Page 313 - How To Implement Lean Manufacturing

An Experiment in Variation, Dependent Events, and Inventory 289

b. Material availability, which is the kits processed and the kits remaining in
WIP (the volume in Rectangle 2)
3. Next to Rectangle 1 is Rectangle 2. It represents the total available material for
the subsequent processing station.
4. Rectangle 3 is then the actual production for that station based on the system
constraint. Rectangle 4 then represents the amount of material left by that station
in that cycle when the instantaneous station capacity (the oval) is the constraint.
This amount of material, the WIP, is then available for the subsequent cycle.
a. To make this material available for the subsequent cycle, write this value in
Rectangle 4 and add it to the value in Rectangle 1 in the subsequent cycle.
b. Place this value in Rectangle 2. This now represents the total amount of
material for this station during the next cycle of production. It is the sum of
the material not used in the previous cycle, plus the amount produced by the
prior station, in that cycle.
5. At the end of the cycle are three rectangles and a triangle. The first two rectangles
are the net production from that cycle. They are the same number. The last
rectangle is the accumulated production from that cycle, plus all previous cycles.
6. The triangle is the total WIP that was accumulated in that cycle. It is the sum of
all the Rectangle 4s in that cycle.
7. A simple check of your logic and math is to add up the cumulative production,
plus the WIP for that cycle. This total should be equal to all the materials
withdrawn (station 1 accumulated totals), up to and including that cycle.
8. A simpler approach is to write me at www.qc-ep.com and I will send the
spreadsheet on a CD. Shipping and handling will be the only charges.
9. For example, I have attached the first three cycles of a spreadsheet.
a. Review that in Cycle 1, station 1, 18 units are withdrawn from the storehouse.
Hence, station 1 does its work and they are processed and transferred to
station 2.
b. However, station 2’s pull capacity is only 12, so six units remain in WIP for
the next cycle, 12 units are passed to station 3, and so on.
c. At station 4, the instantaneous capacity is 21 units; however, there are only
enough raw materials for 12 units, hence only 12 are processed and passed
on. It goes this way thru station 8.
d. Consequently, 12 units are produced, six remain in WIP, which checks since
we started with 18.
e. In Cycle 2, station 1 has the capacity to produce 21, so 21 units are withdrawn
from the storehouse, but six units were left in WIP from the first cycle, so
now station 2 has 27 units of material at its disposal. Station 2 has enough
raw materials to produce 27 units, but its limit is the instantaneous station
capacity of 21, so 21 units are pulled, processed, and sent to station 3. The
six units not pulled by station 2 now remain for the next cycle.
f. In Cycle 2, since the capacity of stations 3 thru 7 all exceed the raw materials
availability, they all process and pass on 21 units until we get to station 8.