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Bottleneck in a Process Described

See attached file for instructions

? Discuss the tube drawing process described below.
? Identify and discuss the main bottleneck in this process.
? Apply Goldratt's theory of constraints to identify and overcome process bottlenecks.


The flowchart above (see file) depicts one process for manufacturing metal tubing. Production capacities are listed in the following table.

Operation Machines Capacity
Ft / Day / Machine Operators Comments
Drill 1 3000 1 Supplier process
Inspection 3000 4
Insert Core 1 300 1
Draw 2 150 1
Anneal 2 150 2
Draw 2 150 1
Remove Core 2 50 2
Cut 1 50 1
Grind 1 100 1
Clean 2 150 2
QC 1 2000 4
Ship 2000 2

Process Description

Drill - Done outside by a contractor in New York. Our factory is located in California so shipping time is included in the capacity calculation.

Inspection - QC checks to see that we have received the right thing. If the tube is the wrong size, we put it back into stock (MRB) to see if there is something we can use if for later.

Insert Core - Insert a soft core in the tube so that it will maintain shape through the process.

Draw - Squeezes the tube through a die to reduce the diameter

Anneal - Heat treat the tube at high temperature to relieve stress

Draw - Reduces the tube diameter again

Remove Core - There are two machines available for this operation. If the core was not inserted properly, there can be yield problems or the time to process can be unusually long. With one machine it is only possible to remove core from 50 feet of tube each day. The machine to remove the core was designed by our engineers and the cost of a new machine is $20,000

Cut - There is only one saw to cut the tube. It can only cut 50 feet a day. A new machine would cost $150,000 but it would be able to cut 200 feet a day.

Clean - Cleaning is done manually. During cleaning operators also inspect the tubes for straightness and scratches. Adding cleaning stations would be relatively inexpensive.

Inspect - QC inspects the tubes for diameter, length, surface scratches and straightness. Ten percent of the lots are rejected and will either be sent back for rework or scrap.

Ship - Shipping has sufficient capacity but they need to wait for a minimum lot of 100 feet before shipping. At the end of the month wait time can slow things down.


Solution Preview

According to Goldratt's theory of constraints, goal attainment is limited by at lease a single constraining process, with the increase of flow through the constraint being the only way to increase throughput. The constraints as observed from the diagram and the processes shown reveal that the constraints are of an internal nature. The first constraint that needs to be examined includes the drilling. As it is done by an external contractor, a cost-benefit analysis needs to be performed in identifying if doing drilling on-site would be better. There is already a cost implication of transportation, so this may be canceled out by bringing the drilling internally and saving both cost and time over the long haul.

In order to avoid any in eventualities, the ...

Solution Summary

The expert discusses the tube drawing process described. The main bottleneck in the process are determined.