Process simulation is key in a lean
manufacturing company hungering for big results.
by Mike Peterman
As companies continue to look for more efficient ways to run their business, improve work flow and increase profits,
they increasingly turn to lean manufacturing, which is used by best-in-class operations to improve their processes, achieve their goals and gain a competitive edge. It's used by some of the
world's most successful companies, including Toyota, Honda, DaimlerChrysler, Volkswagen, Boeing, Delphi Automotive Systems, Dell Corp. and Gorton Fish Co. Process simulation has become an
increasingly important and integral tool as businesses look for ways to strip nonvalue-adding steps from their processes and maximize human and equipment effectiveness, all parts of lean
manufacturing. The beauty of process simulation is that, while it complements and aids in lean manufacturing, it can also stand alone to improve business processes.
What is simulation?
Process simulation is a technology that allows the analysis of complex systems through statistically valid
means. Through a software interface, the user creates a computerized version of a process, otherwise known as a "model." The model construction is a basic flowchart with great
additional capabilities. It is the interface a company uses to build a model of its business process.
Simulation technology has been around for a generation or more, with
early developments mostly in the area of programming languages. In the last 10 to 15 years, a number of off-the-shelf software packages have become available. More recently, these tools have been
simplified to the point that your average business manager with no industrial engineering skills can effectively employ this technology without requiring expert assistance.
Simplicity is the key to today's process simulation software. After flowcharting the process, the user inputs information about how the process operates by simply filling in blanks. While
completing a model, the user answers three questions at each step of the process: How long does the step take, how often does it happen, and who is involved? After the model is built and
verified, it can be manipulated to do two critical things: analyze current operations to identify problem areas and test various ideas for improvement.
The latest improvements
in simulation software have made it an excellent tool for enhancing lean manufacturing, which strives to eliminate eight wastes: overproduction, motion, inventory, waiting, transportation,
defects, underutilized people and extra processing. Lean manufacturing targets nonvalue-added activities--the same activities that contribute to poor product quality.
How does process simulation work with lean manufacturing?
Custom Windows Systems Inc. of Florida recently used process
simulation to analyze production flow with an eye toward creating a lean manufacturing environment. In the process, the company discovered that its manufacturing approach couldn't support the
growing company's goals and would need to be completely rethought.
Custom Windows is a business not unlike many others in the United States. The company is a young, aggressive
manufacturer of custom windows, doors and vinyl porch window products. Business is booming, and the company has seen a steady, promising yearly growth rate of 25 percent for the past five years.
Due to its impressive growth, the company needed to expand the facility from one plant to two and wanted to do it in the most efficient, cost-effective manner possible. John Cwik,
Custom Windows' president, employed the help of the Florida Manufacturing Extension Partnership, whose mission is to help manufacturers become more productive, profitable and competitive.
Florida MEP offers Lean 101 training seminars to manufacturers in groups, from 12 to 20 participants. Four live simulations are
conducted and lean building blocks are added with each round of training. The building blocks for the lean factory are one-piece flow, cellular manufacturing, pull/kanban,
point-of-use storage, quick changeover, quality at the source, batch reduction, teams, standardized work, workplace organization and plant layout.
foundation for this lean factory is a well-utilized workforce, body and mind. Florida MEP trains cross-sectional teams focusing on the "doer" level and
facilitates active participation. One of the implementation success factors is the ability to question everything: Ask "why?" five times. It's common that some
of the most valuable ideas come from people not directly associated with a particular operation.
Florida MEP is part of a national organization, the
Manufacturing Extension Partnership. MEP, a nationwide network of not-for-profit centers in more than 400 locations nationwide, has the sole purpose of providing small-
and medium-sized manufacturers with the help they need to succeed. The centers, serving all 50 states, are linked together through the Department of Commerce's National
Institute of Standards and Technology.
The Florida MEP suggested two projects for Custom Windows: First, employees should attend an introductory lean manufacturing training course. Then, employees were to
complete simulation models aimed at designing the most efficient plant layout.
Armed with the lean concepts learned during their training, the Custom Windows staff was
ready to participate in the process simulation-modeling phase of the project. Cwik defined the following rules for the project: Production output was to increase by 25
percent, shifts were to remain at 40 hours per work week and capital equipment could be purchased.
Process simulation models were constructed for each business unit--glass, vinyls and doors. To build the models, data about the actual
process was gathered. Supervisors of each area timed employees and processes. The Florida MEP physically observed the process and recorded how the operation flowed from one
operation to another: the number of employees in the processes, the time it took to complete the processes and the operating procedures used to build the model.
