Cellular Flow
Designing effective workcells
Cellular Flow and Workcells are also referred to with other names such as:
Concurrent Flow
Lean Flow
Continuous Flow
Simultaneous Flow
Synchronous Flow
Hybrid Layout
Group Technology
Prerequisites tools to review when creating a workcell
5S
Process mapping
Takt time and Loading
7-wastes elimination
Value Stream Mapping (VSM)
Visual Management
Types of Cellular Layouts
Straight (Linear) Layout
PROS:
Multi-capable personnel once trained
Separates raw from finished goods if that is a concern of mixing.
Point-of-use supplies can be placed on one side.
CONS:
Requires access on two sides
Process independent of one another
Cross-training required
These are possible when there is physical access to both sides of the cell. Sometimes the cell may need to be designed against a wall and a U-shaped cell is the better option since raw and finished parts are at the same side.
Cage (ONE person & ONE type of operation)
PROS:
No cross-training required, lower learning curve
Operator can get more efficient
CONS:
Space needed on all sides for maintenance and/or supplies
Employees are separated and more difficult to help one another
Increased WIP and Inventory - more batches
Lead Time increases and ties up more cash
Lack of cross-training, only know how to run one type of equipment
Line balancing is more challenging in caged layouts
Cage (ONE person & >1 type of operation)
PROS:
Multi-capable personnel once trained
Minimal walking for operator
Eliminates any chance of operator interference
CONS:
Space needed on all sides for maintenance and/or supplies
Employees are separated and more difficult to help one another
Cross-training required
U-Shaped Layout
PROS:
Multi-capable personnel once trained
Minimal walking, linear layout requires walking across line to start over.
Only one side of access needed for raw materials and finished parts.
CONS:
May be traffic concerns, raw and finished part delivery all in same area.
Process independent of one another
Cross-training required
Assembling a Workcell
Three elements to be considered, the flow of:
1) People
2) Equipment
3) Materials
Workcells may be as simple as one of the above, or it may be a combination of them. Multiple U-turn workcells are combinations of straight and U-shaped cells.
Questions to consider:
What equipment should go into the cell?
Is cross-training needed?
What risks are being added?
Can they be avoided, prevented, or reduced?
What items or processes should be produced in cells?
How should people operate the cell?
What design is optimal for the cell?
Is there access for maintenance?
What type of manning methods should be employed?
Do I understand the takt time?
What is the capability (loading)?
Do I have a suitable product family?
How should the product family be determined?
Is their space to perform changeovers?
Access for direct and indirect materials?
What can and can not be placed at the point-of-use?
Can the equipment run independently if needed?
Common Obstacles of all Workcells
Cross Training
This is probably the most influential factor in successful cellular implementation. Not only does this satisfy workcells, but this also curbs the dependence on specialized operators, vacations, and absences.
Creating the best product families
Typical characteristics are the geometry, tooling, and process step commonality. Must understand the components that takes longest to set-up or has the least capacity (bottleneck - determine with takt time and balanced loading).
Lack of consideration to Human Factors
Minimize body motion
Unpleasant sounds, whistles, beepers should be avoided
Avoid unnatural postures and movements
Avoid sharp turns in motion
Consider fatigue mats, lighting, double hand controls
Design movements to follow rhythm
Work at shoulder height when possible
Utilize mechanical advantages when applicable.
Put monitors and controls on swivels
Use Visual Aids, lines, shadow boards, labels.
Past Paradigms
Virtually all implementations of significant change or transformation will meet resistance due to past paradigms. The team designing the cell must be enthusiatic, open-minded, and capable. This first cell created will be judged and will set the precedence for the workcell principle and Six Sigma program going forward.
CHALLENGE EVERYTHING! Rules, regulations, standards, work instructions, past practices, are all fair game. All of these items are prone to change and the circumstances of their origin may also be different.
Success Factors
Workcells aren't the answer to all processes, choose wisely
Top personnel on the design team
Cross-functional team
Challenge the past, seek the ultimate future state
Keep the workcell flexible and adaptable
Maintain simplicity
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