When different models have different work content, operations must be flexible enough to deal with the product mix.

• A constantly moving line only lends itself to mixed model production when work content is nearly identical for each station. See Balancing Workcells.

• Small Queues between stations to accommodate short-term variation.

• Adjacent workers share tasks and help each other.

• Fewer stations and longer task times.

For a mixed model assembly line to function, every part for every product must be immediately available.

• Small quantity of every part replenished by Kanban.

Tools and special fixtures must be readily available. (This is seldom a problem when the product is small. It may be a problem with large products such as refrigerators or vehicles.)

• Multi-purpose fixtures & Tools

• Setup Reduction

• Dedicated cells with a permanent setup of fixtures & tools.

Dedicated fabrication equipment is not always available. Long, expensive and/or inconsistent changeovers force large batches and high inventory between fabrication and the mixed model line.

• Setup Reduction In Fabrication with small lots.
• Redesign fabrication processes with more dedicated equipment, even (if necessary) at the cost of decreased labor efficiency.
• Investigate alternate processes.

Variation in demand for each dedicated cell may be larger than the variation for a single line. (Peaks and valleys of demand often cancel when combined.)

• Design assembly cells for multiple levels of staffing.
• Move people between cells to balance output & demand.
• Provide excess equipment capacity to handle peak demands.

Workcells appear simple and this is especially true for assembly cells. In reality they are complex and sometimes sensitive socio-bio-technical systems.

• Design cells from fundamental principles.

This usually involves processes that must be isolated for environmental reasons (Dust, Dirt, Chemicals or Noise).

• Address the environmental problem with dust control, noise control, etc.
• Investigate alternate processes.

Large-scale fabrication processes have too much capacity for a single assembly cell.

• Investigate alternate equipment and methods. (e.g. small, manual paint booth replacing a large paint line)

Certain tasks require extensive skills, experience and/or training but do not require a full-time operator for each cell.

• Tools, fixtures or gages that require less skill
• Train or cross train
• Train cell workers in basics with consultant employee for difficult problems. The daily tasks often do not require high skills or knowledge.