Manufacturing Metrics and Economics

Production performance metrics, manufacturing costs

Operation Cycle Time

Time spent on one work unit being processed/assembled. Cycle time does not include set up time but does include Processing time for operations, Handling time from machining, and tool handling time for changing tools.

Discrete Production

a) Job shop

b) Sequential Batch Production

c) Simultaneous Batch Production

d) Quantity Mass Production

e) Flow-line Mass Production

Production Rate

Expressed as an hourly rate or work units completed every hour

Sequential Batch +Simultaneous Batch + Quantity Type Processing

T_b=T_su+QT_c

T_p=T_b/Q

R_c=60/T_c

Flow Line Mass Production

T_c=MAXT_o+T_r

R_c=60/T_c

Where T_o is operation time at bottle neck and T_r is time to transfer work units between stations

Job Shop Equation

T_p=T_su+T_c

R_^p=60/T_p

Q=1

where T_p is average production time and R^_p is Production Rate

Availability

$A=\frac{\left(MTBF-MTTR\right)}{MTBF}$ Where MTBF is mean time between failures and MTTR is mean time to repair

Production Capacity

Maximum rate of output that a production facility is able to produce under a given set of operating conditions.

$PC=nH_{pc}R_{p}$ Where H_pc is # hours in period

Utilization

Time that a productive resource is used relative to the time available under definition of plant capacity

Workload (WL)

$$WL=\Sigma QT_{p}$$

Total hours required to produce a given number of units during a given week or period

Adjust plant capacity short term

Increase/decrease # of workers

Increase/decrease shifts per week

Increase/decrease hours per shift

Adjust plant capacity long term

Increase number of machines

Increase production rate R_p

Manufacturing Lead Time (MLT)

Total time required to process a given part or product through the plant including time for delays, material handling, queues before machines

Work In Progress (WIP)

Quantity of parts currently located in the factory that are being processed or are between processing operations

Major Categories of manufacturing costs

Fixed costs - remain constant for any output level

Variable costs - vary in proportion to production output level

Overhead Rate

Cost of Equipment Usage

Cost of a Manufactured Part