Workcells and Cellular Flow

Designing effective workcells

Other commonly applied terms are:

Concurrent Flow

Lean Flow

Continuous Flow

Simultaneous Flow

Synchronous Flow

Hybrid Layout

Group Technology 

Prerequisite tools to review when creating a workcell:

5S

Process mapping

Takt time and Loading / Line Balancing

7-wastes elimination

Value Stream Mapping (VSM)

Visual Management 

Economic Order Quantity (need to consider the space)

---

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 on the same side.

---

Cage (ONE person & ONE type of operation)

PROS:

No cross-training required, lower learning curve

Operator can become more efficient 

CONS:

Space is 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.

Processes independent of one another

Cross-training required 

Access to back side of processes for maintenance could be a concern

---

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.

GOAL: Workcells are intended to reduce floor space, improve throughput of smaller batches, provide more predictable production, and improve cross-training. 

Questions to consider for cellular flow:

What equipment should go into the workcell?

Is cross-training needed?

What risks are being added?

Can these risks be avoided, prevented, or reduced?

What items or processes should be produced in workcells?

How should people operate the workcell?

Which 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 there 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?

What if the EOQ changes significantly...do I have the room?

Which direction should the cell be designed (read below)?

---

Human Factors

Clockwise or Counter-Clockwise?

When designing a U-shaped workcell there should be consideration (if using humans) to whether the operators are left or right-handed and perhaps try to accommodate both. 

At some point a direction must be selected and usually counterclockwise is most efficient for people to work within.

Most people are right-handed, right eye is more accurate and stronger for most people. Also consider that track events are usually ran in a counterclockwise direction. 

Movement

Strive to:

• Avoid sharp turns, jerks, or rapid acceleration 
• Avoid static positions for extended period of time
• Make out of control conditions quickly visual - at eye level 
• Keep activity at shoulder height
• Place the most frequently used tools closest to operator and point-of-use
• Use gravity or other mechanical advantages
• Avoid vertical movement and strive for horizontal movement
• Design workstations that suit the operator height (possibly flexible height)
• Design a place for everything (and audit to ensure everything stays in its place)

---

Common Obstacles of 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. The more operators that are cross-trained the more likely the workcell can provide a consistent output. 

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 but also avoid same position for too long

Unpleasant sounds, whistles, beepers should be avoided

Avoid awkward 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 enthusiastic, open-minded, and capable. This first cell created will be judged and will set the precedent 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 appropriately

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

Analyze the work load and takt time calculations carefully and review assumptions

Ensure staffing is in place with qualified alternates (if necessary)
 

---

Test your knowledge of Six Sigma

Templates and Calculators

Six Sigma Practice Exam

Search for active job openings related to Six Sigma

Return to the Six-Sigma-Material Home Page