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GETTING THE MOST FROM MANUFACTURING CELLS
Through Focused Factory Engineering

Author: Kenneth W. Harrison
Contributed by SMW Systems, Inc.

 

 

Is Cellular Manufacturing Reaching its Full Potential?

Most companies using cellular manufacturing have increased their productivity and lowered their product costs. However, not all companies have achieved extraordinary results. There are nine proven principles to gain the maximum benefits from cellular manufacturing.  Before these are covered, let’s review two definitions.

Cellular Manufacturing

In traditional factories, the equipment is arranged with similar machines located together, i.e., all of the lathes are in one line, all of the mills are in another line, the welders are in the weld shop and the assembly line is over in the assembly building.  With cellular manufacturing, all of the equipment to make a complete part is together.  A cellular manufacturing process is designed to efficiently make a specific part or a family of parts.  A typical manufacturing cell could contain the raw material, the band saw to cut the raw material, the lathe to machine it and an assembly/inspection bench.

Focused Factories   

A focused factory unites the cells that produce the parts and subassemblies into a cohesive unit. A large manufacturing plant that produces several types of products could have a unique focused factory for each product line.

Focused Factory Engineering Pumps Productivity

Changing the floor layout is not enough to dramatically reduce product costs.  The layout, product design and the manufacturing process must all change for optimal performance. Focused Factory Engineering (FFE) is the synergism that unites these.  It typically includes the disciplines of Design Engineering, Manufacturing Engineering, Quality Engineering, Production Planning and Manufacturing.

Principle 1, Create Modular Designs

The complete product must be dissected into components that can be made in a manufacturing cell.  For example a transmission manufacturer may have a gear cell, a housing cell, a shaft cell, and an assembly cell.  Whenever possible, parts should be standardized.  In this example, a standard housing could be used to produce transmissions with a variety of gear ratios, or a standard gear could be used in a number of different transmissions.

In order to create modules, standard interfaces must be designed.  This could mean that all gears have a 3/16" diameter hub and a 3/16" keyway, or it could mean that transmissions are made from standard subassemblies.  A transmission with a 180:1 gear ratio could be built by bolting four identical subassemblies together, each with a 45:1 gear ratio.

Principle 2, Create a Standard Process

An electro-mechanical component manufacturer was using 12 different types of solder and inspecting the process to three different soldering specifications.  This is not efficient.  The process must standardize on the fewest number of variations.  Their FFE team found that all products could be made with 3 types of solder and inspected according to one specification.  Providing a processing standard greatly increased their manufacturing efficiency.

Principle 3, Make Similar Components Together

I recently toured two furniture manufacturers.  The recliner company machines all chair frame parts together on the table of their vertical machining center.  After each machining cycle, a complete set of chair components is finished.  This set moves down the production line.  Inventory control is simplified because they always have the correct number of all components on the manufacturing line, and they have found that there is nothing more efficient than making the right parts, in the right quantities, at the right time.

The bed manufacturer, on the other hand,  machines a batch of one part then changes over and runs a batch of the next part, and so on.  Not only do they waste time because they keep changing setups, but they never have an equal number of all required components.  This method is much less efficient than the first.

Principle 4, Schedule Special Processes

With conventional manufacturing, a part moves from one machine in one area to another machine in another area, and so on until the part is finished.  With cellular manufacturing, one person (or a small group of people) completes a part in one area.  The exception to this rule is when there are special processes that require expensive capital equipment.  When this is the case, it is impractical to locate an identical piece of equipment in each cell.  Some examples are heat treating, plating, electron beam welding, and vibration testing.  When these processes can not be eliminated they must be carefully scheduled.

Gulton-Statham is a pressure transducer manufacturer that has a heat treatment area with two furnaces.  Originally the area was organized with a parts in rack and a parts out rack.  The supervisor of the area could not predict what parts would arrive next.  Sometimes a single part would be in process, and before it was completed, another group of parts would arrive that needed exactly the same heat treatment profile.  In order to optimize the equipment, the company appointed one person who scheduled all like materials on the same day.  This eliminated the bottleneck and shortened the manufacturing lead-time.

