CH. 6

Workcenter layout

A process with great flexibility to produce a variety of products, typically at lower volume levels (sometimes referred to as a job shop) similar equipment or functions are grouped together

Inventory turn

An efficiency measure where the cost of goods sold is divided by the average value of inventory (better measure than the total value of inventory) FORMULA****

1. Specify the sequential relationships among tasks using a precedence diagram 2. Determine the required workstation cycle time 3. Determine the theoretical minimum number of workstation 4. Select a primary rile to assign tasks to workstations and a secondary rule to break ties 5. Assign tasks (on at a time) to the first workstation until no more tasks can be added (due to cycle time or sequencing constraints). Repeat for all subsequent workstations until all tasks are assigned 6. Evaluate the efficency of the balance 7. If efficiency is unsatisfactory, rebalance using a different rule

Assembly Line Balancing Rules

workstation cycle time formula

C = Production time per day/ required output per day

Assemble-to-order

Firms that combine a number of preassembled modules to meet a customer's specifications

Make-to-order

Firms that make the customers product from raw materials, parts, and components

theoretical minimum number of workstations (N) required to satisfy the workstation cycle time constraint formula

N = Sum of task times (T)/ Cycle time (C)

-Split the task -Share the task -Use parallel workstations -Use a more skilled worker -Work Overtime -Redesign

Reduce Task Time Requirements

1. Source the parts needed 2. Make the product 3. Deliver the product

Steps of the production processes

Efficiency Formula

Sum of tasks (T)/ Actual number of workstations (N) x workstation cycle time (C)

Lean manufacturing to achieve higher service levels for a given inventory investment

What does Make to Stock firms use to increase their customer service?

Littles Law describes the flow of items through a production process Includes: -Throughput Time -Flow time -Inventory

What is littles law? What are the components within Little's Law?

Essential issue in satisfying customers is to balance the level of inventory against the level of customer service -Easy with unlimited inventory but inventory costs money -Trade off between the costs of inventory and level of customer service must be made

What is the issue with the Make to Stock type of firm?

Most common approach to developing this type of layout is to arrange workcenters in a way that optimizes the movement of material

What is the most common production system design?

Must offer a design that enables as much flexibility as possible in combining components

What must a assemble to order item offer?

Make-to-stock

When firms serve customers from finished goods inventory. On Demand

Customer order decoupling point

Where inventory is positioned in the supply chain. (selection of decoupling points is a strategic decision that determines customer lead times and can greatly impact inventory investment)

customer order decoupling point could be in either raw materials at the manufacturing site or the supplier inventory

Where is customer decoupling point for make to order/engineer to order?

Manufacturing cell

a dedicated area where a group of similar products are produced (typically are scheduled to produce "as needed" in response to customer demand)

product-process matrix

a framework depicting when the different production process types are typically used depending on product volume and how standardized the product is (shows relationship between layout structures)

days-of-supply

a measure of the number of days of supply of an item. Inverse of inventory turn. FORMULA ****

workstation cycle time

a uniform time interval in which a moving conveyor passes a series of workstations

Assembly line

an item is produced through a fixed sequence of workstations, designed to achieve a specific production rate -work processes are arranged according to the progressive steps by which the product is made

continuous process

assembly line only the flow is continuous such as with liquids

assembly line balancing

assigning tasks to a series of workstations so that the required cycle time is met and idle time is minimized

Engineer-to-order

firms will work with the customer to design the product, and then make it from purchased materials, parts, and components

manufacturing cell

formed by allocating dissimilar machines to cells that are designed to work on similar products

1. Maintaining System Balance 2. Frequency of Capacity Additions 3. External Sources of Capacity 4. Decreasing Capacity

list the considerations in changing capacity

1. Group parts into families that follow a common sequence of steps 2. Identify dominant flow patterns for each part family 3. Machines and the associated processes are physically regrouped into cells

manufacturing cell development

Lean manufacturing

many make-to-stock firms invest in these programs in order to achieve higher customer service with minimum levels in inventory investment

developing a high level map of supply chain process -useful to understand how material flows and where inventory is held

production process mapping

Total average value of inventory

sum of the value of the raw materials, work-in-process, and finished goods inventory. (commonly tracked in accounting systems but not so useful for evaluating the performance of a process) FORMULA ***

Throughput

the long-term average rate that items are flowing through the process

Precendence Relationships

the order in which tasks must be performed in an assembly process

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

Project layout

the product remains in a fixed location. manufacturing equipment is moved to the product rather than vice versa (Houses and bridges)

Precedence relationship

the required order in which tasks must be performed in an assembly process

workstation cycle time

the time between successive units coming off the end of an assembly line

Flow time

the time it takes a unit to flow through the process from beginning to end (Flow time= Inventory/Throughput)

Lead Time

the time needed to respond to a customer order

Little's Law

there is a long-term relationship between inventory, throughput, and flow time of a production system in steady state. (Inventory= Throughput rate x Flow time)