Calculate Lead Time

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 78 units. The process time for each step is as follows:

Process Step 1	4	minutes
Process Step 2	7	minutes
Process Step 3	9	minutes
Process Step 4	5	minutes

The time required to move each batch between steps is 18 minutes. In addition, the time to move raw materials to Process Step 1 is also 18 minutes, and the time to move completed units from Process Step 4 to finished goods inventory is 18 minutes.

The new lean layout will allow the company to reduce the batch sizes from 78 units to 5 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 value-added, non-value-added, and total lead times, and the value-added ratio under the present and proposed production approaches. If required, round percentages to one decimal place.

Present Approach		Proposed Approach
Value-added time	?	min	?	min
Non-value-added time	?	min	?	min
Total lead time	?	min	?	min
Value-added ratio (as a percent)	?	%	?	%