After the models were built, each was validated to determine if the simulation model accurately represented the process. It's extremely important to have accurate validation
to ensure that the model is behaving the way the shop is operating. Without an actual representation of the process, the results could be inaccurate.
It's typical for business and manufacturing processes to have more than one bottleneck. Often they're difficult to see until mapped out using a tool such as process
simulation, which does so without changing the actual process.
After the models were built in ProcessModel, a simulation modeling software tool,
Custom Windows' staff watched the simulation animation. Bottlenecks emerged, but not where they were expected. Prior to simulation, supervision had a hunch that a key
bottleneck existed at a cutting operation, and that replacing the saw would significantly increase output. Supervisors had seen the advertisements and knew exactly the saw
they wanted and needed--and it would cost $70,000. They were waiting for the process simulation to verify the need.
In process simulation, the manufacturing process is viewed on screen through animation. Each step in the process has a queue, and animation shows the product or
process actually running through the queue, with bottlenecks highlighted in red. The simulation animation clearly demonstrated that the saw wasn't creating the bottleneck.
Cwik was thrilled he hadn't purchased the wrong piece of equipment; already, simulation had saved the company $70,000. Custom Windows saw that the business process bogged down
in the handling of the windows. The windows were being manufactured using a batching method, 20 windows per batch. Due to the batched manufacturing process,
inventory at the plant was large and lead times were long.
TaKT time, a phrase based on a German acronym for achieving production or output
of the product over the time available, was too long to increase window output with no new shifts. But with people and equipment running at what appeared to be full
capacity, it seemed impossible to clear the bottleneck without new shifts or equipment.
The solution: "what if" models
The next step was to build "what if" models and use the process simulation as a
working laboratory of the manufacturing process. What-if process simulation models demonstrate results when implementing lean manufacturing concepts. The what-if assumption they modeled was a
25 percent increase in window production output. To achieve increased production in the glass line, the team analyzed human resources and model process activities.
TaKT time for the baseline model was 1.23 minutes (40 hour week = 2,400 minutes divided by 1,945 units a week--the current production output). To increase output by
25 percent to 2,400 units per week, the TaKT time would need to be reduced to one minute.
Breaking the glass constraints
Several lean manufacturing concepts were implemented in the process simulations that incorporated a variety of what-ifs. The process simulation was run for 8.5 hours
for ease of analysis. Changes to the baseline model (what-ifs) included:
Unbatching all operations
Creating a flow line for eliminating movement and handling time
Flowing one window at a time using carts up to the assembly tables
Eliminating sorting operations throughout the line by using carts with bins
Adding three employees to the production process (though touch times may require a different balance of workforce)
Increasing or decreasing different steps in the manufacturing process, based on
baseline manufacturing times, to improve the efficiency of the manufacturing process
Doubling the capacity of the glass and washing operations
Using process simulation, Custom Windows discovered its former process paradigm was entirely off. After incorporating process simulation and lean manufacturing
techniques, staff changed their entire manufacturing process and plant layout design. Incorporating these steps into the model broke the process constraints and met the
goals. The model flowed, and no bottlenecks appeared.
Based on the results, Custom Windows decided to implement two one-piece flow
production lines in the glass division, replacing the current batch-process single line.
When the baseline model was built in ProcessModel, the weekly output of 1,945 windows was being met at full-production capacity. After lean manufacturing
principles and simulation modeling techniques were incorporated, the weekly output increased to 2,400 windows daily. "I saved $70,000 or more by not purchasing
equipment that I didn't need," remembers Cwik. "I saved hundreds of thousands of dollars in personnel costs and at the same time increased production by 25 percent."
Even better, because Custom Windows will switch to a one-piece flow design, no new capital or investments will be required; 2,000 square feet of floor space has been
saved for future expansion; and the 40-hour work week will remain intact. Money will be saved in plant operation, storage and facility use. Lead time will be reduced,
increasing customer satisfaction and increasing orders, and the inventory will be decreased. And the employees will be utilized more efficiently, saving money and increasing job satisfaction.
Custom Windows, which now has a much better understanding of how the new lean plant layout will operate, plans to implement it within the next two months.
Lean manufacturing and process simulation go hand in hand. Lean manufacturing is a
highly productive way of manufacturing. Process simulation allows methodology to be tried and tested without any capital investments being made. It produces solid results
proven with statistics and animation that often gives the green light to go ahead with a project. But process simulation's strongest feature is that when all of these aspects are
combined, they effectively communicate ideas for the future.
About the author
Mike Peterman works with Florida Manufacturing Extension Partnership. E-mail him at firstname.lastname@example.org .