Unpaced Lines

In unpaced synchronous lines, job transfers take place only after all of the individual stations have completed their tasks. For instance, a conveyor that cycles only when each of the station operators has pushed a button indicating task completion will function in this manner.  The result is that the cycle time will be the maximum of the processing times of the individual stations. Since in general processing times at the stations are variable, the cycle time, and hence the throughput, for an unpaced synchronous line is variable. However, unlike in the case of a paced synchronous line, the quality (in the sense of assuring that all tasks are completed)  is guaranteed.

Principles for Unpaced Lines

The following principles are applied to all unpaced lines, irrespective of their failure mode.

• Principle (Throughput ands Processing Time): Throughput is decreasing in the mean and standard deviation of the individual process time. 
  
  
• Principle (Length of Line): For a line where all the processing times are identical at all the stations, the throughput is decreasing in the number of the stations in the line.

Further Classification

Depending on how machine failures in the stations affect one another, paced synchronous lines can be further classified as:

• Coupled: if when any of the individual stations fail, all other stations in the line stop working immediately. Thus, the entire line comes to a standstill whenever any machine fails. 
  
  
• Uncoupled: if when an individual station fails, the other stations in the line may continue until they finish their current job. As the stations complete their jobs, they become idled and eventually, when all the stations stop, the line becomes entirely stopped.