Process
Flow Mapping for Improved Flow
Process flow mapping is used to visualize the
process under review. There are many variations of flow mapping, including relationship
map, time function map, IDEF-O, flow charts, PERT Charts and FAST Diagrams. The
first two are common and applicable to improving product flow.
A relationship map describes at a high level relationships between functions / organizations. It shows organizations / functions as boxes on the flow map. Product / Information flows are shown as lines connecting these boxes with a text / numeric indication to show what flows / sequence. One variation I particularly like shows the major inventory locations in between the organizations with major product flows as solid lines, factories with brick graphic. Information flows, the major steps in MRP II, are shown with dashed lines. It is critical to keep detail to a minimum to visualize flow on this process map, This may be used as a starting point to ground a cross-functional team to relationships between functions. It also shows cross flows, disconnects, overloaded / key functions (a lot of in/out flows).
The next process map is more common. There are several
variations, under sequential mapping. This map can be done at the macro (major
function), mid level (factory flow / routing step), job level (element
breakdown - typical of set-up reduction or kaizen process breakdown).
These process maps describe steps in verb-noun
format in sequential order. The time-function map shows functions (e.g.
planning, manufacturing, and logistics...) along the left-hand margin and
aligns steps to those functions. Individual activities have associated work
content time (Time to process one unit) and elapsed time (lead time - largely
made up of queue, delays). Often a macro timeline is shown at the bottom for
groups of tasks. Material and
information flows often use symbols to help visualize the flow. Pictures,
pictograms, other graphics may help in visualization. There are some standard
flow-mapping symbols. One option is to put the map in a software package that
allows computation such as project planning software (PERT chart). Another is to tie the process map to
simulation. Once you have mapped, the next step of simulation is simplified.
The process map provides the basic step in analyzing
a flow. Additional information can be added to the map. Some examples include
defect types / quantities - DPU, issues / problem areas, root causes, and costs
of quality. It is good to do Ishikawa / fishbone diagram, then link root causes
back to flow map. Use this information to plan and later validate flow
improvements. It is also good to do an "as-is" and "to-be" version
of the flow map. A micro cost-time profile can show the dimension of the flow
over cost (work content X charge rate + material cost) vs. time (elapsed time).
This can help to visualize delays (long flat spots), high costs and long
lead-times.
Use a cross-functional team to describe types of
defects observed along the flow path. Take observations on the shop floor
through a combination of scrap / rework, process control data and customer
escaping defect data. Quantify DPU and show amounts on flow map.
Have the team brainstorm the problems they encounter
and root-causes. Show problems where they show up on the flow map, root causes
on causing operation. Identify associated cost of quality. Use combined
information to identify corrective actions. Assign responsible individuals and
track results. Indicate on flow map non-value-added activities, such as
inspections, queues, moves, and delays. These can show opportunities to reduce
cycle time.
The flow map and Pareto ranked defect data can help
with verification. Fishbone diagram with categories of manpower, machinery,
methods, measurement, management is a good interim step for root cause, but be
sure to attach the root causes to flow map to graphically show major source of
defects.
Quality improvements could include mistake proofing
/ fail-safing and statistical process control. Use the flow map to show where
these will be added. Cycle time improvements are based on eliminating
non-value-added steps. Eliminate inspection when operation has demonstrated
process control; eliminate a queue by protecting a bottleneck with a time
buffer or increasing its output (break / lunch coverage, etc.); Reduce lot
sizes and corresponding queues by first reducing set-ups; reduce machine
downtime delays through preventive maintenance, etc. These form the basis of
action plan.
.
Greg Hart is a management and industrial engineering
consultant specializing in material flow, business process and quality
improvement. He earned a MBA in Operations
Management, Finance and Accounting from the University of Rochester Simon
School in 1998 with honors and a BS degree in Industrial Engineering from
Rochester Institute of Technology in 1985 with honors. Greg has over 25 years
of experience in engineering and operations management. He was an Industrial Engineer for Kodak for
twelve years and a retail distribution center manager for The Denver for seven.
He has visited or worked with many other firms - small to Fortune 500.
Hart Innovative Solutions, Inc. (585) 235-1720
www.HartInnovations.com GregHart@HartInnovations.com