Different types of production environments that embrace flow

Although our definition of flow encompasses many processes beyond physical production, we turn our attention now to production environments.

Flow should be an objective of EVERY production environment

Projects (one of a kind) can still benefit from MANY lean teachings - including some aspects of flow.
Job shops have patterns that appear. Those patterns can be made to flow.
Large lot flow is a huge cost and efficiency breakthrough (as compared to a job shop)

There are three production environments that EMBRACE flow

Continuous flow manufacturing (non-discrete products, such as oil)
Repetitive manufacturing (assembly lines)
JIT or Lean manufacturing (work cells)

What they have in common

They embrace the goal of moving a manufactured item quickly from activity to activity without interruption for any of the types of muda. (See Lean & Kaizen Training for definition of Types of Muda)

This flow chart might represent an oil refinery, a repetitive assembly line, or a Lean work cell. The concepts are the same - "flow".

What they all reject

All "flow" processes recoil at the sight of the spaghetti chart that defines work flow in a batch & queue work environment.

Some key differences

	Continuous Flow	Repetitive	Lean
Type of products produced	Food, chemicals, liquids, lumber, paper, textiles, glass, primary metals... Often have lot-controlled products, with co-products and by-products, and differing potencies or grades	Discrete units - produced in large quantities.	Discrete units - produced in small quantities. Often have product lines with high number of possible configurations.
Primary competitive factors	Commodity price. Quality. Delivery reliability. High yields.	Product design. Quality. Design for manufacturability. Price.	Fast delivery of custom products. Quality. Product design cycle time.
Typical processes	Distillation, heating, reduction, bleaching, grading, spinning, curing...	Assembly, stamping, forging, casting, injecting...	Same as repetitive.
Typical plants	Many acres, multiple plants, tanks, silos, trains, waste treatment ponds...	Assembly line with balanced standard work time per operation, and one worker per workstation	Work cell with balanced standard work time per operation. Every person in the cell operates every piece of equipment. Workers "follow each other around".
Scheduling	Focus on utilization of expensive equipment. Scheduled preventative maintenance.	Repetitive Master Schedule for long-term planning. Final Assembly Schedule based on actual customer orders + other demands (such as seasonal build-ups)	Same as repetitive, but very few "other demands". Almost entirely driven by customer orders. Primary objective = flexibility. (which requires "excess capacity")
Process control	Supervisory Data Control & Acquisition (SCADA), distributed control systems (DCS), programmable logic controllers (PLC), statistical process control (SPC), etc. Note: it is not usually important to integrate these process control systems with the ERP system used for inventory planning & cost accounting. Also use Preventative Maintenance (PM), Laboratory Information Systems (LIMS), and regulatory compliance software (e.g. haz mat, FDA...)	Ideally uses visual controls: e.g. kanbans, andon board, poka yoke mistake-proofing... Automated data collection is helpful before and after production - but rarely in WIP. Might use advanced computer process control systems.	Ideally uses visual controls. Theory of Constraints drum-buffer-rope might be helpful. Might use Manufacturing Execution System and automated data collection in production - but the closer to flow, the less needed. Engineering Change Control, Product Data Management, and Workflow software are important.

Pure flow is rare

In reality - you will probably never see a single company with pure "flow" processes throughout. There are usually pockets of flow processes, book-ended by batch & queue processes.

A single process might contain sections of batch & queue (e.g. mixing ingredients), continuous flow, (e.g. to "make goo"), followed by repetitive assembly & packaging. (See Value Stream mapping)

And the product development and order processing processes for this same product can be designed quite independently of the physical production process.

Why are work cells the "holy grail"?

Work cells aren't the only way to achieve process "flow". Assembly lines and continuous process flow lines also work well too.

Although with production lines we have to address the issues of sales forecasting, batch sizes, finished goods inventories, we have at least removed the gross inefficiencies involved within a classic "functional department" process environment.

The work cell is "the holy grail" because it can accommodate a batch size of one. And because it can be employed within work environments that have traditionally been organized in batch & queue departments - which have the most opportunity for improvement.