Background: A center for the inspection and repair of traction motors used on locomotives was facing a large and highly variable increase in demand when a sister facility in another city closed and transferred its work. Traction motors fail more frequently in the winter months when exposed to snow, and less in dry weather. Motors to be repaired often arrive before their paperwork, and so are the earliest indication in increased demand.
Situation: Initially, twenty motors per week were expected, but future work was expected to be as much as three times that during some periods. Historically one mechanic disassembled, repaired, reassembled and tested one motor at his own workstation. The large and variable increase in work would require a variable work force and several additional work stations if work was to be done the same way and without building up a backlog that was unacceptable to the customer.
Analysis: Over the course of a week-long Kaizen event that included training in single piece flow, a number of methods were tried until it became obvious that work had to be done very differently. On Day 4 of the Kaizen event one of the participants recognized that moving the work past the repair equipment on a conveyor – a moving line – might be the best solution.
Improvement: A conveyor was specified to hold four armatures (the rotating part) and geared to convey one length every 8-hour shift, for a 2-hour takt time. Work was balanced into packages well within the takt time to allow for an occasional difficulty. Motor frames (the stationary part) are repaired alongside the conveyor. Several armatures and one frame are kept at the ready should a more extensive repair (done "off-line") be necessary.
Result:The center expects to gain the flexibility to immediately increase production 25% (from 20 per week to 25) by working two hours of overtime per weekday, another 20% (from 25 per week to 30) by working Saturday, and up to 60 units per week by working an second 10-hour shift, while reserving four hours per day and Sundays for plant maintenance. By simply counting incoming traction motors the facility can activate an appropriate shift schedule.