Circuits Assembly - September 2008 - (Page 39)

Cover Story the other half. What are the correct steps to improve OEE while decreasing lot sizes and cycle times, and understanding what process improvements are required to achieve the OEE goal? If you as the manager are going to require engineers and production to maintain an 85% OEE target with a 0.5 min. CT and 100-piece lot sizes, you also will need to support the resources and expenses associated to achieve a combination of reduced changeover time and unplanned DT. In Figure 4, assuming an improvement of 50% to unplanned downtime to 5 min. would require an improvement in C/O time of 75% (around 4 to 5 min.). Is this physically possible with Figure 1. OEE % relation to lot size based on 1 min. CT, your equipment, labor resources and current factory processes? 20 min. C/O, 10 min. unplanned time. The trend in lot sizes seems to be headed from 500 to 50, but Figures 1-3 show the severity to OEE as cycle time drops, assuming constant C/O and DT. Manufacturers with dense, complex boards, or who develop multiup panels requiring longer CTs between machines, are able to Figure 2. OEE % relation to lot size based on 0.9 min. maintain a higher OEE rate with lot sizes closer to 50 (Figure 5). CT, 20 min. C/O, 10 min. unplanned downtime. The first step toward improving profitability is determining whether judging a facility by OEE alone is truly a Key Performance Indicator (KPI). If reducing cycle time resulted in an extra 10% in sales that month, was it really wrong that OEE fell? If I were an operator Figure 3. OEE % relation to lot size based on 0.5 min. on the production floor and my performance based on OEE, CT, 20 min. C/O, 10 min. unplanned downtime. I’d slow all my machines to half speed and have a longer run-time to make my OEE look great. After all, that’s what the manager is judging, not profitability. OEE is just one KPI, but the true KPI should be net profitability. Increases in profitability mandate improvements Figure 4. OEE % relation to lot size based on 0.5 min. in the processes performed to manufacture goods. Focus needs CT, 4 min. C/O, 5 min. unplanned downtime. boards after improving cycle time? OEE drops to 75% from 86% (Figures 1-2). What happened? Now let’s say you made a dramatic improvement in cycle time and reduced it 50% (0.5 min/board). How did improving throughput by 50% result in a 77% OEE with a lot size of 200 and only 63% when lot size is reduced to 100 (Figure 3)? Answer: I changed half the equation and didn’t compensate for circuitsassembly.com Circuits Assembly SEPTEMBER 2008 39 See us at IPC Midwest, booth #218 http://www.seho.de http://circuitsassembly.com http://www.seho.de

Table of Contents Feed for the Digital Edition of Circuits Assembly - September 2008

Circuits Assembly - September 2008 Contents Caveat Lector Industry News Market Watch Talking Heads Focus on Business Global Sourcing On the Forefront Screen Printing Better Manufacturing Reflow Soldering with a SnCu Eutectic Pb-Free Alloy Improving OEE in High Mix Facilities Effectively Managing RF Design in Utility Metering Applications Solder Joint Reliability of Different BGAs Reworked Using Low Melting Point Pb-Free Alloys Tech Tips Wave Soldering Pb-Free Lessons Learned Materials World Process Doctor Equipment Advances Product Spotlight Ad Index Assembly Insider Technical Abstracts

Circuits Assembly - September 2008

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