Engineering management lecture slides

1. Engineering Management
Dr. Abu Bakr Siddique

2. Lecture Outline
• Takt Time vs Cycle Time
• Pull production vs Push production
• Establishing Production flow

3. Takt time vs Cycle time

4. Takt Time
• Takt time is the average time between the start of
production of one unit and the start of production of
the next unit, when these production starts are set to
match the rate of customer demand.
• For example, if the customer demand for a certain
product is 10 units per week, then given a 40-hour
work week (and steady flow through the production
line) the average time between production starts
should be 4 hours, so as to produce 10 units per
week.

5. Takt Time
• Takt time simply reflects the rate of production
needed to match the demand. It represents the pulse
of the market.
• In reality one should also account for things like
machine downtime and scheduled paid employee
breaks, which would mean that the average time
between production starts (takt time) should be less
than 4 hours.
• If each process exceeds the takt time, a shortage of
products will result.

6. Takt Time
• If each process is faster than the takt time, a surplus of
work-in-process and finished products will occur.
• Takt is expressed in seconds per items produced (for
mass-produced items). For slower-moving items, the
takt time may be expressed in minutes or even hours.
• For example, the takt time for a line perfectly matched
with customer demand and producing 80 mattresses in a
day (with workers working for eight hours in a day) is
(8 x 60) / 80 = 6 minutes/mattress.

7. Cycle Time
• Cycle time, on the other hand, equals the actual time
it takes to finish one unit. It is measured as an
average.
• Cycle time is the time it takes to complete the
production of one unit from start to finish.
• By tracking your completed items and your net
production time (NPT), you can determine the time
it takes for you to complete one cycle.

8. Cycle Time
• The cycle time is not based on the pulse of the
market but is rather a statistical average of how long
it takes a company to make a certain product. It is
based on production data.
• The idea behind the JIT is to bring the cycle time as
close as possible to the takt time.
• When the cycle time prolongs abnormalities arise in
the gemba. In practice, however, the cycle time is
often found to be shorter than the takt time in most
companies.

9. Cycle Time
• Due to the lack of accurate market forecasting in
companies that have not adopted JIT, the average
cycle time is in many cases half the takt time. This
leads to a surplus in inventory.
• When takt time is observed properly, the gemba is
moving ahead with the same pulse as the market.
• Once management has achieved sufficient
flexibility, the Gemba can respond instantaneously
to changes in the pulse of the market, producing
only as many pieces as are ordered.

10. Pull Production vs Push
Production

11. Push Production
• Most manufacturing companies today are engaged
in push production.
• Every process produces just as many units as it can
and sends them to the next process, whether the next
process needs them or not.
• This stems in part from the following line of
thinking: “As long as the processes are in order, let’s
make as many units as we can because we never
know when things might go wrong again.”

12. Push Production
• When applying a push strategy, a company’s production
is based on anticipated demand, which can fail to
correspond with the actual demand. Such an imbalance
can create unexpected financial gaps.
• Operators in such an environment do not know, and do
not need to know, the volume and time requirements of
their customers. The finished products find their way to
the warehouse and wait for the order to arrive.
• A push system necessitates batch production, creating
muda of transport and inventory.

13. Pull Production
• A pull system, on the other hand, is a Lean
technique for reducing the waste of any production
process.
• Applying a pull system allows you to start new work
only when there is a customer demand for it.
• Essentially, the purpose of implementing a pull
system is to build products based on actual demand
and not on forecasts.

14. Pull Production
• By doing so, your company can focus on eliminating
waste activities in the production process.
• As a result, you’ll be able to optimize your resources
and reduce the possibility of overstocking.
• Apple is one of the brightest examples how a pull
system can be successful. Have you ever seen those
long waiting queues in front of the Apple stores
during the latest release of an iPhone?

15. Pull Production
• Apple always creates a buzz around their new
products and consumers are always ready to buy.
They want to pull the product from the stores.
• Apple doesn’t overstock their shops or retail
partners. They wait to see if there is a demand for
more and if it increases, they produce more.
• This way, the company optimizes its resources and
achieves high-cost efficiency.

16. Pull Production
• Actually, by using lean pull principles, you can be much
more predictable when planning your future work.
• Pull systems require (force) you to collect historical
data about your workflow and the average cycle time of
tasks.
• Using this data in combination with different
forecasting techniques (such as the Monte Carlo
simulations) will give you a probable forecast about
how much work can be processed in a predefined period
of time.

17. Establishing Production
Flow

18. Work Flow
• In pull production, all processes should be
rearranged so that the work-piece flows through the
workstations in the order in which the processes take
place.
• Once the line is formed, the next step is to start a
one-piece flow, allowing only one piece at a time to
flow from process to process.
• In the simplest of terms, one-piece flow means that
parts are moved through operations from step to step
with no work-in-process (WIP).

19. Work in Process (WIP)
• Work in process is the term used to describe
partially completed goods.
• Work in progress is the cost of unfinished goods in
the manufacturing process.
• In order to better understand the concept of one-
piece flow or connected flow, let us step back and
first understand the concept of batch processing.

20. Batch Processing
• In a typical batch-and-queue manufacturing
environment as illustrated below, parts move from
functional area to functional area in batches, and
each processing step or set of processing steps is
controlled independently by a schedule.

21. One-Piece Flow
• In contrast to batch processing, one-piece flow
allows only one piece at a time to flow from process
to process, as is illustrated below.

22. Drawbacks of Batch Processing
• In batch processing the lack of ‘connected flow’
results in:
–Long manufacturing lead time
–Poor on-time delivery and/or lots of finished
goods inventory to compensate
–Large amounts of WIP
–Large amounts of scrap when a defect is found
because of large batches

23. Relationship b/w Processing Steps
• One-piece flow is the ideal method for creating
connected flow because product is moved from step
to step with essentially no waiting (zero WIP).
• This shortens lead time and makes it difficult for the
line to build up inventory between processes.
• When we achieve connected flow, there is a
relationship between processing steps. On the other
hand, in batch processing there is little relationship
between each manufacturing step and the steps
immediately upstream or downstream.

24. Detection of Abnormalities
• Besides shortening lead times and cutting excess
inventory, one-piece flow also helps workers to
identify quality problems right away because any
problem in the previous process can be detected in
the next process.
• As a result, one-piece flow also allows 100 percent
inspection because every piece goes through the
hands of every operator.

25. Line Stoppage
• Before starting a production line with one-piece
flow, however, such problems as quality, machine
downtime, and absenteeism must be addressed.
• One-piece flow production cannot begin until these
problems are resolved because each time a problem
arises, the line must be stopped, and the problems
that up to now have been regarded lightly become
visible.
• The company loses money when the line is stopped.

26. Single-Tasking Model
• Precisely for this reason, management has to address
the problem, and thus a line with one-piece flow
makes it mandatory to identify and solve problems.
• This may misguide you to the illusion that by
creating a single-tasking model, your team will not
use its full capacity.
• Contrary to the common belief that we should
multitask in order to finish more work, limiting your
WIP will actually let your team members focus on
single tasks until their completion.

27. Advantages of One-Piece Flow
• Having a one-piece approach allows a work unit to:
– Quickly adapt to changes that may occur in the work
process
– Scale the optimal capacity of your team
– Deliver work items much faster
– Reduce waste of resources
– Increase productivity
– Improve flow efficiency