Designing Systems (CONT’D FROM PAGE 1)
ing automatic scanning of load tags to control strap place- ment, and adding a person to assist in dressing loads. Unit height should be the maximum that allows for best truck utilization, and that is within customer specifications. Keep in mind that increasing height from 45-inches to 50-inches results in a savings of more than 10 percent in number of units to strap. This also reduces the length re- quired of the main line conveyor. Similarly, when possible, eliminate cross strapping as this requires units to be rotated. When possible, strap spacing should conform to the unitizer’s head spacing so that all or most straps may be placed simultaneously, and don’t require more than one platen cycle per unit at each stage. Finally, don’t specify more straps than necessary, particularly when they can’t be applied simultaneously. If you determine that you have optimized your process, and your unitizer is still not keeping up, do you have a two-stage system with an external turntable between the stages? Is it equipped with a minimum of three heads per stage, and at what spacing? Are the unitizer and your lay- out conducive to rapid change of strapping reels? Is au- tomated top sheet placement and / or printing on the top sheets practical in your application? Is it cost effective to upgrade your current equipment, or should it be replaced? Keep in mind that enhanced reli- ability and productivity resulting from advances in unitizer technology may justify new equipment.
affected by product design, board quality and crew effi- ciency. Furthermore, run speed doesn’t tell the whole sto- ry, as non-productive set up time reduces the overall rate of pieces produced. Hence, mix, blank configuration, and order quantity must be considered in calculating a more realistic rate. Although not completely within your control, scheduling can alleviate this problem. For example, try not to schedule large runs on each machine at the same time. Rather, schedule a mix of long and short orders so that set- up time on some machines will coincide with those long, If a plant routinely produces 250 units per hour, but its unitizer is only capable of 220 per hour, it is obvious that production will be affected. However, if the unitizer is ade- quate other than during intermittent surges, extending the main line may be sufficient to buffer these surges. The most obvious means of improving unitizer through- put is to add one or more parallel unitizers. Before resort- ing to this expensive and space-intensive solution, evalu- ate if your unitizer is operating at design speed. If not, is the cause mechanical downtime, inability of operators to keep up, unit height, or strapping patterns? fast-running orders. Unitizer Capability Before blaming your operators, consider whether strap patterns need to be entered manually, and/ or protective sheets are being placed by the operator. Consider install-
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