relationships. We use a combination of supplier education, internal planning tools, excellent communication, and strong working relationships with customers and suppliers to help motivate suppliers to support Lean principles.

Six Sigma as an enhancement tool. Six Sigma principles are incorporated in an enhanced, disciplined analytical approach.

EPIC’s in-house reliability laboratory supported new process definition and validation; new product process validation; and resolved internal, supplier and customer quality issues prior to implementation of Six Sigma tools. Six Sigma’s Define, Measure, Analyze, Improve, Control (DMAIC) approach has now been implemented to enhance design for manufacturing/testability (DfM/DfT) analysis, process improvement and/or corrective action effort.

We have three Black Belts and are in a second wave of Green Belt training. The Six Sigma focus has been on scrap and defect reduction. As focus areas are identified, the appropriate project engineer is given the training, tools and mentoring to analyze the project selected for improvement. These improvement projects use the DMAIC approach.

In the Define phase, participants validate that this is a good project, define the improvement goal and define the team and team leader.

In the Measure phase, the real project work starts. Past performance is measured. Pareto charts and process mapping are utilized to determine the high hitters in terms of defects. The measurement system is validated using a gauge R&R tool, since decisions will be based on the data collected. Typically, an experiment is set up where several people are surveyed using several boards to determine whether an induced defect is the defect that everyone recognizes. This statistical tool measures whether the defect assessment is consistent across people or machines.

The Analyze phase focuses on the critical few areas identified to determine root cause of those defects. A cause-and-effect diagram (also called the fishbone diagram) is used. The team conducts a brainstorming session and then tests its hypothesis. Any variances are analyzed. The team also tries to estimate the impact of an input variable, such as raw material, temperature or line speed, on a machine to the output factor to determine which change has the most impact.
In the Improvement phase, there is evidence of problem root cause. The team develops an action item list to identify what needs to be changed and when it will be changed. The recommendations are then validated.

The Control phase ensures the output continues to be monitored to guarantee the corrective action in input variables stays in place. Any changes are documented. This ensures consistency and documentation of institutional knowledge. Any cost savings is measured.

One recent project involved a goal to reduce scrap from 1.1% to 0.8%. It was determined that the root cause was illumination values that were causing misaligned
placement against the pads on certain BGAs and ICs. To improve the parameters, the team used design of experiments to determine the best illumination parameters by shape of components. It then analyzed manufacturer recommendations and experimented with a range of values to get the best results. Once the results were validated, it made the best combination of values the default in all machines. Because we use a standardized SMT placement platform across the company, this fix has been implemented in all facilities.

The board being analyzed has gone from a 1.1% scrap rate to 0.77%. 

Carlos Rodriguez is a Six Sigma Black Belt at EPIC Technologies (www.epitech.com); This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Last Updated on Tuesday, 09 February 2010 21:56
 

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