Principle 5, Eliminate Non-value Added Time

Most manufacturing cells are not dedicated to one single part number.  A housing cell may be required to machine a dozen different housings.  In order for a focused factory to be efficient, setup changes must be made quickly; and they should not interfere with the output of the cell.  Gregg Industries has a machine shop that specializes in machining castings.  They kit a complete setup with all the material, tooling, and inspection gages they need to run a job.  Because they have Setup SwitcherTM manual pallet changer[1] mounted on each of their vertical machining centers, it only takes them a few minutes to change over and start machining a new part.

Principle 6, Create a Traffic Model for Parts

If an assembly is missing one small part, the assembly can not ship. Imagine that the manufacturing process is a toll road that ends in a tollbooth. The production goals are: 1) collect the maximum number of tolls (maximize revenue), and 2) avoid traffic over congestion because the drivers may select an alternate route next time (satisfy the delivery commitments).  If a car travels down the entire length of road but stops before going through the toll booth, that opportunity for revenue is lost, and it will delay the other cars attempting to go through the toll booth.

The same thing happens with manufacturing.  Any job that is scheduled for the month, but does not ship, consumes valuable material, labor and other resources that could have been devoted to a job that would create revenue. In the toll road example, the greatest possible revenue can be generated when there is a uniform and consistent flow through the tollgates.

Sometimes there are so many cars on a toll road that the traffic jams and fewer cars are able to reach the tollbooth.  It is common for manufacturing companies to get so caught up in the daily operation (the utilization of equipment and people) that they focus their efforts on keeping busy and not on generating the maximum revenue.  A well run focused factory will use a production model that only allows new orders to be released at the shipment rate, and only when all parts are available.  A pull through material handling model should be used because it minimizes the work-in-process and efficiently moves the material through the manufacturing process.

Principle 7, Create a Plan for Exceptions

The production line must move at a fast and efficient pace.  Exceptions such as prototypes, rework, design changes, and maintenance should not interfere with production.  If a car stalls on the toll road, it must immediately be moved off of the roadway or the traffic flow will be affected.  The same is true of a production line.

Principle 8, Design the Process to Include Bottlenecks

Most products only contain a few critical manufacturing steps.  These require the most expensive equipment and the most talented operators.  In a focused factory, these critical steps must be the bottlenecks.  All other steps should have built-in excess capacity.  When the capacity of the bottlenecks is known, the maximum capacity of the focused factory will also be known.  Parts should only be released into the process at a rate that is equal to the slowest bottleneck.  Releasing more parts will only result in wasted activity, the unnecessary consumption of raw materials, and an increase in work-in-process costs.

Principle 9, Create Standard Documents

Some companies ask their employees to read and follow every line of the manufacturing documentation.  This is a ridiculously expensive request.  Although good documentation is important, it is a waste of time to ask an assembly worker to read every specification or a machinist to read every drawing note for each part.  Standardization is the key to quality and efficiency.

Manufacturing documentation should have a consistent format.  The only variation should be the process parameters that change because of part variations.  Many businesses have understood the efficiency of using mail merge to create letters, but few have used it to create travelers.  A text template should be created that is consistent for all products that are manufactured in a cell.  Then the variable information for each part number should be merged into the traveler template to create a unique traveler for each part.  An experienced worker will only need to scan the document for the highlighted variables in order to have all of the information they need.

Overcoming Objections to Change

I have heard two common reactions to these principles; 

1)    ”My company is different” and . . .

2)    ”The principles would work if we could start fresh, but we don’t have that opportunity.” Yes, every company must find its own competitive edge.  However, these principles have been used to great advantage in some of the most efficient companies.  It is true that start-up companies do have some advantages, but they often have many more disadvantages.  Every company has the opportunity to follow the path of continuous improvement.  What each company does with that opportunity will determine their future.


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