Teachers

Objective

Lecture Material

The layout of production facilities, in a factory floor as well as the choice of the characteristics of individual production facilities such as type of machine are largely based on the nature of the product and can be categorized in terms of type of production.

1. Flow Line Assembly: System design for large volume standard productions such as cars, televisions, radios, etc. The product is a standard one which can be mass produced.
2. Just in time and flexible manufacturing systems(JIT & FMS): Design for moderate volume but high variety products such as consumer electronics. There are similar products produced but they are in moderate numbers but not in large quantities and there are many batches like these.
3. Job Shop: Every product is unique and hence each has to be produced in different ways. The storage of raw material, work-in-process inventory as well as finished product requires a storage area and a retrieval process. Next subject will touch these issues with the following example.
4. Automated Storage and Retrieval Systems(AS/RS): Design of a automated warehouse system facilitated by conveyor, elevators and barcode readers. The delivery of materials between work centers usually occurs thorough a material handling system. The last example will touch issues in this area.
5. Material Handling systems: Design of automated quickest vehicle track.

Lab Assignment

1. Flow Line Manufacturing systems
2. Flexible Manufacturing
3. Automated Storage and Retrieval Systems.

Flow Line Model

Model Description: Animation screen illustrates a flow line with five serial machines of printed circuit board assembly and finite buffers is being modeled in this case. A machine may be blocked when some buffers before it is full. Inputs to the model are processing rates in parts per hour, percent of machine uptime, meantime to repair a machine, and buffer capacities. The processing rates are assumed to be constant and the failure and repair times follow and exponential distributions.

Objective: Illustrates the serial processing manufacturing system described above and "bottleneck" workstation concept. Allow the student to improve the production rate of the system measured in parts/hour after observing the affect of key variables on the system. Students individually work on improving the systems, analysis are based on group work.

EXPERIMENT 1

• Print out this assignment and,
• Run the simulation model for 3 months.
• Save results in file EXP1.
• Print the results.
• Print the animation screen of the model.
• Explain the system model and the functioning rules.
  i.e., Number of work centers? Machine speeds? Size of buffers in between workcenters?
• Explain the status in terms of utilized, blocked, starved and failed (uptime and repair time) for a machine.
• Observe # of jobs per hour.
• Analyze the simulation results
  i.e., Which machine was blocked the most (the one with no space left in the output buffer)? Which buffers has the maximum and the minimum parts stored?
• Which machine is utilized the most ( the bottleneck machine) and the one least utilized?
• Which machine failed the most?
• Calculate the Total Cost (1)
• Study the economic feasibility of improving the system

EXPERIMENT 2

Will it be feasible to double the output buffer capacity of the most blocked machine?

• Reset the simulation results before running simulation again.
• Double the output buffer size. Run for another 3 months.
• Save results in the file EXP2.
• Analyze results.
• Calculate Total Cost(2)

EXPERIMENT 3

Will it be economically feasible to increase the production capacity by doubling the bottleneck machine?

• Reset the simulation results before running simulation again.
• Double production capacity. Run it for 3 months.
• Save results in file EXP3.
• Analyze results.
• Calculate Total Cost(3).

EXPERIMENT 4

Is it economically feasible to improve the reliability of the most failing machine?

• Reset simulation.
• Choose breakdown time.
• Increase the uptime of most failing machine to 99%
• Lower the mean time to repair to 10.
• Save results in file EXP4 and analyze.
• Calculate Total Cost(4)

COMPARE the Total Costs 1 through 4. Suggest the best improvement for the system and explain your reasoning. (group analysis required)

Calculate the average hourly total cost functions for the above exercises. Assume the following are known:

Total Cost : given in hard copy.

Total Revenue :

Cost Parameters:

Cm = Cost of using a machine Cb = Cost of using a buffer space
Cp = Cost of producing a part Ci = Inventory cost per part/hour
Cd = Idle cost of machine Co = Repair downtime cost of
R = Revenue per part. a machine

Control variables:

M = Number of Machines B = Number of buffer spaces
FR = Failure Rate MTTR = Mean Time to Repair.

Performance Measures

u i = % utilization of workcenter i;
b i = % blocking of workcenter i;
s i = % starvation of workcenter i;
N i = average number of jobs in buffer i;
P r = production rate ( # of parts/hour ).

Example

Assume the following,

Cm = $30 / hr       Cb = $5 / hr     
Cp = $3 / part      Cd = $5 / hr  
Co = $30 / hr       Ci = $5 /part /hr 
R = $ 15 

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