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Before the widespread use of computers the location of warehouses, stores, franchises were often settled by using a ’string map’. Pins were stuck in the map at customer’s locations, and string, usually thread or fishing line, looped over them, the weight on the end of each line being proportional to that customer’s deliveries. The ends of the string were knotted together. Where the knot settled was the center of pull (not gravity).
Evolutionary Operations, first described by George E. P. Box and Norman R. Draper in in their book Evolutionary Operations – A statistical method for process improvement, New York: John Wiley and Sons, 1969. EVOP is Continuous Improvement + Design of Experiments. Basic idea is to replace the routine operation of a process by continuous and systematic plan of slight adjustments of the control variables. The effects of the adjustments are then evaluated just as with DOE. The process is then shifted in the desired direction of improvement. In many product and service processes it is impossible or very expensive to do DOE, especially where trials can be disruptive or the process owner would let you have the necessary time, materials, labor to run your experiments. So rather than running experimental production runs you use actual production by shifting off the base point left, right, up, down all within "spec".
Material Handling Equipment and aisle widths:
Here’s another example for “sizing the wheel” for a mixed model fixed repeating schedule.
Given:
and
Now some math:
So the fixed repeating wheel will turn once in 2.86 days. Production run sizes as follows:
Plus 4 changeovers of 100 min each = 2403 min = 2.86 days. When it comes time to run product A, run 2.86 days worth. Got it? Would be nice if we could run just one piece. But until we can make the 100 minute changeover go away we’re stuck running a batch of some size.
An example from a recent warehouse layout project; analysis leading up to a facility block (zone) layout.
X=preferred, O=workable but not preferred
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