Circuits Assembly - September 2008 - (Page 40)

Cover Story to be on the reduction of non-value-added times, from staging, kitting, changeover, unplanned downtime, material handing, labor resources and quality. A recent episode shows how OEMs can reduce operational costs through proper evaluation of the entire operation, not just the SMT lines. A leading commercial alarm system manufacturer was producing PCBs for its finished products. It recently had reduced lot sizes to meet customer schedule needs, but did not improve internal processes to reduce changeover and downtime. The OEM’s primary concern was improving a shrinking on-time delivery rate, which slipped to 80% from an original target above 95%. The solution: a four-line facility, two-shift operation with each production line containing approximately 25 different models to build. Lot sizes ranged from 10 to 600, with an average of about 60, a changeover time averaging 20 min., and 15 min. of additional unplanned downtime with an average cycle time around 1.1 min. The high percentages of changeover and additional unplanned downtime were due to waiting for the next work order to be ready from kitting, incorrect parts loaded onto feeders, and process steps performed during a changeover. Figure 6 represents the current OEE state of about 60%. After an in-depth, weeklong onsite analysis consisting of observing current factory processes, a new model was developed, approved by management and implemented. The model included development of a combination of fixed feeder and exchange feeder setups on each line, which reduced kitting activities along with changeover activities. Program cycle times were improved through better optimization tools, as well as integration of fixed nozzle changer and board support setups. Tables 1-3 show the solution proposal results. The solution proposal included: • Using customer-provided data of production schedules, volumes and observations during onsite visits, the proposal focused on reduced kitting efforts. • Each line was carefully evaluated to determine part commonality. • Figure 7 shows the feeder tables determined to be most effective to be fixed with specific high use parts across each of the three production lines. • Figure 8 shows benefits gained by assigning specific parts to fixed locations with tape splicing over kitting exact processes. Product family A (SMT2) details: • 50% reduction in exchange carts 8 carts  4 carts. • 33% reduction in changeover time 15min  10 min. • Estimated 40% reduction loading parts into feeders. • Estimated 10% reduction in overall product cycle times. • Estimated 10% increase in line capacity. Product family B (SMT3) details: • 50% reduction in exchange carts 8 carts  4 carts. • 33% reduction in changeover time 15 min  10 min. • 40% reduction loading parts into feeders  239 kitting/ setup man-hours. • 21% reduction in overall product cycle times. • 18% increase in line capacity: Current 200 hr. to produce  Proposed 145 hr. to produce. • Increase possibility to produce within one shift, with occasional OT or 2d shift based on demand spikes. Product family C (SMT4) details: • 25% reduction in exchange carts 8 carts  6 carts. • 33% reduction in changeover time 15 min  10 min. Figure 5. OEE % relation to lot size based on 2 min. CT, 10 min. C/O, 4 min. unplanned downtime. Figure 6. OEE % relation to lot size based on 1.1 min. CT, 20 min. C/O, 25 min. unplanned. 40 Circuits Assembly SEPTEMBER 2008 Figure 7. Most effective feeder tables setup. circuitsassembly.com http://circuitsassembly.com

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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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