Williams Optical Inc. is considering a new lean product cell. The present manufacturing approach produces a product in four separate steps. The production batch sizes are 57 units. The process time for each step is as follows:
Process Step 1  9  minutes 
Process Step 2  8  minutes 
Process Step 3  5  minutes 
Process Step 4  4  minutes 
The time required to move each batch between steps is 15 minutes. In addition, the time to move raw materials to Process Step 1 is also 15 minutes, and the time to move completed units from Process Step 4 to finished goods inventory is 15 minutes.
The new lean layout will allow the company to reduce the batch sizes from 57 units to 3 units. The time required to move each batch between steps and the inventory locations will be reduced to 3 minutes. The processing time in each step will stay the same.
Determine the valueadded, nonvalueadded, and total lead times, and the valueadded ratio under the present and proposed production approaches. If required, round percentages to one decimal place.
Present Approach  Proposed Approach  
Valueadded time  min  min  
Nonvalueadded time  min  min  
Total lead time  min  min  
Valueadded ratio (as a percent)  %  % 
Solution :
Present Approach  Proposed Approach  
Valueadded time 
= 9 + 8 + 5 + 4 = 26 minutes 
= 9 + 8 + 5 + 4 = 26 minutes 

Nonvalueadded time 
= [ 26 * ( 57  1 ) ] + [ 15 * 15 ] = [ 26 * 56 ] + 225 = 1,456 + 225 = 1,681 minutes 
= [ 26 * (3  1 ) ] + [ 15 +15 ] = [ 26 * 2 ] + 30 = 52 + 30 = 82 minutes 

Total lead time 
= 1,681 + 26 = 1,707 minutes 
= 26 + 82 = 108 minutes 


= 26 / 1,707 = 0.01523 = 1.5% 
= 26 / 108 = 0.240 = 24.1% 
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