6.1 Types of Facility Layouts

Facility Layout Types

Facility layout determines how machines, workstations, and resources are physically arranged within a production space. The layout you choose directly affects material flow, production speed, costs, and how easily you can adapt to changes in demand or product mix. This section covers the four main layout types, their trade-offs, and how to pick the right one.

Product and Process Layouts

Product layout arranges equipment and workstations in the sequence that a specific product requires during manufacturing. Each station handles one step, and the product moves down the line from start to finish.

• Optimized for high-volume production of standardized items
• Material handling is straightforward, often using automated conveyors
• Think automobile assembly lines or electronics manufacturing, where every unit follows the same path

Process layout groups similar equipment or functions into departments. Instead of following one fixed path, products travel between departments based on whatever operations they need.

• Supports production of varied products that share some processes
• Common in job shops (machine tool facilities), hospitals (departments like radiology, surgery, pharmacy), and print shops
• Material flow is more complex because different products take different routes through the facility

The core distinction: product layouts are organized around the product's sequence, while process layouts are organized around the type of work being done.

Fixed-Position and Cellular Layouts

Fixed-position layout keeps the product stationary while workers, equipment, and materials come to it. This is the go-to choice when the product is too large or heavy to move.

• Used in shipbuilding, aircraft assembly, and large construction projects
• Scheduling and coordination become the main challenges, since multiple trades and resources converge on one location

Cellular layout blends ideas from both product and process layouts. Workstations are grouped into cells, where each cell is dedicated to producing a family of similar parts or products.

• A cell contains all the different machines needed to complete a product family from start to finish
• Common in electronics and automotive component manufacturing
• Relies on group technology, which classifies parts into families based on similar shapes, sizes, or processing requirements (often using coding systems)

Layout Characteristics at a Glance

Layout Advantages and Disadvantages

Product Layout

Advantages:

• High production rates for standardized products
• Low per-unit costs at high volumes
• Simplified material handling with sequential flow

Disadvantages:

• Inflexible to product changes or customization
• A single equipment breakdown can stop the entire line
• Repetitive tasks can lead to monotonous work and ergonomic strain

Process Layout

Advantages:

• Handles product variety and custom orders well
• Equipment gets better utilization when volumes are low (machines aren't sitting idle waiting for one product type)
• Easier to accommodate changes in processes or new product introductions

Disadvantages:

• Complex material handling with more transportation between departments
• Higher work-in-process (WIP) inventory because products wait in queues between departments
• Longer production lead times overall

Fixed-Position Layout

Advantages:

• Minimizes product movement, reducing the risk of damage to large or delicate items
• Flexible for design changes during production
• Well-suited for highly customized, one-of-a-kind products

Disadvantages:

• Requires extensive space
• Coordinating multiple trades, deliveries, and resources at one site is complex
• Equipment may sit idle between uses, lowering utilization

Cellular Layout

Advantages:

• Reduced setup times when switching between product variants within a family
• Improved quality control because cell operators take ownership of their output
• Lower WIP inventory compared to process layouts, since parts flow continuously within the cell
• Encourages teamwork among cell operators

Disadvantages:

• Upfront reorganization costs to rearrange equipment into cells
• Equipment in individual cells may be underutilized if demand for that product family drops
• Balancing workloads across different cells can be tricky
• Operators typically need cross-training to handle multiple machines within the cell

Choosing the Right Layout

Production Volume and Variety

The relationship between how many products you make and how many different types you make is the starting point for layout selection.

• High volume, low variety → product layout. Examples: beverage bottling, newspaper printing.
• Low volume, high variety → process layout. Examples: custom furniture shops, specialty machine shops.
• Medium volume, moderate variety → cellular layout. Product families can be grouped into cells.
• Very low volume, unique/large products → fixed-position layout. Examples: bridges, ships.

A product-quantity (P-Q) chart is a useful visual tool here. You plot your products on the x-axis (ranked by volume) and quantity on the y-axis. Products on the high-volume end point toward product layouts; those on the low-volume tail point toward process layouts. Products in the middle zone are candidates for cellular layouts.

Material Flow and Hybrid Layouts

Material flow patterns also shape your decision:

• Linear flow (straight-line or U-shaped) suits product layouts
• Branching flow (tree-like) appears when subassemblies feed into a main line
• Network flow (complex interconnections) is typical of process layouts

Many real facilities use hybrid layouts that combine types. An automotive plant, for example, might use a product layout for final assembly while using cellular layouts for subassembly areas. The layout doesn't have to be one-size-fits-all.

Quantitative Layout Optimization

Two common techniques help engineers move beyond intuition:

Systematic Layout Planning (SLP):

1. Chart the relationships between all activities/departments (how closely they need to be to each other)
2. Rate each relationship from "absolutely necessary" to "undesirable"
3. Develop a spatial relationship diagram based on those ratings
4. Adjust for practical constraints (building shape, column locations, utilities)
5. Evaluate and select the best alternative

CRAFT (Computerized Relative Allocation of Facilities Technique):

1. Start with an initial layout and a matrix of material flow volumes between departments
2. The algorithm calculates total material handling cost for the current arrangement
3. It then swaps pairs of departments and recalculates costs
4. Swaps that reduce cost are kept; the process repeats until no further improvement is found

Both methods aim to minimize total material handling cost, but SLP also incorporates qualitative factors (noise, safety, supervision needs) that pure algorithms miss.

Layout Impact on Operations

Productivity and Efficiency

• Throughput: Product layouts typically achieve the highest throughput rates because flow is continuous and predictable. Process layouts have longer cycle times due to material movement and queue waiting.
• Resource utilization: Product layouts keep specialized equipment running at high utilization. Process layouts get better utilization from versatile machines shared across products. Fixed-position layouts often have lower equipment utilization because tools are used intermittently.
• WIP inventory: Process layouts tend to accumulate the most WIP because of batch processing and queue times between departments. Product and cellular layouts reduce WIP through more continuous flow.

Flexibility and Adaptability

Flexibility here means the ability to adapt to changes in product mix, production volume, or product design. Process layouts rank highest for flexibility. Cellular layouts offer a middle ground, handling variety within product families while still maintaining efficient flow.

Material handling costs follow a similar pattern. Product layouts minimize handling through their sequential arrangement. Process layouts require more complex handling systems (forklifts, AGVs, carts) to move materials between scattered departments.

Cellular layouts align well with lean manufacturing principles like one-piece flow and visual management. Product layouts can be optimized for just-in-time production. Process layouts are harder to make lean because of their inherent batch-and-queue nature.

Strategic Considerations

Layout decisions are long-term commitments, so think beyond current production needs:

• Expansion: If growth is expected, modular layouts (especially cellular) are easier to scale by adding new cells
• Quality: Cellular layouts tend to improve quality because operators feel ownership over their cell's output. Product layouts may need dedicated in-line inspection stations to catch defects before they propagate.
• Workforce: Process layouts offer task variety but involve more walking and movement. Product layouts require careful ergonomic design to prevent repetitive stress injuries. Cellular layouts demand cross-trained workers but often lead to higher job satisfaction through team-based work.