Supply Chain MGMT Chapter 8

Inputs to the layout decision

- The specification of the objectives and corresponding criteria to be used to evaluate the design such as amount of space required or distance that must be traveled between elements in the layout are common basic criteria -estimates of product or service demand on the system -processing requirements in terms of number of operations and amount of flow between elements in the layout -space requirements for the elements in the layout -space availability within the facility itself or, if this is a new facility, possible building configurations

Office Layout

-More open offices -Low divider walls -Size and orientation of desks indicates importance of people behind them -ServiceMaster (A major janitorial firm) places its know-how room (tools , manuals) at the center

Assembly Line Design

-a moving conveyor that passes a series of workstations in a uniform time interval called workstation cycle time (the time between successive units coming off the end of the line) -at each workstation, work is performed on a product by adding parts or completing assembly operations -work performed @ each station is made up of tiny bits of work called tasks.

Project layouts

-low number of production units -Visualize the product as the hub of a wheel with materials and equipment arranged concentrically around the production point. -A high degree of task ordering is common. -To the extent that this precedence determines production stages, a project layout might be developed by arranging materials according to their technological priority.

Three steps of shifting from workcenter layout to cellular layout

1. Grouping parts into families that follow a common sequence of steps -often very expensive and requires the use of a computerized parts classification and coding system 2. Identifying dominant flow patterns of parts families as a basis for location or relocation of processes 3. Physically group machines and processes into cells -miscellaneous machines without a family will be placed in a "remainder cell"

Steps in balancing an assembly line

1. Specify sequential relationships using a precedence diagram. 2. Determine the required workstation cycle time (C), using the formula: C= Production time per day / required output per day (in units) 3. Determine theoretical minimum number of workstations (N) required to satisfy the workstation cycle time constraint using the formula: N= sum of task times (T) / Cycle time (C) 4. Select primary rule by which tasks are to be assigned to workstations and a secondary rule to break ties 5. Assign tasks one at a time to the first workstation until the sum of the task times is equal to the workstation cycle time or no other tasks are feasible because of time or sequence restrictions 6. Evaluate the efficiency of the balance derived using the formula: Efficiency = Sum of task times (T) / Actual # of workstations (N) * Workstation Cycle time (C) 7. If efficiency is unsatisfactory, balance using a different decision rule

Splitting Tasks (How to accommodate for longer tasks in shorter cycle times)

1. Split the task 2. Share the task 3. Use parallel workstations 4. Use a more skilled worker 5. Work overtime 6. Redesign

Workcenter

Also called a job-shop or functional layout; a format in which similar equipment or functions are grouped together. -Very typical in hospitals ie: intensive care units, maternity units

Assembly Line

Equipment or work processes are arranged according to the progressive steps by which the product is made. Path for each part is a straight line. -Also called Flow-shop layout -i.e.: shoes, car washes, and chemical plants

Retail Service Layout

Goal—maximize net profit per square foot of floor space -Servicescapes -Ambient conditions - Background characteristics, such as noise -Spatial layout and functionality - Planning the circulation path of customers and grouping merchandise -Signs, symbols, and artifacts Parts of the service that have social significance

Developing a workcenter

Most common approach: arrange workcenters consisting of like processes in a way that optimizes their relative placement -In many installations, this means placing workcenters with large amounts of traffic adjacent to one another.

Marketing Research and Retail Layout

People in supermarkets tend to follow a perimeter pattern in their shopping behavior. Placing high-profit items along the walls of a store will enhance their probability of purchase. Sale merchandise placed at the end of an aisle in supermarkets almost always sells better than the same sale items placed in the interior portion of an aisle. Credit and other non-selling departments that require customers to wait for the completion of their services should be placed either on upper floors or in "dead" areas. In department stores, locations nearest the store entrances and adjacent to front window displays are most valuable in terms of sales potential.

Assembly Line

Progressive assembly linked by some material handling device. -usual assumption is that some form of pacing is present and the allowable processing time is equivalent for all workstations -important differences among line types: material handling devices (belts, roller conveyor, overhead crane) line configuration (u-shape, straight, branching) pacing (mechanical, human) product mix (one product or multiple products) workstation characteristics (workers may sit, stand, walk with the line, or ride the line) length of the line (few or many workers)

Project Layout

The product, because of its sheer bulk or weight, remains fixed in a location. Equipment is moved to the product rather than vice versa. -i.e.: construction sites and movie lots

Objective:

To arrange these elements in a way that ensures smooth workflow (in factories) or a particular traffic pattern (in a service organization)

Systematic Layout Plannig

a technique for solving process layout problems when the use of numerical flow data between departments isn't practical. The technique uses an activity relationship diagram that is adjusted by trial and error until a satisfactory adjacency pattern is obtained.

cells

cellular layouts allocate dissimilar machines into cells to work on products that have similar shapes and processing requirements. -overall objective: to gain the benefit of assembly lines in workcenter kinds of production -benefits include: 1. better human relations- cells contain few workers 2. improved operator expenses: workers see only a limited number of different parts in a finite production cycle 3. Less in-process inventory and material handling- cell combines several production stages, so fewer parts travel through the shop 4. faster production setup- fewer jobs mean reduced tooling and hence faster tooling changes

Elements of layout decisions

determining the placement of departments, work groups within departments, workstations, machines, and stock-holding points within a production facility.

Manufacturing Cell

groups dissimilar machines to work on products that have similar shapes and processing requirements -similar to workcenter because cells are designed to perform a specific set of processes -similar to assembly line because cells are dedicated to a limited range of products.

one hybrid type of workflow

manufacturing cell

assembly-line balancing

the problem of assigning tasks to a series of workstations so that the required cycle time is met and idle time is minimized -this issue is further complicated by the relationships among tasks imposed by product design and process technologies called precedence relationship, or the required order in which tasks must be performed in an assembly process.

Virtual Manufacturing Cell

used when equipment is not easily movable, so dedicate a given machine out of a set of identical machines in a worksheet layout.

Three basic types of workflow

workcenter, assembly line, and project layout